Corrosion of titanium under simulated inflammation conditions: clinical context and in vitro investigations

Osteoarthritic Human Synovial Fluid Alters CoCrMo Electrochemical Properties on a Patient-Specific Basis

Cobalt-chromium-molybdenum (CoCrMo) femoral components are widely used in total knee arthroplasty (TKA). However, recent retrospective clinical trials associate moderate adverse local tissue reactions with CoCrMo release in the knee. Additionally, gaps persist in our understanding of the fundamental corrosion processes that occur at the CoCrMo-synovial fluid interface. In this study, we investigated the electrochemical behavior of CoCrMo in human synovial fluid obtained at the time of primary TKA, using CoCrMo in phosphate-buffered saline (PBS) as a comparison. Synovial fluid was collected from 118 patients immediately before arthroplasty, then transferred to a three-electrode electrochemical cell with a wrought CoCrMo alloy working electrode. To quantify electrochemical properties, open circuit potential (OCP), electrochemical impedance spectroscopy, and linear polarization tests were run. Generally, the properties varied on a patient-by-patient basis and significantly differed (p < 0.05) from comparison tests performed in PBS. In human synovial fluid, we measured OCPs between a range of -0.38 and 0.15 V and corrosion potentials (Ecorr) between -0.95 and -0.2 V. Additionally, we reported instantaneous corrosion rates (1/Rp) spanning nearly four orders of magnitude. The variability we documented suggested that the electrochemical properties of CoCrMo implants may depend on the patient's local physiological environment, influenced by the biological and chemical components of synovial fluid. Statement of Clinical Significance: This study shows that human synovial fluid affects the electrochemical behavior of CoCrMo, evidenced by the variation on a patient-by-patient basis. This study may have implications for long-term biological response to orthopaedic implants, including total knee arthroplasty.

Improved physicochemical properties of structurally modified titanium coated with zein-mesoporous bioactive glass nanoparticles-Commiphora wightii for orthopaedic applications

Titanium (Ti) is an ideal implant material due to its strength, biocompatibility, and corrosion resistance. Ti is often structurally modified to overcome its inert nature. Nanostructures (pores, rods, tubes, etc.) formed on the surface of Ti followed by bioactive and antibacterial coatings can be exploited for many biomedical applications. A combination of zein (a biopolymer with low elastic modulus), mesoporous bioactive glass nanoparticles (MBGNs, a bioactive material) and Commiphora wightii (CW, an antibacterial herb) could result in a multi-functional coating for osteogenic purposes. Zein, not only reduces the stress shielding effect at the bone-implant interface but also acts as a binder for MBGNs and CW particles in the matrix and facilitates their uniform dispersion in the coating. In this work, zein nanoparticles (ZNPs), MBGNs, and CW were deposited on electrochemically synthesized titania nanotubes (TNTs) via electrophoretic deposition (EPD). A uniform and adherent composite coating named ZNPs/MBGNs/CW was obtained. The in-vitro bioactivity test in the simulated body fluid (SBF) revealed the formation of a biologically active calcium-deficient apatitic layer (cd-HA) on the coating surface. The electrophoretically deposited composite coating was also resistant to corrosion in SBF. Furthermore, the viability of MG-63 cells was tested in which coating displayed 100 % viability after 14 days of incubation. The presence of natural herb CW inhibited the growth of gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria. Hence, the results demonstrate that the ZNPs/MBGNs/CW composite coating system may be a strong candidate for orthopaedic applications.

Diagnostic and therapeutic strategies in combating implanted medical device-associated bacterial biofilm infections

Bacterial biofilms exhibit remarkable resistance against conventional antibiotics and are capable of evading the humoral immune response. They account for nearly 80% of chronic infections in humans. Development of bacterial biofilms on medical implants results in their malfunctioning and subsequently leads to high mortality rates worldwide. Therefore, early and precise diagnosis of bacterial biofilms on implanted medical devices is essential to prevent their failure and associated complications. Culture-based methods are time consuming, more prone to contamination and often exhibit low sensitivity. Different molecular, imaging, and physical methods can aid in more accurate and faster detection of implant-associated bacterial biofilms. Biofilm growth on implant surface can be prevented either through modification of the implant material or by application of different antibacterial coatings on implant surface. Experimental studies have shown that pre-existing biofilms from medical implants can be removed by breaking down biofilm matrix, utilizing physical methods, nanomaterials and antimicrobial peptides. The current review delves into mechanism of biofilm formation on implanted medical devices and the subsequent host immune response. Much emphasis has been laid on different ongoing diagnostic and therapeutic strategies to achieve improved patient outcomes and reduced socio-economic burden.

Impact of Titanium Plate Fixation on Diacylglycerol and Growth Factor Levels in the Periosteum of the Mandible and Maxilla in Patients with Dentofacial Deformities After Jaw Osteotomies

Titanium is widely recognized for its biocompatibility and utility in maxillofacial and orthopedic surgery; however, its influence on bone remodeling biomarkers remains underexplored. This study investigates the effects of uncoated titanium plates on both the growth factors and diacylglycerols (DAGs) in the periostea of the maxilla and mandible, as DAG signaling is an essential secondary messenger molecule involved in intracellular signaling connected to various growth factors. The study group comprised 20 patients undergoing bimaxillary osteotomies using miniplates and screws made of Ti6Al4V titanium, from whom bone fixations were removed, while the control group included 20 patients operated on for dentofacial deformities (before the insertion of titanium fixations). Diacylglycerol levels in the serum and periosteum were analyzed using tandem mass spectrometry coupled with ultra-high performance liquid chromatography. Growth factors in the periosteum were measured via ELISA with commercially available assay kits. Our findings demonstrate a significant reduction in growth factors, including IGF-1, PDGF, and FGF-23, alongside decreased total DAG levels, suggesting titanium plate stabilization may modulate bone remodeling dynamics. Notably, while overall DAG levels declined, specific DAG species such as C16:0/16:0 and C18:0/18:0 were elevated, whereas polyunsaturated DAGs showed reductions, indicating selective regulation of lipid signaling pathways. Correlation analyses highlighted complex interactions between growth factors and DAGs, with distinct regional differences observed in the mandibular and maxillary periostea. These alterations may result from chronic titanium exposure, potentially inducing a low-grade immune response or modifying the local biochemical environment. This study emphasizes the need for further research into the long-term effects of titanium implants, particularly their influence on lipid metabolism, growth factor dynamics, and bone healing.

The Effects of Simulated Cobalt-Chromium-Molybdenum Wear Particles on a Macrophage-Lymphocyte Coculture for Evaluating Cellular Corrosion

BACKGROUND

This study examined the impact of simulated wear particles on inflammatory cell-induced corrosion (ICIC).

METHODS

A 30-day macrophage-lymphocyte coculture experiment was conducted using American Society of Testing and Materials F1537 cobalt-chromium-molybdenum disks, with activators and cobalt-chromium-molybdenum particles added at none, low (1:10), medium (1:100), and high (1:500) cell-particle ratios. Supernatants collected on days 10 and 30 were analyzed for tissue necrosis factor alpha (TNFα) and interleukin 6 (IL-6) levels via enzyme-linked immunosorbent assay. Disks were examined for ICIC damage using scanning electron microscopy, and the oxygen percentage on their surfaces was analyzed with energy-dispersive X-ray spectrometry and X-ray photoelectron spectrometry.

RESULTS

Most disks showed damage consistent with ICIC. Day 10 TNFα was higher in medium and high particle groups compared to groups without particles, while IL-6 was unexpectedly lower in those groups. On day 30, the activated medium particle group showed higher IL-6 than the nonactivated group. The energy-dispersive X-ray spectrometry showed no significant differences (P = 0.77), but X-ray photoelectron spectrometry results indicated significant differences (P < 0.0001) at high particle concentrations.

CONCLUSIONS

Overall, the data suggested that increased TNFα reflected a heightened inflammatory response, particles might temporarily inhibit IL-6 release, and there is likely a synergistic effect between activators and particles on cellular responses.

Toxicological evaluation of vanadium and derivation of a parenteral tolerable intake value for medical devices

Vanadium is used in alloys, batteries as well as catalyst and is a known impurity in medical devices and pharmaceuticals. The present work describes the calculation of a parenteral tolerable intake (TI) for vanadium by chronic exposure in implantable medical devices per ISO 10993-17:2023, the applicable standard. The 2023 update of ISO 10993-17 [1] introduces new uncertainty factors (UFs) for calculating a TI. Therefore, we noted differences between the ISO guidance and the ICH Q3D guidance on Permissible Daily Exposure (PDE) for parental elemental pharmaceutical impurities. We derived a TI of 0.20 μg V/kg/day based on the updated ISO guidance, and a PDE of 0.24 μg V/kg/day based on ICH guidance. The latter is considered a more realistic estimate.

Electrically Active Biomaterials for Stimulation and Regeneration in Tissue Engineering

In the human body, bioelectric cues are crucial for tissue stimulation and regeneration. Electrical stimulation (ES) significantly enhances the regeneration of nerves, bones, cardiovascular tissues, and wounds. However, the use of conventional devices with stimulating metal electrodes is invasive and requires external batteries. Consequently, electrically active materials with excellent biocompatibility have attracted attention for their applications in stimulation and regeneration in tissue engineering. To fully exploit the potential of these materials, biocompatibility, operating mechanisms, electrical properties, and even biodegradability should be carefully considered. In this review, we categorize various electrically active biomaterials based on their mechanisms for generating electrical cues, such as piezoelectric effect, triboelectric effect, and others. We also summarize the key material properties, including electrical characteristics and biodegradability, and describe their applications in tissue stimulation and regeneration for nerves, musculoskeletal tissues, and cardiovascular tissues. The electrically active biomaterials hold great potential for advancing the field of tissue engineering and their demonstrated success underscores the importance of continued research in this field.

Integrin β2 regulates titanium particle‑induced inflammation in macrophages: In vitro aseptic loosening model

Aseptic loosening is a major complication of joint replacement surgery, characterized by periprosthetic osteolysis and chronic inflammation at the bone‑implant interface. Cells release chemokines, cytokines and other pro‑inflammatory substances that perpetuate inflammation reactions, while other particle‑stimulated macrophages promote osteoclastic bone resorption and impair bone formation. The present study investigated integrin and inflammatory cytokine expression patterns in RAW 264.7 cells treated with titanium (Ti) particles to elucidate the role of integrins in Ti particle‑mediated inflammatory osteolysis. Assessment was performed by reverse transcription‑quantitative PCR, western blotting, confocal immunofluorescence, flow cytometry and enzyme‑linked immunosorbent assays. Cell migration was evaluated by wound healing assay. It was found that Ti particles significantly induced integrin expression in RAW 264.7 cells, including upregulation of integrins β2 (CD18), aL (CD11a), aM (CD11b) and aX (CD11c). Ti particles also enhanced the expression of Toll‑like receptors (TLRs; TLR1, TLR2, TLR3 and TLR4) and triggered the release of inflammatory cytokines such as tumor necrosis factor α, interleukin (IL)‑1β, IL‑8 and IL‑12. Proteomics showed higher expression and activity levels of TLR2 and TLR4, along with their downstream signaling adaptors myeloid differentiation primary response protein 88 (MyD88) and Mal/TIR‑domain‑containing adapter protein (TIRAP), following Ti treatment. Additionally, Ti treatment significantly enhanced the migration rate of RAW 264.7 cells. The present findings indicated that Ti particles regulate the inflammatory response of RAW 264.7 cells in an in vitro aseptic loosening model by activating the TLR/TIRAP/MyD88 signaling pathway.

Comparison of Biocompatibility of 3D-Printed Ceramic and Titanium in Micropig Ankle Hemiarthroplasty

BACKGROUND

Ankle arthritis is a common degenerative disease that progresses as cartilage damage in the lower tibia and upper talus progresses, resulting in loss of joint function. In addition to typical arthritis, there is also structural bone loss in the talus due to diseases such as talar avascular necrosis. Total talus replacement surgery is the procedure of choice in end-stage ankle arthritis and consists of a tibial, talar component and an insert. However, in cases of severe cartilage and bone damage to the talar bone with less damage to the tibial cartilage, a talar component hemiarthroplasty may be considered. Although the application of total talus replacement surgery using ceramics has been studied, reports on the application of metal 3D printing technology are limited. We aimed to investigate the feasibility of partial talar components using ceramic and titanium 3D printing technology in terms of biocompatibility and stability through animal experiments.

METHODS

Preoperative 3D CT was acquired and converted to STL files to fabricate a partial talus component for ankle hemiarthroplasty using ceramic and titanium. Six minipigs with an average age of 17 months were implanted with three ceramic (C-group) and three titanium talar components (T-group) in the hind limb ankle joint. The surgery was performed under anesthesia in a sterile operating room and was performed by two experienced foot and ankle specialist orthopedic surgeons. Blood analysis and CT were performed before surgery and every month for 3 months after surgery to assess the extent of inflammatory response and physical stability, sacrifices were performed 3 months after surgery, and H&E staining and micro-CT analysis were performed to compare histological biocompatibility. A grading score was calculated to semi-quantitative assess and compare the two groups.

RESULTS

In the postsurgical evaluation, blood analysis revealed that both groups had increased white blood cell counts on the postoperative day after surgery. The white blood cell count increased more in the titanium group (1.85-fold) than in the ceramic group (1.45-fold). After 3 months, all values normalized. During the study, CT analysis confirmed that all artificial samples were displaced from their initial positions. In micro-CT analysis, the adhesive tissue score of the ceramic artificial sample was better than that of the titanium sample (average threshold = 3027.18 ± 405.92). In histologic and grading scores for the inflammatory reactions, the average inflammation indices of the ceramic and titanium groups were 2.0 and 1.21, respectively. Also, the average grade score confirmed based on the results of fibrous tissue proliferation and new blood vessels was 18.4 in the ceramic application group and 12.3 in the titanium application group.

CONCLUSIONS

In conclusion, both titanium and ceramics have excellent biocompatibility for artificial joints, and ceramic materials can be used as novel artificial joints. Further research on the strength and availability of these ceramics is required.

Magnesium-Titanium Alloys: A Promising Solution for Biodegradable Biomedical Implants

Magnesium (Mg) has attracted considerable attention as a biodegradable material for medical implants owing to its excellent biocompatibility, mitigating long-term toxicity and stress shielding. Nevertheless, challenges arise from its rapid degradation and low corrosion resistance under physiological conditions. To overcome these challenges, titanium (biocompatibility and corrosion resistance) has been integrated into Mg. The incorporation of titanium significantly improves mechanical and corrosion resistance properties, thereby enhancing performance in biological settings. Mg-Ti alloys are produced through mechanical alloying and spark plasma sintering (SPS). The SPS technique transforms powder mixtures into bulk materials while preserving structural integrity, resulting in enhanced corrosion resistance, particularly Mg80-Ti20 alloy in simulated body fluids. Moreover, Mg-Ti alloy revealed no more toxicity when assessed on pre-osteoblastic cells. Furthermore, the ability of Mg-Ti-based alloy to create composites with polymers such as PLGA (polylactic-co-glycolic acid) widen their biomedical applications by regulating degradation and ensuring pH stability. These alloys promote temporary orthopaedic implants, offering initial load-bearing capacity during the healing process of fractures without requiring a second surgery for removal. To address scalability constraints, further research is necessary to investigate additional consolidation methods beyond SPS. It is essential to evaluate the relationship between corrosion and mechanical loading to confirm their adequacy in physiological environments. This review article highlights the importance of mechanical characterization and corrosion evaluation of Mg-Ti alloys, reinforcing their applicability in fracture fixation and various biomedical implants.

In Vitro Inflammatory Cell-Induced Corrosion Using a Lymphocyte and Macrophage Coculture

BACKGROUND

Cobalt-chromium-molybdenum (CoCrMo) and titanium alloys have been used for orthopaedic implants for decades. However, recent evidence has shown that inflammatory cell-induced corrosion (ICIC) can damage these metal alloys. This study aimed to investigate the mechanisms of ICIC by coculturing macrophages with lymphocytes. We hypothesized that macrophages would be able to alter the surface oxide layer of CoCrMo and titanium alloy (Ti6Al4V) disks, with greater oxide layer damage occurring in groups with a coculture compared to a macrophage monoculture and in groups with inflammatory activators compared to nonactivated groups.

METHODS

Murine macrophages were cultured on American Society for Testing and Materials F1537 CoCrMo and F136 Ti6Al4V disks for 30 days and activated with interferon gamma and lipopolysaccharide. Interferon gamma and lipopolysaccharide were added to the culture medium to simulate local inflammation. Macrophages were either cultured alone or in a coculture with T helper lymphocytes. After the 30-day experiment, scanning electron microscopy was used to examine the disk surfaces, and oxide levels were found using energy dispersive x-ray spectroscopy.

RESULTS

Pitting features consistent with previous reports of ICIC were found on disks cultured with cells. Both CoCrMo and Ti6Al4V disks had significantly lower oxide levels in all groups with cells compared to control groups with no cells (P < .01). Additionally, CoCrMo disks had significantly lower oxide levels when cultured with activated macrophages and lymphocytes compared to nonactivated macrophages alone (P < .001), activated macrophages alone (P < .01), and nonactivated macrophages and lymphocytes (P < .05). No differences in the oxide levels were found among the Ti6Al4V groups.

CONCLUSIONS

This study demonstrates the ability of macrophages to alter the surface chemistry of commonly used orthopaedic alloys. We found that the addition of lymphocytes and a simulated local inflammatory response may contribute to the ICIC of CoCrMo implants.

Finite element modeling of stress distribution and safety factors in a Ti-27Nb alloy hip implant under real-world physiological loading scenarios

Total hip arthroplasty (THA) is one of the most successful orthopaedic interventions globally, with over 450,000 procedures annually in the U.S. alone. However, issues like aseptic loosening, dislocation, infection and stress shielding persist, necessitating complex, costly revision surgeries. This highlights the need for continued biomaterials innovation to enhance primary implant integrity and longevity. Implant materials play a pivotal role in determining long-term outcomes, with titanium alloys being the prominent choice. However, emerging evidence indicates scope for optimized materials. The nickel-free β titanium alloy Ti-27Nb shows promise with excellent biocompatibility and mechanical properties. Using finite element analysis (FEA), this study investigated the biomechanical performance and safety factors of a hip bone implant made of nickel-free titanium alloy (Ti-27Nb) under actual loading during routine day life activities for different body weights. The FEA modelled physiological loads during walking, jogging, stair ascent/descent, knee bend, standing up, sitting down and cycling for 75 kg and 100 kg body weights. Comparative analyses were conducted between untreated versus 816-hour simulated body fluid (SBF) treated implant conditions to determine in vivo degradation effects. The FEA predicted elevated von Mises stresses in the implant neck for all activities, especially stair climbing, due to its smaller cross-section. Stresses increased substantially with a higher 100 kg body weight compared to 75 kg, implying risks for heavier patients. Safety factors were reduced by up to 58% between body weights, although remaining above the desired minimum value of 1. Negligible variations were observed between untreated and SBF-treated responses, attributed to Ti-27Nb's excellent biocorrosion resistance. This comprehensive FEA provided clinically relevant insights into the biomechanical behaviour and integrity of the Ti-27Nb hip implant under complex loading scenarios. The results can guide shape and material optimization to improve robustness against repetitive stresses over long-term use. Identifying damage accumulation and failure risks is crucial for hip implants encountering real-world variable conditions. The negligible SBF effects validate Ti-27Nb's resistance to physiological degradation. Overall, the study significantly advances understanding of Ti-27Nb's suitability for reliable, durable hip arthroplasties with low revision rates.

Oxide degradation precedes additively manufactured Ti-6Al-4V selective dissolution: An unsupervised machine learning correlation of impedance and dissolution compared to Ti-29Nb-21Zr

Additively manufactured (AM) Ti-6Al-4V devices are implanted with increasing frequency. While registry data report short-term success, a gap persists in our understanding of long-term AM Ti-6Al-4V corrosion behavior. Retrieval studies document β phase selective dissolution on conventionally manufactured Ti-6Al-4V devices. Researchers reproduce this damage in vitro by combining negative potentials (cathodic activation) and inflammatory simulating solutions (H2O2-phosphate buffered saline). In this study, we investigate the effects of these adverse electrochemical conditions on AM Ti-6Al-4V impedance and selective dissolution. We hypothesize that cathodic activation and H2O2 solution will degrade the oxide, promoting corrosion. First, we characterized AM Ti-6Al-4V samples before and after a 48 h -0.4 V hold in 0.1 M H2O2/phosphate buffered saline. Next, we acquired nearfield electrochemical impedance spectroscopy (EIS) data. Finally, we captured micrographs and EIS during dissolution. Throughout, we used AM Ti-29Nb-21Zr as a comparison. After 48 h, AM Ti-6Al-4V selectively dissolved. Ti-29Nb-21Zr visually corroded less. Structural changes at the AM Ti-6Al-4V oxide interface manifested as property changes to the impedance. After dissolution, the log-adjusted constant phase element (CPE) parameter, Q, significantly increased from -4.75 to -3.84 (Scm-2(s)α) (p = .000). The CPE exponent, α, significantly decreased from .90 to .84 (p = .000). Next, we documented a systematic decrease in oxide polarization resistance before pit nucleation and growth. Last, using k-means clustering, we established a structure-property relationship between impedance and the surface's dissolution state. These results suggest that AM Ti-6Al-4V may be susceptible to in vivo crevice corrosion within modular taper junctions.

Atomic layer deposited TiO2 nanofilm on titanium implant for reduced the release of particles

Objective: Titanium implants are widely used in surgeries for their biocompatibility and mechanical properties. However, excessive titanium particle release can cause implant failure. This study explores Atomic Layer Deposition (ALD) to coat commercially pure titanium (Cp-Ti) with TiO2, aiming to improve its frictional and corrosion resistance while reducing particle release. By comparing TiO2 films with varying ALD cycle numbers, we assess surface properties, particle release, friction, and corrosion performance, providing insights into mitigating particle release from implants. Methods: Cp-Ti surfaces were prepared and coated with TiO2 films of 100, 300, and 500 ALD cycles. Surface characterization involved SEM, EDX, and XRD. Friction was tested using SEM, nanoindentation, and ICP-MS. Corrosion resistance was evaluated through immersion tests and electrochemical analysis. Cytotoxicity was assessed using BMSCs. Results: Surface characterization revealed smoother surfaces with increased ALD cycles, confirming successful TiO2 deposition. Friction testing showed reduced friction coefficients with higher ALD cycles, supported by nanoindentation results. Corrosion resistance improved with increasing ALD cycles, as evidenced by electrochemical tests and reduced titanium release. Cytotoxicity studies showed no significant cytotoxic effects. Conclusion: ALD-coated TiO2 films significantly enhance frictional and corrosion resistance of titanium implants while reducing particle release. The study underscores the importance of ALD cycle numbers in optimizing film performance, offering insights for designing implants with improved properties.

Degradable biomedical elastomers: paving the future of tissue repair and regenerative medicine

Degradable biomedical elastomers (DBE), characterized by controlled biodegradability, excellent biocompatibility, tailored elasticity, and favorable network design and processability, have become indispensable in tissue repair. This review critically examines the recent advances of biodegradable elastomers for tissue repair, focusing mainly on degradation mechanisms and evaluation, synthesis and crosslinking methods, microstructure design, processing techniques, and tissue repair applications. The review explores the material composition and cross-linking methods of elastomers used in tissue repair, addressing chemistry-related challenges and structural design considerations. In addition, this review focuses on the processing methods of two- and three-dimensional structures of elastomers, and systematically discusses the contribution of processing methods such as solvent casting, electrostatic spinning, and three-/four-dimensional printing of DBE. Furthermore, we describe recent advances in tissue repair using DBE, and include advances achieved in regenerating different tissues, including nerves, tendons, muscle, cardiac, and bone, highlighting their efficacy and versatility. The review concludes by discussing the current challenges in material selection, biodegradation, bioactivation, and manufacturing in tissue repair, and suggests future research directions. This concise yet comprehensive analysis aims to provide valuable insights and technical guidance for advances in DBE for tissue engineering.

Corrosion and Biological Behaviors of Biomedical Ti-24Nb-4Zr-8Sn Alloy under an Oxidative Stress Microenvironment

Biomaterials can induce an inflammatory response in surrounding tissues after implantation, generating and releasing reactive oxygen species (ROS), such as hydrogen peroxide (H2O2). The excessive accumulation of ROS may create a microenvironment with high levels of oxidative stress (OS), which subsequently accelerates the degradation of the passive film on the surface of titanium (Ti) alloys and affects their biological activity. The immunomodulatory role of macrophages in biomaterial osteogenesis under OS is unknown. This study aimed to explore the corrosion behavior and bone formation of Ti implants under an OS microenvironment. In this study, the corrosion resistance and osteoinduction capabilities in normal and OS conditions of the Ti-24Nb-4Zr-8Sn (wt %, Ti2448) were assessed. Electrochemical impedance spectroscopy analysis indicated that the Ti2448 alloy exhibited superior corrosion resistance on exposure to excessive ROS compared to the Ti-6Al-4V (TC4) alloy. This can be attributed to the formation of the TiO2 and Nb2O5 passive films, which mitigated the adverse effects of OS. In vitro MC3T3-E1 cell experiments revealed that the Ti2448 alloy exhibited good biocompatibility in the OS microenvironment, whereas the osteogenic differentiation level was comparable to that of the TC4 alloy. The Ti2448 alloy significantly alleviates intercellular ROS levels, inducing a higher proportion of M2 phenotypes (52.7%) under OS. Ti2448 alloy significantly promoted the expression of the anti-inflammatory cytokine, interleukin 10 (IL-10), and osteoblast-related cytokines, bone morphogenetic protein 2 (BMP-2), which relatively increased by 26.9 and 31.4%, respectively, compared to TC4 alloy. The Ti2448 alloy provides a favorable osteoimmune environment and significantly promotes the proliferation and differentiation of osteoblasts in vitro compared to the TC4 alloy. Ultimately, the Ti2448 alloy demonstrated excellent corrosion resistance and immunomodulatory properties in an OS microenvironment, providing valuable insights into potential clinical applications as implants to repair bone tissue defects.

Dental Implant Abutment Screw Loss: Presentation of 10 Cases

Re-tightening the loosened dental implant abutment screw is an accepted procedure, however the evidence that such screw will hold sufficiently is weak. The purpose of this study was material analysis of lost dental implant abutment screws made of the TiAlV alloy from various manufacturers, which became lost due to unscrewing or damaged when checking if unscrewed; undamaged screws could be safely re-tightened. Among 13 failed screws retrieved from 10 cases, 10 screws were removed due to untightening and 3 were broken but without mechanical damage at the threads. Advanced corrosion was found on nine screws after 2 years of working time on all surfaces, also not mechanically loaded. Sediments observed especially in the thread area did not affect the corrosion process because of no pit densification around sediments. Pitting corrosion visible in all long-used screws raises the question of whether the screws should be replaced after a certain period during service, even if they are well-tightened. This requires further research on the influence of the degree of corrosion on the loss of the load-bearing ability of the screw.

Increasing temperature accelerates Ti-6Al-4V oxide degradation and selective dissolution: An Arrhenius-based analysis

Ti-6Al-4V selective dissolution occurs in vivo on orthopedic implants as the leading edge of a pitting corrosion attack. A gap persists in our fundamental understanding of selective dissolution and pre-clinical tests fail to reproduce this damage. While CoCrMo clinical use decreases, Ti-6Al-4V and the crevice geometries where corrosion can occur remain ubiquitous in implant design. Additionally, most additively manufactured devices cleared by the FDA use Ti-6Al-4V. Accelerated preclinical testing, therefore, would aid in the evaluation of new titanium devices and biomaterials. In this study, using temperature, we (1) developed an accelerated pre-clinical methodology to rapidly induce dissolution and (2) investigated the structure-property relationship between the dissolving surface and the oxide layer. We hypothesized that solution temperature and H2O2 concentration would accelerate oxide degradation, increase corrosion kinetics and decrease experimental times. To assess this effect, we selected temperatures above (45 °C), below (24 °C), and at (37 °C) physiological levels. Then, we acquired electrochemical impedance spectra during active β dissolution, showing significant decreases in oxide polarization resistance (Rp) both over time (p = 0.000) and as temperature increased (p = 0.000). Next, using the impedance response as a guide, we quantified the extent of selective dissolution in scanning electron micrographs. As the temperature increased, the corrosion rate increased in an Arrhenius-dependent manner. Last, we identified three surface classes as the oxide properties changed: undissolved, transition and dissolved. These results indicate a concentration and temperature dependent structure-property relationship between the solution, the protective oxide film, and the substrate alloy. Additionally, we show how supraphysiological temperatures induce structurally similar dissolution to tests run at 37 °C in less experimental time. STATEMENT OF SIGNIFICANCE: Within modular taper junctions of total hip replacement systems, retrieval studies document severe corrosion including Ti-6AL-4V selective dissolution. Current pre-clinical tests and ASTM standards fail to reproduce this damage, preventing accurate screening of titanium-based biomaterials and implant designs. In this study, we induce selective dissolution using accelerated temperatures. Building off previous work, we use electrochemical impedance spectroscopy to rapidly monitor the oxide film during dissolution. We elucidate components of the dissolution mechanism, where oxide degradation precedes pit nucleation within the β phase. Using an Arrhenius approach, we relate these accelerated testing conditions to more physiologically relevant solution concentrations. In total, this study shows the importance of including adverse electrochemical events like cathodic activation and inflammatory species in pre-clinical testing.

Albumin suppresses oxidation of TiNb alloy in the simulated inflammatory environment

Literature data has shown that reactive oxygen species (ROS), generated by immune cells during post-operative inflammation, could induce corrosion of standard Ti-based biomaterials. For Ti6Al4V alloy, this process can be further accelerated by the presence of albumin. However, this phenomenon remains unexplored for Ti β-phase materials, such as TiNb alloys. These alloys are attractive due to their relatively low elastic modulus value. This study aims to address the question of how albumin influences the corrosion resistance of TiNb alloy under simulated inflammation. Electrochemical and ion release tests have revealed that albumin significantly enhances corrosion resistance over both short (2 and 24 h) and long (2 weeks) exposure periods. Furthermore, post-immersion XPS and cross-section TEM analysis have demonstrated that prolonged exposure to an albumin-rich inflammatory solution results in the complete coverage of the TiNb surface by a protein layer. Moreover, TEM studies revealed that H2O2-induced oxidation and further formation of a defective oxide film were suppressed in the solution enriched with albumin. Overall results indicate that contrary to Ti6Al4V, the addition of albumin to the PBS + H2O2 solution is not necessary to simulate the harsh inflammatory conditions as could possibly be found in the vicinity of a TiNb implant.

Chitosan/NH2-MIL-125 (Ti) scaffold loaded with doxorubicin for postoperative bone tumor clearance and osteogenesis: An in vitro study

Surgical resection remains the primary treatment modality for bone tumors. However, it is prone to local bone defects and tumor recurrence. Therefore, there is an urgent need for multifunctional biomaterials that combine tumor treatment and bone repair after bone tumor surgery. Herein, a chitosan composite scaffold (CS/DOX@Ti-MOF) was designed for both tumor therapy and bone repair. Among them, the amino-functionalized Ti-based metal-organic framework (NH2-MIL-125 (Ti), Ti-MOF) has a high specific surface area of 1116 m2/g and excellent biocompatibility, and promotes osteogenic differentiation. The doxorubicin (DOX) loading capacity of Ti-MOF was 322 ± 21 mg/g, and DOX@Ti-MOF has perfect antitumor activity. Furthermore, the incorporation of DOX@Ti-MOF improved the physical and mechanical properties of the composite scaffolds, making the scaffold surface rough and favorable for cells to attach. CS/DOX@Ti-MOF retains the unique properties of each component. It responds to the release of DOX in the tumor microenvironment to remove residual tumor cells, followed by providing a site for cell attachment, proliferation, and differentiation. This promotes bone repair and achieves the sequential treatment of postoperative bone tumors. Overall, CS/DOX@Ti-MOF may be a promising substitute for postoperative bone tumor clearance and bone defect repair. It also provides a possible strategy for postoperative bone tumor treatment.

Mettl3‑mediated m6A RNA methylation regulates osteolysis induced by titanium particles

Peri‑prosthetic osteolysis (PPO) induced by wear particles is considered the primary cause of titanium prosthesis failure and revision surgery. The specific molecular mechanisms involve titanium particles inducing multiple intracellular pathways, which impact disease prevention and the targeted therapy of PPO. Notably, N6‑methyladenosine (m6A) serves critical roles in epigenetic regulation, particularly in bone metabolism and inflammatory responses. Thus, the present study aimed to determine the role of RNA methylation in titanium particle‑induced osteolysis. Results of reverse transcription‑quantitative PCR (RT‑qPCR), western blotting, ELISA and RNA dot blot assays revealed that titanium particles induced osteogenic inhibition and proinflammatory responses, accompanied by the reduced expression of methyltransferase‑like (Mettl) 3, a key component of m6A methyltransferase. Specific lentiviruses vectors were employed for Mettl3 knockdown and overexpression experiments. RT‑qPCR, western blotting and ELISA revealed that the knockdown of Mettl3 induced osteogenic inhibition and proinflammatory responses comparable with that induced by titanium particle, while Mettl3 overexpression attenuated titanium particle‑induced cellular reactions. Methylated RNA immunoprecipitation‑qPCR results revealed that titanium particles mediated the methylation of two inhibitory molecules, namely Smad7 and SMAD specific E3 ubiquitin protein ligase 1, via Mettl3 in bone morphogenetic protein signaling, leading to osteogenic inhibition. Furthermore, titanium particles induced activation of the nucleotide binding oligomerization domain 1 signaling pathway through methylation regulation, and the subsequent activation of the MAPK and NF‑κB pathways. Collectively, the results of the present study indicated that titanium particles utilized Mettl3 as an upstream regulatory molecule to induce osteogenic inhibition and inflammatory responses. Thus, the present study may provide novel insights into potential therapeutic targets for aseptic loosening in titanium prostheses.

Surface (bio)-functionalization of metallic materials: How to cope with real interfaces?

Metallic materials are an important class of biomaterials used in various medical devices, owing to a suitable combination of their mechanical properties. The (bio)-functionalization of their surfaces is frequently performed for biocompatibility requirements, as it offers a powerful way to control their interaction with biological systems. This is particularly important when physicochemical processes and biological events, mainly involving proteins and cells, are initiated at the host-material interface. This review addresses the state of "real interfaces" in the context of (bio)-functionalization of metallic materials, and the necessity to cope with it to avoid frequent improper evaluation of the procedure used. This issue is, indeed, well-recognized but often neglected and emerges from three main issues: (i) ubiquity of surface contamination with organic compounds, (ii) reactivity of metallic surfaces in biological medium, and (iii) discrepancy in (bio)-functionalization procedures between expectations and reality. These disturb the assessment of the strategies adopted for surface modifications and limit the possibilities to provide guidelines for their improvements. For this purpose, X-ray photoelectrons spectroscopy (XPS) comes to the rescue. Based on significant progresses made in methodological developments, and through a large amount of data compiled to generate statistically meaningful information, and to insure selectivity, precision and accuracy, the state of "real interfaces" is explored in depth, while looking after the two main constituents: (i) the bio-organic adlayer, in which the discrimination between the compounds of interest (anchoring molecules, coupling agents, proteins, etc) and organic contaminants can be made, and (ii) the metallic surface, which undergoes dynamic processes due to their reactivity. Moreover, through one of the widespread (bio)-functionalization strategy, given as a case study, a particular attention is devoted to describe the state of the interface at different stages (composition, depth distribution of contaminants and (bio)compounds of interest) and the mode of protein retention. It is highlighted, in particular, that the occurrence or improvement of bioactivity does not demonstrate that the chemical schemes worked in reality. These aspects are particularly essential to make progress on the way to choose the suitable (bio)-functionalization strategy and to provide guidelines to improve its efficiency.

Fretting and Fretting Corrosion Behavior of Additively Manufactured Ti-6Al-4V and Ti-Nb-Zr Alloys in Air and Physiological Solutions

Additive manufacturing (AM) of orthopedic implants has increased in recent years, providing benefits to surgeons, patients, and implant companies. Both traditional and new titanium alloys are under consideration for AM-manufactured implants. However, concerns remain about their wear and corrosion (tribocorrosion) performance. In this study, the effects of fretting corrosion were investigated on AM Ti-29Nb-21Zr (pre-alloyed and admixed) and AM Ti-6Al-4V with 1% nano yttria-stabilized zirconia (nYSZ). Low cycle (100 cycles, 3 Hz, 100 mN) fretting and fretting corrosion (potentiostatic, 0 V vs. Ag/AgCl) methods were used to compare these AM alloys to traditionally manufactured AM Ti-6Al-4V. Alloy and admixture surfaces were subjected to (1) fretting in the air (i.e., small-scale reciprocal sliding) and (2) fretting corrosion in phosphate-buffered saline (PBS) using a single diamond asperity (17 µm radius). Wear track depth measurements, fretting currents and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) analysis of oxide debris revealed that pre-alloyed AM Ti-29Nb-21Zr generally had greater wear depths after 100 cycles (4.67 +/- 0.55 µm dry and 5.78 +/- 0.83 µm in solution) and higher fretting currents (0.58 +/- 0.07 µA). A correlation (R2 = 0.67) was found between wear depth and the average fretting currents with different alloys located in different regions of the relationship. No statistically significant differences were observed in wear depth between in-air and in-PBS tests. However, significantly higher amounts of oxygen (measured by oxygen weight % by EDS analysis of the debris) were embedded within the wear track for tests performed in PBS compared to air for all samples except the ad-mixed Ti-29Nb-21Zr (p = 0.21). For traditional and AM Ti-6Al-4V, the wear track depths (dry fretting: 2.90 +/- 0.32 µm vs. 2.51 +/- 0.51 μm, respectively; fretting corrosion: 2.09 +/- 0.59 μm vs. 1.16 +/- 0.79 μm, respectively) and fretting current measurements (0.37 +/- 0.05 μA vs. 0.34 +/- 0.05 μA, respectively) showed no significant differences. The dominant wear deformation process was plastic deformation followed by cyclic extrusion of plate-like wear debris at the end of the stroke, resulting in ribbon-like extruded material for all alloys. While previous work documented improved corrosion resistance of Ti-29Nb-21Zr in simulated inflammatory solutions over Ti-6Al-4V, this work does not show similar improvements in the relative fretting corrosion resistance of these alloys compared to Ti-6Al-4V.

Is taper corrosion in modular revision hip stem junctions associated with patient or implant specific factors? A retrieval analysis

Implant modularity within revision total hip arthroplasty (THA) offers multiple implant configurations and allows surgeons a high intraoperative flexibility to restore functionality to the patients joint, even in complex revision cases. However, a rare but devastating complication for patients, clinicians and manufacturers presenting a breakage of the taper junction between the distal stem and the proximal implant part. Aside from implant and patient specific risk factors, corrosion and fretting at the stem junctions have been associated with taper failure. Whether corrosive processes are a precursor of failure or rather an accompaniment of material fatigue is thereby still unclear. Therefore, this study aims to investigate the incidence of taper corrosion in a collection of 17 retrievals from a single type (MRP-Titan, Peter Brehm GmbH) and on the correlation of taper corrosion to implant and patient specific factors. None of the implants was revised for problems related to the taper junction, corrosion or the implant itself. The modular stem junction of all retrievals was visually rated with respect to corrosion, fretting and surface contamination. Additionally, the stability of taper junctions of retrievals where the proximal part with the neck was still assembled to the stem was determined by measuring the loosening moment of the securing screw and the push-out-force for taper dissociation. There was no difference between the mean push-out-force of the retrievals (14 kN ± 1.2 kN) and new reference samples (12.6 kN ± 0.5 kN). Approximately one third of the investigated retrievals showed considerable taper corrosion. The extent of corrosion increased with time in vivo and contamination of the neck piece, while it decreased with the loosening moment of the locking screw. The parameters femoral head offset, neck piece length, lateralized neck pieces, obesity of patients and septic/aseptic revision were not correlated to taper corrosion. Taper corrosion seems to occur regularly in modular taper junctions and is not necessarily connected to taper failure. A correct assembly of the junction and avoiding taper surface contamination during revision surgery is mandatory.

Surface-modified titanium and titanium-based alloys for improved osteogenesis: A critical review

As implantable materials, titanium, and its alloys have garnered enormous interest from researchers for dental and orthopedic procedures. Despite their success in wide clinical applications, titanium, and its alloys fail to stimulate osteogenesis, resulting in poor bonding strength with surrounding bone tissue. Optimizing the surface topology and altered compositions of titanium and titanium-based alloys substantially promotes peri-implant bone regeneration. This review summarizes the utilization and importance of various osteogenesis components loaded onto titanium and its alloys. Further, different surface-modification methods and the release efficacy of loaded substances are emphasized. Finally, we summarize the article with prospects. We believe that further investigation studies must focus on identifying novel loading components, exploring various innovative, optimized surface-modification methods, and developing a sustained-release system on implant surfaces to improve peri-implant bone formation.

Antibiofilm peptides enhance the corrosion resistance of titanium in the presence of Streptococcus mutans

Titanium alloys have gained popularity in implant dentistry for the restoration of missing teeth and related hard tissues because of their biocompatibility and enhanced strength. However, titanium corrosion and infection caused by microbial biofilms remains a significant clinical challenge leading to implant failure. This study aimed to evaluate the effectiveness of antibiofilm peptides 1018 and DJK-5 on the corrosion resistance of titanium in the presence of Streptococcus mutans. Commercially pure titanium disks were prepared and used to form biofilms. The disks were randomly assigned to different treatment groups (exposed to S. mutans supplied with sucrose) including a positive control with untreated biofilms, peptides 1018 or DJK-5 at concentrations of 5 μg/mL or 10 μg/mL, and a negative control with no S. mutans. Dynamic biofilm growth and pH variation of all disks were measured after one or two treatment periods of 48 h. After incubation, the dead bacterial proportion, surface morphology, and electrochemical behaviors of the disks were determined. The results showed that peptides 1018 and DJK-5 exhibited significantly higher dead bacterial proportions than the positive control group in a concentration dependent manner (p < 0.01), as well as far less defects in microstructure. DJK-5 at 10 μg/mL killed 84.82% of biofilms and inhibited biofilm growth, preventing acidification due to S. mutans and maintaining a neutral pH. Potential polarization and electrochemical impedance spectroscopy data revealed that both peptides significantly reduced the corrosion and passive currents on titanium compared to titanium surfaces with untreated biofilms, and increased the resistance of the passive film (p < 0.05), with 10 μg/mL of DJK-5 achieving the greatest effect. These findings demonstrated that antibiofilm peptides are effective in promoting corrosion resistance of titanium against S. mutans, suggesting a promising strategy to enhance the stability of dental implants by endowing them with antibiofilm and anticorrosion properties.

Interaction pathways of implant metal localized corrosion and macrophage inflammatory reactions

Macrophages play a central role in immunological responses to metallic species associated with the localized corrosion of metallic implants, and mediating in peri-implant inflammations. Herein, the pathways of localized corrosion-macrophage interactions were systematically investigated on 316L stainless steel (SS) implant metals. Electrochemical monitoring under macrophage-mediated inflammatory conditions showed a decreased pitting corrosion resistance of 316L SSs in the presence of RAW264.7 cells as the cells would disrupt biomolecule adsorbed layer on the metal surface. The pitting potentials were furtherly decreased when the RAW264.7 cells were induced to the M1 pro-inflammatory phenotype by the addition of lipopolysaccharide (LPS), and pitting corrosion preferentially initiated at the peripheries of macrophages. The overproduction of aggressive ROS under inflammatory conditions would accelerate the localized corrosion of 316L SS around macrophages. Under pitting corrosion condition, the viability and pro-inflammatory polarization of RAW264.7 cells were region-dependent, lower viability and more remarkable morphology transformation of macrophages in the pitting corrosion region than the pitting-free region. The pitting corrosion of 316L SS induced high expression of CD86, TNF-α, IL-6 and high level of intracellular ROS in macrophages. Uneven release of metallic species (Fe2+, Cr3+, Ni2+, etc) and uneven distribution of surface overpotential stimulated macrophage inflammatory responses near the corrosion pits. A synergetic effect of localized corrosion and macrophages was revealed, which could furtherly promote localized corrosion of 316L SS and macrophage inflammatory reactions. Our results provided direct evidence of corrosion-macrophage interaction in metallic implants and disclosed the pathways of this mutual stimulation effect.

Malignant Neoplasms Arising in the Cardiac Pacemaker Cavity: A Systematic Review

Cancer is the abnormal proliferation of physiologically inadequate cells. Studies have identified the cardiac pacemaker pocket as a site of rare neoplasms. To evaluate the clinical outcomes, treatment, prognosis, and individualized management of tumors originating in the cardiac pacemaker pocket, a systematic review was conducted using case reports and case series available in the PubMed/Medline, Science Direct, Cochrane Central, LILACS, and Scientific Electronic Library Online (Scielo) databases. Pacemaker pocket tumors affected patients with a mean age of 72.9 years, with a higher incidence in males (76.9%, n = 10). The average time for neoplasm development was 4.4 years (54.07 months). The most prevalent model was Medtronic (38.4%, n = 5), with titanium (83.3%) being the most common metal composition. Chemotherapy was the most performed procedure among patients (38.4%), followed by radiation therapy (38.4%) and surgical tumor resection (30.7%). Six analyzed cases (46.1%) resulted in death, and four patients (30.7%) achieved a cure. Patients with pacemakers should be routinely evaluated for the occurrence of malignant tumors at the site of device implantation.

Regulation of localized corrosion of 316L stainless steel on osteogenic differentiation of bone morrow derived mesenchymal stem cells

Localized corrosion has become a concerning issue in orthopedic implants as it is associated with peri-implant adverse tissue reactions and implant failure. Here, the pitting corrosion of 316 L stainless steels (316 L SSs) was initiated by electrochemical polarization to simulate the in vivo localized corrosion of orthopedic implants. The effect of localized corrosion on osteogenic differentiation of bone marrow derived mesenchymal stem cells (BMSCs) was systematically studied. The results suggest that pitting corrosion of 316 L SS reduced the viability, adhesion, proliferation, and osteogenic differentiation abilities of BMSCs, especially for the cells around the corrosion pits. The relatively high concentrations of metallic ions such as Cr3+ and Ni2+ released by pitting corrosion could cause cytotoxicity to the BMSCs. The inhomogeneous electrochemical environment resulted from localized corrosion could promote reactive oxygen species (ROS) generation around the corrosion pits and cause oxidative stress of BMSCs. In addition, localized corrosion could also electrochemically interact with the cells and lead to cell membrane depolarization. The depolarized cell membranes and relatively high levels of ROS mediated the degradation of the osteogenic capacity of BMSCs. This work provides new insights into corrosion-mediated cell function degeneration as well as the material-cell interactions.

Subgingival titanium wire implantation induces weak inflammatory responses but does not promote substantial T cell activation

Titanium is a biocompatible material commonly used for dental treatments. However, the detailed mechanism underlying the weak biological activity of titanium has not been elucidated. We investigated both the inflammatory responses and T cell activation induced by solid titanium in the gingiva in mice. Both titanium and nickel wire implantation promoted neutrophil infiltration into the gingiva on day 2. Nickel, but not titanium, wire implantation enhanced proinflammatory cytokine expression and dendritic cell activity in gingival tissue by day 2. Nickel wire implantation enhanced the activity of T cells in draining lymph nodes on day 5. Moreover, T cell and neutrophil infiltration and elevated proinflammatory cytokine expression in the gingival tissue were still observed on day 5. However, no such augmented biological responses were observed after titanium wire implantation. These findings suggest that, unlike nickel, solid titanium does not induce sufficient inflammatory responses leading to T cell activation in gingival tissue.

Boosting Titanium Surfaces with Positive Charges: Newly Developed Cationic Coating Combines Anticorrosive and Bactericidal Properties for Implant Application

Along with poor implant-bone integration, peri-implant diseases are the major causes of implant failure. Although such diseases are primarily triggered by biofilm accumulation, a complex inflammatory process in response to corrosive-related metallic ions/debris has also been recognized as a risk factor. In this regard, by boosting the titanium (Ti) surface with silane-based positive charges, cationic coatings have gained increasing attention due to their ability to kill pathogens and may be favorable for corrosion resistance. Nevertheless, the development of a cationic coating that combines such properties in addition to having a favorable topography for implant osseointegration is lacking. Because introducing hydroxyl (-OH) groups to Ti is essential to increase chemical bonds with silane, Ti pretreatment is of utmost importance to achieve such polarization. In this study, plasma electrolytic oxidation (PEO) was investigated as a new route to pretreat Ti with OH groups while providing favorable properties for implant application compared with traditional hydrothermal treatment (HT). To produce bactericidal and corrosion-resistant cationic coatings, after pretreatment with PEO or HT (Step 1), surface silanization was subsequently performed via immersion-based functionalization with 3-aminopropyltriethoxysilane (APTES) (Step 2). In the end, five groups were assessed: untreated Ti (Ti), HT, PEO, HT+APTES, and PEO+APTES. PEO created a porous surface with increased roughness and better mechanical and tribological properties compared with HT and Ti. The introduction of -OH groups by HT and PEO was confirmed by Fourier transform infrared spectroscopy and the increase in wettability producing superhydrophilic surfaces. After silanization, the surfaces were polarized to hydrophobic ones, and an increase in the amine functional group was observed by X-ray photoelectron spectroscopy, demonstrating a considerable amount of positive ions. Such protonation may explain the enhanced corrosion resistance and dead bacteria (Streptococcus aureus and Escherichia coli) found for PEO+APTES. All groups presented noncytotoxic properties with similar blood plasma protein adsorption capacity vs the Ti control. Our findings provide new insights into developing next-generation cationic coatings by suggesting that a tailorable porous and oxide coating produced by PEO has promise in designing enhanced cationic surfaces targeting biomedical and dental implant applications.

Nanotechnology enabled radioprotectants to reduce space radiation-induced reactive oxidative species

Interest in space exploration has seen substantial growth following recent launch and operation of modern space technologies. In particular, the possibility of travel beyond low earth orbit is seeing sustained support. However, future deep space travel requires addressing health concerns for crews under continuous, longer-term exposure to adverse environmental conditions. Among these challenges, radiation-induced health issues are a major concern. Their potential to induce chronic illness is further potentiated by the microgravity environment. While investigations into the physiological effects of space radiation are still under investigation, studies on model ionizing radiation conditions, in earth and micro-gravity conditions, can provide needed insight into relevant processes. Substantial formation of high, sustained reactive oxygen species (ROS) evolution during radiation exposure is a clear threat to physiological health of space travelers, producing indirect damage to various cell structures and requiring therapeutic address. Radioprotection toward the skeletal system components is essential to astronaut health, due to the high radio-absorption cross-section of bone mineral and local hematopoiesis. Nanotechnology can potentially function as radioprotectant and radiomitigating agents toward ROS and direct radiation damage. Nanoparticle compositions such as gold, silver, platinum, carbon-based materials, silica, transition metal dichalcogenides, and ceria have all shown potential as viable radioprotectants to mitigate space radiation effects with nanoceria further showing the ability to protect genetic material from oxidative damage in several studies. As research into space radiation-induced health problems develops, this review intends to provide insights into the nanomaterial design to ameliorate pathological effects from ionizing radiation exposure. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Nanotechnology Approaches to Biology > Cells at the Nanoscale Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Advanced surface engineering of titanium materials for biomedical applications: From static modification to dynamic responsive regulation

Titanium (Ti) and its alloys have been widely used as orthopedic implants, because of their favorable mechanical properties, corrosion resistance and biocompatibility. Despite their significant success in various clinical applications, the probability of failure, degradation and revision is undesirably high, especially for the patients with low bone density, insufficient quantity of bone or osteoporosis, which renders the studies on surface modification of Ti still active to further improve clinical results. It is discerned that surface physicochemical properties directly influence and even control the dynamic interaction that subsequently determines the success or rejection of orthopedic implants. Therefore, it is crucial to endow bulk materials with specific surface properties of high bioactivity that can be performed by surface modification to realize the osseointegration. This article first reviews surface characteristics of Ti materials and various conventional surface modification techniques involving mechanical, physical and chemical treatments based on the formation mechanism of the modified coatings. Such conventional methods are able to improve bioactivity of Ti implants, but the surfaces with static state cannot respond to the dynamic biological cascades from the living cells and tissues. Hence, beyond traditional static design, dynamic responsive avenues are then emerging. The dynamic stimuli sources for surface functionalization can originate from environmental triggers or physiological triggers. In short, this review surveys recent developments in the surface engineering of Ti materials, with a specific emphasis on advances in static to dynamic functionality, which provides perspectives for improving bioactivity and biocompatibility of Ti implants.

Metal-organic frameworks functionalized biomaterials for promoting bone repair

Bone defects induced by bone trauma, tumors and osteoarthritis greatly affect the life quality and health of patients. The biomaterials with numerous advantages are becoming the most preferred options for repairing bone defects and treating orthopedic diseases. However, their repairing effects remains unsatisfactory, especially in bone defects suffering from tumor, inflammation, and/or bacterial infection. There are several strategies to functionalize biomaterials, but a more general and efficient method is essential for accomplishing the functionalization of biomaterials. Possessing high specific surface, high porosity, controlled degradability and variable composition, metal-organic frameworks (MOFs) materials are inherently advantageous for functionalizing biomaterials, with tremendous improvements having been achieved. This review summarizes recent progresses in MOFs functionalized biomaterials for promoting bone repair and therapeutic effects. In specific, by utilizing various properties of diverse MOFs materials, integrated MOFs functionalized biomaterials achieve enhanced bone regeneration, antibacterial, anti-inflammatory and anti-tumor functions. Finally, the summary and prospects of on the development of MOFs-functionalized biomaterials for promoting bone repair were discussed.

Engineering Antioxidant Surfaces for Titanium-Based Metallic Biomaterials

Prolonged inflammation induced by orthopedic metallic implants can critically affect the success rates, which can even lead to aseptic loosening and consequent implant failure. In the case of adverse clinical conditions involving osteoporosis, orthopedic trauma and implant corrosion-wear in peri-implant region, the reactive oxygen species (ROS) activity is enhanced which leads to increased oxidative stress. Metallic implant materials (such as titanium and its alloys) can induce increased amount of ROS, thereby critically influencing the healing process. This will consequently affect the bone remodeling process and increase healing time. The current review explores the ROS generation aspects associated with Ti-based metallic biomaterials and the various surface modification strategies developed specifically to improve antioxidant aspects of Ti surfaces. The initial part of this review explores the ROS generation associated with Ti implant materials and the associated ROS metabolism resulting in the formation of superoxide anion, hydroxyl radical and hydrogen peroxide radicals. This is followed by a comprehensive overview of various organic and inorganic coatings/materials for effective antioxidant surfaces and outlook in this research direction. Overall, this review highlights the critical need to consider the aspects of ROS generation as well as oxidative stress while designing an implant material and its effective surface engineering.

Preclinical EIS Study of the Inflammatory Response Evolution of Pure Titanium Implant in Hank's Biological Solution

Pure titanium (Ti) is investigated in a pre-clinical study in Hank's biological solution using electrochemical methods, open circuit potential, and electrochemical impedance spectroscopy to highlight the time effect in extreme body conditions, such as inflammatory diseases, on degradability due to corrosion processes occurring on the titanium implant. Electrochemical impedance spectroscopy (EIS) data are presented as Nyquist and Bode plots. The results show the increasing reactivity of titanium implants in the presence of hydrogen peroxide, which is an oxygen-reactive compound that describes inflammatory conditions. The polarization resistance, which results from electrochemical impedance spectroscopy measurements, declined dramatically from the highest value registered in Hank's solution to smaller values registered in all solutions when different concentrations of hydrogen peroxide were tested. The EIS analysis provided insights into titanium's in vitro corrosion behavior as an implanted biomaterial, which could not be solely obtained through potentiodynamic polarization testing.

Biomaterials as Implants in the Orthopedic Field for Regenerative Medicine: Metal versus Synthetic Polymers

Patients suffering bone fractures in different parts of the body require implants that will enable similar function to that of the natural bone that they are replacing. Joint diseases (rheumatoid arthritis and osteoarthritis) also require surgical intervention with implants such as hip and knee joint replacement. Biomaterial implants are utilized to fix fractures or replace parts of the body. For the majority of these implant cases, either metal or polymer biomaterials are chosen in order to have a similar functional capacity to the original bone material. The biomaterials that are employed most often for implants of bone fracture are metals such as stainless steel and titanium, and polymers such as polyethene and polyetheretherketone (PEEK). This review compared metallic and synthetic polymer implant biomaterials that can be employed to secure load-bearing bone fractures due to their ability to withstand the mechanical stresses and strains of the body, with a focus on their classification, properties, and application.

A Review on Nano Ti-Based Oxides for Dark and Photocatalysis: From Photoinduced Processes to Bioimplant Applications

Catalysis on TiO₂ nanomaterials in the presence of H₂O and oxygen plays a crucial role in the advancement of many different fields, such as clean energy technologies, catalysis, disinfection, and bioimplants. Photocatalysis on TiO₂ nanomaterials is well-established and has advanced in the last decades in terms of the understanding of its underlying principles and improvement of its efficiency. Meanwhile, the increasing complexity of modern scientific challenges in disinfection and bioimplants requires a profound mechanistic understanding of both residual and dark catalysis. Here, an overview of the progress made in TiO₂ catalysis is given both in the presence and absence of light. It begins with the mechanisms involving reactive oxygen species (ROS) in TiO₂ photocatalysis. This is followed by improvements in their photocatalytic efficiency due to their nanomorphology and states by enhancing charge separation and increasing light harvesting. A subsection on black TiO₂ nanomaterials and their interesting properties and physics is also included. Progress in residual catalysis and dark catalysis on TiO₂ are then presented. Safety, microbicidal effect, and studies on Ti-oxides for bioimplants are also presented. Finally, conclusions and future perspectives in light of disinfection and bioimplant application are given.

Do Titanium Dioxide Particles Stimulate Macrophages to Release Proinflammatory Cytokines and Increase the Risk for Peri-implantitis?

PURPOSE

Titanium dioxide (TiO₂) particles detached from titanium dental implants by tribocorrosion can be phagocytosed by macrophages, releasing various proinflammatory cytokines at the implant sites that may trigger peri-implantitis. The study objective was to measure the association between peri-implantitis and the presence of non-allergy-related proinflammatory cytokines associated with TiO₂ particles.

METHODS

The investigators implemented a retrospective cross-sectional study and enrolled a sample of 60 subjects from a dental practice. Subjects were excluded if the plaque index was grade 3 (Silness and Löe). The predictor variable was a positive or negative TiO₂ stimulation test, an in vitro macrophage proinflammatory response test. The outcome variable was peri-implantitis status defined as present or absent. Three groups were considered: control group with 20 patients without dental implants (group 1), 2 groups of patients with titanium dental implants, one without peri-implantitis (group 2), and the other with peri-implantitis (group 3) (n = 20 each). For patients with implants, depth of the gingival pockets of the implants were measured, and existing bleeding and suppuration were determined to assess peri-implantitis. Radiographs were taken if one or more factors applied to confirm the diagnosis of peri-implantitis. Further covariates were age, sex, duration of implant wear, and number of implants which were analyzed descriptively. Inferential analyses were undertaken using χ² test, Kruskal-Wallis-, Wilcoxon-two-sample tests, and logistic regressions.

RESULTS

The sample was composed of 35 female and 25 male patients with a mean age of 54.2 years (standard deviation = 14.76). The overall TiO₂ stimulation test positivity frequency was 28.3% and were 30.0%, 5.0%, and 50.0% in the control, implants without peri-implantitis, and implants with peri-implantitis groups. No statistically significant differences could be seen in the frequencies of the TiO₂ stimulation test results between control group and combined groups 2 and 3 (P-value = .84). The risk for positive TiO₂ patients with a titanium implant of developing peri-implantitis was statistically significant and higher compared to negative TiO₂ patients (odds ratio, 19.0 with 95% confidence interval [2.12,170.38]; P-value< .01).

CONCLUSIONS

The data in this study showed a statistically significant relationship between a positive TiO₂ stimulation test and peri-implantitis. Further studies with larger numbers of subjects are recommended to confirm this result.

An Experimental Anodized Titanium Surface for Transgingival Dental Implant Elements-Preliminary Report

The characteristics such as microtopography, physical and chemical properties influence the behavior of an implant in a soft tissue. Anodization-as a potent method of titanium alloy surface modification-of the transgingival abutment or healing screw, has achieved some improvement. One of the possible surface treatment method is low-pressure radiofrequency oxygen plasma treatment. The aim of the study was to evaluate the chemical properties and cytocompatibility of the experimental surface. Titanium discs made of grade-23 titanium alloy (Ti-6Al-4V) anodized (A sample) with different voltage parameters (28, 67, 78, and 98 V) were included in the study. Half of the samples regarded as the "S" group were additionally treated with low-pressure radiofrequency oxygen plasma treatment. The surfaces were characterized using scanning electron microscopy, X-ray spectroscopy and Raman spectroscopy, and electrochemically investigated via a corrosion test. Furthermore, two cell lines were used, including the CHO-compatible reference line and a primary human fibroblast line for the MTT assay; direct (contact) cytotoxicity of the materials was tested with the cells, and the growth of fibroblasts on the surfaces of the different materials was tested. The morphology of the "S"-treated samples did not differ from the morphology of only-anodized samples. However, the oxygen concentration on the surface in that group slightly increased by about 1% as a result of post-trial treatment. The highest corrosion resistance was observed for both A-78 V and S-78 V samples. The cytotoxicity assay revealed no changes in cell morphology or vitality. The MTT test proved comparable culture viability among all groups; however, the "S" samples showed statistically significantly higher fibroblast proliferation and adhesion scores compared to the "A" samples. Through the in vitro study, the low-pressure radiofrequency oxygen plasma treatment of the anodized Ti-6Al-4V alloy presented itself as an auspicious option in the field of transgingival element surface modification of implants.

Biocompatibility of a Zr-Based Metallic Glass Enabled by Additive Manufacturing

The present work explored the use of the selective laser melting (SLM) technique to develop a Zr-based bulk metallic glass (BMG) and investigate the influence of the process parameters on obtaining different levels of surface roughness. Moreover, the potential of the additively manufactured BMG Zr_59.3Cu_28.8Al_10.4Nb_1.5 (trade name AMLOY-ZR01) as an implant material was studied by evaluating the osteoblastic cell response to the alloy and its stability under simulated biological environments. The materials were characterized in terms of degree of crystallinity, surface roughness, and morphology, followed by a systematic investigation of the response of the MC3T3-E1 preosteoblastic cell line to the as-printed samples. The materials supported cell proliferation and differentiation of the preosteoblastic cells, with results comparable to the reference material Ti-6Al-4V. The surface microroughness and surface morphology (porous or groove-type laser tracks) investigated in this study did not have a significant effect on modulating the cell response. Ion release experiments showed a large increase in ion release under inflammatory conditions as compared to regular physiological conditions, which could be attributed to the increased local corrosion under inflammatory conditions. The findings in this work showed that the surface roughness of the additively manufactured BMG AMLOY-ZR01 can be tailored by controlling the laser power applied during the SLM process. The favorable cell response to the as-printed AMLOY-ZR01 represents of a significant advancement of the investigation of additively manufactured BMGs for orthopedic applications, while the results of the ion release study highlights the effect that inflammatory conditions could have on the degradation of the alloy.

Antibacterial Coatings for Titanium Implants: Recent Trends and Future Perspectives

Titanium and its alloys are widely used as implant materials for biomedical devices owing to their high mechanical strength, biocompatibility, and corrosion resistance. However, there is a significant rise in implant-associated infections (IAIs) leading to revision surgeries, which are more complicated than the original replacement surgery. To reduce the risk of infections, numerous antibacterial agents, e.g., bioactive compounds, metal ions, nanoparticles, antimicrobial peptides, polymers, etc., have been incorporated on the surface of the titanium implant. Various coating methods and surface modification techniques, e.g., micro-arc oxidation (MAO), layer-by-layer (LbL) assembly, plasma electrolytic oxidation (PEO), anodization, magnetron sputtering, and spin coating, are exploited in the race to create a biocompatible, antibacterial titanium implant surface that can simultaneously promote tissue integration around the implant. The nature and surface morphology of implant coatings play an important role in bacterial inhibition and drug delivery. Surface modification of titanium implants with nanostructured materials, such as titanium nanotubes, enhances bone regeneration. Antimicrobial peptides loaded with antibiotics help to achieve sustained drug release and reduce the risk of antibiotic resistance. Additive manufacturing of patient-specific porous titanium implants will have a clear future direction in the development of antimicrobial titanium implants. In this review, a brief overview of the different types of coatings that are used to prevent implant-associated infections and the applications of 3D printing in the development of antibacterial titanium implants is presented.

Influence of Surface Modification of Titanium and Its Alloys for Medical Implants on Their Corrosion Behavior

Titanium and its alloys are often used for long-term implants after their surface treatment. Such surface modification is usually performed to improve biological properties but seldom to increase corrosion resistance. This paper presents research results performed on such metallic materials modified by a variety of techniques: direct voltage anodic oxidation in the presence of fluorides, micro-arc oxidation (MAO), pulse laser treatment, deposition of chitosan, biodegradable Eudragit 100 and poly(4-vinylpyridine (P4VP), carbon nanotubes, nanoparticles of TiO₂, and chitosan with Pt (nano Pt) and polymeric dispersant. The open circuit potential, corrosion current density, and potential values were determined by potentiodynamic technique, and microstructures of the surface layers and coatings were characterized by scanning electron microscopy. The results show that despite the applied modifications, the corrosion current density still appears in the region of very low values of some nA/cm². However, almost all surface modifications, designed principally for the improvement of biological properties, negatively influence corrosion resistance. The reasons for observed effects can vary, such as imperfections and permeability of some coatings or accelerated degradation of biodegradable deposits in simulated body fluids during electrochemical testing. Despite that, all coatings can be accepted for biological applications, and such corrosion testing results are presumed not to be of major importance for their applications in medicine.

Microstructural Modification of TiAl6V4 Alloy to Avoid Detrimental Effects Due to Selective In Vivo Crevice Corrosion

TiAl6V4 wrought alloy is a standard material used for endoprostheses due to its ideal characteristics in terms of osseointegration. However, the insufficient wear and crevice corrosion resistance of TiAl6V4 are limiting factors that can cause clinical problems. Therefore, the objective of this study was to analyze and identify suitable phases and microstructural states of TiAl6V4 alloy with advantageous implant properties by thermal treatments. By varying the temperature and cooling rate, four heat treatment strategies were derived that produced different microstructural states that differed in morphology, arrangement and proportions of phases present. All TiAl6V4 modifications were characterized regarding their microstructure, mechanical, corrosive and tribological properties, as well as cell adhesion. The acicular, martensitic microstructure achieves a significant hardness increase by up to 63% and exhibits improved corrosion and wear resistance compared to the forged condition. Whereas the modified microstructures showed similar electrochemical properties in polarization tests using different electrolytes (PBS with H₂O₂ and HCl additives), selective α or β phase dissolution occurred under severe inflammatory crevice conditions after four weeks of exposure at 37 °C. The microstructurally selective corrosion processes resemble the damage patterns of retrieved Ti-based implants and provide a better understanding of clinically relevant in vivo crevice corrosion mechanisms. Furthermore, a microstructural effect on cell attachment was determined and is correlated to the size of the vanadium-rich β phase. These key findings highlight the relevance of an adapted processing of TiAl6V4 alloy to increase the longevity of implants.

Evaluation of the Biocompatibility and Osteogenic Properties of Metal Oxide Coatings Applied by Magnetron Sputtering as Potential Biofunctional Surface Modifications for Orthopedic Implants

Biomaterials with adequate properties to direct a biological response are essential for orthopedic and dental implants. The surface properties are responsible for the biological response; thus, coatings with biologically relevant properties such as osteoinduction are exciting options to tailor the surface of different bulk materials. Metal oxide coatings such as TiO₂, ZrO₂, Nb₂O₅ and Ta₂O₅ have been suggested as promising for orthopedic and dental implants. However, a comparative study among them is still missing to select the most promising for bone-growth-related applications. In this work, using magnetron sputtering, TiO₂, ZrO₂, Ta₂O₅, and Nb₂O₅ thin films were deposited on Si (100) substrates. The coatings were characterized by Optical Profilometry, Scanning Electron Microscopy, Energy-Dispersive X-ray Spectroscopy, X-ray Photoelectron Spectroscopy, X-ray Diffraction, Water Contact Angle measurements, and Surface Free Energy calculations. The cell adhesion, viability, proliferation, and differentiation toward the osteoblastic phenotype of mesenchymal stem cells plated on the coatings were measured to define the biological response. Results confirmed that all coatings were biocompatible. However, a more significant number of cells and proliferative cells were observed on Nb₂O₅ and Ta₂O₅ compared to TiO₂ and ZrO_2. Nevertheless, Nb₂O₅ and Ta₂O₅ seemed to induce cell differentiation toward the osteoblastic phenotype in a longer cell culture time than TiO₂ and ZrO₂.

Influence of FeCl3 and H2O2 in corrosion testing of modular taper connections in total hip arthroplasty: An in vitro study

Corrosion at the modular taper junctions in total hip arthroplasty is clinically relevant because wear particles and ions generated at this interface can lead to adverse local tissue reactions or even implant failure. In vitro tribo-corrosion tests are usually accomplished in saline solutions or calf serum (CS), but the addition of H₂O₂ and FeCl₃ have been suggested to mimic inflammatory conditions in the joint. Inflammatory conditions may aggravate corrosive processes and, therefore, should lead in vitro to a more severe and realistic tribo-corrosive material attack. Corrosion testing at 12/14 tapers comprising a CoCrMo head taper and a Ti6Al4V trunnion was accomplished in five electrolytes (Ringer's solution (RS), RS with 30 mM H₂O₂ and/or 0.7 mM FeCl₃ and CS) under dynamical loading for five million cycles. Resulting material loss was determined gravimetrically and by ion analysis. The tribo-corrosive material degradation was investigated by light and electron microscopy. FeCl₃ enhanced the material loss from taper connections while H₂O₂ did not lead to a significant alteration of total material loss. In comparison to pure RS, corrosion testing in CS decreased material loss at the head taper while it increased material loss at the trunnion. The combination of FeCl₃ and H₂O₂ led to an enhanced occurrence of micro cracks at the trunnion surface. Adding FeCl₃ and optionally also H₂O₂ aggravates material loss in in vitro corrosion testing of taper junctions and leads to harsher and probably more realistic testing conditions. STATEMENT OF SIGNIFICANCE: Tribo-corrosive processes at taper connections in hip implants are complex and can lead to major clinical implications. Joint inflammation is assumed to aggravate taper corrosion in vivo, why FeCl₃ and H₂O₂ have been proposed as additives to electrolytes to simulate inflammatory conditions in vitro. Often used fretting test setups, however, do not involve real taper geometries. Besides, testing is often accomplished in saline solutions or calf serum, which do not induce a clinically significant amount of corrosive material degradation. This study presents an approach to increase tribo-corrosive processes at realistic taper connections by adding FeCl₃ and/or H₂O₂. Unlike H₂O₂, FeCl₃ increased material loss from taper connections. The combination of both additives enhanced micro crack formation at the trunnion surfaces.