A comprehensive review on metallic implant biomaterials and their subtractive manufacturing

Conductive MeCbl/PEDOT:PSS/HA hydrogels with electrical stimulation for enhanced peripheral nerve regeneration

Peripheral nerve regeneration (PNR) represents a substantial challenge in the medical field, primarily due to the limited regenerative capacity of the peripheral nerve system (PNS). Current research efforts are focused on developing advanced medical polymer materials to enhance nerve recovery. Despite significant progress, several critical issues remain unresolved, including biocompatibility, stability, mechanical strength, controlled degradation rates, and sustained release of therapeutic agents. This study examines the utilization of hyaluronic acid hydrogels, doped with mecobalamin (MeCbl) and conductive poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), in combination with exogenous electrical stimulation (ES) for PNR of rats. The strategy utilizes the MeCbl hydrogel to create a regenerative microenvironment and provide nutritional support for nerve cells, while PEDOT:PSS facilitates enhanced electrical signal conduction. ES has been shown to promote PNR and functional recovery, thereby demonstrating considerable potential. This study aims to comprehensively analyze the synergistic effects and potential value of this combined therapeutic approach, providing novel insights and pathways for the effective PNR.

Functionalized zeolite regulates bone metabolic microenvironment

The regulation of bone metabolic microenvironment imbalances in diseases such as osteoporosis, bone defects, infections, and tumors remains a significant challenge in orthopedics. Therefore, it has become urgent to develop biomaterials with effective bone metabolic microenvironmental regulatory functions. Zeolites, as advanced biomedical materials, possess distinctive physicochemical properties such as multi-level pore structures, adjustable frameworks, easily modifiable surfaces, and excellent adsorption capabilities. These advantageous characteristics give zeolites broad application prospects in regulating the bone metabolic microenvironment. Therefore, this paper first classifies zeolites used to regulate the bone metabolic microenvironment based on their topological structures and compositional frameworks. Subsequently, it provides a detailed description of modification strategies for zeolite materials aimed at regulating this microenvironment. Next, a comprehensive summary was provided on the preparation strategies for zeolite materials aimed at regulating the bone metabolic microenvironment. Additionally, the paper focuses on the specific applications of zeolite materials in conditions of bone metabolic imbalance, such as osteoporosis, bone defects, orthopedic infections, and bone tumors, highlighting their potential in enhancing osteogenic microenvironments, controlling infections, and treating bone tumors. Finally, it outlines the prospects and challenges associated with the application of zeolites in regulating the bone metabolic microenvironment. This review comprehensively summarizes zeolites used for bone metabolic regulation, aiming to provide guidance for future research and application development.

Hierarchical Porous Aerogel-Hydrogel Interlocking Bioelectronic Interface for Arrhythmia Management

Carbon aerogels with exceptional electrical properties are considered promising materials for bioelectronics in signal detection and electrical stimulation. To address the mechanical incompatibilities of carbon aerogels with bio-interfaces, particularly for dynamic tissues and organs, the incorporation of hydrogels is an effective strategy. However, achieving excellent electrical performance in carbon aerogel-hydrogel hybrids remains a significant challenge. Two key factors contribute to this difficulty: 1) unrestricted hydrogel infiltration during preparation can lead to complete encapsulation of the conductive aerogel, and 2) the high swelling behavior of hydrogels can cause disconnection of the aerogel. Herein, a stretchable, highly conductive bioelectronic interface is achieved by forming an interlocking network between hierarchical porous carbon aerogel (PA) with polyvinyl alcohol (PVA) hydrogel. Partial exposure of the PA due to confined infiltration of PVA into the porous structure maintains the electrical performance, while the non-swellable PVA ensures mechanical stretchability and stability. The hybrid demonstrates excellent conductivity (370 S·m-1), high charge storage capacity (1.66 mC cm-2), remarkable stretchability (250%), and long-term stability over three months, enabling effective signal recording and electrical stimulation. For the first time, carbon aerogel-hydrogel hybrids enable cardiac pacing both ex vivo and in vivo in rat heart models. Compared to conventional platinum electrodes, the PA-PVA electrodes require lower pacing voltages, suggesting potential advantages in power efficiency and reduced tissue damage. The electrodes can be integrated with a wireless implantable device for in vivo synchronous electrocardiogram monitoring and cardiac pacing, underscoring their potential for arrhythmia management.

Identification of a surface texture parameter panel characterizing surface micromorphologies of differently processed oral implant surfaces

OBJECTIVES

Inconsistent characterization of oral implant microtopography makes it difficult to compare and evaluate available data on microtopography and the biological response to topographical characteristics. The aim of this investigation was therefore to identify a surface texture parameter panel that enables a discriminative characterization of differently processed oral implant surfaces.

MATERIALS AND METHODS

Surface micromorphologies of titanium- and ceramic-based biomaterials processed by machining or by machining and subsequent post-processing, including blasting, etching, anodization or porous sintering, were analyzed by scanning electron microscopy and white light interferometry. It was then analyzed which of the parameters Sa, Sq, Sz, Ssk, Sku, Str, Sal, Spd, Spc, Sdq and Sdr best characterized morphological surface features and hence should be reported as minimum parameter panel for implant surface characterization.

RESULTS

SEM demonstrated that each surface processing resulted in a specific and biomaterial-dependent micromorphology. The data revealed that the micromorphology of machined surfaces was best characterized by Sa, Sdr, Str and Ssk, and that for post-processed surfaces Spd and Spc were additionally required. Based on these data, Sa, Sdr, Str, Ssk, Spd and Spc were identified as minimum parameter panel for discriminative description of the investigated implant microtopographies.

SIGNIFICANCE

The present investigation identified Sa, Sdr, Str, Ssk, Spd and Spc as minimum parameter panel for discriminative oral implant surface characterization. The widespread use of such a panel combined with biological data will help to identify cell-relevant implant surface structures, thus enabling the design of oral implants with predefined biological response.

Natural potential difference induced functional optimization mechanism for Zn-based multimetal bone implants

Zn-based biodegradable metals (BMs) are regarded as revolutionary biomaterials for bone implants. However, their clinical application is limited by insufficient mechanical properties, delayed in vivo degradation, and overdose-induced Zn2+ toxicity. Herein, innovative multi-material additive manufacturing (MMAM) is deployed to construct a Zn/titanium (Ti) hetero-structured composite. The biodegradation and biofunction of Zn exhibited intriguing characteristics in composites. A potential difference of about 300 mV naturally existed between Zn and Ti. This natural potential difference triggered galvanic coupling corrosion, resulting in 2.7 times accelerated degradation of Zn. The excess release of Zn2+ induced by accelerated degradation enhanced the antibacterial function. A voltage signal generated by the natural potential difference also promoted in vitro osteogenic differentiation through activating the PI3K-Akt signaling pathway, and inhibited the toxicity of overdose Zn2+ in vivo, significantly improving bone regeneration. Furthermore, MMAM technology allows for the specific region deployment of components. In the future, Ti and Zn could be respectively deployed in the primary and non-load-bearing regions of bone implants by structural designs, thereby achieving a functionally graded application to overcome the insufficient mechanical properties of Zn-based BMs. This work clarifies the functional optimization mechanism for multimetal bone implants, which possibly breaks the application dilemma of Zn-based BMs.

Therapeutic functions of medical implants from various material categories with integrated biomacromolecular systems

Medical implants are designed to replace missing parts or improve body functions and must be capable of providing structural support or therapeutic intervention for a medical condition. Advances in materials science have enabled the development of devices made from metals, polymers, bioceramics, and composites, each with its specific advantages and limitations. This review analyzes the incorporation of biopolymers, proteins, and other biomacromolecules into implants, focusing on their role in biological integration and therapeutic functions. It synthesizes advancements in surface modification, discusses biomacromolecules as carriers for controlled drug release, and explores the application of nanoceramics and composites to improve osseointegration and tissue regeneration. Biomacromolecule systems are capable of interacting with device components and therapeutic agents - such as growth factors (GFs), antibiotics, and nanoceramics - allowing control over substance release. Incorporating therapeutic agents into these systems enables localized treatments for tissue regeneration, osseointegration, post-surgery infection control, and disease and pre-existing conditions. The review highlights these materials' therapeutic advantages and customization opportunities, by covering mechanical and biological perspectives. Developing composites and hybrid drug delivery systems align with recent efforts in interdisciplinary personalized medicine and implant innovations. For instance, a trend was observed for integrating inorganic (especially nanoceramics, e.g., hydroxyapatite) and organic phases in composites for better implant interaction with biological tissues and faster recovery. This article supports understanding how integrating these materials can create more personalized, functional, durable, and biocompatible implant devices.

Bone Regeneration: Mini-Review and Appealing Perspectives

Bone is a natural mineral-organic nanocomposite protecting internal organs and allowing mobility. Through the ages, numerous strategies have been developed for repairing bone defects and fixing fractures. Several generations of bone repair biomaterials have been proposed, either based on metals, ceramics, glasses, or polymers, depending on the clinical need, the maturity of technologies, and knowledge of the natural constitution of the bone tissue to be repaired. The global trend in bone implant research is shifting toward osteointegrative, bioactive and possibly stimuli-responsive biomaterials and, where possible, resorbable implants that actively promote the regeneration of natural bone tissue. In this mini-review, the fundamentals of bone healing materials and clinical challenges are summarized and commented on with regard to progressing scientific discoveries. The main types of bone-healing materials are then reviewed, and their specific relevance to the field is reminded, with the citation of reference works. In the final part, we highlight the promise of hybrid organic-inorganic bioactive materials and the ongoing research activities toward the development of multifunctional or stimuli-responsive implants. This contribution is expected to serve as a commented introduction to the ever-progressing field of bone regeneration and highlight trends of future-oriented research.

Prevalence of metal implants among US adults aged 40 years and older

Metal implants are commonly used in clinical practice. However, little is known regarding the prevalence of metal implants. Therefore, this study aimed to evaluate the prevalence of metal implants in the United States (US) among individuals aged ≥ 40 years. This study conducted a serial cross-sectional analysis of US adults aged ≥ 40 years who participated in the National Health and Nutrition Examination Survey (NHANES) (2015-2016 and 2017-March 2020). Self-reported questionnaires were used to assess whether the participants had metal implants inside their bodies. The primary outcome was the prevalence of metal implants among adults aged 40 years and older. Furthermore, weighted logistic regression analysis was employed to determine the changes in the prevalence of metal implants from 2015 to March 2020. Moreover, this study investigated the variation in metal implant prevalence by demographic factors based on the pooled NHANES cycles. All analyses were conducted based on 3,736 participants from the NHANES 2015-2016 and 6,387 participants from the NHANES 2017-March 2020. This study observed a high prevalence of metal implants among adults aged 40 and older (2015-2016: 27.23%; 2017-March 2020: 31.53%). Moreover, the results of the weighted logistic regression analysis showed that the prevalence of metal implants significantly increased from 2015 to March 2020, especially among older individuals, men, and White individuals. In addition, the results of the weighted logistic regression analysis indicated that the metal implant prevalence differed by age and race/ethnicity, in which older individuals and White individuals showed a significantly higher prevalence of metal implants than younger individuals and non-White individuals, respectively. There was a high prevalence of metal implants among US adults aged 40 and older, and the prevalence of metal implants significantly increased from 2015 to March 2020. Therefore, more attention needs to be paid to this special population, and it may be necessary to ensure accessibility and affordability and assess the potential long-term health impacts of metal implants, considering the increased prevalence of metal implants.

In situ phosphorus-modified Mg2Ge/Zn-Cu composite with improved mechanical, degradation, biotribological properties, and in vitro and in vivo osteogenesis and osteointegration performance for biodegradable bone-implant applications

Zinc (Zn)-based composites are promising biodegradable bone-implant materials because of their good biocompatibility, processability, and biodegradability. Nevertheless, the low interfacial bonding strength, coordinated deformation capacity, and mechanical strength of current Zn-based composites hinder their clinical application. In this study, we developed a biodegradable in situ 4Mg2Ge/Zn-0.3Cu-0.05P composite (denoted ZMGCP) via phosphorus (P) modification and hot-rolling for bone-implant applications. The mechanical properties, corrosion behavior, biotribological performance, in vitro cytocompatibility and osteogenic differentiation, and in vivo osteogenesis and osteointegration of the as-cast (AC) and hot-rolled (HR) ZMGCP samples were systematically evaluated and compared to those of 4Mg2Ge/Zn-0.3Cu (denoted ZMGC). The primary and eutectic reinforcement Mg2Ge phases formed during solidification were refined after P modification and hot-rolling. The HR ZMGCP exhibited the best tensile properties among all the samples with an ultimate tensile strength of 288.9 MPa, a yield strength of 194.5 MPa, and an elongation of 17.7 %. The HR ZMGCP showed the lowest corrosion rate of 336 μm/a, 186 μm/a, and 61.7 μm/a as measured by potentiodynamic polarization, electrochemical impedance spectroscopy, and immersion testing, respectively, among all the samples in Hanks' solution. The HR ZMGCP also showed higher biotribological resistance than its ZMGC counterpart. The HR ZMGCP exhibited the highest in vitro cytocompatibility, the best osteogenesis capability and angiogenesis property among the HR samples of pure Zn, ZMGC, and ZMGCP. Furthermore, the HR ZMGCP displayed complete in vivo biocompatibility, osteogenesis, osteointegration capability, and an appropriate degradation rate, showing significant potential for a biodegradable bone-implant material.

COVALENT GRAFTING OF TANFLOC ON TITANIA NANOTUBE ARRAYS: AN APPROACH TO MITIGATE BACTERIAL ADHESION AND IMPROVE THE ANTIBACTERIAL EFFICACY OF TITANIUM IMPLANTS

Implanted medical devices often face the challenge of infections, which can compromise their successful integration and use. To address this issue, this study demonstrates the covalent grafting of a tannin-based antimicrobial biopolymer tanfloc (TAN) onto the titania nanotube arrays (TiNTs) surface to enhance antibacterial properties. Due to its polyphenolic and ionic structural configuration, tanfloc possesses unique properties that enable it to interact with and disrupt bacterial cell walls and membranes. Combining the topographical effect of TiNTs with the inherent antibacterial properties of tanfloc, this approach aims to mitigate bacterial threats on medical implants effectively. The successful attachment of tanfloc on TiNTs was confirmed through X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT-IR). The antibacterial and antibiofilm efficacy of the tanfloc-functionalized TiNTs was evaluated against Staphylococcus aureus (Gram-positive) and Pseudomonas aeruginosa (Gram-negative) bacteria. The findings suggest that the covalent conjugation of tanfloc onto TiNTs is a promising approach to improve the infection resistance of titanium-based medical implants, with potential applications in orthopedic, dental, and other biomedical device areas.

Developments, challenges and future trends in advanced sustainable machining technologies for preparing array micro-holes

The use of array micro-holes is becoming increasingly prevalent across a range of industries, including the aerospace, automotive, electronics, medical and chemical industries. The utilization of advanced sustainable machining technologies offers distinctive advantages and is pivotal for the sustainable manufacture of array micro-holes. This paper examines the sustainable machining techniques commonly employed in the production of array micro-holes, including electrical discharge machining, laser machining, electrochemical machining and composite machining technologies. The paper begins with an elaboration of the processing principles and characteristics of multiple non-traditional machining techniques. The performance indicators of the most commonly used processing technologies in industrial production are summarized from seven perspectives. Six significant avenues for the advancement of sustainable manufacturing technology for array micro-holes have been identified and categorized. This article provides a summary and evaluation of the previous relevant literature, with the aim of offering guidance for the development of array micro-hole processing technologies.

From bone to nacre - development of biomimetic materials for bone implants: a review

The field of bone repair and regeneration has undergone significant advancements, yet challenges persist in achieving optimal bone implants or scaffolds, particularly load-bearing bone implants. This review explores the current landscape of bone implants, emphasizing the complexity of bone anatomy and the emerging paradigm of biomimicry inspired by natural structures. Nature, as a master architect, offers insights into the design of biomaterials that can closely emulate the mechanical properties and hierarchical organization of bone. By drawing parallels with nacre, the mollusk shells renowned for their exceptional strength and toughness, researchers have endeavored to develop bone implants with enhanced biocompatibility and mechanical robustness. This paper surveys the literature on various nacre-inspired composites, particularly ceramic/polymer composites like calcium phosphate (CaP), which exhibit promising similarities to native bone tissue. By harnessing the principles of hierarchical organization and organic-inorganic interfaces observed in natural structures, researchers aim to overcome existing limitations in bone implant technology, paving the way for more durable, biocompatible, and functionally integrated solutions in orthopedic and dental applications.

Study on the Enhanced Degradable Rate of the Zn-0.4Li Alloys as Biodegradable Implants by Anodization

Biodegradable Zn-0.4Li alloys have been considered as medical implants due to their excellent mechanical properties and desirable biocompatibility. In this work, anodization was applied to modified corrosion resistance of the Zn-0.4Li alloy by forming a uniform and neat flower-like nanowire coating on the surface. After anodization for 7 min, the anodized Zn-0.4Li alloy had a yield strength of 253.6 MPa, ultimate tensile strength of 389.5 MPa, and elongation at a break of 66.0%. The corrosion rate of the Zn-0.4Li-7 min sample reached 0.5741 mm/y in the SBF, which was almost 18 times higher than that of the Zn-0.4Li alloy. The anodized Zn-0.4Li alloy exhibited higher antibacterial properties than that of the Zn-0.4Li alloy against Escherichia coli and Staphylococcus aureus. These results suggested that anodization may be an effective method to modulate the corrosion behavior of zinc alloys, which can be applied in the surface modification of biodegradable implants.

Bubble Printing of Liquid Metal Colloidal Particles for Conductive Patterns

Bubble printing is a patterning method in which particles are accumulated by the convection of bubbles generated by laser focusing. It is attracting attention as a method that enables the high-speed, high-precision patterning of various micro/nanoparticles. Although the bubble printing method is used for metallic particles and organic particles, most reports have focused on the patterning of solid particles and not on the patterning of liquid particles. In this study, liquid metal wiring patterns were fabricated using a bubble printing method in which eutectic gallium‒indium alloy (EGaIn) colloidal particles (≈diameter 0.7 µm) were fixed on a glass substrate by generating microbubbles through heat generation by focusing a femtosecond laser beam on the EGaIn colloidal particles. The wiring was then made conductive by replacing gallium oxide, which served as a resistance layer on the surface of the EGaIn colloidal particles, with silver via galvanic replacement. Fine continuous lines of liquid metal colloids with a line width of 3.4 µm were drawn by reducing the laser power. Liquid metal wiring with a conductivity of ≈1.5 × 105 S/m was formed on a glass substrate. It was confirmed that the conductivity remained consistent even when the glass substrate was bent to a curvature of 0.02 m-1.

Recent development and applications of electrodeposition biocoatings on medical titanium for bone repair

Bioactive coatings play a crucial role in enhancing the osseointegration of titanium implants for bone repair. Electrodeposition offers a versatile and efficient technique to deposit uniform coatings onto titanium surfaces, endowing implants with antibacterial properties, controlled drug release, enhanced osteoblast adhesion, and even smart responsiveness. This review summarizes the recent advancements in bioactive coatings for titanium implants used in bone repair, focusing on various electrodeposition strategies based on material-structure synergy. Firstly, it outlines different titanium implant materials and bioactive coating materials suitable for bone repair. Then, it introduces various electrodeposition methods, including electrophoretic deposition, anodization, micro-arc oxidation, electrochemical etching, electrochemical polymerization, and electrochemical deposition, discussing their applications in antibacterial, osteogenic, drug delivery, and smart responsiveness. Finally, it discusses the challenges encountered in the electrodeposition of coatings for titanium implants in bone repair and potential solutions.

Evaluation of the immune response of peripheral blood mononuclear cells cultured on Ti6Al4V-ELI polished or etched surfaces

INTRODUCTION

While titanium and its alloys exhibit excellent biocompatibility and corrosion resistance, their polished surfaces can hinder fast and effective osseointegration and other biological processes, such as angiogenesis, due to their inert and hydrophobic properties. Despite being commonly used for orthopedic implants, research focuses on developing surface treatments to improve osseointegration, promoting cell adhesion and proliferation, as well as increasing protein adsorption capacity. This study explores a chemical treatment intended for titanium-based implants that enhances tissue integration without compromising the mechanical properties of the Ti6Al4V substrate. However, recognizing that inflammation contributes to nearly half of early implant failures, we assessed the impact of this treatment on T-cell viability, cytokine production, and phenotype.

METHODS

Ti6Al4V with extra low interstitial (ELI) content discs were treated with hydrofluoric acid followed by a controlled oxidation step in hydrogen peroxide that creates a complex surface topography with micro- and nano-texture and modifies the chemistry of the surface oxide layer. The acid etched surface contains an abundance of hydroxyl groups, crucial for promoting bone growth and apatite precipitation, while also enabling further functionalization with biomolecules.

RESULTS

While cell viability remained high in both groups, untreated discs triggered an increase in Th2 cells and a decrease of the Th17 subset. Furthermore, peripheral blood mononuclear cells exposed to untreated discs displayed a rise in various pro-inflammatory and anti-inflammatory cytokines compared to the control and treated groups. Conversely, the treated discs showed a similar profile to the control, both in terms of immune cell subset frequencies and cytokine secretion.

DISCUSSION

The dysregulation of the cytokine profile upon contact with untreated Ti6Al4V-ELI discs, namely upregulation of IL-2 could be responsible for the decrease in Th17 frequency, and thus might contribute to implant-associated bacterial infection. Interestingly, the chemical treatment restores the immune response to levels comparable to the control condition, suggesting the treatment's potential to mitigate inflammation by enhancing biocompatibility.

Unveiling the governing role of 'remodeling triangle area' in soft-hard tissue interface equilibrium for metal implants advancement

Metal implants holds significant promise for diverse fixed prostheses. However, their long-term reliability and broader application are hindered by challenges related to the disequilibrium at the soft-hard tissue interface. By using anti-inflammatory (PDA/IL4) and pro-inflammatory (PDA/LPS/IFNγ) coatings to modulate distinct immune characteristics, we discovered a dynamic bioactive structure at the soft-hard tissue interface around metal implant, which we have named the 'Remodeling Triangle Area' (RTA). We further demonstrate that the RTA can be influenced by the PDA/IL4 coating to favor a phenotype that enhances both innate and adaptive immunity. This leads to stronger epithelial adhesion, the formation of dense connective tissue via IGF1 secretion, and a more balanced soft-hard tissue interface through the OPG/RANKL axis. Conversely, the PDA/LPS/IFNγ coating shifts the RTA towards a phenotype that activates the innate immune response. This results in a less cohesive tissue structure and bone resorption, characterized by reduced IGF1 secretion and an imbalanced OPG/RANKL axis. Over all, our study introduces the novel concept termed the 'Remodeling Triangle Area' (RTA), an immune-rich anatomical region located at the nexus of the implant interface, epithelial, connective, and bone tissue, which becomes highly interactive post-implantation to modulate the soft-hard tissue interface equilibrium. We believe that an RTA-centric, immunomodulatory approach has the potential to revolutionize the design of next-generation metal implants, providing unparalleled soft-hard tissue interface equilibrium properties.

Robust, stretchable bioelectronic interfaces for cardiac pacing enabled by interfacial transfer of laser-induced graphene via water-response, nonswellable PVA gels

Implantable cardiac pacemakers are crucial therapeutic tools for managing various cardiac conditions. For effective pacing, electrodes should exhibit flexibility, deformability, biocompatibility, and high conductivity/capacitance. Laser-induced graphene (LIG) shows promise due to its exceptional electrical and electrochemical properties. However, the fragility of LIG and the non-stretchability of polyimide substrates pose challenges when interfacing with the beating heart. Here, we present a simple method for fabricating robust, flexible, and stretchable bioelectronic interfaces by transferring LIG via water-responsive, nonswellable polyvinyl alcohol (PVA) gels. PVA solution penetrates the porous structure of LIG and solidifies into PVA xerogel as the solvent evaporates. The robust PVA xerogel enables the smooth transfer of LIG and prevents stretching of the LIG network during this process, which helps maintain its conductivity. When hydrated, the xerogel becomes a stable, nonswellable hydrogel. This gives the LIG-PVA hydrogel (LIG-PVA-H) composites with excellent conductivity (119.7 ± 4.3Ω sq-1), high stretchability (up to 420%), reliability (cyclic stretch under 15% strain, with ∼ 1-time resistance increase), and good stability in phosphate buffered saline. The LIG-PVA-H composites were used as biointerfaces for electrocardiogram signal recording and electrical pacing on rat hearts ex vivo and in vivo, using commercial setups and a custom-built implantable wireless device. This work expands the application of LIG in bioelectronic interfaces and facilitates the development of electrotherapy for cardiac diseases.

Biomedical Device Surface Treatment by Laser-Driven Hydroxyapatite Penetration-Synthesis Technique for Gapless PEEK-to-Bone Integration

Polyetheretherketone (PEEK), a bioinert polymer known for its mechanical properties similar to bone, is capable of averting stress shielding. Due to these attributes, it finds applications in diverse fields like orthopedics, encompassing cervical disc replacement for the neck and spine, along with dentistry and plastic surgery. However, due to insufficient bonding with bone, various methods such as hydroxyapatite (HA) coating on the surface are attempted. Nonetheless, the interface between the polymer and ceramic, two different materials, tended to delaminate after transplantation, posing challenges in preventing implant escape or dislodgement. This research delves into the laser-driven hydroxyapatite penetration-synthesis technique. Differing from conventional coating methods that bond layers of dissimilar materials like HA and PEEK, this technology focuses on synthesizing and infiltrating ionized HA within the PEEK substrate resulting in an interface-free HA-PEEK surface. Conversely, HA-PEEK with this technology applied achieves complete, gap-free direct bone-implant integration.  Our research involved the analysis of various aspects. By means of these, we quantitatively assesed the enhanced bone bonding characteristics of HA-PEEK surfaces treated with this approach and offered and explanation for the mechanism responsible for direct bone integration.

Advancements in supervised deep learning for metal artifact reduction in computed tomography: A systematic review

BACKGROUND

Metallic artefacts caused by metal implants, are a common problem in computed tomography (CT) imaging, degrading image quality and diagnostic accuracy. With advancements in artificial intelligence, novel deep learning (DL)-based metal artefact reduction (MAR) algorithms are entering clinical practice.

OBJECTIVE

This systematic review provides an overview of the performance of the current supervised DL-based MAR algorithms for CT, focusing on three different domains: sinogram, image, and dual domain.

METHODS

A literature search was conducted in PubMed, EMBASE, Web of Science, and Scopus. Outcomes were assessed using peak signal-to-noise ratio (PSNR) and structural similarity index measure (SSIM) or any other objective measure comparing MAR performance to uncorrected images.

RESULTS

After screening, fourteen studies were selected that compared DL-based MAR-algorithms with uncorrected images. MAR-algorithms were categorised into the three domains. Thirteen MAR-algorithms showed a higher PSNR and SSIM value compared to the uncorrected images and to non-DL MAR-algorithms. One study showed statistically significant better MAR performance on clinical data compared to the uncorrected images and non-DL MAR-algorithms based on Hounsfield unit calculations.

CONCLUSION

DL MAR-algorithms show promising results in reducing metal artefacts, but standardised methodologies are needed to evaluate DL-based MAR-algorithms on clinical data to improve comparability between algorithms.

CLINICAL RELEVANCE STATEMENT

Recent studies highlight the effectiveness of supervised Deep Learning-based MAR-algorithms in improving CT image quality by reducing metal artefacts in the sinogram, image and dual domain. A systematic review is needed to provide an overview of newly developed algorithms.

Additive manufacturing of ceria and yttria incorporated toughened monolithic zirconia dental ceramic crowns: In vitro simulated aging behavior

STATEMENT OF PROBLEM

The comprehensive characterization of additively manufactured zirconia-based dental prostheses can promote widespread clinical application. However, simulated in vitro analysis of the aging behavior is lacking.

PURPOSE

The purpose of this in vitro study was to assess the simulated in vitro durability of monolithic transformation toughened additively manufactured zirconia-based restorations with different compositions to predict the clinical reliability depending on their ceramic composition.

MATERIAL AND METHODS

Crowns were 3-dimensionally (3D) printed by using a combination of custom-made stereolithography and a laser polymerized digital light processing process with high solid content slurries with suitable photo-interactive polymers. The main characteristics tested for mechanical behavior (structural reliability and flexural strength) were overall toughness and fatigue limits. Combinations of chemical compositions including yttria and ceria additives and processing conditions including pressing and sintering temperatures were applied to transform custom stereolithography and digitally light activated polymerized green parts to high strength and toughened ceramic crowns. The fluctuations in strength and toughness of as-sintered parts before and after physical thermocycling, physiochemical hydrothermal aging, and mechanical mastication simulation were studied via statistical methods (ANOVA) to indicate variable dependencies (α=.05).

RESULTS

Near theoretical density as high as 99.1%, minimum surface porosity as low as 0.25%, medium translucency, and high contrasts were achieved. The high original hardness near 19 GPa, a toughness of 6 to 7 MPa.m1/2, and 1300 MPa flexural strength with 95% confidence interval in as-sintered specimens satisfied the requirements for crowns. The simultaneously yttria and ceria stabilized systems should be able to resist low-temperature degradation aging with decreases as small as 2% in flexural strength and near 25% in fatigue fracture limits. The structure and process dependency of the mechanical properties of flexural strength (P<.020), hardness (P<.030), and modulus of elasticity (P<.020) were statistically significant while the toughness showed significant dependency (P≤.001).

CONCLUSIONS

The 3D printed posterior crowns with enhanced mechanical properties and augmented simulated in vitro durability can be manufactured by adding tetragonal phase stabilizer oxides (ceria and yttria) to zirconia-based ingredients. The combination of both oxide stabilizers in the additive manufacturing of crowns is a significant approach to improving clinical performance, enhanced toughness, and fatigue limit before and after physicomechanical, mechanochemical, and thermocyclic aging analysis.

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.

Therapeutic biomaterials with liver X receptor agonists based on the horizon of material biology to regulate atherosclerotic plaque regression in situ for devices surface engineering

Percutaneous coronary interventional is the main treatment for coronary atherosclerosis. At present, most studies focus on blood components and smooth muscle cells to achieve anticoagulation or anti-proliferation effects, while the mediated effects of materials on macrophages are also the focus of attention. Macrophage foam cells loaded with elevated cholesterol is a prominent feature of atherosclerotic plaque. Activation of liver X receptor (LXR) to regulate cholesterol efflux and efferocytosis and reduce the number of macrophage foam cells in plaque is feasible for the regression of atherosclerosis. However, cholesterol efflux promotion remains confined to targeted therapies. Herein, LXR agonists (GW3965) were introduced on the surface of the material and delivered in situ to atherogenic macrophages to improve drug utilization for anti-atherogenic therapy and plaque regression. LXR agonists act as plaque inhibition mediated by multichannel regulation macrophages, including lipid metabolism (ABCA1, ABCG1 and low-density lipoprotein receptor), macrophage migration (CCR7) and efferocytosis (MerTK). Material loaded with LXR agonists significantly reduced plaque burden in atherosclerotic model rats, most importantly, it did not cause hepatotoxicity and adverse reactions such as restenosis and thrombosis after material implantation. Both in vivo and in vitro evaluations confirmed its anti-atherosclerotic capability and safety. Overall, multi-functional LXR agonist-loaded materials with pathological microenvironment regulation effect are expected to be promising candidates for anti-atherosclerosis and have potential applications in cardiovascular devices surface engineering.

Pediatric Diaphyseal Forearm Fracture Management with Biodegradable Poly-L-Lactide-Co-Glycolide (PLGA) Intramedullary Implants: A Longitudinal Study

Background: Pediatric forearm fractures represent a substantial proportion of childhood injuries, requiring effective and minimally invasive treatments. Our study investigated the mid-term outcomes of biodegradable poly-L-lactide-co-glycolide (PLGA) intramedullary implants in managing diaphyseal forearm fractures in children. Methods: A follow-up cohort study was conducted with 38 patients treated with PLGA implants. Control examinations were performed one year post-operation, assessing bone healing through radiographic evaluations and functional outcomes using injured and uninjured limb range of motion (ROM) comparisons. Scarring was evaluated employing the Vancouver Scar Scale (VSS), and satisfaction via a questionnaire. Results: Children were predominantly female (76.4%), with a mean age of 9.71 (SD: 2.69) years. Effective fracture stabilization and bone healing were found in all patients, with a minor reduction (mean difference of -1.5°, p = 0.282) in elbow flexion on the operated side (139.3°) compared to the intact (140.8°). Elbow extension presented negligible average changes (0.2°, p = 0.098). Forearm movements were slightly reduced on the operated side (mean pronation: 80.8° vs. 83.7°, p = 0.166; average supination: 83.5° vs. 85.7°, p = 0.141). Wrist palmar flexion and dorsiflexion showed no significant differences. VSS ratings indicated minimal scarring (mean guardian and doctor scores were 1.13 and 0.55, respectively, p = 0.020), and all patients reported satisfaction with the treatment outcomes. Conclusions: Biodegradable implants are effective for pediatric forearm fractures, providing stable bone healing while preserving functional ROM with minimal scarring and high patient satisfaction. PLGA proved to be a viable alternative to traditional metal implants, eliminating secondary removal surgeries.

Exploring the potential of intermetallic alloys as implantable biomaterials: A comprehensive review

This review delves into the utilization of intermetallic alloys (IMAs) as advanced biomaterials for medical implants, scrutinizing their conceptual framework, fabrication challenges, and diverse manufacturing techniques such as casting, powder metallurgy, and additive manufacturing. Manufacturing techniques such as casting, powder metallurgy, additive manufacturing, and injection molding are discussed, with specific emphasis on achieving optimal grain sizes, surface roughness, and mechanical properties. Post-treatment methods aimed at refining surface quality, dimensional precision, and mechanical properties of IMAs are explored, including the use of heat treatments to enhance biocompatibility and corrosion resistance. The review presents an in-depth examination of IMAs-based implantable biomaterials, covering lab-scale developments and commercial-scale implants. Specific IMAs such as Nickel Titanium, Titanium Aluminides, Iron Aluminides, Magnesium-based IMAs, Zirconium-based IMAs, and High-entropy alloys (HEAs) are highlighted, with detailed discussions on their mechanical properties, including strength, elastic modulus, and corrosion resistance. Future directions are outlined, with an emphasis on the anticipated growth in the orthopedic devices market and the role of IMAs in meeting this demand. The potential of porous IMAs in orthopedics is explored, with emphasis on achieving optimal pore sizes and distributions for enhanced osseointegration. The review concludes by highlighting the ongoing need for research and development efforts in IMAs technologies, including advancements in design and fabrication techniques.

Challenges and Pitfalls of Research Designs Involving Magnesium-Based Biomaterials: An Overview

Magnesium-based biomaterials hold remarkable promise for various clinical applications, offering advantages such as reduced stress-shielding and enhanced bone strengthening and vascular remodeling compared to traditional materials. However, ensuring the quality of preclinical research is crucial for the development of these implants. To achieve implant success, an understanding of the cellular responses post-implantation, proper model selection, and good study design are crucial. There are several challenges to reaching a safe and effective translation of laboratory findings into clinical practice. The utilization of Mg-based biomedical devices eliminates the need for biomaterial removal surgery post-healing and mitigates adverse effects associated with permanent biomaterial implantation. However, the high corrosion rate of Mg-based implants poses challenges such as unexpected degradation, structural failure, hydrogen evolution, alkalization, and cytotoxicity. The biocompatibility and degradability of materials based on magnesium have been studied by many researchers in vitro; however, evaluations addressing the impact of the material in vivo still need to be improved. Several animal models, including rats, rabbits, dogs, and pigs, have been explored to assess the potential of magnesium-based materials. Moreover, strategies such as alloying and coating have been identified to enhance the degradation rate of magnesium-based materials in vivo to transform these challenges into opportunities. This review aims to explore the utilization of Mg implants across various biomedical applications within cellular (in vitro) and animal (in vivo) models.

Exploring the Interplay between Tribocorrosion and Surface Chemistry of the ASTM F139 Surgical Stainless Steel in Phosphate-Buffered Saline Solution

Surgical ASTM F139 stainless steel is used for temporary fixtures in the biomedical field. Tribocorrosion is a major concern in this application. The aim of the present work was to study the interplay between tribocorrosion behavior and the surface chemistry of the ASTM F139 stainless steel in phosphate-buffered saline solution (PBS). Sliding wear tests were conducted against alumina balls at different electrochemical potentials: open circuit potential (OCP), cathodic potential (-100 mV versus the OCP), and anodic potentials (+200 mVAg/AgCl and +700 mVAg/AgCl). The normal load was 20 N. The wear volume was estimated based on micrographs obtained from the wear tracks using confocal laser scanning microscopy. Moreover, the wear tracks were also examined by scanning electron microscopy (SEM). The surface chemistry of the ASTM F139 specimens was analyzed by X-ray photoelectron spectroscopy (XPS). The wear volume was dependent on the electrochemical potential, being maximized at +700 mVAg/AgCl. Delamination areas and grooves were observed in the wear tracks. Detailed assessment of the surface chemistry inside the wear tracks allowed identification of the main chemical species and their relative quantities, thus enabling correlation of the passive film composition with the observed tribocorrosion behavior.

Recent Advances in Two-Dimensional Nanomaterials for Healthcare Monitoring

The development of advanced technologies for the fabrication of functional nanomaterials, nanostructures, and devices has facilitated the development of biosensors for analyses. Two-dimensional (2D) nanomaterials, with unique hierarchical structures, a high surface area, and the ability to be functionalized for target detection at the surface, exhibit high potential for biosensing applications. The electronic properties, mechanical flexibility, and optical, electrochemical, and physical properties of 2D nanomaterials can be easily modulated, enabling the construction of biosensing platforms for the detection of various analytes with targeted recognition, sensitivity, and selectivity. This review provides an overview of the recent advances in 2D nanomaterials and nanostructures used for biosensor and wearable-sensor development for healthcare and health-monitoring applications. Finally, the advantages of 2D-nanomaterial-based devices and several challenges in their optimal operation have been discussed to facilitate the development of smart high-performance biosensors in the future.

Current update and trend of 3D printing in spinal surgery: A bibliometric analysis and review of literature

Incorporation of three-dimensional (3D) printing technology into the field of spinal surgery is on the rise. A bibliometric analysis of the current topic was carried out to elaborate the trend and to navigate future research. A Scopus database search was conducted with keywords related to 3D printing, spine, and surgery. The final 792 articles were extracted and further analyzed with VOSviewer 1.6.19 and Biblioshiny. The first published article was in 2002. A notable increase in articles in 2014 might be attributable to the availability of cheaper 3D printers which rose significantly on a global scale in 2011. China leads in terms of published research on 3D printing in spinal surgery, followed by the US, Australia, and India. The author's keyword co-occurrence analysis reveals 8 theme clusters, including preoperative and intraoperative measures, biomodelling, spinal neoplasms, biomechanics of 3D-printed materials, degenerative spinal diseases, minimally invasive surgery, and bioprinting. The top 15 of the most recently cited keywords are listed to provide future researchers to produce impactful articles. Two strategic diagrams of 2 periods (2002-2018 and 2018-2023) show the theme's evolution. We found 6 consistent themes in keyword co-occurrence analysis and the strategic diagram analysis, that are promising subjects for future research. Overall, this bibliographic study indicates the expanding importance of 3D printing in spinal surgery and suggests several critical themes and impactful keywords for future researchers.

Titanium Surfaces with a Laser-Produced Microchannel Structure Enhance Pre-Osteoblast Proliferation, Maturation, and Extracellular Mineralization In Vitro

The clinical success of dental titanium implants is profoundly linked to implant stability and osseointegration, which comprises pre-osteoblast proliferation, osteogenic differentiation, and extracellular mineralization. Because of the bio-inert nature of titanium, surface processing using subtractive or additive methods enhances osseointegration ability but limits the benefit due to accompanying surface contamination. By contrast, laser processing methods increase the roughness of the implant surface without contamination. However, the effects of laser-mediated distinct surface structures on the osteointegration level of osteoblasts are controversial. The role of a titanium surface with a laser-mediated microchannel structure in pre-osteoblast maturation remains unclear. This study aimed to elucidate the effect of laser-produced microchannels on pre-osteoblast maturation. Pre-osteoblast human embryonic palatal mesenchymal cells were seeded on a titanium plate treated with grinding (G), sandblasting with large grit and acid etching (SLA), or laser irradiation (L) for 3-18 days. The proliferation and morphology of pre-osteoblasts were evaluated using a Trypan Blue dye exclusion test and fluorescence microscopy. The mRNA expression, protein expression, and protein secretion of osteogenic differentiation markers in pre-osteoblasts were evaluated using reverse transcriptase quantitative polymerase chain reaction, a Western blot assay, and a multiplex assay, respectively. The extracellular calcium precipitation of pre-osteoblast was measured using Alizarin red S staining. Compared to G- and SLA-treated titanium surfaces, the laser-produced microchannel surfaces enhanced pre-osteoblast proliferation, the expression/secretion of osteogenic differentiation markers, and extracellular calcium precipitation. Laser-treated titanium implants may enhance the pre-osteoblast maturation process and provide extra benefits in clinical application.

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.

Evaluation of Time-Dependent Corrosion Inhibition Rate for f-MWCNT-BCP Composite Coatings on 316L Stainless Steel in Simulated Body Fluid for Orthopedic Implantation

A well-developed-multiwall carbon nanotube (f-MWCNT)/biphasic calcium phosphate (BCP) composites were synthesized using ultrasonication method for orthopedic implantation applications. The formation of composites and its phase was confirmed by using X-ray diffraction. The presence of various functional groups was identified by using Fourier transform infra-red (FT-IR) spectroscopy. The presence of f-MWCNT was confirmed by Raman spectroscopy. High-resolution transmission electron microscopy (HR-TEM) analysis revealed that BCP units were bound by the surface of f-MWCNTs. The synthesized composites were coated on medical grade 316L stainless steel substrates using electro deposition technique. To determine its corrosion resistance characteristics, the developed substrates were exposed to a simulated bodily fluid (SBF) solution for 0, 4, and 7 days. These results strongly suggest that the coated composites can be utilized for bone tissue repair.

Impact of mechanical engineering innovations in biomedical advancements

Abstract

The principal objective of the present paper is to meticulously review the family of biomaterials used in implants. A spectrum of applications of biomaterials in the perspective of prosthesis is also presented. This paper also emphasises on the review of the recent advancements in the field of biomedical implants with respect to mechanical engineering perspective. The latest technologies such as finite element modelling of prosthetic implants, additive manufacturing of implants and certain experimental methods adopted in the field of prosthesis are discussed. Moreover, various models were modelled using SOLIDWORKS® 2022 modelling software and analysed using ANSYS® 2021 R2 finite element analysing software and implant models were additive manufactured to make this review more interesting and for better understanding. Overall, the latest technology in the field of mechanical engineering that fuels its impact in life-saving biomedical engineering has been discussed briefly.

Graphical abstract

Near-infrared Ⅱ light-assisted Cu-containing porous TiO2 coating for combating implant-associated infection

Treatment implant-associated infections remains a severe challenge in the clinical practice. This work focuses on the fabrication of Cu-containing porous TiO2 coatings on titanium (Ti) by a combination of magnetron sputtering and dealloying techniques. Additionally, photothermal therapy is employed to enhance the effect of Cu ions in preventing bacterial infection. After the dealloying, most of Cu element was removed from the magnetron sputtered Cu-containing films, and porous TiO2 coatings were prepared on Ti. The formation of porous nanostructures significantly enhanced the photothermal conversion performance under NIR-II light irradiation. The combined effect of hyperthermia and Cu ions demonstrated enhanced antibacterial activity in both in vitro and in vivo experiments, and the antibacterial efficiency can reach 99% against Streptococcus mutans. Moreover, the porous TiO2 coatings also exhibited excellent biocompatibility. This modification of the titanium surface structure through dealloying changes may offer a novel approach to enhance the antimicrobial properties of titanium implants.

Design of Laser Activated Antimicrobial Porous Tricalcium Phosphate-Hydroxyapatite Scaffolds for Orthopedic Applications

The field of bone tissue engineering is steadily being improved by novel experimental approaches. Nevertheless, microbial adhesion after scaffold implantation remains a limitation that could lead to the impairment of the regeneration process, or scaffold rejection. The present study introduces a methodology that employs laser-based strategies for the development of antimicrobial interfaces on tricalcium phosphate-hydroxyapatite (TCP-HA) scaffolds. The outer surfaces of the ceramic scaffolds with inner porosity were structured using a femtosecond laser (λ = 800 nm; τ = 70 fs) for developing micropatterns and altering local surface roughness. The pulsed laser deposition of ZnO was used for the subsequent functionalization of both laser-structured and unmodified surfaces. The impact of the fs irradiation was investigated by Raman spectroscopy and X-ray diffraction. The effects of the ZnO-layered ceramic surfaces on initial bacterial adherence were assessed by culturing Staphylococcus aureus on both functionalized and non-functionalized scaffolds. Bacterial metabolic activity and morphology were monitored via the Resazurin assay and microscopic approaches. The presence of ZnO evidently decreased the metabolic activity of bacteria and led to impaired cell morphology. The results from this study have led to the conclusion that the combination of fs laser-structured surface topography and ZnO could yield a potential antimicrobial interface for implants in bone tissue engineering.

Tuning biodegradability, bone-bonding capacity, and wear resistance of zinc-30% magnesium intermetallic alloy for use in load-bearing bone applications

This work aimed to improve the rapid biodegradation, poor wear resistance properties, and lack of bioactivity of metallic biomaterials to be used in orthopedic applications. In this context, zinc-magnesium (Zn-Mg) alloy with successive contents of calcium silicate (CaSiO3) and silicon nitride (Si3N4) was prepared using powder metallurgy technique. After sintering, their phase composition and microstructure were investigated using the X-ray diffraction technique and scanning electron microscopy (SEM), respectively. Furthermore, their degradation behavior and ability to form hydroxyapatite (HA) layer on the sample surface after immersion in simulated body fluid (SBF) were monitored using weight loss measurements, inductively coupled plasma-atomic emission spectroscopy, and SEM. Moreover, their tribo-mechanical properties were measured. The results obtained showed that the successive contents of CaSiO3 were responsible for improving the bioactivity behavior as indicated by a good formation of the HA layer on the samples' surface. Additionally, ceramic materials were responsible for a continuous decrease in the released ions in the SBF solution as indicated by the ICP results. The tribology properties were significantly improved even after exposure to different loads. Based on the above results, the prepared nanocomposites are promising for use in orthopedic applications.

Development of bioactive and antimicrobial nano-topography over selective laser melted Ti6Al4V implant and its in-vitro corrosion behavior

Additive manufacturing (AM) or 3D printing of bone defect models is gaining much attention in the biomedical field as it could significantly facilitate the development of customized implants with a high degree of dimensional accuracy. Due to their satisfactory biocompatibility and minimal stress shielding effect, Ti6Al4V (Ti64) alloys are increasingly preferred in the development of such implants. However, their poor osseointegration abilities and lack of antibacterial properties often cause implant loosening and microbial infections, leading to implant failure. To address these drawbacks, we propose in this work a simple surface modification approach of customized Ti64 alloys (3D printed Ti6Al4V) that enables the formation of porous calcium titanate (CT) over their surface as well as the incorporation of silver nanoparticles (AgNPs) into the thus formed porous network. The successful CT formation with the incorporation of AgNPs throughout the 3D printed Ti64 surface and their influence in changing the morphological and mechanical behaviour were studied by Raman spectroscopy, SEM, AFM, Contact angle measurement, XPS, HR-TEM and nano-indentation. Antibacterial studies using Staphylococcus aureus and Escherichia coli, and in-vitro cell studies using MG-63 cell lines showed that surface modified samples resulting from the proposed method exhibit satisfactory antimicrobial property and are highly biocompatible. The obtained surface modified samples also showed a significant improvement in corrosion resistance as compared to unmodified 3D printed Ti64 alloys. The improvement in corrosion resistance was revealed by electrochemical impedance Spectroscopy (EIS). Obtained results emphasis that thus surface modified 3D printed Ti64 alloys are promising candidates for hard tissue implant applications.

Fibronectin Conformations after Electrodeposition onto 316L Stainless Steel Substrates Enhanced Early-Stage Osteoblasts' Adhesion but Affected Their Behavior

The implantation of metallic orthopedic prostheses is increasingly common due to an aging population and accidents. There is a real societal need to implement new metal implants that combine durability, good mechanical properties, excellent biocompatibility, as well as affordable costs. Since the functionalization of low-cost 316L stainless steel substrates through the successive electrodeposition of a polypyrrole film (PPy) and a calcium phosphate deposit doped with silicon was previously carried out by our labs, we have also developed a bio-functional coating by electrodepositing or oxidating of fibronectin (Fn) coating. Fn is an extracellular matrix glycoprotein involved in cell adhesion and differentiation. Impacts of either electrodeposition or oxidation on the structure and functionality of Fn were first studied. Thus, electrodeposition is the technique that permits the highest deposition of fibronectin, compared to adsorption or oxidation. Furthermore, electrodeposition seems to strongly modify Fn conformation by the formation of intermingled long fibers, resulting in changes to the accessibility of the molecular probes tested (antibodies directed against Fn whole molecule and Fn cell-binding domain). Then, the effects of either electrodeposited Fn or oxidized Fn were validated by the resulting pre-osteoblast behavior. Electrodeposition reduced pre-osteoblasts' ability to remodel Fn coating on supports because of a partial modification of Fn conformation, which reduced accessibility to the cell-binding domain. Electrodeposited Fn also diminished α5 integrin secretion and clustering along the plasma membrane. However, the N-terminal extremity of Fn was not modified by electrodeposition as demonstrated by Staphylococcus aureus attachment after 3 h of culture on a specific domain localized in this region. Moreover, the number of pre-osteoblasts remains stable after 3 h culture on either adsorbed, oxidized, or electrodeposited Fn deposits. In contrast, mitochondrial activity and cell proliferation were significantly higher on adsorbed Fn compared with electrodeposited Fn after 48 h culture. Hence, electro-deposited Fn seems more favorable to pre-osteoblast early-stage behavior than during a longer culture of 24 h and 48 h. The electrodeposition of matrix proteins could be improved to maintain their bio-activity and to develop this promising, fast technique to bio-functionalize metallic implants.

Evaluation of Gelatin/Hyaluronic Acid-Generated Bridging in a 3D-Printed Titanium Cage for Bone Regeneration

3D-printed titanium (Ti) cages present an attractive alternative for addressing issues related to osteoporosis-induced fractures, accidental fractures, and spinal fusion surgery due to disc herniation. These Ti-based bone implants possess superior strength compared to other metals, allowing for versatile applications in orthopedic scenarios. However, when used as standalone solutions, certain considerations may arise, such as interaction with soft tissues. Therefore, to overcome these issues, the combination with hydrogel has been considered. In this study, to impart Ti with regenerative abilities a 3D-printed Ti cage was loaded with gelatin and hyaluronic acid (G-H) to improve the cell attachment ability of the Ti-based bone implants. The void spaces within the mesh structure of the 3D Ti cage were filled with G-H, creating a network of micro-sized pores. The filled G-H acted as the bridge for the cells to migrate toward the large inner pores of the 3D Ti cage. Due to the microporous surface and slow release of gelatin and hyaluronic acid, the biocompatibility of the coated Ti cage was increased with an elevation in osteoconduction as depicted by the up-regulation of bone-related gene expressions. The in vivo implantation in the rabbit femur model showed enhanced bone regeneration due to the coated G-H on the Ti cage compared to the pristine hollow Ti cage. The G-H filled the large holes of the 3D Ti cage that acted as a bridge for the cells to travel inside the implant and aided in the fast regeneration of bone.

Revolutionizing biomedicine: advancements, applications, and prospects of nanocomposite macromolecular carbohydrate-based hydrogel biomaterials: a review

Nanocomposite hydrogel biomaterials represent an exciting Frontier in biomedicine, offering solutions to longstanding challenges. These hydrogels are derived from various biopolymers, including fibrin, silk fibroin, collagen, keratin, gelatin, chitosan, hyaluronic acid, alginate, carrageenan, and cellulose. While these biopolymers possess inherent biocompatibility and renewability, they often suffer from poor mechanical properties and rapid degradation. Researchers have integrated biopolymers such as cellulose, starch, and chitosan into hydrogel matrices to overcome these limitations, resulting in nanocomposite hydrogels. These innovative materials exhibit enhanced mechanical strength, improved biocompatibility, and the ability to finely tune drug release profiles. The marriage of nanotechnology and hydrogel chemistry empowers precise control over these materials' physical and chemical properties, making them ideal for tissue engineering, drug delivery, wound healing, and biosensing applications. Recent advancements in the design, fabrication, and characterization of biopolymer-based nanocomposite hydrogels have showcased their potential to transform biomedicine. Researchers are employing strategic approaches for integrating biopolymer nanoparticles, exploring how nanoparticle properties impact hydrogel performance, and utilizing various characterization techniques to evaluate structure and functionality. Moreover, the diverse biomedical applications of these nanocomposite hydrogels hold promise for improving patient outcomes and addressing unmet clinical needs.

Bisphosphonate-incorporated coatings for orthopedic implants functionalization

Bisphosphonates (BPs), the stable analogs of pyrophosphate, are well-known inhibitors of osteoclastogenesis to prevent osteoporotic bone loss and improve implant osseointegration in patients suffering from osteoporosis. Compared to systemic administration, BPs-incorporated coatings enable the direct delivery of BPs to the local area, which will precisely enhance osseointegration and bone repair without the systemic side effects. However, an elaborate and comprehensive review of BP coatings of implants is lacking. Herein, the cellular level (e.g., osteoclasts, osteocytes, osteoblasts, osteoclast precursors, and bone mesenchymal stem cells) and molecular biological regulatory mechanism of BPs in regulating bone homeostasis are overviewed systematically. Moreover, the currently available methods (e.g., chemical reaction, porous carriers, and organic material films) of BP coatings construction are outlined and summarized in detail. As one of the key directions, the latest advances of BP-coated implants to enhance bone repair and osseointegration in basic experiments and clinical trials are presented and critically evaluated. Finally, the challenges and prospects of BP coatings are also purposed, and it will open a new chapter in clinical translation for BP-coated implants.

Oxygen-Deficient Bioceramics: Combination of Diagnosis, Therapy, and Regeneration

The journey of ceramics in medicine has been synchronized with an evolution from the first generation-alumina, zirconia, etc.-to the third -3D scaffolds. There is an up-and-coming member called oxygen-deficient or colored bioceramics, which have recently found their way through biomedical applications. The oxygen vacancy steers the light absorption toward visible and near infrared regions, making the colored bioceramics multifunctional-therapeutic, diagnostic, and regenerative. Oxygen-deficient bioceramics are capable of turning light into heat and reactive oxygen species for photothermal and photodynamic therapies, respectively, and concomitantly yield infrared and photoacoustic images. Different types of oxygen-deficient bioceramics have been recently developed through various synthesis routes. Some of them like TiO2- x , MoO3- x , and WOx have been more investigated for biomedical applications, whereas the rest have yet to be scrutinized. The most prominent advantage of these bioceramics over the other biomaterials is their multifunctionality endowed with a change in the microstructure. There are some challenges ahead of this category discussed at the end of the present review. By shedding light on this recently born bioceramics subcategory, it is believed that the field will undergo a big step further as these platforms are naturally multifunctional.

Machine Learning Paves the Way for High Entropy Compounds Exploration: Challenges, Progress, and Outlook

Machine learning (ML) has emerged as a powerful tool in the research field of high entropy compounds (HECs), which have gained worldwide attention due to their vast compositional space and abundant regulatability. However, the complex structure space of HEC poses challenges to traditional experimental and computational approaches, necessitating the adoption of machine learning. Microscopically, machine learning can model the Hamiltonian of the HEC system, enabling atomic-level property investigations, while macroscopically, it can analyze macroscopic material characteristics such as hardness, melting point, and ductility. Various machine learning algorithms, both traditional methods and deep neural networks, can be employed in HEC research. Comprehensive and accurate data collection, feature engineering, and model training and selection through cross-validation are crucial for establishing excellent ML models. ML also holds promise in analyzing phase structures and stability, constructing potentials in simulations, and facilitating the design of functional materials. Although some domains, such as magnetic and device materials, still require further exploration, machine learning's potential in HEC research is substantial. Consequently, machine learning has become an indispensable tool in understanding and exploiting the capabilities of HEC, serving as the foundation for the new paradigm of Artificial-intelligence-assisted material exploration.

Deploying a Novel Approach to Prepare Silver Nanoparticle Bellamya bengalensis Extract Conjugate Coating on Orthopedic Implant Biomaterial Discs to Prevent Potential Biofilm Formation

This study is based on the premise of investigating antibacterial activity through a novel conjugate of silver nanoparticles (AgNPs) and antimicrobial peptides (AMPs) in line with a green synthesis approach by developing antimicrobial-coated implants to prevent bacterial resistance. The AMPs were obtained from Bellamya Bengalensis (BB), a freshwater snail, to prepare the nanocomposite conjugate, e.g., AgNPs@BB extract, by making use of UV-Visible spectroscopy. The antimicrobial assessment of AgNPs@BB extract conjugate was performed using the Resazurin Microtiter Assay Method (REMA), followed by the use of three biocompatible implant materials (titanium alloys, Ti 6AL-4V stainless steel 316L, and polyethylene). Finally, the coating was analyzed under confocal microscopy. The results revealed a significant reduction of biofilm formation on the surfaces of implants coated with conjugate (AgNPs@BB extract) in comparison to uncoated implants. For the MTT assay, no significant changes were recorded for the cells grown on the AgNPs/AMP++ sample in high concentrations. Staphylococcus epidermidis, however, showed more prominent growth on all implants in comparison to Staphylococcus aureus. It is evident from the results that Staphylococcus epidermidis is more susceptible to AgNPs@BB extract, while the minimum inhibitory concentration (MIC) value of AgNPs@BB extract conjugates and biosynthesized AgNPs was also on the higher side. This study indicates that AgNPs@BB extract carries antibacterial activity, and concludes that an excessive concentration of AgNPs@BB extract may affect the improved biocompatibility. This study recommends using robust, retentive, and antimicrobial coatings of AgNPs@BB extract for implantable biocompatible materials in accordance with the novel strategy of biomaterial applications.

Advances and Prospects in Materials for Craniofacial Bone Reconstruction

The craniofacial region is composed of 23 bones, which provide crucial function in keeping the normal position of brain and eyeballs, aesthetics of the craniofacial complex, facial movements, and visual function. Given the complex geometry and architecture, craniofacial bone defects not only affect the normal craniofacial structure but also may result in severe craniofacial dysfunction. Therefore, the exploration of rapid, precise, and effective reconstruction of craniofacial bone defects is urgent. Recently, developments in advanced bone tissue engineering bring new hope for the ideal reconstruction of the craniofacial bone defects. This report, presenting a first-time comprehensive review of recent advances of biomaterials in craniofacial bone tissue engineering, overviews the modification of traditional biomaterials and development of advanced biomaterials applying to craniofacial reconstruction. Challenges and perspectives of biomaterial development in craniofacial fields are discussed in the end.

Recent developments in nanomaterials for upgrading treatment of orthopedics diseases

Nanotechnology has changed science in the last three decades. Recent applications of nanotechnology in the disciplines of medicine and biology have enhanced medical diagnostics, manufacturing, and drug delivery. The latest studies have demonstrated this modern technology's potential for developing novel methods of disease detection and treatment, particularly in orthopedics. According to recent developments in bone tissue engineering, implantable substances, diagnostics and treatment, and surface adhesives, nanomedicine has revolutionized orthopedics. Numerous nanomaterials with distinctive chemical, physical, and biological properties have been engineered to generate innovative medication delivery methods for the local, sustained, and targeted delivery of drugs with enhanced therapeutic efficacy and minimal or no toxicity, indicating a very promising strategy for effectively controlling illnesses. Extensive study has been carried out on the applications of nanotechnology, particularly in orthopedics. Nanotechnology can revolutionize orthopedics cure, diagnosis, and research. Drug delivery precision employing nanotechnology using gold and liposome nanoparticles has shown especially encouraging results. Moreover, the delivery of drugs and biologics for osteosarcoma is actively investigated. Different kind of biosensors and nanoparticles has been used in the diagnosis of bone disorders, for example, renal osteodystrophy, Paget's disease, and osteoporosis. The major hurdles to the commercialization of nanotechnology-based composite are eventually examined, thus helping in eliminating the limits in connection to some pre-existing biomaterials for orthopedics, important variables like implant life, quality, cure cost, and pain and relief from pain. The potential for nanotechnology in orthopedics is tremendous, and most of it looks to remain unexplored, but not without challenges. This review aims to highlight the up tp date developments in nanotechnology for boosting the treatment modalities for orthopedic ailments. Moreover, we also highlighted unmet requirements and present barriers to the practical adoption of biomimetic nanotechnology-based orthopedic treatments.

Solid implantable devices for sustained drug delivery

Implantable drug delivery systems (IDDS) are an attractive alternative to conventional drug administration routes. Oral and injectable drug administration are the most common routes for drug delivery providing peaks of drug concentrations in blood after administration followed by concentration decay after a few hours. Therefore, constant drug administration is required to keep drug levels within the therapeutic window of the drug. Moreover, oral drug delivery presents alternative challenges due to drug degradation within the gastrointestinal tract or first pass metabolism. IDDS can be used to provide sustained drug delivery for prolonged periods of time. The use of this type of systems is especially interesting for the treatment of chronic conditions where patient adherence to conventional treatments can be challenging. These systems are normally used for systemic drug delivery. However, IDDS can be used for localised administration to maximise the amount of drug delivered within the active site while reducing systemic exposure. This review will cover current applications of IDDS focusing on the materials used to prepare this type of systems and the main therapeutic areas of application.

Biological Activity and Thrombogenic Properties of Oxide Nanotubes on the Ti-13Nb-13Zr Biomedical Alloy

The success of implant treatment is dependent on the osseointegration of the implant. The main goal of this work was to improve the biofunctionality of the Ti-13Nb-13Zr implant alloy by the production of oxide nanotubes (ONTs) layers for better anchoring in the bone and use as an intelligent carrier in drug delivery systems. Anodization of the Ti-13Nb-13Zr alloy was carried out in 0.5% HF, 1 M (NH₄)₂SO₄ + 2% NH₄F, and 1 M ethylene glycol + 4 wt.% NH₄F electrolytes. Physicochemical characteristics of ONTs were performed by high-resolution electron microscopy (HREM), X-ray photoelectron spectroscopy (XPS), and scanning Kelvin probe (SKP). Water contact angle studies were conducted using the sitting airdrop method. In vitro biological properties and release kinetics of ibuprofen were investigated. The results of TEM and XPS studies confirmed the formation of the single-walled ONTs of three generations on the bi-phase (α + β) Ti-13Nb-13Zr alloy. The ONTs were composed of oxides of the alloying elements. The proposed surface modification method ensured good hemolytic properties, no cytotoxity for L-929 mouse cells, good adhesion, increased surface wettability, and improved athrombogenic properties of the Ti-13Nb-13Zr alloy. Nanotubular surfaces allowed ibuprofen to be released from the polymer matrix according to the Gallagher-Corrigan model.

Effect of Si Content on the Thermal Expansion of Ti15Mo(0-2 Si) Biomaterial Alloys during Different Heating Rates

Thermal expansion measurements were used to characterize phase transformations in metastable β-Ti alloys (Ti15MoxSi) without and with various Si additions (where x = 0, 0.5, 1.0, 1.5, and 2 in wt.%) during linear heating at two heating rates of 5 and 10 °C/min up to 850 °C. For this study, five alloys were developed and examined in terms of their presence phases, microstructures, and starting and final transformation temperatures. According to the results, all of the as-cast samples primarily include an equiaxed β-Ti phase. The influence of phase transformation on the material dimensions was discussed and compared with the variations in Si contents. The transformation was investigated using a dilatometric technique for the developed alloys during continuous heating and cooling. The dilatometric curve of heating revealed two distinct reflection points as the heating temperature increased. The starting transformation temperature (T_s) to obtain the ω-phase was reported at 359 °C without Si addition; whereas the final transformation temperature (T_f) of the dissolution of α-phase was obtained at 572 °C at a heating rate of 10 °C/min. At 2 wt.% Si, the first derivative curves reported T_s and T_f transforming temperatures of 314-565 °C (at a 5 °C/min heating rate) and 270-540 °C (at a 10 °C/min heating rate), respectively. The T_s and T_f transforming temperatures were significantly decreased with Si additions, which decreased the β-transus temperature. Moreover, the thermal expansion coefficient curves of the investigated alloys without and with 2 wt.% Si were studied. The transformation heating curves have an S-shaped pattern, according to the results.

Surface modification of biodegradable Mg alloy by adapting µEDM capabilities with cryogenically-treated tool electrodes

Biomaterials are engineered to develop an interaction with living cells for therapeutic and diagnostic purposes. The last decade reported a tremendously rising shift in the requirement for miniaturized biomedical implants exhibiting high precision and comprising various biomaterials such as non-biodegradable titanium (Ti) alloys and biodegradable magnesium (Mg) alloys. The excellent mechanical properties and lightweight characteristics of Mg AZ91D alloy make it an emerging material for biomedical applications. In this regard, micro-electric discharge machining (µEDM) is an excellent method that can be used to make micro-components with high dimensional accuracy. In the present research, attempts were made to improve the µEDM capabilities by using cryogenically-treated copper (CTCTE) and brass tool electrodes (CTBTE) amid machining of biodegradable Mg AZ91D alloy, followed by their comparison with a pair of untreated copper (UCTE) and brass tool electrodes (UBTE) in terms of minimum machining-time and dimensional-irregularity. To investigate the possible modification on the surfaces achieved with minimum machining-time and dimensional-irregularity, the morphology, chemistry, micro-hardness, corrosion resistance, topography, and wettability of these surfaces were further examined. The surface produced by CTCTE exhibited the minimum surface micro-cracks and craters, acceptable recast layer thickness (2.6 µm), 17.45% improved micro-hardness, satisfactory corrosion resistance, adequate surface roughness (Ra: 1.08 µm), and suitable hydrophobic behavior (contact angle: 119°), confirming improved biodegradation rate. Additionally, a comparative analysis among the tool electrodes revealed that cryogenically-treated tool electrodes outperformed the untreated ones. CTCTE-induced modification on the Mg AZ91D alloy surface suggests its suitability in biodegradable medical implant applications.