Surface mechanical properties, corrosion resistance, and cytocompatibility of nitrogen plasma-implanted nickel-titanium alloys: a comparative study with commonly used medical grade materials

The passive behavior of biomedical alloys in simulated physiological solutions

Passive alloys are commonly considered to exhibit a current that is essentially independent of potential over the passive range in neutral chloride solutions. However, the current-potential dependence of Ti and its alloys, CoCr alloys, and 316L stainless steel in buffered, simulated physiological solutions containing phosphate differs from that usually reported for the alloys in chloride-only solutions. An analysis of potentiodynamic polarization data from previous studies showed that these alloys typically exhibit an exponential dependence of current on potential-as reflected by Tafel-type behavior-over the initial part of the passive range in buffered solutions. This behavior is consistent with that predicted by the Generalized Growth Model for film growth and dissolution in the case of thin films where cation migration through the film is the rate-controlling step and where the anodic current is associated predominantly with dissolution. Film growth is thought to be impeded in the buffered solutions, allowing the rate of migration and hence dissolution to remain relatively high over a wider potential range. Analysis of the apparent Tafel slopes indicated that the Ti and CoCr alloys exhibit a similar corrosion mechanism, with a small difference in the slopes for the two groups of alloys being attributable to the difference in the type of oxide. Stainless steel 316L exhibits a distinctly higher apparent Tafel slope, which is likely associated in large part with the duplex nature of the oxide.

Electrochemical, Tribological and Biocompatible Performance of Electron Beam Modified and Coated Ti6Al4V Alloy

Vacuum cathodic arc TiN coatings with overlaying TiO₂ film were deposited on polished and surface roughened by electron beam modification (EBM) Ti6Al4V alloy. The substrate microtopography consisted of long grooves formed by the liner scan of the electron beam with appropriate frequencies (500 (AR500) and 850 (AR850) Hz). EBM transformed the α + β Ti6Al4V mixed structure into a single α'-martensite phase. Тhe gradient TiN/TiO₂ films deposited on mechanically polished (AR) and EBM (AR500 and AR850) alloys share the same surface chemistry and composition (almost stoichiometric TiN, anatase and rutile in different ratios) but exhibit different topographies (S_a equal to approximately 0.62, 1.73, and 1.08 μm, respectively) over areas of 50 × 50 μm. Although the nanohardness of the coatings on AR500 and AR850 alloy (approximately 10.45 and 9.02 GPa, respectively) was lower than that measured on the film deposited on AR alloy (about 13.05 GPa), the hybrid surface treatment offered improvement in critical adhesive loads, coefficient of friction, and wear-resistance of the surface. In phosphate buffer saline, all coated samples showed low corrosion potentials and passivation current densities, confirming their good corrosion protection. The coated EBM samples cultured with human osteoblast-like MG63 cells demonstrated increased cell attachment, viability, and bone mineralization activity especially for the AR500-coated alloy, compared to uncoated polished alloy. The results underline the synergetic effect between the sub-micron structure and composition of TiN/TiO₂ coating and microarchitecture obtained by EBM.

Chronic nickel (II) exposure induces the stemness properties of cancer cells through repressing isocitrate dehydrogenase (IDH1)

BACKGROUND

Nickel is a component of biomedical alloys that is released during corrosion or friction and causes cytotoxicity, mutation, differentiation or even carcinogenesis in tissues. However, the mechanisms underlying the potential hazards of Nickel-containing alloys implanted in the human body by surgery remain uncertain.

OBJECTIVE

To study the effect of Ni(II) (NiCl_2•6H₂O) on cancer cells.

METHODS

A549 and RKO cells were treated with various concentrations of Ni(II) to determine the effect of Ni(II) on cellular viability using a CCK8 assay. Flow cytometry was performed to analyze the effect of Ni(II) on apoptosis and the cell cycle. Sphere-forming assays were conducted to examine the stemness properties of A549 and RKO cells. Western blotting was to evaluate the expression levels of SOX2, IDH1, HIF-1ɑ and β-catenin. The expression of isocitrate dehydrogenase (IDH1) in rectum adenocarcinoma (READ) was analyzed by Gene Expression Profiling Interactive Analysis (GEPIA). Kaplan-Meier analysis was used to calculate the correlation between survival and IDH1 expression.

RESULTS

Long-term exposure (120 days) to 100 µM Ni(II) significantly repressed cell proliferation, decreased colony formation and arrested the cell cycle at the G₀/G₁ phase. In addition, the stem-like traits of A549 and RKO cells were significantly augmented. Ni(II) also significantly decreased the protein expression of IDH1 and the synthesis rate of NAPDH, which competitively inhibited α-ketoglutarate (α-KG) generation. The downregulation of IDH1 not only promoted β-catenin accumulation in the cell nucleus in a HIF-1ɑ signaling-dependent manner but also induced the expression of the transcription factor SOX2 to maintain the stemness properties of cancer cells. Moreover, IDH1 expression negatively correlated with the clinicopathologic characteristics of READ.

CONCLUSION

These findings demonstrate that chronic and continuous release of Ni(II) to the microenvironment suppresses IDH1 expression and augments the stemness properties of cancer cells via the activation HIF-1ɑ/β-catenin/SOX2 pathway to enhance local tumor recurrence in patients with implanted Nickel-containing alloys at surgical sites.

Fabrication of chondrocytes/chondrocyte-microtissues laden fibrin gel auricular scaffold for microtia reconstruction

Fibrin gel-based scaffolds have promising potential for microtia reconstruction. Autologous chondrocytes and chondrocyte cell sheets are frequently used seed cell sources for cartilage tissue engineering. However, the aesthetic outcome of chondrocyte-based microtia reconstruction is still not satisfactory. In this study, we aimed to fabricate the chondrocytes/chondrocyte-microtissues laden fibrin gel auricular scaffold for microtia reconstruction. We designed a unique auricular mold that could fabricate a fibrin gel scaffold resembling human auricle anatomy. Primary chondrocytes were harvested from rabbit auricular cartilage, and chondrocyte cell sheets were developed. Chondrocyte-microtissues were prepared from the cell sheets. The mixture of chondrocytes/chondrocyte-microtissues was laden in fibrin gel during the auricular scaffold fabrication. The protrusions and recessed structure in the auricular scaffold surface were still clearly distinguishable. After a one-week in vitro culture, the 3 D structure and auricular anatomy of the scaffold were retained. And followed by eight-week subcutaneous implantation, cartilaginous tissue was regenerated in the artificial auricular structure as indicated by the results of H&E, Toluidine blue, Safranin O, and type II collagen (immunohistochemistry) staining. Protrusions and depressions of the auricular scaffold were slightly deformed, but the overall auricular anatomy was maintained after 8-week in vivo implantation. Extracellular matrix components content were similar in artificial auricular cartilage and rabbit native auricular cartilage. In conclusion, the mixture of chondrocytes/chondrocyte-microtissues laden fibrin gel auricular scaffold showed a promising potential for cartilaginous tissue regeneration, suggesting this as an effective approach for autologous chondrocyte-based microtia reconstruction.

A novel scoliosis instrumentation using special superelastic nickel-titanium shape memory rods: a biomechanical analysis using a calibrated computer model and data from a clinical trial

STUDY DESIGN

Biomechanical analysis of scoliosis instrumentation using superelastic Nickel-titanium shape memory (SNT) rods.

OBJECTIVE

To compare SNT with conventional Titanium (Ti) and Cobalt-chrome (Co-Cr) rods. A clinical trial has documented comparable efficacy between two adolescent idiopathic scoliosis (AIS) cohorts instrumented using SNT versus conventional Ti rods. The shape memory and superelasticity of the SNT rod are thought to allow easy rod insertion, progressive curve correction, and correction from spinal tissue relaxation, but study is yet to be done to assess the effects of the shape memory and superelasticity.

METHODS

Instrumentations of AIS patients from the clinical trial were computationally simulated using SNT, Ti and Co-Cr rods (5.5 or 6 mm; 30°, 50° or 60° sagittal contouring angles; 0°, 25° or 50° coronal over-contouring angles). Curve correction, its improvement from stress relaxation in the spine, and loads in the instrumentation constructs were computed and compared.

RESULTS

The simulated main thoracic Cobb angles (MT) and thoracic kyphosis with the SNT rods were 4°-7° higher and 1°-2° lower than the Ti and Co-Cr rods, respectively. Bone-implant forces with Ti and Co-Cr rods were higher than the SNT rods by 84% and 130% at 18 °C and 35% and 65% at 37 °C, respectively (p < 0.001). Further corrections of the MT from the simulated stress relaxation in the spine were 4°-8° with the SNT rods versus 2°-5° with the Ti and Co-Cr rods (p < 0.001).

CONCLUSION

This study concurs with clinical observation that the SNT rods are easier to insert and can result in similar correction to the conventional rods. The SNT rods allow significantly lower bone-implant forces and have the ability to take advantage of post-instrumentation correction as the tissues relax.

Implants for Vertebral Body Replacement - Which Systems are Available and Have Become Established

Since the first vertebral body replacement operations over 50 years ago until now, there were developed numerous methods and implants. Vertebral body replacement after corpectomy nowadays is a standard procedure in spinal surgery. At the beginning mainly bone grafts were used. Due to continuous development, PMMA and titanium implants were developed. Nowadays various expandable and non-expandable implants are available. Numerous implants can still be justified. The question arises which methods and systems are on the market and which ones have proven themselves? This article describes and compares the advantages and disadvantages of each implant type.

Osteoarthritic process modifies expression response to NiTi alloy presence

Nickel-titanium alloy (nitinol, NiTi) is a biomaterial with unique thermal shape memory, superelasticity and high damping properties. Therefore NiTi has been used in medical applications. In this in vitro study, the effect of NiTi alloy (with two surface modifications - helium and hydrogen) on gene expression profile of selected interleukins (IL-1β, IL-6 and IL-8) and matrix metalloproteinases (MMP-1 and MMP-2) in human physiological osteoblasts and human osteoarthritic osteoblasts was examined to respond to a question of the different behavior of bone tissue in the implantation of metallic materials in the presence of cells affected by the osteoarthritic process. The cells were cultivated in contact with NiTi and with or without LPS (bacterial lipolysaccharide). Changes in expression of target genes were calculated by 2^-ΔΔCt method. An increased gene expression of IL-1β in osteoarthritic osteoblasts, with even higher expression in cells collected directly from the metal surface was observed. In case of physiological osteoblasts, the change in expression was detected after LPS treatment in cells surrounding the disc. Higher expression levels of IL-8 were observed in osteoarthritic osteoblasts after NiTi treatment in contact with alloy, and in physiological osteoblasts without relation to location in combination of NiTi and LPS. IL-6 was slightly increased in physiological osteoblastes after application of LPS. MMP-1 expression level was obviously significantly higher in osteoarthritic osteoblasts with differences regarding the metal surface and location. MMP-2 expression was decreased in both cell lines after LPS treatment. In conclusion, results of present study show that the NiTi alloy and the treatment by LPS, especially repeated doses of LPS, change the gene expression of selected ILs and MMPs in human osteoblast cell cultures. Some of the changes were depicted solely to osteoarthritic osteoblasts.

Mechanical and Clinical Evaluation of a Shape Memory Alloy and Conventional Struts in a Flexible Scoliotic Brace

Smart materials have attracted considerable attention in the medical field. In particular, shape memory alloys (SMAs) are most commonly utilized for their superelasticity (SE) in orthopaedic treatment. In this study, the resin struts of a flexible brace for adolescent idiopathic scoliosis (AIS) are replaced with different conventional materials and an SMA. The corrective mechanism mainly depends on the compressive force applied by the brace at the desired location. Therefore, the mechanical properties of the materials used and the interface pressure are both critical factors that influence the treatment effectiveness. The results indicate that titanium is the most rigid among the five types of materials, whereas the brace with SMA struts presents the best recovery properties and the most stable interface pressure. A radiographic examination of two patients with AIS is then conducted to validate the results, which shows that the SMA struts can provide better correction of thoracic curvature. These findings suggest that SMAs can be applied in orthoses because their SE allows for continuous and controllable corrective forces.

A randomized double-blinded clinical trial to evaluate the safety and efficacy of a novel superelastic nickel-titanium spinal rod in adolescent idiopathic scoliosis: 5-year follow-up

PURPOSE

To evaluate the safety and efficacy of a superelastic shape-memory alloy (SNT) rod used in the treatment of adolescent idiopathic scoliosis (AIS).

METHODS

AIS Patients with Lenke 1 curves undergoing fusion surgery were randomized (1:1) at the time of surgery to receive either the SNT or a conventional titanium alloy (CTA) rod. Radiographs were obtained preoperatively and postoperatively up to 5 years of follow-up. Parameters assessed included coronal and sagittal Cobb angles, and overall truncal and shoulder balance. Sagittal profiles were subcategorized into Types A (<20°), B (20-40°), and C (>40°).

RESULTS

Twenty-four patients with mean age of 15 years were recruited. A total of 87.0% of subjects were followed up till postoperative 5 years, but all patients had minimum 2 years of follow-up. The fulcrum-bending correction index for the SNT group was 113% at postoperative day 4 and 127% at half-year, while the CTA group was 112% at postoperative day 4 and only 106% at half-year. In terms of sagittal profile, the SNT group moved toward type B profile at half-year follow-up with a mean correction of 7.6°, while no significant change was observed in the CTA group (-0.7°). Nickel levels remained normal, and there were no complications.

CONCLUSIONS

This is the first randomized clinical trial of a novel SNT rod for treating patients with AIS, noting it to be safe and has potential to gradually correct scoliosis over time. This study serves as a pilot and platform to properly power future large-scale studies to demonstrate efficacy and superiority.

Ultra-structural evaluation of an anodic oxidated titanium dental implant

Anodic oxidation is used for the surface treatment of commercial implants to improve their functional properties for clinical success. Here we conducted ultrastructural and chemical investigations into the micro- and nanostructure of the anodic oxide film of a titanium implant. The anodic oxidized layer of a Ti6Al4V alloy implant was examined ultrastructurally by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). They were also analyzed using energy dispersive X-ray spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS). The TEM revealed that the oxide layer of the Ti6Al4V implant prepared through anodic oxidation was separated into two layers. Al and V were not present on the top surface of the anodic oxide. This can be attributed to the biocompatibility of the anodic oxidized Ti6Al4V alloy implant, because the release of harmful metal ions such as Al and V can be suppressed by the biocompatibility.

Titanium-Nitride Coating of Orthopaedic Implants: A Review of the Literature

Surfaces of medical implants can be enhanced with the favorable properties of titanium-nitride (TiN). In a review of English medical literature, the effects of TiN-coating on orthopaedic implant material in preclinical studies were identified and the influence of these effects on the clinical outcome of TiN-coated orthopaedic implants was explored. The TiN-coating has a positive effect on the biocompatibility and tribological properties of implant surfaces; however, there are several reports of third body wear due to delamination, increased ultrahigh molecular weight polyethylene wear, and cohesive failure of the TiN-coating. This might be due to the coating process. The TiN-coating process should be optimized and standardized for titanium alloy articulating surfaces. The clinical benefit of TiN-coating of CoCrMo knee implant surfaces should be further investigated.

Engineering and functionalization of biomaterials via surface modification

Recent progress pertaining to the surface treatment of implantable macro-scale biomaterials and using micro- and nano-biomaterials for disease diagnosis and drug/gene delivery is reviewed.

Behavior of osteoblasts on TI surface with two different coating designed for orthodontic devices

In the present study we coated Ti surfaces with polytetrafluorethylene (PTFE) and titanium nitride (TiN) and investigated in vitro the behavior of osteoblasts on these surfaces. MG-63 osteoblasts were cultured on titanium discs with different surface treatment: uncoated Ti6Al4V, TiN-coated, PTFE-coated. Cell viability/proliferation was detected by MTT assay. Gene-expression levels of alkaline phosphatase (ALP), osteocalcin (OC), type I collagen, receptor activator of nuclear factor-kappa-B ligand (RANKL), and osteoprotegerin (OPG) were determined by qPCR. Cell behavior on different surfaces was observed by time-lapse microscopy. Cells grown on PTFE-coated Ti surface exhibited delayed surface attachment and decreased proliferation after 48 h. However, after 168 h of culture cells grown on PTFE-coated surface exhibited higher viability/proliferation, higher expression levels of ALP and OC, and higher OPG/RANKL ratio compared to uncoated surface. No effect of TiN-coating on any investigated parameter was found. Our results shows that PTFE coating exhibits no toxic effect on MG-63 cells and slightly stimulates expression of several genes associated with osteogenesis. We propose that PTFE coating could be considered as a possible choice for a surface treatment of temporary skeletal anchorage devices in orthodontics.

The effects of 3D bioactive glass scaffolds and BMP-2 on bone formation in rat femoral critical size defects and adjacent bones

Reconstruction of critical size defects in the load-bearing area has long been a challenge in orthopaedics. In the past, we have demonstrated the feasibility of using a biodegradable load-sharing scaffold fabricated from poly(propylene fumarate)/tricalcium phosphate (PPF/TCP) loaded with bone morphogenetic protein-2 (BMP-2) to successfully induce healing in those defects. However, there is limited osteoconduction observed with the PPF/TCP scaffold itself. For this reason, 13-93 bioactive glass scaffolds with local BMP-2 delivery were investigated in this study for inducing segmental defect repairs in a load-bearing region. Furthermore, a recent review on BMP-2 revealed greater risks in radiculitis, ectopic bone formation, osteolysis and poor global outcome in association with the use of BMP-2 for spinal fusion. We also evaluated the potential side effects of locally delivered BMP-2 on the structures of adjacent bones. Therefore, cylindrical 13-93 glass scaffolds were fabricated by indirect selective laser sintering with side holes on the cylinder filled with dicalcium phosphate dehydrate as a BMP-2 carrier. The scaffolds were implanted into critical size defects created in rat femurs with and without 10 μg of BMP-2. The x-ray and micro-CT results showed that a bridging callus was found as soon as three weeks and progressed gradually in the BMP group while minimal bone formation was observed in the control group. Degradation of the scaffolds was noted in both groups. Stiffness, peak load and energy to break of the BMP group were all higher than the control group. There was no statistical difference in bone mineral density, bone area and bone mineral content in the tibiae and contralateral femurs of the control and BMP groups. In conclusion, a 13-93 bioactive glass scaffold with local BMP-2 delivery has been demonstrated for its potential application in treating large bone defects.

Management of long-term and reversible hysteroscopic sterilization: a novel device with nickel-titanium shape memory alloy

BACKGROUND

Female sterilization is the second most commonly used method of contraception in the United States. Female sterilization can now be performed through laparoscopic, abdominal, or hysteroscopic approaches. The hysteroscopic sterilization may be a safer option than sterilization through laparoscopy or laparotomy because it avoids invading the abdominal cavity and undergoing general anaesthesia. Hysteroscopic sterilization mainly includes chemical agents and mechanical devices. Common issues related to the toxicity of the chemical agents used have raised concerns regarding this kind of contraception. The difficulty of the transcervical insertion of such mechanical devices into the fallopian tubes has increased the high incidence of device displacement or dislodgment. At present, Essure® is the only commercially available hysteroscopic sterilization device being used clinically. The system is irreversible and is not effective immediately.

PRESENTATION OF THE HYPOTHESIS

Our new hysteroscopic sterility system consists of nickel-titanium (NiTi) shape memory alloy and a waterproof membrane. The NiTi alloy is covered with two coatings to avoid toxic Ni release and to prevent stimulation of epithelial tissue growth around the oviducts. Because of the shape memory effect of the NiTi alloy, the device works like an umbrella: it stays collapsed at low temperature before placement and opens by the force of shape memory activated by the body temperature after it is inserted hysteroscopically into the interstitial tubal lumen. The rim of the open device will incise into interstitial myometrium during the process of unfolding. Once the device is fixed, it blocks the tube completely. When the patient no longer wishes for sterilization, the device can be closed by perfusing liquid with low temperature into the uterine cavity, followed by prospective hysteroscopic removal. After the device removal, the fallopian tube will revert to its physiological functions.

TESTING THE HYPOTHESIS

Currently, experimental and clinical studies are needed to attest the safety, efficiency and reversibility of the novel sterilization device.

IMPLICATIONS OF THE HYPOTHESIS

If our hypothesis is confirmed, appropriate and reversible contraceptive can be achieved with the device we have designed, which may have significant repercussions for numerous women worldwide.

The molecular mechanism for effects of TiN coating on NiTi alloy on endothelial cell function

The aim of this study is to systematically investigate the molecular mechanism of different effects of nickel titanium (NiTi) alloy surface and titanium nitride (TiN) coating on endothelial cell function. Release of nickel (Ni) ion from bare and TiN-coated NiTi alloys and proliferation of endothelial cells on the two materials were evaluated, and then influence of the two materials on cellular protein expression profiles was investigated by proteomic technology. Subsequently, proteomic data were analyzed with bioinformatics analyses and further validated using a series of biological experiments. Results showed that although the two materials did not affect cell proliferation, the Ni ions released from bare NiTi alloy generated inhibition on pathways associated with actin cytoskeleton, focal adhesion, energy metabolism, inflammation, and amino acid metabolism. In comparison, TiN coating not only effectively prevented release of Ni ions from NiTi alloy, but also promoted actin cytoskeleton and focal adhesion formation, increased energy metabolism, enhanced regulation of inflammation, and promoted amino acid metabolism. Furthermore, the two processes, "the initial mediation of adsorbed serum protein layer to endothelial cell adhesion and growth on the two materials" from our previous study, and "the following action of the two materials on cellular protein expression profile", were linked up and comprehensively analyzed. It was found that in stage of cell adhesion (within 4 h), release of Ni ions from bare NiTi alloy was very low, and the activation of adsorbed proteins to cell adhesion and growth related biological pathways (such as regulation of actin cytoskeleton, and focal adhesion pathways) was almost as same as TiN-coated NiTi alloy. This indicated that the released Ni ions did not affect the mediation of adsorbed proteins to endothelial cell adhesion. However, in stage of cell growth and proliferation, the release of Ni ions from bare NiTi alloy increased with time and reached a higher level, which inhibited endothelial cell function at molecular level, whereas TiN coating improved endothelial cell function.

Rods in spinal surgery: a review of the literature

BACKGROUND CONTEXT

Spinal instrumentation has been used for more than five decades. Since the introduction of the Harrington rod in 1962, new rod materials and concepts have been developed. Rigid rod fixation has achieved higher fusion rates than previous methods. Recently, semirigid rod fixation devices have been used for both dynamic stabilization and fusion fixation. Memory rods, which have an interesting ability to return to their pre-bent shape when the temperature increases, are expected to be used for scoliosis correction.

PURPOSE

To review the previous literature regarding biofunctionality and biocompatibility of rods in spinal surgery.

CONCLUSION

The properties of each type of rod need to be taken into consideration when performing spinal instrumentation surgery.

A comparative study of the cytotoxicity and corrosion resistance of nickel-titanium and titanium-niobium shape memory alloys

Nickel-titanium (NiTi) shape memory alloys (SMAs) are commonly used in a range of biomedical applications. However, concerns exist regarding their use in certain biomedical scenarios due to the known toxicity of Ni and conflicting reports of NiTi corrosion resistance, particularly under dynamic loading. Titanium-niobium (TiNb) SMAs have recently been proposed as an alternative to NiTi SMAs due to the biocompatibility of both constituents, the ability of both Ti and Nb to form protective surface oxides, and their superior workability. However, several properties critical to the use of TiNb SMAs in biomedical applications have not been systematically explored in comparison with NiTi SMAs. These properties include cytocompatibility, corrosion resistance, and alterations in alloy surface composition in response to prolonged exposure to physiological solutions. Therefore, the goal of the present work was to comparatively investigate these aspects of NiTi (49.2 at.% Ti) and TiNb (26 at.% Nb) SMAs. The results from the current studies indicate that TiNb SMAs are less cytotoxic than NiTi SMAs, at least under static culture conditions. This increased TiNb cytocompatibility was correlated with reduced ion release as well as with increased corrosion resistance according to potentio-dynamic tests. Measurements of the surface composition of samples exposed to cell culture medium further supported the reduced ion release observed from TiNb relative to NiTi SMAs. Alloy composition depth profiles also suggested the formation of calcium phosphate deposits within the surface oxide layers of medium-exposed NiTi but not of TiNb. Collectively, the present results indicate that TiNb SMAs may be promising alternatives to NiTi for certain biomedical applications.

Copper and silver ion implantation of aluminium oxide-blasted titanium surfaces: proliferative response of osteoblasts and antibacterial effects

Implant infection still represents a major clinical problem in orthopedic surgery. We therefore tested the in vitro biocompatibility and antibacterial effects of copper (Cu)- and silver (Ag)-ion implantation. Discs of a commonly used titanium alloy (Ti6AlV4) with an aluminium oxide-blasted surface were treated by Cu- or Ag-ion implantation with different dosage regimen (ranging from 1e15-17 ions cm(-2) at energies of 2-20 keV). The samples were seeded with primary human osteoblasts and cell attachment and proliferation was analyzed by an MTT-assay. In comparison to the reference titanium alloy there was no difference in the number of attached viable cells after two days. After seven days the number of viable cells was increased for Cu with 1e17 ions cm(-2) at 2 and 5 keV, and for Ag with 1e16 ions cm(-2) at 5 keV while it was reduced for the highest amount of Ag deposition (1e17 ions cm(-2) at 20 keV). Antibacterial effects on S.aureus and E.coli were marginal for the studied dosages of Cu but clearly present for Ag with 1e16 ions cm(-2) at 2 and 5 keV and 1e17 ions cm(-2) at 20 keV. These results indicate that Ag-ion implantation may be a promising methodological approach for antibacterial functionalization of titanium implants.

Cytocompatibility of medical biomaterials containing nickel by osteoblasts: a systematic literature review

The present review is based on a survey of 21 studies on the cytocompatibility of medical biomaterials containing nickel, as assessed by cell culture of human and animal osteoblasts or osteoblast-like cells. Among the biomaterials evaluated were stainless steel, NiTi alloys, pure Ni, Ti, and other pure metals. The materials were either commercially available, prepared by the authors, or implanted by various techniques to generate a protective layer of oxides, nitrides, acetylides. The observation that the layers significantly reduced the initial release of metal ions and increased cytocompatibility was confirmed in cell culture experiments. Physical and chemical characterization of the materials was performed. This included, e.g., surface characterization (roughness, wettability, corrosion behavior, quantity of released ions, microhardness, and characterization of passivation layer). Cytocompatibility tests of the materials were conducted in the cultures of human or animal osteoblasts and osteoblast-like cells. The following assays were carried out: cell proliferation and viability test, adhesion test, morphology (by fluorescent microscopy or SEM). Also phenotypic and genotypic markers were investigated. In the majority of works, it was found that the most cytocompatible materials were stainless steel and NiTi alloy. Pure Ni was rendered and less cytocompatible. All the papers confirmed that the consequence of the formation of protective layers was in significant increase of cytocompatibility of the materials. This indicates the possible further modifications of the manufacturing process (formation of the passivation layer).