In vitro and in vivo investigations into the biocompatibility of diamond-like carbon (DLC) coatings for orthopedic applications

Feasibility of using diamond-like carbon films in total joint replacements: a review

Diamond-like Carbon (DLC) has been used as a coating material of choice for a variety of technological applications owing to its favorable bio-tribo-thermo-mechanical characteristics. Here, the possibility of bringing DLC into orthopedic joint implants is examined. With ever increasing number of patients suffering from osteoarthritis as well as with the ingress of the osteoarthritic joints' malaise into younger and more active demographics, there is a pressing need to augment the performance and integrity of conventional total joint replacements (TJRs). Contemporary joint replacement devices use metal-on-polymer articulations to restore function to worn, damaged or diseased cartilage. The wear of polymeric components has been addressed using crosslinking and antioxidants; however, in the context of the metallic components, complications pertaining to corrosion and metal ion release inside the body still persist. Through this review article, we explore the use of DLC coatings on metallic bearing surfaces and elucidate why this technology might be a viable solution for ongoing electrochemical challenges in orthopedics. The different characteristics of DLC coatings and their feasibility in TJRs are examined through assessment of tribo-material characterization methods. A holistic characterization of the coating-substrate interface and the wear performance of such systems are discussed. As with all biomaterials used in TJRs, we need mindful consideration of potential in-vivo challenges. We present a few caveats for DLC coatings including delamination, hydrophobicity, and other conflicting as well as outdating findings in the literature. We recommend prudently exploring DLC films as potential coatings on metallic TJR components to solve the problems pertaining to wear, metal ion release, and corrosion. Ultimately, we advise bringing DLC into clinical use only after addressing all challenges and concerns outlined in this article.

The activity of monocyte-derived macrophages after stimulation with platelet-rich and platelet-poor concentrates. Study on an ovine model of insertion of a tibial implant coated with silicon-doped diamond-like carbon

Introduction

Macrophages are crucial immune cells that play a role in tissue repair and can exhibit pro- or anti-inflammatory behaviour based on environmental stimulation. Their functional phenotype can be affected by platelet-derived products as determined by those products' composition. When the inflammatory response caused by implantation is excessive, it can lead to rejection of the implant. Therefore, a thorough evaluation of implant haemocompatibility is necessary to minimise undesirable consequences.

Material and Methods

In an in vitro study, monocyte-derived macrophages (MDMs) were obtained from the whole blood of sheep after a silicon-doped diamond-like carbon-coated implant insertion. These MDMs were then exposed to autologous platelet-derived products for functional marker analysis.

Results

Platelet-poor plasma (PPP) and pure platelet-rich plasma (P-PRP) stimulation increased arginase-1 activity, while leukocyte-rich PRP stimulation produced a mixed response involving higher O2- (6.49 ± 2.43 nM vs non-stimulated 3.51 ± 1.23 nM, P-value < 0.05) and NO (3.28 ± 1.38 μM vs non-stimulated 2.55 ± 0.32μM, P-value < 0.05) generation.

Conclusion

Using PPP and P-PRP stimulation in post-implantation procedures may contribute to the polarisation of macrophages towards the M2-like pro-resolving phenotype, thereby accelerating wound healing. This would also prevent implant degradation due to an excessive inflammatory process.

Diamond-like Carbon Coatings in the Biomedical Field: Properties, Applications and Future Development

Repairment and replacement of organs and tissues are part of the history of struggle against human diseases, in addition to the research and development (R&D) of drugs. Acquisition and processing of specific substances and physiological signals are very important to understand the effects of pathology and treatment. These depend on the available biomedical materials. The family of diamond-like carbon coatings (DLCs) has been extensively applied in many industrial fields. DLCs have also been demonstrated to be biocompatible, both in vivo and in vitro. In many cases, the performance of biomedical devices can be effectively enhanced by coating them with DLCs, such as vascular stents, prosthetic heart valves and surgical instruments. However, the feasibility of the application of DLC in biomedicine remains under discussion. This review introduces the current state of research and application of DLCs in biomedical devices, their potential application in biosensors and urgent problems to be solved. It will be useful to build a bridge between DLC R&D workers and biomedical workers in order to develop high-performance DLC films/coatings, promote their practical use and develop their potential applications in the biomedical field.

In vivo biocompatibility of diamond-like carbon films containing TiO2 nanoparticles for biomedical applications

Hybrid diamond-like carbon (DLC) with incorporated titanium dioxide (TiO₂) nanoparticle coatings have low friction coefficient, high wear resistance, high hardness, biocompatibility, and high chemical stability. They could be employed to modify biomedical alloys surfaces for numerous applications in biomedical engineering. Here we investigate for the first time the in vivo inflammatory process of DLC coatings with incorporated TiO₂ nanoparticles. TiO₂-DLC films were grown on AISI 316 stainless-steel substrates using plasma-enhanced chemical vapor deposition. The coated substrates were implanted in CF1 mice peritoneum. The in vivo cytotoxicity and biocompatibility of the samples were analyzed from macrophage lavage. Analysis in the first weeks after implantation could be helpful to evaluate the acute cytotoxicity generated after a possible inflammatory process. The in vivo results showed no inflammatory process. A significant increase in nitric oxide production on the uncoated substrates was confirmed through cytometry, and the coated substrates demonstrated biocompatibility. The presence of TiO₂ nanoparticles enhanced the wound healing activity, due to their astringent and antimicrobial properties. DLC and TiO₂-DLC coatings were considered biocompatible, and the presence of TiO₂ nanoparticles reduced the inflammatory reactions, increasing DLC biocompatibility.

Biological activity and antimicrobial property of Cu/a-C:H nanocomposites and nanolayered coatings on titanium substrates

Infection associated with titanium based implants remains the most serious problem in implant surgery hence it is important to find optimal strategies to prevent infections. In the present study, we investigated the surface properties, antibacterial activity and biocompatibility of nanocomposite coatings based on an amorphous hydrocarbon (a-C:H) film containing copper nanoparticles (CuNPs) deposited on Ti discs via a gas aggregation cluster source. Three different Cu/a-C:H coatings with approximately the same amount of embedded CuNPs with and without barrier a-C:H layer were fabricated. The obtained results revealed that different structures of the produced coatings have significantly different release rates of Cu ions from the coatings into the aqueous media. This subsequently influences the antibacterial efficiency and osteoblast cell viability of the treated coatings. Coatings with the highest number of CuNPs resulted in excellent antibacterial activity exhibiting approximately 4 log reduction of E.coli and S.aureus after 24 h incubation. The cytotoxicity study revealed that after 7 day cell seeding, even the coating with the highest Cu at.% (4 at.%) showed a cell viability of ̴90%. Consequently, the coating, formed with a properly tailored number of CuNPs and a-C:H barrier thickness offer a strong antibacterial effect without any harm to osteoblast cells.

Enhanced physicochemical and biological properties of C/Cu dual ions implanted medical titanium

It is increasingly popular for titanium and its alloys to be utilized as the medical implants. However, their bio-inert nature and lack of antibacterial ability limit their applications. In this work, by utilizing plasma immersion ion implantation and deposition (PIII&D) technology, the titanium surface was modified by C/Cu co-implantation. The mechanical property, corrosion resistance, antibacterial ability and cytocompatibility of modified samples were studied. Results indicate that after C/Cu co-implantation, copper nanoparticles were observed on the surface of titanium, and titanium carbide existed on the near surface region of titanium. The modified surface displayed good mechanical property and corrosion resistance. The Cu/C galvanic corrosion existed on the titanium surface implanted by C/Cu dual ions, and release of copper ions can be effectively controlled by the galvanic corrosion effect. Moreover, improved antibacterial performance of titanium surface can be achieved without cytotoxicity.

Investigation of Ag/a-C:H Nanocomposite Coatings on Titanium for Orthopedic Applications

One of the leading causes of failure for any bone implant is implant-associated infections. The implant-bone interface is in fact the crucial site of infection where both the microorganisms and cells compete to populate the newly introduced implant surface. Most of the work dealing with this issue has focused on the design of implant coatings capable of preventing infection while ignoring cell proliferation or vice versa. The present study is therefore focused on investigating the antibacterial and biological properties of nanocomposite coatings based on an amorphous hydrocarbon (a-C:H) matrix containing silver nanoparticles (AgNPs). a-C:H coatings with varying silver concentrations were generated directly on medical grade titanium substrates using a combination of a gas aggregation source (GAS) and a plasma-enhanced chemical vapor deposition (PE-CVD) process. The obtained results revealed that the surface silver content increased from 1.3 at % to 5.3 at % by increasing the used DC magnetron current in the GAS from 200 to 500 mA. The in vitro antibacterial assays revealed that the nanocomposites with the highest number of silver content exhibited excellent antibacterial activities resulting in a 6-log reduction of Escherichia coli and a 4-log reduction of Staphylococcus aureus after 24 h of incubation. An MTT assay, fluorescence live/dead staining, and SEM microscopy observations of MC3T3 cells seeded on the uncoated and coated Ti substrates also showed that increasing the amount of AgNPs in the nanocomposites had no notable impact on their cytocompatibility, while improved cell proliferation was especially observed for the nanocomposites possessing a low amount of AgNPs. These controllable Ag/a-C:H nanocomposites on Ti substrates, which simultaneously provide an excellent antibacterial performance and good biocompatibility, could thus have promising applications in orthopedics and other biomedical implants.

Effect of DLC Films with and without Silver Nanoparticles Deposited On Titanium Alloy

Abstract Diamond-like carbon (DLC) film is a biocompatible hard coating material that can prevent the leaching of metal ions. This study evaluates the structural characteristics of DLC, with and without silver nanoparticles, deposited by plasma (PECVD) on titanium alloy (Ti-6Al-4V) and bone formation in contact with DLC films. Sixty Ti-6Al-4V samples were used divided in: uncoated, coated with DLC and coated with DLC-Ag. After structural characterization, samples were fixed bilaterally at the rabbit's mandible. After 15 and 90 days, samples were characterized again and bone formation in the area was analyzed by histomorphometry. Statistical analysis was performed by two-way ANOVA. Both the DLC and DLC-Ag films were firmly adhered and showed a high electrical resistance without significant changes in the Raman spectrum after in vivo integration. After 15 days, there were immature bone trabeculae in the interface and partially covering the surface. After 90 days, mature bone filled the interface and coved the surface. There was no statistically significant difference among the three groups in both periods. In conclusion, osseointegration with DLC, DLC-Ag and uncoated Ti-6Al-4V is similar. However, DLC and DLC-Ag coverings have the advantage of electrical insulation and can presumably control bacterial activity and ion leaching.

The Influence of Carbon Coatings on the Functional Properties of X39Cr13 and 316LVM Steels Intended for Biomedical Applications

Carbon coatings are used in many different industrial areas, for example in cutting, electronics, or medical applications. On the one hand, carbon coatings have improved the functional properties of medical products because of their high biotolerance, which makes them an important material for implant coatings. On the other hand, high rigidity and abrasion resistance are properties needed in case of surgical tools. Thus, the aim of this research was to study the influence of mechanical abrasion by tumbling and chemical passivation on carbon coatings deposited by reactive magnetron sputtering (RMS) and radio frequency plasma activated chemical vapor deposition (RF PACVD) of X39Cr13 (mainly used for surgical tools) and 316LVM (mainly used for implants). Functional properties, such as roughness, coatings adhesion (scratch test), and wettability were investigated. As a result, DLC coatings applied by magnetron sputtering were found to be the optimum surface treatment in terms of adhesion and wettability properties, being more appropriate for the use of X39Cr13 base than 316LVM for carbon layer deposition.

Role of ILK/p38 pathway in mediating the enhanced osteogenic differentiation of bone marrow mesenchymal stem cells on amorphous carbon coating

Amorphous carbon (a-C) film is a promising candidate for metallic implant surface coatings to improve corrosion resistance and osteogenesis in vivo.

Effect of carbon ion implantation on the tribology of metal-on-metal bearings for artificial joints

Metal-on-metal (MoM) bearings have become popular due to a major advantage over metal-on-polymer bearings for total hip arthroplasty in that the larger femoral head and hydrodynamic lubrication of the former reduce the rate of wear. However, concerns remain regarding adverse reactions to metal debris including metallosis caused by metal wear generated at the taper-head interface and another modular junction. Our group has hypothesized that carbon ion implantation (CII) may improve metal wear properties. The purpose of this study was to investigate the wear properties and friction coefficients of CII surfaces with an aim to ultimately apply these surfaces to MoM bearings in artificial joints. CII was applied to cobalt-chromium-molybdenum (Co-Cr-Mo) alloy substrates by plasma source ion implantation. The substrates were characterized using scanning electron microscopy and a 3D measuring laser microscope. Sliding contact tests were performed with a simple geometry pin-on-plate wear tester at a load of 2.5 N, a calculated contact pressure of 38.5 MPa (max: 57.8 MPa), a reciprocating velocity of 30 mm/s, a stroke length of 60 mm, and a reciprocating cycle count of 172,800 cycles. The surfaces of the CII substrates were generally featureless with a smooth surface topography at the same level as untreated Co-Cr-Mo alloy. Compared to the untreated Co-Cr-Mo alloy, the CII-treated bearings had lower friction coefficients, higher resistance to catastrophic damage, and prevented the adhesion of wear debris. The results of this study suggest that the CII surface stabilizes the wear status due to the low friction coefficient and low infiltration of partner materials, and these properties also prevent the adhesion of wear debris and inhibit excessive wear. Carbon is considered to be biologically inert; therefore, CII is anticipated to be applicable to the bearing surfaces of MoM prostheses.

Clinical outcomes of ceramicized ball heads in total hip replacement bearings: a literature review

BACKGROUND

Metallic ball heads for total hip replacement (THR) bearings with ceramicized surfaces were introduced in orthopedics during the second half of the 1980s, with the aim of decreasing the wear of polyethylene cups.

METHODS

An analysis was made of the literature regarding outcomes for metallic ball heads with ceramicized surfaces now in clinical use (TiN, TiNbN, ZrN, monoclinic ZrO2), as well as carbon coatings (pyrolytic carbon, diamond-like carbon) and silicon nitride as coatings in ball heads for THR bearings.

RESULTS

Notwithstanding the diffusion of ceramicized ball heads in THRs, there are few reports about their clinical outcomes in hip arthroplasty. In addition, several clinical studies and some registry data are putting under scrutiny the clinical advantages of ceramicized ball heads over cobalt chrome (CoCr) alloy and ceramic ball heads.

CONCLUSIONS

The wear of THR bearings with ceramicized ball heads looks like it depends more on the behavior of the polyethylene cups than on the treatment of the ball head surface. The risk of coating damage and of its consequences has to be taken into account in selecting this type of bearing.

Adhesion and differentiation of Saos-2 osteoblast-like cells on chromium-doped diamond-like carbon coatings

Diamond-like carbon (DLC) thin films are promising for use in coating orthopaedic, dental and cardiovascular implants. The problem of DLC layers lies in their weak layer adhesion to metal implants. Chromium is used as a dopant for improving the adhesion of DLC films. Cr-DLC layers were prepared by a hybrid technology, using a combination of pulsed laser deposition (PLD) from a graphite target and magnetron sputtering. Depending on the deposition conditions, the concentration of Cr in the DLC layers moved from zero to 10.0 at.%. The effect of DLC layers with 0.0, 0.9, 1.8, 7.3, 7.7 and 10.0 at.% Cr content on the adhesion and osteogenic differentiation of human osteoblast-like Saos-2 cells was assessed in vitro. The DLC samples that contained 7.7 and 10.0 at.% of Cr supported cell spreading on day 1 after seeding. On day three after seeding, the most apparent vinculin-containing focal adhesion plaques were also found on samples with higher concentrations of chromium. On the other hand, the expression of type I collagen and alkaline phosphatase at the mRNA and protein level was the highest on Cr-DLC samples with a lower concentration of Cr (0-1.8 at.%). We can conclude that higher concentrations of chromium supported cell adhesion; however DLC and DLC doped with a lower concentration of chromium supported osteogenic cell differentiation.

Evaluation of Subretinal Implants Coated with Amorphous Aluminum Oxide and Diamond-like Carbon

Retinal prostheses may be used to support patients suffering from age-related macular degeneration (AMD) or retinitis pigmentosa (RP). A hermetic encapsulation of the poly(imide) (PI)-based prosthesis is important in order to prevent the leakage of water and ions into the electric circuitry embedded in the poly(imide) matrix. The deposition of amorphous aluminum oxide (by sputtering) and diamond like carbon (by pulsed laser ablation) were made for applications in retinal prostheses. The thin films obtained were characterized for composition, thickness, adhesion and smoothness by scanning electron microscopy-energy dispersive spectroscopy, atomic force microscopy, profilometry and light microscopy. Biocompatibility was tested in vivo by implanting coated specimen subretinally in the eye of Yucatan pigs. While amorphous aluminum oxide is more readily deposited with sufficient adhesion quality, superior biocompatibility behavior was shown by diamond-like carbon. Amorphous aluminum oxide had more adverse effects and caused more severe damage to the retinal tissue.

Bonding and bio-properties of hybrid laser/magnetron Cr-enriched DLC layers

Chromium-enriched diamond-like carbon (DLC) layers were prepared by a hybrid technology using a combination of pulsed laser deposition (PLD) and magnetron sputtering. XRD revealed no chromium peaks, indicating that the layers are mostly amorphous. Carbon (sp(2) and sp(3) bonds) and chromium bonds were determined by XPS from C 1s, O 1s, and Cr 2p photoelectron peaks. Depending on the deposition conditions, the concentration of Cr in DLC layers moved from zero to 10 at.% for as-received sample surfaces, and to about 31 at.% after mild sputter-cleaning by argon ion cluster beam. It should be noted that the most stable Cr(3+) bonding state is in Cr2O3 and Cr(OH)3, and that there is the toxic Cr(6+) state in CrO3. The surface content of hexavalent chromium in the Cr 2p3/2 spectra is rather low, but discernible. The population density of Saos-2 cells was the highest in samples containing higher concentrations of chromium 7.7 and 10 at.%. This means that higher concentrations of chromium supported the cell adhesion and proliferation. In addition, as revealed by a LIVE/DEAD viability/cytotoxicity kit, the cells on all Cr-containing samples maintained high viability (96 to 99%) on days 1 and 3 after seeding. However, this seemingly positive cell behavior could be associated with the risk of dedifferentiation and oncogenic transformation of cells.

Nanocarbon-Coated Porous Anodic Alumina for Bionic Devices

A highly-stable and biocompatible nanoporous electrode is demonstrated herein. The electrode is based on a porous anodic alumina which is conformally coated with an ultra-thin layer of diamond-like carbon. The nanocarbon coating plays an essential role for the chemical stability and biocompatibility of the electrodes; thus, the coated electrodes are ideally suited for biomedical applications. The corrosion resistance of the proposed electrodes was tested under extreme chemical conditions, such as in boiling acidic/alkali environments. The nanostructured morphology and the surface chemistry of the electrodes were maintained after wet/dry chemical corrosion tests. The non-cytotoxicity of the electrodes was tested by standard toxicity tests using mouse fibroblasts and cortical neurons. Furthermore, the cell-electrode interaction of cortical neurons with nanocarbon coated nanoporous anodic alumina was studied in vitro. Cortical neurons were found to attach and spread to the nanocarbon coated electrodes without using additional biomolecules, whilst no cell attachment was observed on the surface of the bare anodic alumina. Neurite growth appeared to be sensitive to nanotopographical features of the electrodes. The proposed electrodes show a great promise for practical applications such as retinal prostheses and bionic implants in general.

Articulating Biomaterials

This chapter examines the importance of surface characteristics such as microstructure, composition, crystallographic texture, and surface free energy in achieving desired biocompatibility and tribological properties thereby improving in vivo life of artificial articulating implants. Current implants often fail prematurely due to inadequate mechanical, tribological, biocompatibility, and osseointegration properties, apart from issues related to design and surgical procedures. For long-term in vivo stability, artificial implants intended for articulating joint replacement must exhibit long-term stable articulation surface without stimulating undesirable in vivo effects. Since the implant's surface plays a vital and decisive role in their response to biological environment, and vice versa, surface modification of implants assumes a significant importance. Therefore, overview on important surface modification techniques, their capabilities, properties of modified surfaces/implants are presented in the chapter. The clinical performance of surface modified implants and new surfaces for potential next-generation articulating implant applications are discussed at the end.

Biocompatibility of soft-templated mesoporous carbons

Soft-templated mesoporous carbon is morphologically a non-nano type of carbon. It is a relatively newer variety of biomaterial, which has already demonstrated its successful role in drug delivery applications. To investigate the toxicity and biocompatibility, we introduced three types of mesoporous carbons with varying synthesis conditions and pore textural properties. We compared the Brunauer-Emmett-Teller (BET) surface area and pore width and performed cytotoxicity experiments with HeLa cells, cell viability studies with fibroblast cells and hemocomapatibility studies. Cytotoxicity tests reveal that two of the carbons are not cytotoxic, with cell survival over 90%. The mesoporous carbon with the highest surface area showed slight toxicity (∼ 70% cell survival) at the highest carbon concentration of 500 μg/mL. Fibroblast cell viability assays suggested high and constant viability of over 98% after 3 days with no apparent relation with materials property and good visible cell-carbon compatibility. No hemolysis (<1%) was confirmed for all the carbon materials. Protein adsorption experiments with bovine serum albumin (BSA) and fibrinogen revealed a lower protein binding capacity of 0.2-0.6 mg/m(2) and 2-4 mg/m(2) for BSA and fibrinogen, respectively, with lower binding associated with an increase in surface area. The results of this study confirm the biocompatibility of soft-templated mesoporous carbons.

Biological characteristics of the MG-63 human osteosarcoma cells on composite tantalum carbide/amorphous carbon films

Tantalum (Ta) is a promising metal for biomedical implants or implant coating for orthopedic and dental applications because of its excellent corrosion resistance, fracture toughness, and biocompatibility. This study synthesizes biocompatible tantalum carbide (TaC) and TaC/amorphous carbon (a-C) coatings with different carbon contents by using a twin-gun magnetron sputtering system to improve their biological properties and explore potential surgical implant or device applications. The carbon content in the deposited coatings was regulated by controlling the magnetron power ratio of the pure graphite and Ta cathodes. The deposited TaC and TaC/a-C coatings exhibited better cell viability of human osteosarcoma cell line MG-63 than the uncoated Ti and Ta-coated samples. Inverted optical and confocal imaging was used to demonstrate the cell adhesion, distribution, and proliferation of each sample at different time points during the whole culture period. The results show that the TaC/a-C coating, which contained two metastable phases (TaC and a-C), was more biocompatible with MG-63 cells compared to the pure Ta coating. This suggests that the TaC/a-C coatings exhibit a better biocompatible performance for MG-63 cells, and they may improve implant osseointegration in clinics.

Characterization of multiwalled carbon nanotube-reinforced hydroxyapatite composites consolidated by spark plasma sintering

Pure HA and 1, 3, 5, and 10 vol% multiwalled carbon nanotube- (MWNT-) reinforced hydroxyapatite (HA) were consolidated using a spark plasma sintering (SPS) technique. The relative density of pure HA increased with increasing sintering temperature, but that of the MWNT/HA composite reached almost full density at 900°C, and then decreased with further increases in sintering temperature. The relative density of the MWNT/HA composites increased with increasing MWNT content due to the excellent thermal conductivity of MWNTs. The grain size of MWNT/HA composites decreased with increasing MWNT content and increased with increasing sintering temperature. Pull-out toughening of the MWNTs of the MWNT/HA composites was observed in the fractured surface, which can be used to predict the improvement of the mechanical properties. On the other hand, the existence of undispersed or agglomerate MWNTs in the MWNT/HA composites accompanied large pores. The formation of large pores increased with increasing sintering temperature and MWNT content. The addition of MWNT in HA increased the hardness and fracture toughness by approximately 3~4 times, despite the presence of large pores produced by un-dispersed MWNTs. This provides strong evidence as to why the MWNTs are good candidates as reinforcements for strengthening the ceramic matrix. The MWNT/HA composites did not decompose during SPS sintering. The MWNT-reinforced HA composites were non-toxic and showed a good cell affinity and morphology in vitro for 1 day.

Assessment of cellular viability on calcium sulphate/hydroxyapatite injectable scaffolds

Cements for maxillofacial reconstruction of jaw defects through calcification of rotated muscle have been tested. The objective of this study was to investigate the visibility of loading of two types of commercially available cements, Cerament(™) Spine Support and Cerament Bone Void Filler with mesenchymal cells and cytokines (bone morphogenetic protein) to act as a biomimetic scaffolding for future clinical application. Determination of basic biocompatibility (cell viability) using methyl thiazolyl tetrazolium and live/dead assay was carried out using MG-63 cells at various time points. Next, in order to inform potential subsequent in vivo experiments, a collagen tissue mimic was used for characterization of rabbit mesenchymal stromal cells using immunofluorescent cytoskeleton staining, and simultaneous and then sequential injection of Cerament Spine Support cement and cells into collagen gels. Results indicated that Cerament Spine Support was more biocompatible and that sequential injection of cement and then rabbit mesenchymal stromal cells into the tissue mimics is an optimal approach for clinical applications.

Formation and in vitro biocompatibility of biomimetic hydroxyapatite coatings on chemically treated carbon substrates

Carbon derived materials such as pyrolytic carbon or carbon-carbon composites (CCCs) exhibit excellent mechanical properties making them promising candidates for bone replacement. However, these materials are considered bioinert and not to induce bone formation in vivo. In this study, a two-step chemical surface treatment including etching with HCl/HNO3 solution and subsequent soaking in CaCl2 solution was applied to carbon substrates in order to activate the materials surface towards bioactive behavior. The bioactivity was proven by soaking the samples in simulated body fluid (SBF) and formation of carbonated hydroxyapatite layer (HCA), which indicates the ability of the material to bond to bone in vivo. The materials surface is shown to be functionalized through the chemical etching creating COO(-)Ca(2+) complexes on the surface as confirmed by FTIR and XPS analyses. These ionic complexes provide nucleation sites for HAp precipitation. After similar immersion time in SBF under the condition of local supersaturation the thickness and homogeneity of the HAp layer were found to depend on the chemical pretreatment with HCl/HNO3. Homogenous HAp layers with a thickness ranging from ∼ 6 to ∼ 17 μm were achieved. The proposed bioactivating treatment of carbon stimulates HAp formation in vivo and can be considered an easy biomimetic approach for coating carbon derived materials with bone-like hydroxyapatite. In vitro cell assay with osteosarcoma cells (MG-63) showed increased cell viability (+70%) on HAp coated carbon substrates as compared to uncoated reference while both materials induced ALP expression in MG-63 cells confirming the osteoblastic phenotype.

Skeletal muscle-derived cell cultures as potent models in regenerative medicine research

Cell cultures have been used extensively by many scientists in recent decades to study various cell and tissue mechanisms. The use of cell cultures has many advantages over use of in vivo experimental models, but there are also limitations. As skeletal muscle-derived cell cultures become more commonly utilized in studies of muscle regeneration processes the question of their relevance in experimentation is highlighted with regard to in vivo experimental models. This article reviews studies that have been performed simultaneously in in vivo and in vitro experiments on skeletal muscle and assesses the correlation of results. Although they seem to correlate, no such studies on humans have been performed so far.

Graphene coatings for biomedical implants

Atomically smooth graphene as a surface coating has potential to improve implant properties. This demonstrates a method for coating nitinol alloys with nanometer thick layers of graphene for applications as a stent material. Graphene was grown on copper substrates via chemical vapor deposition and then transferred onto nitinol substrates. In order to understand how the graphene coating could change biological response, cell viability of rat aortic endothelial cells and rat aortic smooth muscle cells was investigated. Moreover, the effect of graphene-coatings on cell adhesion and morphology was examined with fluorescent confocal microscopy. Cells were stained for actin and nuclei, and there were noticeable differences between pristine nitinol samples compared to graphene-coated samples. Total actin expression from rat aortic smooth muscle cells was found using western blot. Protein adsorption characteristics, an indicator for potential thrombogenicity, were determined for serum albumin and fibrinogen with gel electrophoresis. Moreover, the transfer of charge from fibrinogen to substrate was deduced using Raman spectroscopy. It was found that graphene coating on nitinol substrates met the functional requirements for a stent material and improved the biological response compared to uncoated nitinol. Thus, graphene-coated nitinol is a viable candidate for a stent material.

In vitro comparison of the hemocompatibility of diamond-like carbon and carbon nitride coatings with different atomic percentages of N

Carbon nitride (CN( x )) and diamond-like carbon (DLC) coatings were prepared by dc magnetron sputtering at room temperature. Different partial pressures of N(2) were used to synthesize CN( x ) to evaluate the relationship between the atomic percentage of nitrogen and hemocompatibility. Auger electron spectroscopy and atomic force microscopy indicated atomic percentages of N of 0.12 and 0.22 and that the CN( x ) coatings were smooth. An in vitro study of the hemocompatibility of the coatings revealed that both CN( x ) coatings had better anticoagulant properties and lower platelet adhesion than DLC. Compared with CN(0.12), the CN(0.22) coating showed longer dynamic clotting time (about 42 min), static clotting time (23.6 min) and recalcification time (45.6 s), as well as lower platelet adhesion (102 cells μm(-2)), aggregation, and activation. The presence of nitrogen in the CN( x ) coatings induced their enhanced hemocompatibility compared with DLC.

Vincristine-sulphate-loaded liposome-templated calcium phosphate nanoshell as potential tumor-targeting delivery system

Vincristine-sulfate-loaded liposomes were prepared with an aim to improve stability, reduce drug leakage during systemic circulation, and increase intracellular uptake. Liposomes were prepared by the thin-film hydration method, followed by coating with calcium phosphate, using the sequential addition approach. Prepared formulations were characterized for size, zeta potential, drug-entrapment efficiency, morphology by transmission electron microscopy (TEM), in vitro drug-release profile, and in vitro cell cytotoxicity study. Effect of formulation variables, such as drug:lipid ratio as well as nature and volume of hydration media, were found to affect drug entrapment, and the concentration of calcium chloride in coating was found to affect size and coating efficiency. Size, zeta potential, and TEM images confirmed that the liposomes were effectively coated with calcium phosphate. The calcium phosphate nanoshell exhibited pH-dependent drug release, showing significantly lower release at pH 7.4, compared to the release at pH 4.5, which is the pH of the tumor interstitium. The in vitro cytotoxicity study done on the lung cancer cell line indicated that coated liposomes are more cytotoxic than plain liposomes and drug solution, indicating their potential for intracellular drug delivery. The cell-uptake study done on the lung cancer cell line indicated that calcium-phosphate-coated liposomes show higher cell uptake than uncoated liposomes.

Evaluation of trabecular bone formation in a canine model surrounding a dental implant fixture immobilized with an antimicrobial peptide derived from histatin

JH8194 induces osteoblast differentiation, although it was originally designed to improve antifungal activity. This suggests that JH8194 is useful for implant treatment. Therefore, the aim of this study was to evaluate the osseointegration capacity of JH8194-modified titanium dental implant fixtures (JH8194-Fi). The implants were randomly implanted into the edentulous ridge of dog mandibles. Healing abutments were inserted immediately after implant placement. Three weeks later, peri-implant bone levels, the first bone-to-implant contact points, and trabecular bone formation surrounding the implants were assessed by histological and digital image analyses based on microcomputed tomography (microCT). The histological analysis revealed an enhancement of mature trabecular bone around the JH8194-Fi compared with untreated fixtures (control-Fi). Similarly, microCT combined with analysis by Zed View™ also showed increased trabecular bone formation surrounding the JH8194-Fi compared with the control-Fi (Student's t-test, P < 0.05). JH8194 may offer an alternative biological modification of titanium surfaces to enhance trabecular bone formation around dental implants, which may contribute to the transient acquirement of osseointegration and the long-term success of implant therapy.

In vitro adhesion of staphylococci to diamond-like carbon polymer hybrids under dynamic flow conditions

This study compares the ability of selected materials to inhibit adhesion of two bacterial strains commonly implicated in implant-related infections. These two strains are Staphylococcus aureus (S-15981) and Staphylococcus epidermidis (ATCC 35984). In experiments we tested six different materials, three conventional implant metals: titanium, tantalum and chromium, and three diamond-like carbon (DLC) coatings: DLC, DLC-polydimethylsiloxane hybrid (DLC-PDMS-h) and DLC-polytetrafluoroethylene hybrid (DLC-PTFE-h) coatings. DLC coating represents extremely hard material whereas DLC hybrids represent novel nanocomposite coatings. The two DLC polymer hybrid films were chosen for testing due to their hardness, corrosion resistance and extremely good non-stick (hydrophobic and oleophobic) properties. Bacterial adhesion assay tests were performed under dynamic flow conditions by using parallel plate flow chambers (PPFC). The results show that adhesion of S. aureus to DLC-PTFE-h and to tantalum was significantly (P < 0.05) lower than to DLC-PDMS-h (0.671 ± 0.001 × 10(7)/cm(2) and 0.751 ± 0.002 × 10(7)/cm(2) vs. 1.055 ± 0.002 × 10(7)/cm(2), respectively). No significant differences were detected between other tested materials. Hence DLC-PTFE-h coating showed as low susceptibility to S. aureus adhesion as all the tested conventional implant metals. The adherence of S. epidermidis to biomaterials was not significantly (P < 0.05) different between the materials tested. This suggests that DLC-PTFE-h films could be used as a biomaterial coating without increasing the risk of implant-related infections.

Biocompatibility and mechanical properties of diamond-like coatings on cobalt-chromium-molybdenum steel and titanium-aluminum-vanadium biomedical alloys

Diamond-like carbon (DLC) films are favored for wear components because of diamond-like hardness, low friction, low wear, and high corrosion resistance (Schultz et al., Mat-wiss u Werkstofftech 2004;35:924-928; Lappalainen et al., J Biomed Mater Res B Appl Biomater 2003;66B:410-413; Tiainen, Diam Relat Mater 2001;10:153-160). Several studies have demonstrated their inertness, nontoxicity, and the biocompatibility, which has led to interest among manufacturers of surgical implants (Allen et al., J Biomed Mater Res B Appl Biomater 2001;58:319-328; Uzumaki et al., Diam Relat Mater 2006;15:982-988; Hauert, Diam Relat Mater 2003;12:583-589; Grill, Diam Relat Mater 2003;12:166-170). In this study, hydrogen-free amorphous, tetrahedrally bonded DLC films (ta-C) were deposited at low temperatures by physical vapor deposition on medical grade Co28Cr6Mo steel and the titanium alloy Ti6Al4V (Scheibe et al., Surf Coat Tech 1996;85:209-214). The mechanical performance of the ta-C was characterized by measuring its surface roughness, contact angle, adhesion, and wear behavior, whereas the biocompatibility was assessed by osteoblast (OB) attachment and cell viability via Live/Dead assay. There was no statistical difference found in the wettability as measured by contact angle measurements for the ta-C coated and the uncoated samples of either Co28Cr6Mo or Ti6Al4V. Rockwell C indentation and dynamic scratch testing on 2-10 μm thick ta-C films on Co28Cr6Mo substrates showed excellent adhesion with HF1 grade and up to 48 N for the critical load L(C2) during scratch testing. The ta-C coating reduced the wear from 3.5 × 10(-5) mm(3)/Nm for an uncoated control sample (uncoated Co28Cr6Mo against uncoated stainless steel) to 1.1 × 10(-7) mm(3)/Nm (coated Co28Cr6Mo against uncoated stainless steel) in reciprocating pin-on-disk testing. The lowest wear factor of 3.9 × 10(-10) mm(3)/Nm was measured using a ta-C coated steel ball running against a ta-C coated and polished Co28Cr6Mo disk. Student's t-test found that the ta-C coating had no statistically significant (p < 0.05) effect on OB attachment, when compared with the uncoated control samples. There was no significant difference (p < 0.05) in the Live/Dead assay results in cell death between the ta-C coated Co28Cr6Mo and Ti6Al4V samples and the uncoated controls. Therefore, these ta-C coatings show improved wear and corrosion (Dorner-Reisel et al., Diam Relat Mater 2003;11:823-827; Affato et al., J Biomed Mater Res B Appl Biomater 2000;53:221-226; Dorner-Reisel et al., Surf Coat Tech 2004;177-178:830-837; Kim et al., Diam Relat Mater 2004;14:35-41) performance and excellent in vitro cyto-compatibility, when compared with currently used uncoated Co28Cr6Mo and Ti6Al4V implant materials.

Thin film composites of nanocrystalline ZrO(2) and diamond-like carbon: Synthesis, structural properties and bone cell proliferation

We report on the synthesis of thin composites of diamond-like carbon (DLC) and nanocrystalline ZrO(2) deposited using pulsed direct current plasma-enhanced chemical vapor deposition at low temperatures (<120 degrees C). Films containing up to 21at.% Zr were prepared (hydrogen was not included in the calculation) and their structural and surface properties were determined using a number of spectroscopic methods and contact angle measurements. Bone cell adhesion to the films was studied using a 3 day cell culture with osteoblasts. These nanocomposites (DLC-ZrO(2)) consist of tetragonal ZrO(2) nanocrystals with an average size of 2-5 nm embedded in an amorphous matrix consisting predominantly of DLC. The surface water contact angle of the films increased from approximately 60 degrees to 80 degrees as the Zr content increased from 0 to 21at.%. The cell culture study revealed that although the cell counts were not significantly different, the morphology of the osteoblasts growing on the DLC-ZrO(2) nanocomposites was markedly different from that of cells growing on DLC alone. Cells growing on the DLC-ZrO(2) surfaces were less spread out and had a smaller cell area in comparison with those growing on DLC surfaces. In some areas on the DLC-ZrO(2) surfaces, large numbers of cells appeared to coalesce. It is postulated that the difference in cell morphology between osteoblasts on DLC-ZrO(2) surfaces and DLC surfaces is related to the presence of very small tetragonal nanocrystals of ZrO(2) in the composite film.

TiO2 nanotubes on Ti: Influence of nanoscale morphology on bone cell-materials interaction

Ti being bioinert shows poor bone cell adhesion with an intervening fibrous capsule. Ti could be made bioactive by several methods including growing in situ TiO2 layer on Ti-surface. TiO2 nanotubes were grown on Ti surface via anodization process and the bone cell-material interactions were evaluated. Human osteoblast cell attachment and growth behavior were studied using an osteoprecursor cell line for 3, 7, and 11 days. An abundant amount of extracellular matrix (ECM) between the neighboring cells was noticed on anodized nanotube surface with filopodia extensions coming out from cells to grasp the nanoporous surface of the nanotube for anchorage. To better understand and compare cell-materials interactions, anodized nanoporous sample surfaces were etched with different patterns. Preferential cell attachment was noticed on nanotube surface compare to almost no cells in etched Ti surface. Cell adhesion with vinculin adhesive protein showed higher intensity, positive contacts on nanoporous surface and thin focal contacts on the Ti-control. Immunochemistry study with alkaline phosphatase showed enhanced osteoblastic phenotype expressions in nanoporous surface. Osteoblast proliferation was significantly higher on anodized nanotube surface. Surface properties changed with the emergence of nanoscale morphology. Higher nanometer scale roughness, low contact angle and high surface energy in nanoporous surface enhanced the osteoblast-material interactions. Mineralization study was done under simulated body fluid (SBF) with ion concentration nearly equal to human blood plasma to understand biomimetic apatite deposition behavior. Although apatite layer formation was noticed on nanotube surface, but it was nonuniform even after 21 days in SBF.

Incorporation of Si and SiO(x) into diamond-like carbon films: impact on surface properties and osteoblast adhesion

The interaction of human osteoblast cells with diamond-like carbon films incorporating silicon and silicon oxide (SiO(x), 1 < or = x < or = 1.5) and synthesized using the direct-current plasma-activated chemical vapour deposition method was investigated. Cell culture studies were performed for films with Si contents ranging from approximately 4 at.% to 15 at.%. Substantial differences between Si-incorporated and SiO(x)-incorporated films were found for the bonding environments of Si atoms and the hybridization of underlying carbon structures. However, osteoblast-attachment studies did not show statistically significant trends in properties of cell growth (count, area and morphology) that can be attributed either to the Si content of the films or to the chemical structure of the films. The surface energy decreased by 40% as the Si content of the SiO(x) incorporated DLC films increased to 13 at.%. The cell adhesion properties however did not change in response to lowering of the surface energy. The incorporation of both Si and SiO(x) leads to a beneficial reduction in the residual stress of the films. The average roughness of the films increases and the hardness decreases when Si and SiO(x) are added to DLC films. The impact of these changes for load-bearing biomedical applications can be determined only by carefully controlled experiments using anatomic simulators.