Surface Modification Of Titanium Implants Research Articles

A novel titanium implant surface modification by plasma electrolytic oxidation (PEO) preventing tendon adhesion

Titanium is one of the most commonly used materials for implants in trauma applications due to its low density, high corrosion resistance and biocompatibility. Nevertheless, there is still a need for improved surface modifications of Titanium, in order to change surface properties such as wettability, antibacterial properties or tissue attachment. In this study, different novel plasma electrolytic oxidation (PEO) modifications have been investigated for tendon adhesion to implants commonly used in hand surgery. Titanium samples with four different PEO modifications were prepared by varying the electrolyte composition and analyzed with regards to their surface properties. Unmodified titanium blanks and Dotize® coating served as controls. Samples were examined using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), contact angle measuring system and analyzed for their biocompatibility and hemocompatibility (according to DIN ISO 10993-5 and 10,993–4). Finally, tendon adhesion of these specific surfaces were investigated by pull-off tests.Our findings show that surface thickness of PEO modifications was about 12–20 μm and had porous morphology. One modification demonstrated hydrophilic behavior accompanied by good biocompatibility without showing cytotoxic properties. Furthermore, no hemolytic effect and no significant influence on hemocompatibility were observed. Pull-off tests revealed a significant reduction of tendon adhesion by 64.3% (35.7% residual adhesion), compared to unmodified titanium (100%). In summary, the novel PEO-based ceramic-like porous modification for titanium surfaces might be considered a good candidate for orthopedic applications supporting a more efficient recovery.

Zn-doped MnO2 nanocoating with enhanced catalase-mimetic activity and cytocompatibility protects pre-osteoblasts against H2O2-induced oxidative stress

Therapeutic application in prevention and treatment of bone diseases, particularly osteoporosis, has recently started to emerge for manganese dioxide (MnO2) nanoparticles and nanocoatings whereby their antioxidant catalase-mimetic property can be exploited to control oxidative stress by reducing the amount of H2O2. Doping is an efficient method to enhance the catalase-mimetic activity of MnO2, which can potentially ameliorate osteogenesis under oxidative stress. Herein, Zn2+ doped MnO2 (Zn-MnO2) nanocoating was fabricated on orthopedic titanium implant by a facile UV-photolysis reaction. The Zn-MnO2 nanocoating showed better cytocompatibility than the MnO2 nanocoating, as indicated by enhanced cell proliferation, differentiation and mineralization of MC3T3-E1 pre-osteoblasts. This was probably due to the increased surface hydrophilicity as well as the combination effect of released Zn2+ and Mn2+ from the Zn-MnO2 nanocoating. Importantly, the Zn-MnO2 nanocoating with enhanced catalase-like activity exerted greater effects to suppress the intracellular oxidation products generation and prevent the depletion of dismutase superoxide levels under H2O2-induced oxidative stress, which in turn protected MC3T3-E1 pre-osteoblast functions. Overall, surface modification of titanium implants with the Zn-MnO2 nanocoating could be utilized to ameliorate oxidative stress-inhibited osteogenesis.

Surface modification of titanium implants by silk fibroin/Ag co-functionalized strontium titanate nanotubes for inhibition of bacterial-associated infection and enhancement of in vivo osseointegration

Surface modification of surgical grade titanium implants to promote bone cell integration and prevent infection is an urgent problem in orthopedic surgery. The synergistic effect of silk fibroin (SF) and strontium (Sr) has the dual functions of promoting bone formation and inhibiting osteoclasts, and silver (Ag) has excellent antibacterial activity. Therefore, this research uses technologies such as anodizing, hydrothermal synthesis, and layered self-assembly to load SF-Ag into Sr-loaded titanium dioxide nanotubes (SFAgSTN), which makes the titanium surface produce “antibacterial-bone formation” effect. The results of water contact angle and protein adsorption show that SFAgSTN has proper hydrophilicity and protein adsorption capacity, which indicates its excellent biocompatibility. The antibacterial test shows that the functional coating has excellent antibacterial activity because it can inhibit the proliferation of E. coli and S. aureus at the same time. The cross-linking effect of silk fibroin can slow down the release rate of Ag+, avoid the sudden release of ions, extend its antibacterial cycle and reduce the cytotoxicity of Ag+. In vitro, the SFAgSTN coating can promote the adhesion, proliferation and differentiation of MC3T3-E1 osteoblasts, showing good cell compatibility. In vivo, SFAgSTN promotes early osseointegration between Ti substrate and bone tissue. SFAgSTN shows excellent antibacterial, osteogenic differentiation, and new bone formation activity, and can be used as a highly potential anti-infective bone repair implant.

Nanoparticles and Nanostructured Surface Fabrication for Innovative Cranial and Maxillofacial Surgery.

A novel strategy to improve the success of soft and hard tissue integration of titanium implants is the use of nanoparticles coatings made from basically any type of biocompatible substance, which can advantageously enhance the properties of the material, as compared to its similar bulk material. So, most of the physical methods approaches involve the compaction of nanoparticles versus micron-level particles to yield surfaces with nanoscale grain boundaries, simultaneously preserving the chemistry of the surface among different topographies. At the same time, nanoparticles have been known as one of the most effective antibacterial agents and can be used as effective growth inhibitors of various microorganisms as an alternative to antibiotics. In this paper, based on literature research, we present a comprehensive review of the mechanical, physical, and chemical methods for creating nano-structured titanium surfaces along with the main nanoparticles used for the surface modification of titanium implants, the fabrication methods, their main features, and the purpose of use. We also present two patented solutions which involve nanoparticles to be used in cranioplasty, i.e., a cranial endoprosthesis with a sliding system to repair the traumatic defects of the skull, and a cranial implant based on titanium mesh with osteointegrating structures and functional nanoparticles. The main outcomes of the patented solutions are: (a) a novel geometry of the implant that allow both flexible adaptation of the implant to the specific anatomy of the patient and the promotion of regeneration of the bone tissue; (b) porous structure and favorable geometry for the absorption of impregnated active substances and cells proliferation; (c) the new implant model fit 100% on the structure of the cranial defect without inducing mechanical stress; (d) allows all kinds of radiological examinations and rapid osteointegration, along with the patient recover in a shorter time.

Research progress on the osseointegration of titanium implants promoted by cold atmospheric plasma

The application of cold atmospheric plasma to titanium surface modification has recently become a research focus in the area of material modification. Previous studies found that cold atmospheric plasma can affect the colonization of bacteria and biological behaviors of osteoblasts by changing the surface characteristics of titanium in vitro. In vivo studies reveal that cold atmospheric plasma can promote the process of osseointegration of titanium implants. This review focuses on research on the effects of the surface modification of titanium implants with cold atmospheric plasma on osseointegration.

Surface modification of titanium implants by ZIF-8@Levo/LBL coating for inhibition of bacterial-associated infection and enhancement of in vivo osseointegration

Bone implant-associated infection is one of the major concerns in orthopedics, and may even result in implant failure. To this end, we developed a strategy for the fabrication of an antibacterial coating on titanium (Ti) implants with pH-response to combat bacteria-mediated acidification of the local microenvironment. It includes three steps: first, we synthesized levofloxacin (Levo)-loaded zeolitic imidazolate framework-8 (ZIF-8@Levo) nanoparticles; second, the nanoparticles were loaded onto the collagen-modified Ti substrates by the cathode electrophoresis deposition (EPD) method; third, gelatin (Gel) and chitosan (Chi) multilayers were spin-coated on the modified Ti substrates, since the chelating effect of Gel and Chi would reduce the hydrolysis of ZIF-8@Levo for a sustained release of Levo and Zn2+. The fabricated samples of MOF@Levo/LBL promoted in vitro adhesion, proliferation, and differentiation of osteoblasts. Moreover, the MOF@Levo/LBL samples exhibited strong antibacterial ability against Escherichia coli and Staphylococcus aureus through hydrolysis of ZIF-8 nanoparticles, thereby creating a marginally alkaline microenvironment. Furthermore, in vivo implantation in a femur-infected rat model revealed that MOF@Levo/LBL implants effectively inhibited bacterial adhesion, apart from significantly improving osseointegration of the Ti implants. The study provides a promising alternative for fabricating multifunctional Ti implants with strong antibacterial capacity and enhanced bone formation for potential orthopedic application.

Chitosan/hydroxyapatite composite coatings on porous Ti6Al4V titanium implants: in vitro and in vivo studies.

PurposeTitanium implants are widely used in the treatment of dentition defects; however, due to problems such as osseointegration failure, peri-implant bone resorption, and peri-implant inflammation, their application is subject to certain restrictions. The surface modification of titanium implants can improve the implant success rate and meet the needs of clinical applications. The goal of this study was to evaluate the effect of the use of porous titanium with a chitosan/hydroxyapatite coating on osseointegration.MethodsTitanium implants with a dense core and a porous outer structure were prepared using a computer-aided design model and selective laser sintering technology, with a fabricated chitosan/hydroxyapatite composite coating on their surfaces. In vivo and in vitro experiments were used to assess osteogenesis.ResultsThe quasi-elastic gradient and compressive strength of porous titanium implants were observed to decrease as the porosity increased. The in vitro experiments demonstrated that, the porous titanium implants had no biological toxicity; additionally, the porous structure was shown to be superior to dense titanium with regard to facilitating the adhesion and proliferation of osteoblast-like MC3T3-E1 cells. The in vivo experimental results also showed that the porous structure was beneficial, as bone tissue could grow into the pores, thereby exhibiting good osseointegration.ConclusionsPorous titanium with a chitosan/hydroxyapatite coating promoted MC3T3-E1 cell proliferation and differentiation, and also improved osseointegration in vitro. This study has meaningful implications for research into ways of improving the surface structures of implants and promoting implant osseointegration.

Micro/nanostructured TiO2/ZnO coating enhances osteogenic activity of SaOS-2 cells

Although titanium implants account for a large proportion of the commercial dental market, their bioactivity are inadequate in many applications. A micro- and nano- scale hierarchical surface topography of the implant is suggested for rapid osseointegration from the biomimetic perspective. Moreover, Zinc (Zn) is an essential element in the skeletal system. Thus, a micro/nanostructured TiO2/ZnO coating, produced by micro-arc oxidation, and hydrothermal treatment, and heat treatment, was designed to endow the implant surface with enhanced osteogenic capacity. Physiochemical properties and biological effects of this coating were investigated in our study. The annealed micro/nanostructured TiO2/ZnO coating exhibited higher hydrophilicity and fibronectin adsorption ability compared to the micro-arc oxidation modified TiO2 coating. SaOS-2 cells grown on the annealed micro/nanostructured TiO2/ZnO coating showed increased alkaline phosphatase activity and collagen secretion, and immunofluorescence labeling revealed an upregulation of osteopontin, collagen type ι and osteocalcin. The micro/nanostructure and incorporation of Zn were considered to perform positive effect on the enhanced osteogenic activity of SaOS-2 cells. In conclusion, the micro/nanostructured TiO2/ZnO structure is simple, stable, and easy to produce and scale up, has promising applications in the surface modification of titanium implants.

Advances in titanium dental implant surface modification

Titanium dental implants have wide clinical application due to their many advantages, including comfort, aesthetics, lack of damage to adjacent teeth, and significant clinical effects. However, the failure of osseointegration, bone resorption, and peri-implantitis limits their application. Physical-chemical and bioactive coatings on the surface of titanium implants could improve the successful rate of dental implants and meet the clinical application requirements. This paper reviews the characteristics of surface modification of titanium implants from the aspects of physics, chemistry, and biology. Results provide information for research and clinical application of dental implant materials.

Surface engineering of titanium-based implants using electrospraying and dip coating methods

Titanium and its alloys due to their low density, good mechanical and biological properties are of the most common orthopedic metals. One of the main challenges regarding to titanium implants is their loosening after long term implantation in patient's body. Many methods such as alteration in surface topography with focus on improving osseointegration or biocompatibility in overall are supposed to overcome this issue. In this research, titanium surface topography is altered via electrospraying a solution of titanium salt, carrier polymer (polyvinylpyrrolidone) and solvents. The dip coated samples in the same solution are prepared and investigated as control. The electrosprayed or dip coated samples were pyrolysised in furnace at 500 °C to remove polymeric components. Then the stabilized microstructures on the surfaces were evaluated via scanning electron microscopy (SEM), water contact angle (WCA) measurement, X-ray diffraction (XRD) and atomic force microscope (AFM). Also, in order to study the bioactivity of modified samples, they were immersed in simulated body fluid (SBF) and their precipitates were studied. The cellular investigations were done by studying the cell morphology, MTT and alkaline phosphatase (ALP) activity assays. The results showed improvement in bioactivity and cellular response for DP3 and SP15 more than other samples implying the promising potential of these two approaches for titanium implant surface modification.

Surface modification of titanium with hydroxyapatite layer induced by phase-transited lysozyme coating

Surface modification of titanium with a hydroxyapatite (HAP) coating can improve the bioactivity of pristine titanium. The traditional techniques for coating HAP on titanium involve nonmild treatments using strong bases or acids or high temperatures. In this study, the coating of HAP was carried out by a novel methodology called phase-transited lysozyme-assisted hydroxyapatite formation (PAH); in this process of biomimetic mineralization, the abundant functional carboxyl groups of phase-transited lysozyme (PTL) were responsible for the nucleation of HAP crystals by concentrating Ca2+ ions at the interface between PTL and CaCl2 solution and for the subsequent growth of HAP crystals occurring in simulated body fluid (SBF). In vitro and in vivo experiments verified that the surface of titanium modified with the HAP/PTL-Ti multilayer was endowed with improved biocompatibility and osteoinductivity compared with those of pristine titanium. Therefore, PAH is a simple, rapid, low-cost and green process for the surface modification of titanium with an HAP coating and thus will be a promising methodology for the surface modification of titanium implants.

Enhanced cell attachment and hemocompatibility of titanium by nanoscale surface modification through severe plastic integration of magnesium-rich islands and porosification

Besides the wide applications of titanium and its alloys for orthopedic and biomedical implants, the biocompatible nature of titanium has emerged various surface modification techniques to enhance its bioactivity and osteointegration with living tissues. In this work, we present a new procedure for nanoscale surface modification of titanium implants by integration of magnesium-rich islands combined with controlled formation of pores and refinement of the surface grain structure. Through severe plastic deformation of the titanium surface with fine magnesium hydride powder, Mg-rich islands with varying sizes ranging from 100 nm to 1000 nm can be integrated inside a thin surface layer (100–500 µm) of the implant. Selective etching of the surface forms a fine structure of surface pores which their average size varies in the range of 200–500 nm depending on the processing condition. In vitro biocompatibility and hemocompatibility assays show that the Mg-rich islands and the induced surface pores significantly enhance cell attachment and biocompatibility without an adverse effect on the cell viability. Therefore, severe plastic integration of Mg-rich islands on titanium surface accompanying with porosification is a new and promising procedure with high potential for nanoscale modification of biomedical implants.

The effect of titanium implant surface modification on the dynamic process of initial microbial adhesion and biofilm formation

PurposeThe aim of the study was to investigate the dynamic process of biofilm adhesion on titanium implant with two surface treatments, either pickled (PT) or moderately roughened by sandblasting with large grits and acid-etched (SLA). Materials and methodsTwo types of titanium disks with various surface treatments, i.e. PT and SLA with respective surface roughness (Sa) of 0.3μm and 1.4μm, were used as substrata. Three types of biofilms, Streptococcus mutans, Streptococcus sanguinis and polymicrobial biofilms (Microcosm), were grown on the two respective types of titanium disks for 2h, 1 day, and 7 days. The formation of the biofilms was quantified by colony forming unit (CFU) count, and the structure of the biofilms on the titanium disks was observed by scanning electron microscope (SEM). ResultsAt 2h, the number of bacterial cells adhered to SLA surfaces was significantly higher than those to PT surfaces for all tested microorganisms. On day 1 and 7, no differences in biofilm CFU counts were observed between SLA and PT surfaces for S. mutans and Microcosm biofilms, while the S. sanguinis biofilm formation on SLA surfaces was significantly higher than the biofilm on PT surfaces throughout the whole test period. SEM images showed the increasing biofilm formation in time for all types of biofilms. Microcosm biofilms displayed different morphology from the other two single-species biofilms. ConclusionsThe higher roughness of a titanium surface would favor the early bacterial adhesion of S. mutans, S. sanguinis and Microcosm. However, as the biofilm became mature, the influence of surface roughness was diminished in a bacterial species dependent manner. Our results underline the importance of dynamic biofilm formation process in the implant study.

Effect of stiffness of polyelectrolyte multilayer on titanium surface on bacterium adhesion

To provide a theoretical basis for surface modification of titanium implants, the effects of the stiffness of polyelectrolyte multilayer films on titanium surface on bacterium adhesion was explored. Via layer-by-layer technique, catechol functionalized polyelectrolyte multilayer film (cPEM) was constructed on titanium surface by using catechol functionalized hyaluronic acid (cHA) and lipopolysaccharide-amine nanopolymersomes (NP). The stiffness of cPEM was controlled by adjusting the catechol substitution degree of cHA (5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%). Titanium samples covered with cPEM were selected as test group, and the cPEM was constructed with the lowest, medium and highest stiffness. The polished titanium was used as a control. The surface topography of titanium before and after film construction was observed by scanning electron microscopy (SEM). At 1 and 24 h after incubation, the adhesion and clonal formation of Streptococcus mutans (S. mutans) on different titanium surfaces were quantified, and their morphology and survival status were observed by SEM and laser scanning confocal microscope (LSCM). When the catechol grafting ratio was 5%, 30% and 70%, the lowest, medium and highest cPEM stiffness were obtained, and the cPEM stiffness were (10.69±4.54) GPa(cPEM-L), (20.99± 5.81) GPa (cPEM-M) and (32.57±6.93) GPa (cPEM-H) respectively, and the stiffness of polished titanium was (107.12±8.68) GPa (P<0.05). SEM observation showed that after cPEM coating, the titanium surface became smoother. After incubation for 1 and 24 h, the amount of adhesion and clonal formation of S. mutans on cPEM were higher than those on control titanium, and the difference was statistically significant (P<0.05). SEM images showed that for 1 h incubation, softer surfaces were beneficial for S. mutans adhering and agglomerating, while this difference nearly disappeared at 24 h. Observation under LSCM revealed that most of bacteria were alive on titanium disks at 1 h, and their amount decreased with the increase of stiffness. At 24 h, the living/dead bacterium ratios on cPEM-L and control titanium was higher than that on cPEM-M and cPEM-H, and cPEM-L surface was dominated by living bacteria, while stiffer cPEM-M and cPEM-H had more dead bacteria than living bacteria. Increasing the stiffness of polyelectrolyte films on titanium limits the adhesion of S. mutans. As an independent factor, stiffness influences the bacterium adhesion.

Preparation of 0.7SiO2·0.3CaO/PCL hybrid layers via sol–gel dip coating for the surface modification of titanium implants: characterization, bioactivity and biocompatibility evaluation

When reactive coatings are applied to medical implants by means of the sol–gel dip-coating technique, the biological properties of the implant surface can be modified to simulate the properties of the surrounding tissues in such a way to provide a firm fixation of the implant. The aim of this study has been to modify the surface of titanium grade 4 (a material generally used in dental application) by dip coating with sol–gel synthesized organic/inorganic hybrid materials in order to improve their osseointegration ability. Different hybrids have been obtained, consisting of an inorganic 0.7SiO2·0.3CaO-based matrix in which a biodegradable polymer, poly-e-caprolactone (PCL), has been incorporated in different percentages. These materials, still in the sol phase, have been used to coat the titanium substrates by means of the dip-coating technique. Fourier transform infrared spectroscopy allowed the characterization of the materials and their classification as Class I hybrids, whereas a microstructural analysis of the obtained coatings, performed using scanning electron microscopy (SEM), detected that the PCL content affects film morphology. The potential applications of these coatings in the biomedical field have been evaluated by bioactivity and biocompatibility tests. SEM–EDS analysis of the coated titanium surfaces showed that the hydroxylapatite deposition occurs after 21 days of immersion in a simulated body fluid, an index of in vivo bone-bonding capability. Moreover, a WST-8 assay has shown that the vitality of fibroblast cells (3T3) seeded on the titanium specimens is higher when the coatings are applied and that the biocompatibility depends on PCL amount.

Characterization and biological properties of TiO2/PCL hybrid layers prepared via sol–gel dip coating for surface modification of titanium implants

Surface modification of implants to facilitate the integration process of the biomaterials is a strategy which has been attracting increasing attention. In this work, the sol–gel method has been used to synthesize organic–inorganic nanocomposite materials consisting of an inorganic titania matrix in which different percentages of a biocompatible polymer, the poly-ε-caprolactone (PCL), have been incorporated. The synthesized materials, still in sol phase, have been used to dip-coat titanium grade 4 substrates to improve the biological properties of the surface. Fourier transform infrared spectroscopy detected the formation of H-bonds between the CO of PCL chains and the –OH groups of the sol–gel matrix. The morphological analysis of films has been performed via scanning electron microscopy (SEM) and has shown that the PCL addition allows the preparation of crack-free and porous coatings; however, uncoated areas develop if PCL is present in high percentages. Bioactivity properties of the coatings have been investigated by soaking coated substrates in a fluid simulating the human blood plasma and evaluating at a later stage the formation of a hydroxyapatite layer on the surface by means of SEM/EDX (energy dispersive X-ray). Coating biocompatibility has been studied by WST-8 assay using 3T3 cells seeded on coated and uncoated substrates.

In vivo behavior of surface-modified titanium implants after chemical processing at room temperature

There has been a concerted effort among materials scientists and clinicians worldwide to improve the performance of dental implants with the aim of accelerating and maintaining their integration into hard and soft tissues and/or extending their range of application. The surface characteristics of implant materials affect the rate and extent of osseointegration. Vandrovcova et al. have recently reviewed the growing evidence demonstrating that surface-modified materials are highly effective for adhesion, growth, and osteogenic differentiation of cells. A recent advance in dental implant research is the modification of the surface of implant materials at the nanometer level. 4 Techniques that provide an increased surface area and finer surface roughness may yield better tissue-titanium mechanical interlocking. However, more importantly, such nanoscopic features are also believed to directly affect osteogenic cell behavior around implant fixtures possessing non-conventional surfaces, creating a biomimetic relationship between alloplastic surfaces and host tissues by mimicking the natural cellular environment at the nanometer level. 4, 6 The nanostructure used in this study is known as a titanium nanosheet (TNS), which is a kind of lowdimensional nanostructured oxide material and is similar to that of TiO2 nanotubes (TNT) created by processing in a chemical solution of TiO2 powders, titanium deposition using the process of TiO2 sputtering, and/or electrochemical oxidization processing of the titanium metal. Recently, it was shown that nanotube and TNS structures can be created by treatment of titanium surfaces with an aqueous solution of 10 M NaOH at 30°C. The surface properties and structures of the materials play important roles in the adsorption of proteins, which might influence cell behavior. A previous study reported that TNS produced via chemical processing promotes the osteogenic differentiation of rat bone marrow cells. In vitro experiments have shown that cell activity may be modulated by nanoscale structures. Reproducing the nanotopography present in bone may improve early and long-term interactions between host bone and osseointegrated implants. Moreover, the biomolecules and cells involved in the early healing In vivo behavior of surface-modified titanium implants after chemical processing at room temperature

Titanium surface hydrophilicity enhances platelet activation.

Titanium implant surface modification is a key strategy used to enhance osseointegration. Platelets are the first cells that interact with the implant surface whereupon they release a wide array of proteins that influence the subsequent healing process. This study therefore investigated the effect of titanium surface modification on the attachment and activation of human platelets. The surface characteristics of three titanium surfaces: smooth (SMO), micro-rough (SLA) and hydrophilic micro-rough (SLActive) and the subsequent attachment and activation of platelets following exposure to these surfaces were determined. The SLActive surface showed the presence of significant nanoscale topographical features. While attached platelets appeared to be morphologically similar, significantly fewer platelets attached to the SLActive surface compared to both the SMO and SLA surfaces. The SLActive surface however induced the release of the higher levels of chemokines β-thromboglobulin and platelet factor 4 from platelets. This study shows that titanium surface topography and chemistry have a significant effect on platelet activation and chemokine release.

Modified Titanium Surface-Mediated Effects on Human Bone Marrow Stromal Cell Response.

Surface modification of titanium implants is used to enhance osseointegration. The study objective was to evaluate five modified titanium surfaces in terms of cytocompatibility and pro-osteogenic/pro-angiogenic properties for human mesenchymal stromal cells: amorphous microporous silica (AMS), bone morphogenetic protein-2 immobilized on AMS (AMS + BMP), bio-active glass (BAG) and two titanium coatings with different porosity (T1; T2). Four surfaces served as controls: uncoated Ti (Ti), Ti functionalized with BMP-2 (Ti + BMP), Ti surface with a thickened titanium oxide layer (TiO2) and a tissue culture polystyrene surface (TCPS). The proliferation of eGFP-fLuc (enhanced green fluorescence protein-firefly luciferase) transfected cells was tracked non-invasively by fluorescence microscopy and bio-luminescence imaging. The implant surface-mediated effects on cell differentiation potential was tracked by determination of osteogenic and angiogenic parameters [alkaline phosphatase (ALP); osteocalcin (OC); osteoprotegerin (OPG); vascular endothelial growth factor-A (VEGF-A)]. Unrestrained cell proliferation was observed on (un)functionalized Ti and AMS surfaces, whereas BAG and porous titanium coatings T1 and T2 did not support cell proliferation. An important pro-osteogenic and pro-angiogenic potential of the AMS + BMP surface was observed. In contrast, coating the Ti surface with BMP did not affect the osteogenic differentiation of the progenitor cells. A significantly slower BMP-2 release from AMS compared to Ti supports these findings. In the unfunctionalized state, Ti was found to be superior to AMS in terms of OPG and VEGF-A production. AMS is suggested to be a promising implant coating material for bioactive agents delivery.

Solution casting of chitosan membranes for in vitro evaluation of bioactivity

BackgroundConsiderable research is focusing on the surface modification of titanium implants for the treatment of orthopaedic tissue injuries to increase the success of orthopaedic fixations. Chitosan is one of the natural materials under investigation based on several favourable properties. Numerous techniques have been described for the preparation of chitosan membranes, including solution casting methods for the investigation of bioactivity before applying coatings onto potential titanium implants. Solution casting enables the easy in-house evaluation of chitosan membranes and allows for the selection of promising chitosan materials.ResultsWe present a method for the standardized and easily applied preparation of chitosan membranes by solution casting. This protocol is suitable for chitosan materials spanning a wide degree of deacetylation, being derived from different chitin sources and chitosan derivatives with novel properties. We detail the preparation and quality control methods in order to prepare membranes with favourable bioactivity, sustaining cell attachment and proliferation for extended culture periods.ConclusionsThe possibilities associated with the use of chitosan in tissue engineering applications are far from being exhausted and numerous challenges remain prior to successful translation into the clinics. Based on our experience, we have developed simple in-house methods for quality control of homogeneous membrane casting and early prediction of successful experimental outcome.