Anode glow discharge plasma treatment of titanium plates facilitates adsorption of extracellular matrix proteins to the plates

Redox signaling induces laminin receptor ribosomal protein-SA expression to improve cell adhesion following radiofrequency glow discharge treatments

Current biomaterials effectively replace biological structures but are limited by infections and long-term material failures. This study examined the molecular mechanisms of radio frequency glow discharge treatments (RFGDT) in mediating the disinfection of biomaterial surfaces and concurrently promoting cell attachment and proliferation. Dental biomaterials were subjected to RFGDT, and viability of oral microbial species, namely Streptococcus mutants (SM), Streptococcus gordonii (SG), Moraxella catarrhalis (MC), and Porphyromonas gingivalis (PG), were assessed. Cell attachment and survival of a pre-odontoblast cell line, MDPC-23, was examined. Finally, mechanistic investigations into redox generation and biological signaling were investigated. Based on their compositions, dental biomaterials induced reactive oxygen species (ROS) following dose-dependent RFGDT. Reduced microbial viability was evident following RFGDT in the catalase-negative (SM and SG) species more prominently than catalase-positive (MC and PG) species. Cell adhesion assays noted improved MDPC-23 attachment and survival. Pretreatments with N-acetylcysteine (NAC) and catalase abrogated these responses. Immunoassays noted redox-induced downstream expression of a laminin receptor, Ribosomal Protein SA, following RFGDT. Thus, RFGDT-induced redox mediates antimicrobial and improves cell responses such as adhesion and proliferation. These observations together provide a mechanistic rationale for the clinical utility of RFGDT with dental biomaterials for regenerative clinical applications.

Hydrophilic implants generated using a low-cost dielectric barrier discharge plasma device at the time of placement exhibit increased osseointegration in an animal pre-clinical study: An effect that is sex-dependent

OBJECTIVES

Increased wettability of titanium and titanium alloy surfaces due to processing and storage methods increases osteoprogenitor cell differentiation and osseointegration compared to microroughness alone. Implants that are exposed to air have a hydrophobic surface due to adsorption of atmospheric hydrocarbons, which can limit overall implant success. Dielectric barrier discharge plasma (DBD) is one method to increase surface hydrophilicity. Although current DBD methods yield a hydrophilic surface, adsorbed hydrocarbons rapidly restore hydrophobicity. We demonstrated that application of DBD to implants previously packaged in a vacuum, generates a hydrophilic surface that supports osteoblastic differentiation in vitro and this can be done immediately prior to use. In the present study, we tested the hypothesis that DBD treatment to alter surface wettability at the time of implant placement will improve osseointegration in vivo.

MATERIALS AND METHODS

Twenty male and sixteen female rabbits were used in a preclinical trans-axial femur model of osseointegration. Control and DBD treatment implants were inserted randomized per hind limb in each rabbit (1 implant/hind-limb). At 6 weeks post-surgery, bone-to-implant contact, adjacent bone volume, and torque to failure were assessed by micro-CT, calcified histology, and mechanical testing.

RESULTS

DBD plasma treatment of vacuum-sealed implants increased surface wettability and did not change surface chemistry or roughness. Peak torque and torsional energy, and bone-to-implant contact increased with DBD treatment in males. In contrast, female rabbits showed increased osseointegration equal to DBD treated male implants regardless of DBD plasma treatment.

CONCLUSION

DBD treatment is an effective method to enhance osseointegration by increasing surface wettability; however, this response is sex dependent. In healthy female patients, DBD treatment may not be necessary but in older patients or patients with compromised bone, this treatment could be an effective measure to ensure implant success.

Titanium and Protein Adsorption: An Overview of Mechanisms and Effects of Surface Features

Titanium and its alloys, specially Ti6Al4V, are among the most employed materials in orthopedic and dental implants. Cells response and osseointegration of implant devices are strongly dependent on the body-biomaterial interface zone. This interface is mainly defined by proteins: They adsorb immediately after implantation from blood and biological fluids, forming a layer on implant surfaces. Therefore, it is of utmost importance to understand which features of biomaterials surfaces influence formation of the protein layer and how to guide it. In this paper, relevant literature of the last 15 years about protein adsorption on titanium-based materials is reviewed. How the surface characteristics affect protein adsorption is investigated, aiming to provide an as comprehensive a picture as possible of adsorption mechanisms and type of chemical bonding with the surface, as well as of the characterization techniques effectively applied to model and real implant surfaces. Surface free energy, charge, microroughness, and hydroxylation degree have been found to be the main surface parameters to affect the amount of adsorbed proteins. On the other hand, the conformation of adsorbed proteins is mainly dictated by the protein structure, surface topography at the nano-scale, and exposed functional groups. Protein adsorption on titanium surfaces still needs further clarification, in particular concerning adsorption from complex protein solutions. In addition, characterization techniques to investigate and compare the different aspects of protein adsorption on different surfaces (in terms of roughness and chemistry) shall be developed.

Zn- or Cu-containing CaP-Based Coatings Formed by Micro-Arc Oxidation on Titanium and Ti-40Nb Alloy: Part II-Wettability and Biological Performance

This work describes the wettability and biological performance of Zn- and Cu-containing CaP-based coatings prepared by micro-arc oxidation on pure titanium (Ti) and novel Ti-40Nb alloy. Good hydrophilic properties of all the coatings were demonstrated by the low contact angles with liquids, not exceeding 45°. An increase in the applied voltage led to an increase of the coating roughness and porosity, thereby reducing the contact angles to 6° with water and to 17° with glycerol. The free surface energy of 75 ± 3 mJ/m² for all the coatings were determined. Polar component was calculated as the main component of surface energy, caused by the presence of strong polar PO₄³⁻ and OH⁻ bonds. In vitro studies showed that low Cu and Zn amounts (~0.4 at.%) in the coatings promoted high motility of human adipose-derived multipotent mesenchymal stromal cells (hAMMSC) on the implant/cell interface and subsequent cell ability to differentiate into osteoblasts. In vivo study demonstrated 100% ectopic bone formation only on the surface of the CaP coating on Ti. The Zn- and Cu-containing CaP coatings on both substrates and the CaP coating on the Ti-40Nb alloy slightly decreased the incidence of ectopic osteogenesis down to 67%. The MAO coatings showed antibacterial efficacy against Staphylococcus aureus and can be arranged as follows: Zn-CaP/Ti > Cu-CaP/TiNb, Zn-CaP/TiNb > Cu-CaP/Ti.

Effects of statherin on the biological properties of titanium metals subjected to different surface modification

The failure of dental implants is usually caused by bacteria infection, poor bioactivity and biocompatibility. It is a common phenomenon clinically. Statherin, a salivary protein, plays a crucial role of mediator between materials and cells/bacteria. However, the conformation of statherin might be changed by the implants in vivo. In this study, we investigated the effects of statherin on the bioactivities, antibacterial abilities and biocompatibilities of the titanium metals and the reaction mechanism. We found that the conformation of statherin was mainly influenced by surface composition, surface structure, surface roughness, surface hydrophilia and Ti-OH groups of materials. Statherin could decrease the cell biocompatibility of the titanium metals including pure titanium (PT), anodic oxidation (AO), sandblasting and etching (SLA) and plasma spraying hydroxyapatite (HA) coating in HGF cell experiments, regulate the bio-mineralization ability of HA coating in SBF, and enhance the antibacterial properties of PT and HA coating. This study revealed that surface properties of materials could change the conformation of statherin, which influenced the bioactivities, antibacterial properties and biocompatibilities of the materials in return.

Osteogenic differentiation of mesenchymal stem cells modulated by a chemically modified super-hydrophilic titanium implant surface

This study investigated the osteogenic functionality of multipotent mesenchymal stem cells (MSCs) modulated by a chemically modified super-hydrophilic titanium (Ti) bone implant surface to elucidate the biological mechanism underlying the bone healing capacity of this modified Ti surface. A microstructured Ti surface incorporating bioactive ions (in this study, phosphate (P) ions) was prepared by wet chemical treatment. The results showed that the hydrothermally obtained crystalline P-incorporated Ti surface (P surface) displayed long-term super-hydrophilicity (water contact angles <5°) during a 36-week observation period. The hydrophilic P surface enhanced early cellular functions and osteogenic differentiation of multipotent MSCs derived from mouse bone marrow and human adipose tissue. The expression of critical integrins affecting subsequent osteoblast function and osteoblast phenotype genes was notably upregulated in multipotent MSCs grown on the P surface compared with the commercially available grit-blasted microrough clinical oral implant surface. The P surface supported better cell spreading, focal adhesion and ALP activity of MSCs. These results indicate that a super-hydrophilic P-incorporated Ti surface accelerates implant bone healing by enhancing the early osteogenesis functions of multipotent MSCs.

Surface Modifications of the PMMA Optic of a Keratoprosthesis to Improve Biointegration

Biointegration of a keratoprosthesis (KPro) is critical for the mitigation of various long-term postoperative complications. Biointegration of a KPro occurs between the haptic skirt (corneal graft) and the central optic [poly(methyl methacrylate) (PMMA)]. Various studies have highlighted common problems associated with poor bonding and biointegration between these 2 incompatible biomaterials. Resolution of these issues could be achieved by surface modification of the inert material (PMMA). A calcium phosphate (CaP) coating deposited on dopamine-activated PMMA sheets by simulated body fluid incubation (d-CaP coating) was shown to improve adhesion to collagen type I (main component of corneal stroma) compared with untreated PMMA and PMMA with other surface modifications. However, the d-CaP coating could easily undergo delamination, thereby reducing its potential for modification of KPro optical cylinders. In addition, the coating did not resemble the Ca and P composition of hydroxyapatite (HAp). A novel dip-coating method that involves the creation of cavities to trap and immobilize HAp nanoparticles on the PMMA surface was introduced to address the problems associated with the d-CaP coating. The newly obtained coating offered high hydrophilicity, resistance to delamination, and preservation of the Ca and P composition of HAp. These advantages resulted in improved adhesion strength by more than 1 order of magnitude compared with untreated PMMA. With respect to biointegration, human corneal stromal fibroblasts were able to adhere strongly and proliferate on HAp-coated PMMA. Furthermore, the new coating technique could be extended to immobilization of HAp nanoparticles on 3-mm-diameter PMMA cylinders, bringing it closer to clinical application.

Nanoscale Surface Modifications of Orthopaedic Implants: State of the Art and Perspectives

Background:

Orthopaedic implants such as the total hip or total knee replacement are examples of surgical interventions with postoperative success rates of over 90% at 10 years. Implant failure is associated with wear particles and pain that requires surgical revision. Improving the implant - bone surface interface is a key area for biomaterial research for future clinical applications. Current implants utilise mechanical, chemical or physical methods for surface modification.

Methods:

A review of all literature concerning the nanoscale surface modification of orthopaedic implant technology was conducted.

Results:

The techniques and fabrication methods of nanoscale surface modifications are discussed in detail, including benefits and potential pitfalls. Future directions for nanoscale surface technology are explored.

Conclusion:

Future understanding of the role of mechanical cues and protein adsorption will enable greater flexibility in surface control. The aim of this review is to investigate and summarise the current concepts and future directions for controlling the implant nanosurface to improve interactions.

Fibronectin-Grafted Titanium Dental Implants: An In Vivo Study

Modification of the physiochemical properties of titanium surfaces using glow discharge plasma (GDP) and fibronectin coating has been shown to enhance the surface hydrophilicity, surface roughness, cell adhesion, migration, and proliferation. This in vivo study aimed to evaluate the bone integration efficacy of a biologically modified implant surface. Two different surface-modified implants (Ar-GDP and GDP-fib) were placed in the mandibular premolar area of six beagle dogs for 2–8 weeks. Three techniques [histologic evaluation, resonance frequency analysis (RFA), and microcomputed tomography (micro-CT) evaluation] were used to detect the implant stability and bone-implant contact. The implant stability quotient values of GDP-fib implants were significantly greater than the Ar-GDP implants at 2 and 4 weeks (P < 0.01). The bone volume/total volume ratio of GDP-fib implants was greater than the Ar-GDP implants in micro-CT evaluation. A high positive correlation was observed between RFA and micro-CT measurements. At 2 weeks, osteoblasts were seen to line the implant surface, and multinuclear osteoclasts could be seen on the surface of old parent bone. After 8 weeks, a majority of the space in the wound chamber appeared to be replaced by bone. Enhancement of the stability of biologically modified implants was proved by the results of RFA, micro-CT, and histological analysis. This enhanced stability may help fasten treatment and be clinically beneficial.

In Vitro Analysis of Fibronectin-Modified Titanium Surfaces

Background

Glow discharge plasma (GDP) procedure is an effective method for grafting various proteins, including albumin, type I collagen, and fibronectin, onto a titanium surface. However, the behavior and impact of titanium (Ti) surface modification is yet to be unraveled.

Purpose

The purpose of this study is to evaluate and analyze the biological properties of fibronectin-grafted Ti surfaces treated by GDP.

Materials and Methods

Grade II Ti discs were initially cleaned and autoclaved to obtain original specimens. Subsequently, the specimens were GDP treated and grafted with fibronectin to form Ar-GDP (Argon GDP treatment only) and GDP-fib (fibronectin coating following GDP treatment) groups. Blood coagulation test and MG-63 cell culture were performed to evaluate the biological effects on the specimen.

Results

There was no significant difference between Ar-GDP and GDP-fib groups in blood compatibility analysis. While in the MTT test, cellular proliferation was benefited from the presence of fibronectin coating. The numbers of cells on Ar-GDP and GDP-fib specimens were greater than those in the original specimens after 24 h of culturing.

Conclusions

GDP treatment combined with fibronectin grafting favored MG-63 cell adhesion, migration, and proliferation on titanium surfaces, which could be attributed to the improved surface properties.

Surface properties and early murine pre-osteoblastic cell responses of phosphoric acid modified titanium surface

AIMS

The present study investigated the surface properties and murine pre-osteoblast cell (MC3T3-E1) responses of phosphoric acid (H3PO4) treated commercially pure titanium.

METHODS

Titanium discs were treated with various concentration of H3PO4 (5%, 10%, and 20%; v/v) at 90 °C for 30 min. Surface properties were evaluated by profilometer, contact angle meter, and scanning electron microscopy (SEM) with energy dispersive X-rays. MC3T3-E1 attachment and spreading were evaluated by SEM and phalloidin immunohistochemistry staining.

RESULTS

Surface roughness and wettability were not statistically difference among all experimental and control groups. Phosphate and oxygen were detected on H3PO4 treated surfaces. At 20 min, cell attachment was significantly higher in 10% and 20% H3PO4 treated groups compared to the control. Cells exhibited orientated-cytoskeleton fibers on 20% H3PO4 modified titanium surface. Though, there was no difference in cell spreading stage among all treatment groups.

CONCLUSION

H3PO4 treatment on titanium may influence early cell response, particularly on attachment and spreading.

Surface modification of silicone tubes by functional carboxyl and amine, but not peroxide groups followed by collagen immobilization improves endothelial cell stability and functionality

Surface modification by functional groups promotes endothelialization in biohybrid artificial lungs, but whether it affects endothelial cell stability under fluid shear stress, and the release of anti-thrombotic factors, e.g. nitric oxide (NO), is unknown. We aimed to test whether surface-modified silicone tubes containing different functional groups, but similar wettability, improve collagen immobilization, endothelialization, cell stability and cell-mediated NO-release. Peroxide, carboxyl, and amine-groups increased collagen immobilization (41-76%). Only amine-groups increased ultimate tensile strength (2-fold). Peroxide and amine enhanced (1.5-2.5 fold), but carboxyl-groups decreased (2.9-fold) endothelial cell number after 6 d. After collagen immobilization, cell numbers were enhanced by all group-modifications (2.8-3.8 fold). Cells were stable under 1 h-fluid shear stress on amine, but not carboxyl or peroxide-group-modified silicone (>50% cell detachment), while cells were also stable on carboxyl-group-modified silicone with immobilized collagen. NO-release was increased by peroxide and amine (1.1-1.7 fold), but decreased by carboxyl-group-modification (9.8-fold), while it increased by all group-modifications after collagen immobilization (1.8-2.8 fold). Only the amine-group-modification changed silicone stiffness and transparency. In conclusion, silicone-surface modification of blood-contacting parts of artificial lungs with carboxyl and amine, but not peroxide-groups followed by collagen immobilization allows the formation of a stable functional endothelial cell layer. Amine-group-modification seems undesirable since it affected silicone's physical properties.

Cellular attachment and differentiation on titania nanotubes exposed to air- or nitrogen-based non-thermal atmospheric pressure plasma

The surface topography and chemistry of titanium implants are important factors for successful osseointegration. However, chemical modification of an implant surface using currently available methods often results in the disruption of topographical features and the loss of beneficial effects during the shelf life of the implant. Therefore, the aim of this study was to apply the recently highlighted portable non-thermal atmospheric pressure plasma jet (NTAPPJ), elicited from one of two different gas sources (nitrogen and air), to TiO₂ nanotube surfaces to further improve their osteogenic properties while preserving the topographical morphology. The surface treatment was performed before implantation to avoid age-related decay. The surface chemistry and morphology of the TiO₂ nanotube surfaces before and after the NTAPPJ treatment were determined using a field-emission scanning electron microscope, a surface profiler, a contact angle goniometer, and an X-ray photoelectron spectroscope. The MC3T3-E1 cell viability, attachment and morphology were confirmed using calcein AM and ethidium homodimer-1 staining, and analysis of gene expression using rat mesenchymal stem cells was performed using a real-time reverse-transcription polymerase chain reaction. The results indicated that both portable nitrogen- and air-based NTAPPJ could be used on TiO₂ nanotube surfaces easily and without topographical disruption. NTAPPJ resulted in a significant increase in the hydrophilicity of the surfaces as well as changes in the surface chemistry, which consequently increased the cell viability, attachment and differentiation compared with the control samples. The nitrogen-based NTAPPJ treatment group exhibited a higher osteogenic gene expression level than the air-based NTAPPJ treatment group due to the lower atomic percentage of carbon on the surface that resulted from treatment. It was concluded that NTAPPJ treatment of TiO₂ nanotube surfaces results in an increase in cellular activity. Furthermore, it was demonstrated that this treatment leads to improved osseointegration in vitro.

Surface analysis of titanium biological modification with glow discharge

BACKGROUND

Glow discharge plasma (GDP) technology has been used to graft various proteins to the titanium surface, including albumin, type I collagen, but without fibronectin.

PURPOSE

The aim of this study was to evaluate and analyze the physical properties of fibronectin-grafted titanium surfaces after GDP treatment.

MATERIALS AND METHODS

Grade II titanium discs after cleaning and autoclaving were considered as original specimens, thus divided into four groups. The groups were different upon two treatments (GDP only and fibronectin grafting after GDP) and two storage temperature (4°C and 25°C). The implant surface morphology was characterized by scanning electron microscopy (SEM), roughness measurement, and wettability evaluation. The concentration relationship of fibronectin was by fluorescein isothiocyanate (FITC) labeling.

RESULTS

SEM images showed that regular planar texture revealed on the surface of GDP-treated group, and irregular-folding protein was found on the fibronectin-grafted discs. Fibronectin-grafted groups had higher hydrophilicity and greater surface roughness than GDP-treated specimens. The storage temperature did not make obvious difference on the surface topography, wettability, and roughness. The number of fibronectin dots on the titanium surface labeling by FITC had positive relationship with the concentration of fibronectin solution used.

CONCLUSIONS

Biologically modified titanium surface is more hydrophilic and rougher than GDP-treated ones. GDP treatment combined with fibronectin grafting increased the surface hydrophilicity and surface roughness of titanium discs, which may attribute to the affinity of cell adhesion, migration, proliferation, and differentiation.

Increased bone apposition on a titanium oxide surface incorporating phosphate and strontium

OBJECTIVE

This study investigated the osteoconductivity of titanium (Ti) implants with a phosphate (P)- and strontium (Sr) ion-incorporated oxide surface, produced by hydrothermal treatment in the rabbit cortical and cancellous bone, for future biomedical applications as a biocompatible endosseous implant surface.

MATERIAL AND METHODS

The P- and Sr ion-incorporated Ti implants (P/Sr implant) were produced by hydrothermal treatment using a P- and Sr-containing solution. The surface characteristics were evaluated by scanning electron microscopy, thin-film X-ray diffractometry, X-ray photoelectron spectroscopy and optical profilometry. Forty screw implants (20 control and 20 experimental) were placed in the tibiae and femoral condyles of 10 New Zealand White rabbits. The surface in vivo osteoconductivity of the P/Sr implants was compared with micro-arc oxidized (TO) implants with surface calcium and P chemistry by histomorphometric analysis in the cortical and cancellous bone after 4 weeks of implantation.

RESULTS

The P/Sr implants showed moderately rough surface features and had lower R(a) values than the TO implants. Histologically, more direct bone apposition was observed on the surface of the P/Sr implants. The P/Sr implants displayed significantly higher bone-to-implant contact percentages compared with the TO implant in both the tibiae and the femoral condyles (P<0.01).

CONCLUSION

The results indicate that the hydrothermally produced P- and Sr ion-incorporated Ti oxide surface may be effective in improving implant osseointegration in both cortical and cancellous bone by increasing bone apposition, due to its surface properties combining micro-topography, P/Sr chemistry and superior wettability.

Improved pre-osteoblast response and mechanical compatibility of ultrafine-grained Ti-13Nb-13Zr alloy

OBJECTIVE

Metallic implantation materials having high yield strength, low elastic modulus, and non-cytotoxic alloying elements would be advantageous for the long-term stability of implants. This study assessed the surface and mechanical properties, and also in vitro osteoconductivity of ultrafine-grained (UFG) Ti-13Nb-13Zr alloy produced by dynamic globularization without any severe deformation for future biomedical applications as an endosseous implant material.

MATERIAL AND METHODS

The surface characteristics and mechanical properties were investigated by orientation image microscopy, contact angle measurements, optical profilometry, and uniaxial tension tests. Mouse calvaria-derived pre-osteoblastic cell (MC3T3-E1) attachment, spreading, viability, alkaline phosphatase (ALP) activity, and quantitative analysis of osteoblastic gene expression on UFG Ti-13Nb-13Zr alloy were compared with coarse-grained (CG) Ti-13Nb-13Zr and CG Ti-6Al-4V alloys.

RESULTS

Dynamic globularized Ti-13Nb-13Zr alloy has an ultrafine grain size (0.3 μm) and an excellent combination of yield strength and elastic modulus compared with CG alloys, which displayed significantly lower water contact angles compared with CG alloys (P<0.05). The UFG and CG Ti-13Nb-13Zr alloys displayed significantly increased cellular attachment compared with CG Ti-6Al-4V alloy (P<0.05). The UFG Ti-13Nb-13Zr supported better cell spreading and more numerous focal adhesions. ALP activity (P<0.05) and mRNA expressions of the osteoblast transcription factor genes (osterix, Runx2) and marker gene for osteoblast differentiation (osteocalcin) were markedly increased in cells grown on the UFG substrate compared with CG substrates at early incubation timepoints.

CONCLUSION

Enhanced pre-osteoblast response to UFG Ti-13Nb-13Zr substrate is attributable to the non-cytotoxic alloying elements and the submicron scale grain size contributes to the superior surface hydrophilicity and abundant grain boundaries favorable for cell behavior. These findings indicate that dynamic globularized UFG Ti-13Nb-13Zr alloy is promising for load-bearing endosseous implant material because of excellent mechanical and biological compatibilites.

Surface oxide net charge of a titanium alloy: comparison between effects of treatment with heat or radiofrequency plasma glow discharge

In the current study, we have compared the effects of heat and radiofrequency plasma glow discharge (RFGD) treatment of a Ti6Al4V alloy on the physico-chemical properties of the alloy's surface oxide. Titanium alloy (Ti6Al4V) disks were passivated alone, heated to 600 °C, or RFGD plasma treated in pure oxygen. RFGD treatment did not alter the roughness, topography, elemental composition or thickness of the alloy's surface oxide layer. In contrast, heat treatment altered oxide topography by creating a pattern of oxide elevations approximately 50-100 nm in diameter. These nanostructures exhibited a three-fold increase in roughness compared to untreated surfaces when RMS roughness was calculated after applying a spatial high-pass filter with a 200 nm-cutoff wavelength. Heat treatment also produced a surface enrichment in aluminum and vanadium oxides. Both RFGD and heat treatment produced similar increases in oxide wettability. Atomic force microscopy (AFM) measurements of metal surface oxide net charge signified by a long-range force of attraction to or repulsion from a (negatively charged) silicon nitride AFM probe were also obtained for all three experimental groups. Force measurements showed that the RFGD-treated Ti6Al4V samples demonstrated a higher net positive surface charge at pH values below 6 and a higher net negative surface charge at physiological pH (pH values between 7 and 8) compared to control and heat-treated samples. These findings suggest that RFGD treatment of metallic implant materials can be used to study the role of negatively charged surface oxide functional groups in protein bioactivity, osteogenic cell behavior and osseointegration independently of oxide topography.

Osteoconductivity of hydrophilic microstructured titanium implants with phosphate ion chemistry

This study investigated the surface characteristics and bone response of titanium implants produced by hydrothermal treatment using H(3)PO(4), and compared them with those of implants produced by commercial surface treatment methods - machining, acid etching, grit blasting, grit blasting/acid etching or spark anodization. The surface characteristics were evaluated by scanning electron microscopy, thin-film X-ray diffractometry, X-ray photoelectron spectroscopy, contact angle measurement and stylus profilometry. The osteoconductivity of experimental implants was evaluated by removal torque testing and histomorphometric analysis after 6 weeks of implantation in rabbit tibiae. Hydrothermal treatment with H(3)PO(4) and subsequent heat treatment produced a crystalline phosphate ion-incorporated oxide (titanium oxide phosphate hydrate, Ti(2)O(PO(4))(2)(H(2)O)(2); TiP) surface approximately 5microm in thickness, which had needle-like surface microstructures and superior wettability compared with the control surfaces. Significant increases in removal torque forces and bone-to-implant contact values were observed for TiP implants compared with those of the control implants (p<0.001). After thorough cleaning of the implants removed during the removal torque testing, a considerable quantity of attached bone was observed on the surfaces of the TiP implants.

Type I collagen grafting on titanium surfaces using low-temperature glow discharge

To improve the bioactivity of titanium surfaces, glow discharge was used to facilitate collagen grafting on titanium disks. Titanium test specimens were pre-treated by glow discharge fed with a mixture of argon and allylamine (AA) gases. Treated titanium disks were then grafted with type I collagen using glutaraldehyde (GA) as a crosslinking agent. The surfaces of collagen-grafted titanium disks were evaluated using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS). MG-63 osteoblast-like cells were cultured on the grafted titanium surfaces to examine the effect of collagen grafting in terms of cell morphology. Our results demonstrated that collagen component elements could be detected on the titanium surfaces. Morphology of the cells on the surfaces of collagen-grafted titanium disks indicated differentiation. These findings showed that type I collagen could be successfully grafted onto titanium surfaces using glow discharge technology, with enhanced biofunctionality demonstrated on osteoblastic cells.

Surface chemistry influences implant biocompatibility

Implantable medical devices are increasingly important in the practice of modern medicine. Unfortunately, almost all medical devices suffer to a different extent from adverse reactions, including inflammation, fibrosis, thrombosis and infection. To improve the safety and function of many types of medical implants, a major need exists for development of materials that evoked desired tissue responses. Because implant-associated protein adsorption and conformational changes thereafter have been shown to promote immune reactions, rigorous research efforts have been emphasized on the engineering of surface property (physical and chemical characteristics) to reduce protein adsorption and cell interactions and subsequently improve implant biocompatibility. This brief review is aimed to summarize the past efforts and our recent knowledge about the influence of surface functionality on protein:cell:biomaterial interactions. It is our belief that detailed understandings of bioactivity of surface functionality provide an easy, economic, and specific approach for the future rational design of implantable medical devices with desired tissue reactivity and, hopefully, wound healing capability.