Bone formation after 4 weeks around blood-plasma-modified titanium implants with varying surface topographies: an in vivo study

Biomimetic polyetheretherketone microcarriers with specific surface topography and self-secreted extracellular matrix for large-scale cell expansion

Reusable microcarriers with appropriate surface topography, mechanical properties, as well as biological modification through decellularization facilitating repeated cell culture are crucial for tissue engineering applications. Herein, we report the preparation of topological polyetheretherketone (PEEK) microcarriers via gas-driven and solvent exchange method followed by hydrothermal treatment at high temperature and pressure. After hydrothermal treated for 8 h, the resulting topological PEEK microcarriers exhibit walnut-like surface topography and good sphericity as well as uniform size distribution of 350.24 ± 19.44 µm. And the average width between ravine-patterned surface of PEEK microcarriers is 780 ± 290 nm. After repeated steam sterilization by autoclaving for three times, topological PEEK microcarriers show nearly identical results compared with previous ones indicating strong tolerance to high temperature and pressure. This is a unique advantage for large-scale cell expansion and clinical applications. Moreover, PEEK microcarriers with special topography possess higher protein adsorption efficiency. In addition, the reutilization and biofunctionalization with repeated decellularization of topological PEEK microcarriers show highly beneficial for cell adhesion and proliferation. Therefore, our study is of great importance for new generation microcarriers with micro-and nano-scale surface feature for a broad application prospect in tissue engineering.

Interaction of a tripeptide with titania surfaces: RGD adsorption on rutile TiO2(110) and model dental implant surfaces

The adsorption of peptides on metal oxides is an area of significant interest, both fundamentally and in a number of technologically important areas. These range from the integration of biomaterials in the body, to denaturation of protein therapeutics and the use of biomolecules and bioinspired materials in synthesis and stabilization of novel nanomaterials. Here we present a study of the tripeptide arginylglycylaspartic acid (RGD) on the surfaces of vacuum-prepared single crystalline TiO₂(110), pyrocatechol-capped TiO₂(110), and model SLA and SLActive dental implant samples. X-ray Photoelectron Spectroscopy and Scanning Tunneling Microscopy show that the RGD adsorption mode on the single crystal is consistent with bonding through the deprotonated carboxylate groups of the peptide to surface Ti atoms of the substrate. Despite the increased hydrophobicity of the pyrocatechol-capped TiO₂(110) surface RGD adsorption from solution increases following this surface treatment. RGD adsorption on SLA and SLActive surfaces shows that the SLActive surface has a greater uptake of RGD. The RGD uptake on the pyrocatechol capped single crystal and the model implant surfaces suggest that the ease with which surface contaminant hydrocarbons are removed from the surface has a greater influence on peptide adsorption than hydrophobicity/hydrophilicity of the surface.

Evaluation of biological properties of electron beam melted Ti6Al4V implant with biomimetic coating in vitro and in vivo

Background

High strength porous titanium implants are widely used for the reconstruction of craniofacial defects because of their similar mechanical properties to those of bone. The recent introduction of electron beam melting (EBM) technique allows a direct digitally enabled fabrication of patient specific porous titanium implants, whereas both their in vitro and in vivo biological performance need further investigation.

Methods

In the present study, we fabricated porous Ti6Al4V implants with controlled porous structure by EBM process, analyzed their mechanical properties, and conducted the surface modification with biomimetic approach. The bioactivities of EBM porous titanium in vitro and in vivo were evaluated between implants with and without biomimetic apatite coating.

Results

The physical property of the porous implants, containing the compressive strength being 163 - 286 MPa and the Young’s modulus being 14.5–38.5 GPa, is similar to cortical bone. The in vitro culture of osteoblasts on the porous Ti6Al4V implants has shown a favorable circumstance for cell attachment and proliferation as well as cell morphology and spreading, which were comparable with the implants coating with bone-like apatite. In vivo, histological analysis has obtained a rapid ingrowth of bone tissue from calvarial margins toward the center of bone defect in 12 weeks. We observed similar increasing rate of bone ingrowth and percentage of bone formation within coated and uncoated implants, all of which achieved a successful bridging of the defect in 12 weeks after the implantation.

Conclusions

This study demonstrated that the EBM porous Ti6Al4V implant not only reduced the stress-shielding but also exerted appropriate osteoconductive properties, as well as the apatite coated group. The results opened up the possibility of using purely porous titanium alloy scaffolds to reconstruct specific bone defects in the maxillofacial and orthopedic fields.

The effect of microrough surface treatment on miniscrews used as orthodontic anchors

OBJECTIVES

The aim of this study was to investigate the effects of two different microrough surface treatments on miniscrews with loading over different time periods in vivo.

MATERIAL AND METHODS

Twenty-four New Zealand white rabbits were selected. One hundred and forty-four miniscrews with a machined (MA), sandblasted and acid-etched (SLA) or sandblasted and alkaline-etched (SL/NaOH) surface were implanted into the tibia of the rabbits. Then, orthodontic forces with Ni-Ti coils were applied immediately to two of the three miniscrews in each tibia, with the center one serving as the control. After 2, 4, 8 and 12 weeks, the rabbits were sacrificed. The removal torque value (RTV) was tested and bone-to-implant contact (BIC) was examined.

RESULTS

In most groups, there were no differences between the RTV in the unloaded and loaded conditions at different time periods. In the loaded condition, the RTV of the SLA groups increased significantly after 4 weeks of healing. The RTV in the SL/NaOH groups increased after 8 weeks, and reached a significant difference with the SLA groups after 12 weeks. After 12 weeks, the BIC in the SLA and SL/NaOH groups was higher than in the MA groups. A regression test revealed a moderate correlation between the BIC and the RTV.

CONCLUSIONS

There were no differences between the loaded and unloaded conditions in most groups. The RTV and BIC increased with time. In the loaded condition, the RTV of the SLA surface increased earlier, at 4 weeks, while the SL/NAOH group showed the highest RTV after 8 weeks.

Osseointegration of oxidized and turned implants in circumferential bone defects with and without adjunctive therapies: an experimental study on BMP-2 and autogenous bone graft in the dog mandible

The aim of the study was to compare the integration and implant stability of turned and oxidized titanium implants when placed in experimental bone defects with autogenous bone graft, BMP-2 or without adjunctive therapy. Four defects were prepared on each side of the mandible of 12 mongrel dogs five months after tooth extractions. Implants with turned and oxidized surfaces were placed in the defects. The circumferential gaps were filled with either autogenous bone grafts, a BMP-allogeneic dog mixture in a thermoplastic carrier, carrier alone or left without any treatment (control). There were no statistically significant differences between control and treated sites, neither for turned nor for oxidized implants with regard to histomorphometric measurements in ground sections and to implant stability as measured with resonance frequency analysis (RFA) after 4 and 12 weeks of healing. However, oxidized implants showed a significantly higher stability after 4 weeks and a tendency (p < 0.1) of that after 12 weeks. Histomorphometry showed more bone contacts for oxidized than for turned implants. It is concluded that oxidized implants gain stability more rapidly and integrate with more bone contacts than implants with a turned surface when placed in bone defects.

Characterization of surface modified Ti-6Al-7Nb alloy

In the last years different types of surface modifications were developed with the aim of improving the osteointegration ability of titanium alloys. The chemical composition, crystallographic structure and morphology of a surface layer can be modified in order to obtain a better interaction between the implant, the cells and the organic fluids. The final goal is to obtain a more efficient bone growth also in critical clinical cases. In the present paper were reported several data about the characterization of the Ti-6Al-7Nb alloy treated by two innovative surface treatments. They consist of blasting, followed by a two step chemical etching and heat treatment performed in air or in vacuum. TEM, XRD and SEM investigations were performed in order to assess the structure and morphology of the modified surfaces. The surface chemical composition was investigated by XPS ad AES analyses. The ability to interact with physiological fluids was tested by immersion of the treated materials in an acellular simulated body fluid (SBF). Metal ion concentration analyses of the fluid and SEM observations of the samples were performed after different times of soaking. The mechanical characterization involved scratch and fatigue tests. The surface of treated samples shows chemical, structural and morphological modifications. The passivation pre-treatment has influence on the surface modification. The treated samples evidenced a quite low metal ion release and interact with SBF solution, showing a moderate bioactivity. A relevant decrease in fatigue strength was observed on modified samples.

Adsorption of cationic antibacterial on collagen-coated titanium implant devices

Two different cationic antimicrobial molecules, chlorhexidine (CH) and poly(hexamethylenebiguanide) (PH), were adsorbed from aqueous solution to titanium implant devices surface-modified by the covalent coupling of collagen on a polyanionic acrylic acid overlayer. Results show that more antimicrobial was adsorbed on surface modified implants as compared to control titanium devices. Moreover, the kinetic of release was affected by the interaction between the polyanionic overlayer and the cationic antimicrobial, leading to slower kinetic of release in the case of CH and stable adsorption in the case of polycationic PH . These data indicate that biochemically modified collagen coated surfaces could be endowed also by antimicrobial properties, in the spirit of present researches on multifunctional implant surfaces.

Surface engineering of titanium by collagen immobilization. Surface characterization and in vitro and in vivo studies

Collagen was covalently linked to the surface of Titanium (Ti) by a surface modification process involving deposition of a thin film from hydrocarbon plasma followed by acrylic acid grafting. The composition and properties of surface-modified Ti were investigated by a number of surface sensitive techniques: XPS, ATR-IR, atomic force microscopy and AFM force-separation curves. In vitro tests were performed to check samples cytotoxicity and the behavior of osteoblast-like SaOS-2 cells. In vivo experiments involved 12 weeks implants in rabbit muscle as general biocompatibility assessment and 1-month implants in rabbit bone to evaluate the effect of surface modification on osteointegration rate. Results of XPS measurements show how surface chemistry is affected throughout each step of the surface modification process, finally leading to a complete and homogeneous collagen overlayer on top of the Ti samples. AFM data clearly display the modification of the surface topography and of the surface area of the samples as a consequence of the grafting and coupling process. AFM force-distance curves show that the interfacial structure responds by shrinking or swelling to variations of ionic force of the surrounding aqueous environment, suggesting that the aqueous interface of the biochemically modified Ti samples has enhanced degrees of freedom as compared to the inorganic surface of plain Ti. As to biological evaluations, the biochemically modified Ti samples are safe in terms of cytotoxicity and in vivo biocompatibility assessment. SaOS-2 cells growth rate is lower on collagen modified surfaces, and no significant difference is detected in terms of alkaline phosphatase production as compared to control Ti. Importantly, implants in rabbit femur show a significant increase of bone growth and bone-to-implant contact in the case of the collagen modified samples, confirming that biochemical modifications of Ti surface can enhance the rate of bone healing as compared to plain Ti.