Fabrication and characterization of hydroxyapatite-coated polystyrene disks for use in osteoprogenitor cell culture.

A simple method is reported for fabricating polystyrene disk inserts coated with biomimetic carbonated hydroxyapatite (cHA) to be used for culturing osteoprogenitor cells or other stem cells. Roughened disks cut from tissue-culture polystyrene (TCPS) were coated in simulated body fluid with 5 x normal physiologic ionic concentrations (SBFx5) by a 2-step, 2-day method. The coatings were rigorously characterized by various methods and assessed in cell culture. An adherent, nearly 10 mm thick, relatively uniform layer of single-phase cHA was formed in two days. MC3T3-E1 and mouse calvaria-derived osteoprogenitor cells (pCOBs) were cultured on the cHA for various time points. Despite less initial attachment of both cell types to the cHA, proliferation rates on cHA were similar to that on TCPS. Two-fold greater cell attachment (P < 0.05) of the MC3T3-E1 cells was observed relative to the pCOBs, on both the TCPS and the cHA. Importantly, the coatings were relatively smooth, without the extensive agglomerates observed in other studies and remained adherent and morphologically unchanged after 21 days of culture. This technique can be used to rapidly produce high-quality cHA-coated TCPS disks for cell-culture studies.

Polypeptide-catalyzed silica for dental applications.

Polypeptides such as polylysine have been shown to catalyze the condensation and direct the structure of silica from precursor solutions under ambient conditions. Several of the reaction parameters have been shown to mediate this activity. Specifically, mechanical perturbation seems to play a role in the formation of hierarchical structures. Most studies have been conducted in solution, but biomedical and particularly dental applications will likely require control of biosilicified coatings, films or particle formation on surfaces. Tetraethylorthosilicate was reacted with polylysine and then spin coated onto a surface. The process parameters catalyst structure, pH, buffer: ethanol ratio and percentage of cocatalyst polyethyleneimine were varied to determine their effects on the formed silica. The chemical nature and morphology of the silica were investigated with FTIR and SEM, respectively and reaction rates were monitored with a colorimetric assay. Our results show that these process parameters had only minor effects on composition, but the catalyst conformation influenced the degree of hydration while the pH, choice of solvent and cocatalyst strongly influenced morphology. We also found that perturbation from spin coating significantly influences the silicification dynamics. The ability to catalyze nano- to micron-sized mineral with different morphologies using polypeptides could have numerous dental applications including, sealing of dentin tubules, in situ reinforcement of resin interfaces or preparation of implant surfaces.

Surface analysis and biocorrosion properties of nanostructured surface sol-gel coatings on Ti6Al4V titanium alloy implants.

Surfaces of biocompatible alloys used as implants play a significant role in their osseointegration. Surface sol-gel processing (SSP), a variant of the bulk sol-gel technique, is a relatively new process to prepare bioreactive nanostructured titanium oxide for thin film coatings. The surface topography, roughness, and composition of sol-gel processed Ti6Al4V titanium alloy coatings was investigated by atomic force microscopy (AFM) and X-ray electron spectroscopy (XPS). This was correlated with corrosion properties, adhesive strength, and bioreactivity in simulated body fluids (SBF). Electroimpedance spectroscopy (EIS) and polarization studies indicated similar advantageous corrosion properties between sol-gel coated and uncoated Ti6Al4V, which was attributed to the stable TiO2 composition, topography, and adhesive strength of the sol-gel coating. In addition, inductive coupled plasma (ICP) and scanning electron microscopy with energy dispersive spectrometry (SEM-EDS) analysis of substrates immersed in SBF revealed higher deposition of calcium and phosphate and low release rates of alloying elements from the sol-gel modified alloys. The equivalent corrosion behavior and the definite increase in nucleation of calcium apatite indicate the potential of the sol-gel coating for enhanced bioimplant applications.

Osteoblast adhesion and matrix mineralization on sol-gel-derived titanium oxide.

The biological events occurring at the bone-implant interface are influenced by the topography, chemistry and wettability of the implant surface. The surface properties of titanium alloy prepared by either surface sol-gel processing (SSP), or by passivation with nitric acid, were investigated systematically using X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy and contact angle metrology. The bioreactivity of the substrates was assessed by evaluating MC3T3-E1 osteoblastic cell adhesion, as well as by in vitro formation of mineralized matrix. Surface analysis of sol-gel-derived oxide on Ti6Al4V substrates showed a predominantly titanium dioxide (TiO(2)) composition with abundant hydroxyl groups. The surface was highly wettable, rougher and more porous compared to that of the passivated substrate. Significantly more cells adhered to the sol-gel-coated surface, as compared with passivated surfaces, at 1 and 24h following cell seeding, and a markedly greater number of mineralized nodules were observed on sol-gel coatings. Collectively our results show that the surface properties of titanium alloy can be modified by SSP to enhance the bioreactivity of this biomaterial.