Santiago Medina, Pricilla

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    The effects of the nanotopography of titanium surfaces on osteoblast adhesion and differentiation
    (2013) Santiago Medina, Pricilla; Diffoot Carlo, Nanette; College of Arts and Sciences - Sciences; Navas Almeyda, Vivian; Sundaram, Paul A.; Alfaro, Monica; Department of Biology; Rodríguez Carías, Abner
    The principal problem in current orthopedic implants is their loosening due to poor osseointegration. Many efforts have been made to modify the surface composition and topography of titanium alloy implants to attain improved osseointegration. A good combination of porous and thick oxide films on titanium alloy substrates have been obtained with the use of the micro arc oxidation (MAO) procedure. This technique incorporates calcium and phosphorus forming calcium phosphate, a chemical commonly applied to metallic implants as a coating material for fast and firm fixation. The first step in determining the biocompatibility of such modified surfaces is to study cell attachment and proliferation on these substrates. Hence, in the work described herein, the adhesion of human osteoblasts to micro arc oxidized Ti-6Al-4V and γ-TiAl surfaces was examined in vitro. hFOB 1.19 cells were seeded on micro arc oxidized γ- TiAl (MAOGTi) and Ti-6Al-4V (MAOTiV) disks, respectively. Cell adhesion on γ-TiAl and Ti- 6Al-4V thermally oxidized at both 500oC and 800oC were also evaluated. The human fetal osteoblast cell line (hFOB 1.19) consists of immortalized cells that can be subcultured for a long period of time (up to eight months). In addition, they have the ability to differentiate into mature osteoblasts. For comparison purposes, cell morphology and differentiation was observed on thermally oxidized Ti-6Al-4V and γTiAl alloys at 500°C (GTi5, TiV5) and at 800°C (GTi8, TiV8). These alloys were incubated with human fetal osteoblast cell line (hFOB 1.19) at different incubation time points (3 days at 33.5°C and 7 days at 39.5°C) and analyzed by Scanning Electron Microscopy (SEM) and the Alkaline Phosphatase Assay (ALP). Glass coverslips, positive control, were also incubated at these time points.Scanning Electron Microscopy (SEM) and an Alkaline Phosphatase Assay were used to evaluate cell adhesion and cell differentiation on the different surfaces. The Alkaline Phosphatase Assay, at 10 days post seeding, showed significant differences in cell differentiation demonstrating that the roughest surface with treatment and time of exposure of 225mA and 4 minutes was more favorable and Ti-6Al-4V and γ-TiAl alloys without treatment were less favorable, with p values < 0.05 between micro arc oxidized and thermally oxidized coated alloys, Ti-6Al-4V and γ-TiAl, respectively. All SEM images showed that cells adhered on all but TiV8 surfaces, 10 days post seeding. In addition, these highly porous, uniform and thick coatings produced on the surface of both alloys were studied and compared using Atomic Force Microscopy (AFM). A significant relationship was found between the coating characteristics and the voltage-current conditions applied during the micro arc oxidation process. This demonstrated that the surface exposed to the (225mA and 4 minutes) most amperage and time of exposure was the roughest. The SEM analysis demonstrated that hFOB 1.19 cells were able to attach and proliferate on both micro arc oxidized and thermally oxidized γ-TiAl surfaces in a similar manner; however, ALP analysis demonstrated that cell differentiation was significantly higher in the γ-TiAl micro arc oxidized alloys in comparison to Ti-6Al-4V alloys.