The Interactions Between Surface Topography Of Biomaterial And Protein And Cell

Protein adsorption on interface and cell responsive behaviors such as adhesion, spreading and proliferationon on biomaterial's surface plays a vital role in determining biomaterial's biocompatibility. As is known to us, proteins (from body fluid) adsorption on surface is the first response after biomaterials contacting with biological environment and this preadsorbed protein layer could further mediate subsequent cell behaviors. Since surface topography has evident effects on protein adsorption and cell responsive behaviors; investigating and elucidating the relationship among surface topography, protein and cell is significant for the designing of rational surface of biomaterials and the improvement of their biocompatibility.In this research, different surface topographical features were prepared on the substrates of poly(dimethylsiloxane) and bioceramic by micro/nano fabrication techniques. Further experiments were conducted to investigate the single effect of either chemical homogeneous or chemical heterogeneous surface topography as well as the synergic effect of surface topography and chemical composition on protein adsorption and cell responsive behaviors. Detail works were concluded as follows:1. Effect of chemical homogeneous surface topography on protein and cellDifferent surface topographical features (ordered hydroxyapatite (HA) nanorod arrays (Ceramic 1), disordered HA nanorod arrays (Ceramic 2) and HA nanosheet arrays (Ceramic 3)) were prepared on 45S5 bioactive glass-ceramic substrate through hydrothermal process. Protein adsorption (single protein adsorption and human plasma adsorption environment), protein electrophoresis (SDS-PAGE), Western-Blot and cell culture experiments were conducted to investigate the effect of surface topography on protein adsorption and cell adhesion. Results indicated that surfaces with micro/nano topography could enhance protein adsorption in both adsorption environment and higher specific surface area (Ceramic 1>Ceramic 2>Ceramic 3) meant a higher protein adsorption amount. Primary human bone marrow cells adhesion and spreading status on the surface of nanorod array samples were better than that on nanosheet array surface, and cell behaviors on ordered nanorod array sample were the best of all. It is concluded that surface topographical feature is the chief factor in mediating protein adsorption and cell responsive behaviors for chemical homogeneous surface topography.2. Effect of chemical heterogeneous patterned surface topography on proteinadsorption and cell behaviorAllyl-polyethylene glycol (PEG) was grafted onto poly(dimethylsiloxane) surface (PDMS-PEG) using hydrosilylation reaction. Then chemical heterogeneous patterned PDMS-PEG surface topography was fabricated by ultraviolet lithography (Xe2 excimer:172nm) with copper mesh as a photomask. Fluorescence labelled protein (Fg-FITC) adsorption results indicated that, as PEG in UV exposed domains was etched and PDMS substrate was revealed which could promote protein adsorption while reserved PEG in unexposed regions effectively resisted protein adsorption, fibrinogen (Fg) restrictively adsorbed on UV exposed domains and presented a patterned distribution in accord with the patterned substrate. Likewise, proteins in cell culture medium (including cell adhesive proteins, such as fibronectin (Fn) and vitronectin (Vn)) were confined in UV exposed domains, which promoted L929 cell adhesion and spreading, forming a regular cell pattern. Our results informed that chemical composition is the dominant issue in mediating protein adsorption and cell responsive behaviors for chemical heterogeneous surface topography.3. The synergic effect of surface topography and chemistry on protein and cellAkermanite bioceramics were immersed in simulated body fluid to obtain bone-like apatite layer coated samples (Akermanite-HAp). Scanning electron microscope (SEM) and X-ray diffraction (XRD) characterizations demonstrated that this apatite layer exhibited specific micro/nano topography with a chemical composition of hydroxyapatite. Investigation of protein adsorption and bone marrow mesenchymal stem cells (BMSC) proliferation were conducted with unmodified bioceramics (Akermanite) as control samples. Results showed that micro/nano-scale rods topography in apatite layer could enhance protein adsorption, which resulted in a higher protein adsorption amount on Akermanite-HAp than that on Akermanite. This preadsorbed protein layer (including cell adhesive proteins, such as Fn and Vn) could favor BMSC adhesion and differentiation on Akermanite-HAp. Besides, microstructure of bone-like apatite layer may increase the capacity of biological liquid adsorption into ceramic substrates, enhance ionic exchanging with body fluids and facilitate the transporting of oxygen and nutrients, which could permit the close contact of cells on surface and provide convenient sites for bone cell colonization. Furthermore, the newly-formed apatite layer could promote the adhesion and proliferation of osteoblast cells due to its bioactivity. This synergic effect of surface topography and chemical composition made Akermanite-HAp more favorable for cell adhesion and proliferation than that of Akermanite. These results suggested that surface topography and chemical composition were closely interconnected and complementary to each other, affecting protein adsorption and cell responsive behaviors on surface together.