Osteoblast Adhesion on Poly(l-lactic Acid)/Polystyrene Demixed Thin Film Blends:  Effect of Nanotopography, Surface Chemistry, and Wettability

Abstract

Biomaterial surface characteristics are critical cues that regulate cell function. We produced a novel series of poly(l-lactic acid) (PLLA) and polystyrene demixed nanotopographic films to provide nonbiological cell-stimulating cues. The increase in PLLA weight fraction (phi) in blend solutions resulted in topography changes in spin-cast films from pit-dominant to island-dominant morphologies having nanoscale depth or height (3-29 nm). Lower molecular weight PLLA segregated to the top surface of demixed films, as observed by X-ray photoelectron spectroscopy and secondary ion mass spectroscopy (SIMS). For phi > or = 0.5, the topmost film layer was predominantly filled with PLLA (>96% by SIMS at 20-A depth). Nanotextured substrata stimulated osteoblastic cell adhesion to a greater degree than did flat PLLA (phi = 1), and this effect was more pronounced for nanoisland (phi = 0.7 and 0.9) relative to nanopit topographies (phi = 0.5). Demixed films having relatively lower water contact angles generally enhanced cell adhesion and spreading. Our results reveal that cell adhesion is affected by surface chemistry, topography, and wettability simultaneously and that nanotextured surfaces may be utilized in regulating cell adhesion.

Cell-material interaction

“…On a surface with grooves, osteoblastic cells expressed a higher RNA level of osteopontin and osteocalcin than on a flat surface [19]. Experiments using defined sizes of pits demonstrated that activity of alkaline phosphatase as a marker for osteogenic differentiation was more stimulated on 11 nm islands compared with 85 nm islands [20]. On the titanium nanotubes, tube diameters of 70 and 100 nm enhanced the expression of different osteogenic markers in mesenchymal stem cells compared with cells on a flat titanium surface [21].…”

Influence of substratum surface chemistry/energy and topography on the human fetal osteoblastic cell line hFOB 1.19: Phenotypic and genotypic responses observed in vitro☆

“…However, it was observed that contact angles decreased (water wettability increased) with either laser or mechanical treatment (presumably due to an increase in oxygen content on treated surfaces), indicating both topographic and surface-chemical modification. Lim et al [110,111] recently reported studies of hFOB adhesion and proliferation on polymer systems with varying surface texture, chemical composition, and wettability. As surfaces varied from smooth-to-textured with different topographic feature scale, hFOB adhesion was observed to exhibit statistically-significant differences in cell-substratum compatibility; although the full range in adhesion efficiency varied only about 20% among surfaces studied.…”

Simulation of the cytoskeletal response of cells on grooved or patterned substrates

“…For example, natural bone ECM (extracellular matrix) is a highly organized nano-composite consisting of, among other things, molecules of type-I collagen. Collagen type-I forms fibrils with an interfibrillar spacing of 68 nm and 35 nm depth [5] and a number of studies [6][7][8] have demonstrated that mimicking such roughness in vitro has beneficial effects on osteoblast proliferation. The role of the collagen fibrillar organization in controlling the arrangement of the actin cytoskeleton has sometimes been referred to as 'contact guidance' [9,10].…”