Nanoporous aluminum oxide membranes coated with atomic layer deposition-grown titanium dioxide for biomedical applications: An in vitro evaluation
The surface topographies of nanoporous anodic aluminum oxide (AAO) and titanium dioxide (TiO 2 ) membranes have been shown to modulate cell response in orthopedic and skin wound repair applications. In this study, we: (1) demonstrate an improved atomic layer deposition (ALD) method for coating the porous structures of 20, 100, and 200 nm pore diameter AAO with nanometer-thick layers of TiO 2 and (2) evaluate the effects of uncoated AAO and TiO 2 -coated AAO on cellular responses. The TiO 2 coatings were deposited on the AAO membranes without compromising the openings of the nanoscale pores. The 20 nm TiO 2 -coated membranes showed the highest amount of initial protein adsorption via the micro bicinchoninic acid (micro-BOA) assay; all of the TiO 2 -coated membranes showed slightly higher protein adsorption than the uncoated control materials. Cell viability, proliferation, and inflammatory responses on the TiO 2 -coated AAO membranes showed no adverse outcomes. For all of the tested surfaces, normal increases in proliferation (DNA content) of L929 fibroblasts were observed over from 4 hours to 72 hours. No increases in TNF-alpha production were seen in RAW 264.7 macrophages grown on TiO 2 -coated AAO membranes compared to uncoated AAO membranes and tissue culture polystyrene (TOPS) surfaces. Both uncoated AAO membranes and TiO 2 -coated AAO membranes showed no significant effects on cell growth and inflammatory responses. In conclusion, the results suggest that TiO 2 -coated AAO may serve as a reasonable prototype material for the development of nanostructured wound repair devices and orthopedic implants.