Presented in this paper is a study of the biocompatibility of a hydrophilic alumina thin film and a hydrophobic variation deposited on standard glass cover slips using atomic layer deposition (ALD) techniques. The pure alumina ALD coating exhibits a water contact angle of 55 ¿ 5 degrees, due in part to a high concentration of ¿OH groups on the surface. The hydrophobic coating (produced by incorporating tridecafluoro-1,1,2,2-tetrahydro-octyl-methyl-bis(dimethylamino)silane) has a water contact angle of 108 ¿ 2 degrees. When compared with uncoated substrates, human coronary artery smooth muscle cells show normal cell proliferation on the ALD alumina and hydrophobic surface as observed by differential interference contrast microscopy. Using a colorimetric assay technique to assess the concentration of viable cells, the coatings appear to be biocompatible but as expected, with the hydrophobic coating showing reduced biocompatibility. From these results, atomic layer deposited alumina is considered biocompatible for short-term in vitro applications with additional control possible over cell growth by incorporating hydrophobic moieties. The advantages of ALD alumina in terms of its applicability to micro electro mechanical systems (MEMS) can be extended into bio-MEMS applications such as sensors and actuators or microfluidics. The ALD process is particularly useful since it provides conformal coatings that have been shown in the case of MEMS to prevent electrical shorting. Other advantages are that ALD deposited thin films can be patterned post-deposition and the final properties (such as electrical, surface energy and chemistry) tailored to a given application. While this study is only concerned with the measurement of the biocompatibility of ALD coated alumina and a hydrophobic variance, other studies are under way to study the effect of changes in the surface chemistry and electrical properties of the coatings with the aim of optimizing the biocompatibility of these coatings to enable them to be used for a range of Bio-MEMS applications.
Citation: J. Biomed. Mater. Res. B: Appl. Biomater.
Pub Type: Journals
atomic layer deposition, biocompatibility, Bio-MEMS, conformal coatings, hydrophilicity, hydrophobicity, vascular smooth muscle cells