Effects of selected emulsion components; (bovine serum albumin, lipase and glutaraldehyde), on the surface properties of Polydimethylsiloxane.

Abstract

The purpose of this study was to investigate the effects of bovine serum albumin (BSA), lipase and glutaraldehyde on the surface of polydimethylsiloxane (PDMS). PDMS blocks of 15 by 15mm were fabricated using replica micromolding. To determine the effects of BSA, clean PDMS blocks were immersed in 20, 50 and 100mg/ml BSA, respectively. For the effect of lipase, the concentration was 20, 50 and 70mg/ml. To determine the effect of glutaraldehyde, 5, 10, 20, 30, 40 and 50% concentration was used. All the PDMS blocks were immersed for 10, 20 and 30 minutes. The water contact angle was measured on all the PDMS surfaces, including a clean surface as a control. This analysis was done using a drop shape analyzer, DSA 100 machine. The PDMS surfaces were further analyzed by Fourier Transform InfraRed (FTIR spectroscopy), using a Pelkin-Elmer FT-IR spectrometer. PDMS blocks which were pre-immersed in 5% glutaraldehyde and then in BSA and lipase solutions, respectively, were also added for FTIR analysis. The water surface tension was measured for both BSA and lipase and interfacial tension was measured for glutaraldehyde, using the DSA 100. The results indicated that the water contact angle decreases after the PDMS surface has been immersed in all the solutions prepared. FTIR analysis showed new peaks on the PDMS surface immersed in BSA, and in BSA and glutaraldehyde; however, there were no peaks formed on the PDMS surface immersed in lipase and washed, in glutaraldehyde, and in lipase and glutaraldehyde together. Surface tension measurements showed that BSA and lipase decreases the surface tension of water. Interfacial tension measurements also showed that glutaraldehyde decreases the interfacial tension of oil. BSA, lipase and glutaraldehyde therefore decrease the hydrophobicity of the PDMS surface. BSA adsorbs on the PDMS surface and the adsorption is irreversible. The adsorption of lipase on the PDMS surface is reversible. Glutaraldehyde does not adsorb on the surface or the adsorption is not detectable. BSA, lipase and glutaraldehyde all have surface active properties. The CMC value of BSA is 50mg/ml and of lipase is 15mg/ml.