Influence of coating properties on the adhesion of proteins to atmospheric plasma modified surfaces

Protein adhesion is of key importance for the biocompatibility of medical devices. This study
investigates the adsorption of protein, bovine serum albumin (BSA), onto both uncoated silicon
wafers and nanometre thick fluorosiloxane coated wafers. A plasma polymerised coating was
deposited from a mixture of tetramethylcyclotetrasiloxane (TC) and
perfluorooctyltriethoxysilane (FS) (1:1 by vol. ratio). The liquid precursor mixture was nebulised
into an atmospheric plasma jet formed using the PlasmaStreamTM system. The adsorption of
protein on the plasma polymerised coatings was evaluated under dynamic flow conditions
using a spectroscopic ellipsometry technique. The rate of protein adsorption onto coated and
uncoated silicon wafer substrates was monitored over time after the BSA solution was
introduced into a flow cell. These measurements indicated the adsorption of a 2 nm thick BSA
protein layer on the uncoated silicon wafers. The ellipsometry thickness measurements of
adsorbed protein on silicon wafer were confirmed using quartz crystal microbalance
measurements (QCM). The BSA adsorption studies were then repeated with a fluorosiloxane
coating. These coatings exhibited a highly textured surface morphology with low surface energy
and a high water contact angle of 156 . The ellipsometry flow cell tests with BSA indicated
almost no adsorption of protein onto the superhydrophobic fluorosiloxane coating. This study
demonstrated the ability of ellipsometry to measure protein adsorption under dynamic flow
2
conditions and the influence of surface properties on protein adsorption.