Mucin Adsorption to Hydrophobic Surfaces

Abstract

The adsorption isotherm of bovine submaxillary gland mucin (BSM) onto a hydrophobic polystyrene surface was determined by using the solution depletion method, in which mucin concentrations were analyzed by amino acid analysis. Adsorption and desorption kinetics of BSM onto hydrophobic polystyrene surfaces were also studied by the solution depletion method, in which mucin solution concentrations were determined by measuring UV absorbance at a wavelength of 280 nm and by a BCA colorimetric assay with final calibration by amino acid analysis. From the adsorption isotherm, we found that the saturated surface concentration (Γmax) was 2.3 mg/m2, and the adsorption constant (K) was calculated as 0.099 (ml/mg). By using a Langmuir adsorption model and nonlinear fitting, kinetics parameters, kon and koff, were found to be 8.13×10−3 cm3 mg−1 s−1 and 5.67×10−4 s−1, respectively. The coating was found to be very stable with very limited desorption (less than 2%) from a long-term observation (28 h). The mucin coating layer thickness was investigated by several analytical techniques: flow field–flow–fractionation, photon correlation spectroscopy, scanning electron microscopy, and atomic force microscopy. The thickness was measured as 4–5 nm, from which a monolayer coating was concluded. Finally, the weight average molecular weight of purified bovine submaxillary gland mucin (BSM) was determined as 1.6×106 Da by using static light scattering.