Wettability and surface free energy of bovine serum albumin films

Measurements of the contact angle for water, glycerol, formamide, ethylene glycol, and diiodomethane on polymethyl methacrylate covered by adsorptive bovine serum albumin (BSA) films were made. Adsorption was performed from s olutions in the concentration range 0-100 9/L. From the obtained contact an gles the Lifshitz-van der Waals components and the values of the electron-a cceptor and electron-donor parameters of the acid-base components of the fi lms were calculated for six triplets of liquids. The biggest changes in the BSA film structure occurred under a monolayer coverage (i.e., at BSA conce ntrations of <2.5 g/L). On the basis of the contact angles of glycerol, eth ylene glycol, and formamide it was concluded that the density of BSA polar groups was almost constant. The surface density of the hydrophobic part of the BSA film also seemed constant regardless of the concentration of the so lution from which the BSA adsorptive film was created. This conclusion coul d be drawn from the almost constant contact angle of diiodomethane.