Adsorption behavior of oxidized galactomannans onto amino-terminated surfaces and their interaction with bovine serum albumin

Galactomannans extracted from Cassia fastuosa (CF) and Leucaena leucocephala (LL) seeds were purified and oxidized with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) to form the uronic acid-containing polysaccharides CFOX with a degree of oxidation (DO) of 0.22 and LLOX with DO of 0.66, respectively. The adsorption behavior of CFOX and LLOX onto amino-terminated surfaces was studied by means of ellipsometric measurements. The influence of pH and ionic strength on the adsorption was investigated. A strong dependence of pH on the adsorbed amount of CFOX and LLOX was observed. At pH 4, there was a maximum in the adsorbed amount caused by strong electrostatic attraction between the substrate and the oxidized galactomannans. On the other hand, no ionic strength effect on the adsorption of CFOX and LLOX was observed. The immobilization of bovine serum albumin onto LLOX and CFOX was studied as a function of pH. LLOX proved to be a more attractive substrate for BSA than CFOX, indicating that the favorable interactions between the carboxylate groups and the BSA segments have driven the adsorption process. At the isoelectric point of BSA a maximum in the adsorbed amount was found for both surfaces.