Conditioning Film-Induced Modification of Substratum Physicochemistry—Analysis by Contact Angles

Abstract

Stainless steel, germanium, polypropylene, and perspex were coated with films derived from marine and freshwater samples and from solutions of model compounds (bovine serum albumin, lactoglobulin, myoglobin, and humic acids). Contact angles of water, formamide, and diiodomethane measured on clean and conditioned interfaces were used to calculate physicochemical surface properties by the Lifshitz–van der Waals acid–base approach, including interfacial parameters for the interaction of carbon- and nitrogen-limited cells of the Gram-negative bacterium SW8 with these surfaces. The interaction parameter φ was evaluated as an indicator of the chemical constitution of conditioned interfaces. Surface free energy and its Lifshitz–van der Waals component were modified by 59 and 66% of conditioning films, respectively, but these alterations were relatively small. The acid–base components of surface free energy and the free energy of adhesion of bacteria to substrata were, however, substantially affected by the coatings. Most films did not modify the interaction parameter φ. Those which did increased the φ of polymeric surfaces and decreased it on stainless steel. The solid–water interfacial tension (γSW), which was larger than the solid–bacterium interfacial tension (γSB) on 97% of surfaces, was reduced by 61% of the conditioning films and increased by 14% of the coatings. The γSBof nitrogen-limited cells was smaller than the γSBof carbon-limited organisms on 92% of substrata. Values of γSBof carbon- and nitrogen-limited organisms were negative on 17 and 69% of the surfaces, respectively. More coatings modified the γSBof nitrogen-limited cells (97%) than the γSBof carbon-limited SW8 (72%). The free energy of adhesion was negative on 31% of interfaces but similar for both phenotypes. It was altered by 91% of conditioning films, which generally reduced its value.