Effect of support surface chemistry on lipase adsorption and activity

The functional group controlled surfaces (S-F, functional groups including NH2, COOH, OH, CH3 and CF3) were fabricated by mixing polystyrene (PS) respectively with functional group-ended polystyrenes (PS-Fs). These surfaces were used as model supports to investigate the effect of surface chemistry on lipase adsorption and activity. The order of the amount of adsorbed lipase on the surface with similar functional group density was S-CH3 > PS > S-CF3 > S-NH2 > S-COOH > S-OH. It could be found that on the surface containing hydrophobic group, lipase could take more side-on orientations with larger spreading, while on the surface containing hydrophilic group, lipase could take more end-on orientations with smaller spreading. Lipase immobilized on the surface containing OH showed the highest activity. The adsorption of substrates and products on the functional group controlled surfaces was also measured. The surface containing NH2 showed a higher activity which might be ascribed to the fact that there was a high substrate concentration on the lipase/support interface. The order of the activity retention of the immobilized lipase was S-OH > S-NH2 > S-COOH > S-CF3 > S-CH3 > PS.