Effect of solvent on the adsorption behavior and on the surface properties of Sterculia striata polysaccharide

Characterization of Sterculia striata polysaccharide (SSP) films adsorbed onto Si wafers from solutions prepared in ethyl methyl imidazolium acetate (EmimAc), water or NaOH 0.01 mol/L was systematically studied by means of ellipsometry, atomic force microscopy and contact angle measurements. SSP adsorbed from EmimAc onto Si wafer as homogeneous monolayers (∼0.5 nm thick), while from water or NaOH 0.01 mol/L SSP formed layers of ∼4.0 nm and ∼1.5 nm thick, respectively. Surface energy values found for SSP adsorbed from EmimAc or water were 68 ± 2 mJ/m2 and 65 ± 2 mJ/m2, respectively, whereas from NaOH it amounted to 57 ± 3 mJ/m2. The immobilization of lysozyme (LYS) onto SSP films was also investigated. The mean thickness of LYS (dLYS) immobilized onto SSP films adsorbed from each solvent tended to increase with the decrease of γSp and γStotal. However, the enzymatic activity of LYS molecules was higher when they were immobilized onto SSP films with higher γSp and γStotal values.