Effect of polymers on the retention and aging of enzyme on bioactive papers

The effect of polymer on the retention and the thermal stability of bioactive enzymatic papers was measured using a colorimetric technique quantifying the intensity of the enzyme–substrate product complex. Alkaline phosphatase (ALP) was used as model enzyme. Three water soluble polymers: a cationic polyacrylamide (CPAM), an anionic polyacrylic acid (PAA) and a neutral polyethylene oxide (PEO) were selected as retention aids. The model polymers increased the enzyme adsorption on paper by around 50% and prevented enzyme desorption upon rewetting of the papers. The thermal deactivation of ALP retained on paper with polymers follows two sequential first order reactions. This was also observed for ALP simply physisorbed on paper. The retention aid polymers instigated a rapid initial deactivation which significantly decreased the longevity of the enzymatic papers. This suggests some enzyme–polymer interaction probably affecting the enzyme tertiary structure. A deactivation mathematical model predicting the enzymatic paper half-life was developed.