Enzyme activity of β-galactosidase immobilized in polyelectrolyte multilayers deposited on corona charged composite substrates

Abstract

Abstract In the present paper chitosan and xanthan polyelectrolyte multilayers (PEMs) deposited on composite multicomponent poly(D-lactic acid) (PDLA) / poly(ε-caprolactone) (PEC) substrates were investigated. The substrates' melting phenomena and degree of crystallinity were investigated by differential scanning calorimetry (DSC). Based on the melting behaviour it was suggested that PLA and PEC are not miscible at molecular level and no co-crystallization is realized. The substrates obtained were charged in a corona discharge. Positive or negative 5 kV voltages were applied to the corona electrode and 1 kV voltage of the same polarity - to the grid. The normalized surface potential dependences on the storage times were investigated. The results obtained show that the values of the normalized surface potential decay faster for negatively charged substrates. Layer-by-layer (LbL) technique was used for multilayer deposition on the substrates. PEMs with 8 layers were obtained. The enzyme of β-galactosidase was immobilized in the obtained polyelectrolyte multilayers. The enzyme activity of the immobilized enzyme was studied. The experimental results obtained show that the enzyme immobilization in positively charged films have higher activity compared to the negatively charged ones, independently of substrates type.