Evaluation of whole lysosomal enzymes directly immobilized on titanium (IV) oxide used in the development of antimicrobial agents

Lysosomal enzymes isolated from egg white were directly immobilized on titanium (IV) oxide (TiO2) particles using shaking methods (150 rpm, room temperature, 10 min), and the immobilization efficiency, activity, and stability of lysosomal enzymes immobilized on TiO2 were evaluated. Of the various mass ratios (w/w) of lysosomal enzymes to TiO2 tested, we found that 100% immobilization efficiency was observed at a ratio of 1:20 (enzymes:TiO2; w/w). Furthermore, the antimicrobial activities of the immobilized lysosomal enzymes were confirmed using viable cell counts against Escherichia coli. Our results showed that the antimicrobial activity of immobilized lysosomal enzymes is stable and can be maintained up to one month, but the antimicrobial activity of free enzymes without immobilization completely disappeared after five days in storage. In addition, enhanced immobilization efficiency was shown in TiO2 pretreated with a divalent, positively charged ion. Ca2+, and the antimicrobial activity for E. coli increased as a function of increasing ratio of immobilized enzymes. However, K+, a monovalent, positively charged ion, did not have any positive effect on immobilization or antimicrobial activity. Finally, we suggest that activity and stability of immobilized lysosomal enzymes can be maintained for a longer time than those properties of free lysosomal enzymes. (C) 2011 Elsevier Inc. All rights reserved.