Enhanced catalysis and enantioselective resolution of racemic naproxen methyl ester by lipase encapsulated within iron oxide nanoparticles coated with calix[8]arene valeric acid complexes

Abstract

In this study, two types of nanoparticles have been used as additives for the encapsulation of Candida rugosa lipase via the sol–gel method. In one case, the nanoparticles were covalently linked with a new synthesized calix[8]arene octa valeric acid derivative (C[8]-C₄-COOH) to produce new calix[8]arene-adorned magnetite nanoparticles (NP-C[8]-C₄-COOH), and then NP-C[8]-C₄-COOH was used as an additive in the sol–gel encapsulation process. In the other case, iron oxide nanoparticles were directly added into the sol–gel encapsulation process in order to interact electrostatically with both C[8]-C₄-COOH and Candida rugosa lipase. The catalytic activities and enantioselectivities of two novel encapsulated lipases (Enc-NP-C[8]-C₄-COOH and Enc-C[8]-C₄-COOH@Fe₃O₄) in the hydrolysis reaction of racemic naproxen methyl ester were evaluated. The results showed that the activity and enantioselectivity of the lipase were improved when the lipase was encapsulated in the presence of calixarene-based additives. Indeed, the encapsulated lipases have an excellent rate of enantioselectivity, with E = 371 and 265, respectively, as compared to the free enzyme (E = 137). The lipases encapsulated with C[8]-C₄-COOH and iron oxide nanoparticles (Enc-C[8]-C₄-COOH@Fe₃O₄) retained more than 86% of their initial activities after 5 repeated uses and 92% with NP-C[8]-C₄-COOH.