Enhanced L-asparaginase stability through immobilization in supramolecular nanogels of PEG-grafted poly HPMA with bis(α-cyclodextrin)

Abstract

This paper presents the fabrication of a biocompatible supramolecular nanogel containing immobilized L-asparaginase (ASNase), an anti-leukemic therapeutic agent, to improve the enzyme’s physicochemical stability. The ASNase-conjugated random copolymer of N-(2-Hydroxypropyl)methacrylamide (HPMA) and polyethylene glycol (PEG) acrylate was simply combined with inter-molecularly crosslinked α-cyclodextrin (bisCD) in physiologic condition to prepare inclusion complex nanogels. The introduction of bisCD led to the formation of discrete, homogenous, and spherical nanogels with a mean projected diameter of 148 nm for the best formulation of ASNase bioconjugate in terms of polymer succination ratio and polymer:protein ratio. The Michaelis-Menten constant (Km) for immobilized ASNase was 1.6-fold lower than the free form, indicating a higher affinity for the asparagine substrate. The ASNase immobilization significantly extended the pH stability range. In addition, when compared to the free enzyme, ASNase-bisCD nanogel exhibited superior stability against elevated temperature, freeze-thaw cycles, and proteolysis. Overall, the immobilization of ASNase in bisCD nanogels yields a novel stabilized preparation with promising biomedical applications.