Immobilization of L-Asparaginase on Magnetic Nanoparticles for Cancer Treatment

In this presented work, magnetic poly(HEMA-GMA) nanoparticles were synthesized, characterized, and used for immobilization of an anti-leukemic enzyme L-asparaginase. The average particle size of the synthesized magnetic nanoparticles was found to be as 117.5 nm. L-asparaginase was successfully immobilized onto the synthesized magnetic nanoparticles, and attached amount of L-asparaginase was found to be as 66.43 mg/g nanoparticle. The effects of the medium pH, temperature, and substrate concentration on the L-asparaginase activity were also tested. Optimum pH of the free and immobilized L-asparaginase was found to be as 7.5 and 6.5, respectively. Optimum temperature of the free L-asparaginase was 45 °C, while optimum temperature was shifted to 55 °C after immobilization onto the magnetic nanoparticles. Also, k_cat value of free L-asparaginase (47,356 min^-1) was calculated to be higher than that of immobilized L-asparaginase (497 min^-1). Thermal stability of both asparaginase preparation was followed for 10 h, and at the end of the incubation time, free asparaginase almost lost its activity, while immobilized asparaginase protected 50% of its initial activity. Storage stabilities of free and immobilized asparaginase were also tested, and at the end of the 40 days storage, free asparaginase lost all of its activity, while immobilized asparaginase still showed 30% activity. Operational stability of immobilized asparaginase was tested for 8 successive usage, and immobilized asparaginase lost only 15% of its initial activity. In present study, activities of free and immobilized L-asparaginase were tested in artificial human serum medium, to foresee the in vivo efficiency, and it was demonstrated here that immobilized L-asparaginase protected its 74.74% of its initial activity in artificial serum medium.