Asparaginase immobilized, magnetically guided, and bubble-propelled micromotors

In this study, tubular poly(3,4-ethylene dioxythiophene)-polypyrrole/Ni/ Pt (PEDOT-PPy-COOH/Ni/Pt) micromotors were prepared and modified with L-asparaginase, which is an anti-leukemic drug. Inner Pt layer of the micromotor decomposes H2O2 to produce O2 and allows the motor for self-propulsion, while the Ni segment enables remote control of the motors via a magnetic field. These tiny motors have self-propulsion capability and can be easily controlled by an external magnetic field. By immobilizing asparaginase, these enzyme-carrying motors demonstrated improved activity for the L-asparagine hydrolysis. At the end of the immobilization process, the enzyme showed improved thermal and pH stability, ascending protease resistance, longer storage time, and reusability. Kinetic parameters of free and immobilized asparaginase were also evaluated. It was shown that affinity for asparaginase towards its substrate did not change significantly upon immobilization. Besides Vmax value of immobilized L-asparaginase was found to be higher than that of free enzyme. Stability against protease trypsin was also tested and it was demonstrated that immobilized L-asparaginase was more stable for trypsin than free L-asparaginase. Finally, artificial serum experiments were also constructed to show the possible in vivo usage, and it was realized that L-asparaginase immobilized micromotor exhibited higher activity than free enzyme and control static micromotor experiments.