Multifunctional magnetic particles for effective suppression of non-specific adsorption and coimmobilization of multiple enzymes by DNA directed immobilization

The overall stability and activity of immobilized enzyme systems have suffered from non-specific adsorption immobilization of enzymes at the surface of carriers through electrostatic and hydrophobic interactions. Elimination of these non-specific adsorptions of enzymes on the surface of carriers is critical for enzyme reactions. Herein, for the first time, we have prepared zwitterion-functionalized magnetic particles with amino, phosphonate, and thiol functional groups to coimmobilize glucose oxidase and horseradish peroxidase by DNA directed immobilization. The zwitterionic surface of the multifunctional magnetic particles could efficiently suppress non-specific adsorption of different kinds of enzymes, and the immobilized multienzyme catalyst without non-specifically adsorbed enzymes exhibited excellent enzymatic activity, stability, and reusability compared with those of free and nonspecifically adsorbed enzymes. The immobilized multienzymes maintained 87% of their enzymatic activity after two weeks of storage at 4 degrees C and 58% of their enzymatic activity after 90 min of thermal incubation at 60 degrees C. Furthermore, the immobilized multienzymes exhibited more than 87% enzymatic activity after reuse for 10 cycles. The apparent K-m and catalytic efficiency (K-cat/K-m) values of the immobilized multienzymes were 12.6 mM and 4.03 s(-1) mM(-1), respectively, which were 0.2- and 11.8-fold better than those of the free enzymes, indicating effective cascade efficiency and substrate affinity. The optimal ratio of GOx and HRP was 1:5, and the prepared immobilized enzymes could detect low concentrations of glucose (0.5 mu M) with excellent selectivity. Therefore, we believe that the strategy developed in this study can be widely applied in biotechnology, industrial catalysis, and biomedical engineering.