Development of biocompatible PAMAM 'dendrizyme' to maintain catalytic activity in biological complex medium

The dendrimer based synthetic enzyme mimic, so-called 'dendrizyme', has been of great interest since the early days of dendrimers. However, there is a lack of an effective way to obtain a natural enzyme mimic showing both good biocompatibility and high preservation of catalytic activity in biological complex medium simultaneously. Here we report a novel approach - the synthesis of a generation five dendrimer of poly(amido amine) (PAMAM) incorporating hemin through capping with carboxybetaine acrylamide (CBAA), which could function as peroxidase. Results showed that the nanocapsules of hemin using CBAA-modified PAMAM dendrimers (CBAA-H-PAMAM) exhibited excellent biocompatibility and full preservation of catalytic activity in bovine serum albumin (BSA) solution, compared with free hemin. Results indicated that the ultra-thin shell of zwitterionic CBAA groups reduced nonspecific interaction with proteins while it did not cause any obvious rise in hindrance to mass transfer. Furthermore, the synthetic peroxidase mimic (CBAA-H-PAMAM) exhibited remarkable temperature endurance as compared with natural proteins. Taken together, our results indicate that protein surface mimicking through CBAA attachment might open a new route for synthetic enzymes in biomedical related applications.