Nano-Biocatalysts of Cyt c@ZIF-8/GO Composites with High Recyclability via a de Novo Approach

Qianqian Zhu, Wei Zhuang, Yong Chen, Zhanke Wang, Byron Villacorta Hernandez, Jinglan Wu, Pengpeng Yang, Dong Liu, Chenjie Zhu, Hanjie Ying, Zhonghua Zhu

In order to improve the stability and recyclability of enzymes immobilized on metal organic framewoks (MOFs), graphene oxide (GO) with surface oxygen-rich functional groups was selected to form ZIF-8/GO nanocomposites with the zeolitic imidazolate framework (ZIF-8) for Cytochrome c (Cyt c) immobilization. It was found that functional groups on GO surface were involved in the growth of ZIF-8 without affecting the crystal structure, but their particle sizes reduced to about 200 nm. The storage stability and resistance toward to organic solvents of Cyt c were obviously improved after immobilization on the ZIF-8/GO nanocomposite. On one hand, compared to Cyt c@ZIF-8 and Cyt c@GO with 30% and 60% protein leakage, the Cyt c@ZIF-8/GO displayed little protein leakage after 60 h of storage. On the other hand, the Cyt c@ZIF-8/GO retained a residual activity of approximately 100% after being stored in ethanol and acetone for 2 h, while the free enzyme, Cyt c@ZIF-8 and Cyt c@GO retained only about 10%, 50% and 40%, respectively. In addition, the Cyt c@ZIF-8/GO nanocomposites can be utilized up to 4 cycles with virtually no loss of activity, and may be further applied on H2O2 biosensing systems. The synergistic effect between MOFs and GO in ZIF-8/GO nanocomposites provides infinite possibilities as immobilized enzyme carriers.