3-(aminomethyl)phenylboronic acid hydrochloride was purchased from Frontier Scientific, Inc. Sodium borohydride and acryloyl chloride were purchased from Aladdin Industrial Inc. Emodin (95%) was purchased from J&K Scientific Ltd. Dubelcoo’s Modified Eagle’s Medium (DMEM) with no glucose was purchased from Genom Pharmaceutical Co., Ltd. 4',6-diamidino-2-phenylindole (DAPI) was obtained from Sigma-Aldrich. All reagents were purchased from Beijing Chemical Works without any further purification. Ultrapure water was obtained from UNIQUE-R20 system (18.2 MΩ cm−1). Carbon-coated copper grids were purchased from Beijing Xinxing Braim Technology Co., Ltd.