were purchased from Shenzhen Kangti Life Science (Shenzhen, China),
and E. coli SHuffle T7 express lysY from NEB31 (link),32 (link) was used for Fab expression of antidigoxin antibody. Plasmid extraction
and gel recovery kits were purchased from Vazyme Biotechnology Co.,
Ltd. (Nanjing, China). The restriction enzyme used for constructing
the recombinant plasmid was purchased from New England Biolabs (NEB;
Ipswich, MA, USA). The Ni-NTA Sefinose Resin for protein purification
was purchased from Changzhou Smart-Lifesciences Biotechnology Co.,
Ltd. (Changzhou, China), and Dig-BSA was purchased from Wuhan Yunclon
Technology Co., Ltd. (Wuhan, China). ATTO520-C2-maleimide was obtained
from ATTO-TEC (Siegen, Germany) and TAMRA-C5-maleimide was obtained
from Biotium (Hayward, CA, USA). Other reagents, if not specified,
were purchased from Sigma-Aldrich, Shanghai Sango Biotechnology, and
Beijing Solarbio Biotechnology Co. Ltd. (Beijing, China). Primers
used in this study were synthesized by Shanghai Sangong Biotechnology
Co., Ltd. (Shanghai China).