[Prokaryotic expression of prostate-specific membrane antigen (PSMA) nanoantibody gene and screening of natural phage nanoantibody library].

Objective To screen nanobodies against prostate specific membrane antigen (PSMA). Methods Based on the naive phage display library, three rounds of screening were performed targeting the PSMA antigen, and positive clones were identified by ELISA and sequencing was performed. The positive cloned gene sequence was inserted into the pET28a prokaryotic expression vector and transformed into E.coli BL21. The expression of the recombinant protein was induced by IPTG and purified using Ni column, with the purified product verified by SDS-PAGE. Results Four PSMA nanobodies VHH1, VHH2, VHH3 and VHH4 were obtained by screening. The VHH1 failed to obtain protein expression, while the VHH2, VHH3 and VHH4 proteins were expressed. The purity of anti-PSMA nanobodies showed high and relative molecular mass (M) of about 17 000. Conclusion The sequence of anti-PSMA nanobody was successfully obtained by screening the naive phage nanobody library and were subjected to prokaryotic expression and purified.