A novel His-tag-binding aptamer for recombinant protein detection and T cell-based immunotherapy.

Screening novel aptamers for recombinant protein detection is of great significance in industrial mass production of antibody drugs. In addition, construction of structurally stable bispecific circular aptamers (bc-apts) may provide a tumor-targeted treatment strategy by simultaneously binding two different cell types. In this study, we obtained a high-affinity hexahistidine tag (His-tag)-binding aptamer 20S and explored its application in recombinant protein detection and T cell-based immunotherapy. We developed a new molecular beacon (MB) 20S-MB to detect His-tagged proteins in vitro and in vivo with high sensitivity and specificity, and the results showed high consistency with the enzyme-linked immunosorbent assay (ELISA). Moreover, we constructed two kinds of bc-apts by cyclizing 20S or another His-tag-binding aptamer, 6H5-MU, with Sgc8, which specifically recognizes protein tyrosine kinase 7 (PTK7) on tumor cells. After forming a complex with His-tagged OKT3, an anti-CD3 antibody for T cell activation, we utilized these aptamer-antibody complexes (ap-ab complex) to enhance cytotoxicity of T cells by linking T cells and target cells together, and 20S-sgc8 exhibited antitumor efficacy superior to that of 6H5-sgc8. In conclusion, we screened a novel His-tag-binding aptamer and used it to construct a new type of MB for rapid detection of recombinant proteins, as well as establish a feasible approach for T cell-based immunotherapy.