Highly sensitive detection of CTLA-4-positive T-cell subgroups based on nanobody and fluorescent carbon quantum dots

The detection of cytotoxic T-lymphocyte antigen-4-positive (CTLA-4⁺) T-cell subgroups in peripheral blood samples and tumor tissues is of great significance. In the present study, a rapid, succinct and efficient method was designed for the detection of CTLA-4⁺ human T cells using a CTLA-4-specific nanobody-fluorescent carbon quantum dots complex (QDs-Nb36). QDs-Nb36 was used for high sensitivity detection of CTLA-4⁺ T cells by flow cytometry or immumofluorescent staining. The present study demonstrated that the novel technique was more specific and effective in the detection of CTLA-4⁺ T-cell ratio in the peripheral blood and tumor tissues compared with a traditional monoclonal antibody approach. Furthermore, no significant toxicity was identified in vitro and in vivo, thus suggesting that the method may have broad applications for the detection of certain lowly expressed targets.