Detection of CD22 Expression in Living Cancer Cells by Semiconductor Quantum Dots.

CD22 is an important drug target for the treatment of autoimmune diseases and B cell-derived malignancies. In this study, N-acetylneuraminic acid functionalized quantum dots nanoconjugate was synthesized and used for targeting and fluorescence imaging of CD22 on living cells. The nanoprobe was prepared by conjugating N-acetylneuraminic acid (NANA) on the carboxyl groups modified CdSe/ZnS quantum dots (COOH-QDs) via NHS/EDC mediated esterification. The NANA-QDs nanoprobe showed excellent size distribution, very low cytotoxicity and super fluorescent properties for biological imaging applications. The specificity of NANA-QDs nanoparticles for CD22 on living cancer cells was validated by cellular uptake inhibition assays, colocalization of the immunofluorescence staining with both anti-CD22 antibody and NANA-QDs nanoparticles. Furthermore, CD22 mediated endocytosis of NANA-QDs nanoparticles was investigated by cellular internalization kinetics in Daudi cells at multiple time points. The newly developed NANA-QDs based assay was successfully used to determine the expression levels of CD22 on various cancer cells, which were highly consistent with the results determined by immunofluorescence staining assay and western blotting. All these findings demonstrated that NANA-QDs nanoparticles system was a practical fluorescent nanoprobe for bioimaging of CD22, which held great promise in a wide variety of biomedical applications of CD22 related studies.