DNA‐Mediated, On‐Membrane Sequential Assembly of Conjugated Polymer Nanoparticles for Sensitive Detection of Cell Surface Markers

Abstract Flow cytometry can provide detailed information about protein expression on cell surface and is, therefore, widely used in clinical testing. However, owing to the limited sensitivity of fluorescence signals, detection of low‐expression cell surface markers is challenging. The present report describes a DNA‐mediated, on‐membrane assembly of conjugated polymer nanoparticles (Pdots) that amplifies fluorescence signal from surface markers for sensitive detection via flow cytometry. Single‐stranded DNA (ssDNA)‐conjugated antibodies are first bound to cell surface markers, from which ssDNA‐modified Pdots are sequentially assembled using DNA hybridization. The use of DNA as a linker enables the distance‐controlled assembly of Pdots to prevent fluorescence quenching, whereas their on‐membrane sequential assembly allows amplification of the fluorescence signal without reducing binding ability of antibodies. Thus, two rounds of Pdot assembly achieve 31‐fold amplification of the fluorescence signal from CD19 on Nalm‐6 cells, which is 125‐fold brighter than that obtained using the conventional fluorescent dye‐based method. Moreover, the sequential assembly of 22 nm Pdots shows 24‐fold higher fluorescence than one‐step labeling with 81 nm Pdots, suggesting the advantage of the sequential assembly strategy in avoiding steric hindrance. The proposed method is expected to contribute to the sensitive detection of low‐expression surface markers for early and accurate diagnosis.