Antibody-Modified, Zwitterionic, and Fluorescent Polymeric Nanoparticles for Targeted Cellular Imaging

Bright and specific fluorescent probes are key to the performance of fluorescent bioimaging and biosensing techniques, ranging from lateral flow assays to image-guided surgery. Fluorescently labeled antibodies are of particular interest as probes due to their high specificity. However, their labeling with molecular fluorophores is limited with respect to brightness due to self-quenching and a decrease of affinity. This can be overcome by using antibody-modified nanoparticles, yet in this case, the effect of NP size and surface chemistry has to be considered in detail. Here, we propose a streamlined assembly of bright antibody-modified stealth fluorescent nanoparticles. Our approach is based on the nanoprecipitation of zwitterion- and azide-bearing polymers together with a large amount of dye salts, followed by the coupling of the obtained nanoparticles to Trastuzumab through click chemistry. The size of the resulting nanoparticles was tuned between 15 and 30 nm. Labeling of HER2-expressing cells could be achieved, showing a clear increase in labeling intensity for antibody-modified nanoparticles compared to antibodies labeled with molecular dyes. Interestingly, the most efficient labeling was achieved with the smaller nanoparticles. The specificity of the labeling of cells with high versus low expression of HER2 through our antibody nanoparticles was shown directly in co-culture using multicolor imaging. The ease of assembly together with the high brightness and specificity makes the obtained nanoparticles attractive for the development of assays based on single-molecule detection and imaging.