Bioconjugation of IgG Secondary Antibodies to Polymer Dots for Multicolor Subcellular Imaging

Multiplexed subcellular imaging has attracted widespread attention in biology and medicine. Because the fluorescence brightness and stability of organic dyes and fluorescent proteins are not sufficient, the development of fluorescent nanoparticles is of broad interest. Semiconducting polymer dots (Pdots) exhibit prominent luminescence properties. However, the Pdot-IgG bioconjugates are largely unexplored in biological imaging. Here, we developed multicolor Pdots covalently conjugated with IgG secondary antibodies for specific labeling of different subcellular structures. By comparing the two functional polymers, we found that the functionalization by poly(styrene-co-maleic anhydride) (PSMA) could reliably produce Pdot-IgG conjugates for specific subcellular labeling, while those by a comb-like amphiphilic polymer show strong nonspecific binding in an intracellular environment. In addition, we minimize nonspecific adsorption of the Pdot bioconjugates by using bovine serum albumin and poly(ethylene glycol) as passivation agents, respectively. We finally demonstrate that the Pdot-PSMA-IgGs hold great potential in multiplexed visualization of the subcellular structure.