Described are compositions comprising amphiphilic polymer nanoparticles, such as DSPE-PEG, encapsulating a photostable agent with aggregation-induced emission (AIE) characteristic. The photostable AIE agents are preferably small organic molecules with tetraphenylethylene moieties. The nanoparticles are synthesized by a modified nanoprecipitation method and the size of the nanoparticles is controlled by varying the loading ratio, the solvent ratio and the tatio of hydrophilic to hydrophobic length of the polymer. The nanoparticles are surface modified with a conjugatable group for covalently linking to at least one targeting moiety, such as antibodies or affibodies to IgG, EGFR and Her2. Methods for immunostaining or imaging or detecting or tracking a live cell, such as cancer cells, using the nanoparticle compositions are described.
