Aqueous self-assembly and surface-functionalized nanodots for live cell imaging and labeling

Nanoparticles have enormous potential for bioimaging and biolabeling applications, in which conventional organically based fluorescent labels degrade and fail to provide long-term tracking. Thus, the development of approaches to make fluorescent probes water soluble and label cells efficient is desirable for most biological applications. Here, we report on the fabrication and characterization of self-assembled nanodots (SANDs) from 3-aminopropyltriethoxysilane (APTES) as a probe for protein labeling. We show that fluorescent SAND probes exhibit both bright photoluminescence and biocompatibility in an aqueous environment. Selective in vitro imaging using protein and carbohydrate labeling of hepatoma cell lines are demonstrated using biocompatible SANDs conjugated with avidin and galactose, respectively. Cytotoxicity tests show that conjugated SAND particles have negligible effects on cell proliferation. Unlike other synthetic systems that require multistep treatments to achieve robust surface functionalization and to develop flexible bioconjugation strategies, our results demonstrate the versatility of this one-step SAND fabrication method for creating multicolor fluorescent probes with the tailored functionalities, efficient emission, as well as excellent biocompatibility, required for broad biological use.