Antibody-based nanoprobe for measurement of a fluorescent analyte in a single cell

We report here the application of an antibody-based nanoprobe for in situ m easurements of a single cell. The nanoprobe employs antibody-based receptor s targeted to a fluorescent analyte, benzopyrene tetrol (BPT), a metabolite of the carcinogen benzo[a]pyrene (BaP) and of the BaP-DNA adduct. Detectio n of BPT is of great biomedical interest, since this species can serve as a biomarker for monitoring DNA damage due to BaP exposure and for possible p recancer diagnosis. The measurements were performed on the rat liver epithe lial clone 9 cell line, which was used as the model cell system. Before mak ing measurements, the cells were treated with BPT. Nanoprobes were inserted into individual cells, incubated 5 min to allow antigen-antibody binding, and then removed for fluorescence detection. We determined a concentration of 9.6 +/- 0.2 x 10(-11) M for BPT in the individual cells investigated. Th e results demonstrate the possibility of in situ measurements inside a sing le cell using an antibody-based nanoprobe.