Development of a cell-nanoparticle system with high nanoparticle
uptake is essential to photothermal conversion. Herein, the
cellular uptake of the BSA-coated sAuNRs and BSA-coated bAuNRs
is evaluated by real-time fluorescence microscopy as shown in
Fig. 3. In the direct observation, FITC, a versatile fluorescent agent, is
used to label the BSA-coated AuNRs with green fluorescence. The
emission spectra (lex ¼ 490 nm) of the BSA-coated AuNRs after FITC
labeling with different concentrations are shown in Fig. S2. It can be
observed that the fluorescence intensity of the FITC is proportional
to the concentration of the AuNRs. In contrast, the bare AuNRs
(without BSA coating) after FITC labeling showno FITC fluorescence
(see Fig. S2). Although AuNRs are well-known fluorescence
quenchers, the results demonstrate that attachment of FITC
through the BSA spacer produces obvious fluorescence.