Figure 1.

Characterization of the nanocarrier platform. (a) R-GFP fluorescence was partially quenched when bound to HGN; however, fluorescence increased upon exposure to laser excitation power of 1.5 W/cm² for 30 s. Imidazole competes with histidine for the linker chelator groups on the HGN, chemically releasing the protein from the nanocarrier, resulting in maximum dequenching. R-GFP-HGN UV–vis absorbance decreased after laser exposure, indicative of changes to the core structure. (b) Quantification of R-GFP release from HGN after laser treatment at various laser powers and exposure times. R-GFP remaining on the HGN after laser exposure is released by imidazole competition and presented as the “retained” value, which is greater for lower laser powers and exposure times. Error bars represent the standard deviation. The expected sum of laser followed by imidazole is ∼100%. Reabsorption of R-GFP onto freshly exposed gold surfaces and partial protein denaturation may explain the incomplete release under certain conditions, as nonspecifically bound proteins would not be susceptible to imidazole competition. (c) R-GFP-HGN was internalized into PPC-1 cells, which were then treated with various combinations of laser power and exposure time. Decreased viability was observed in cells exposed to 2.3 W/cm² fluence for 60 s (p < 0.05, *), well above the optimal release conditions. No loss in cell viability was observed with laser in the absence of HGN.