Study on interaction between gold nanorod and bovine serum albumin

In this work we present the results of the study on the interactions between bovine serum albumin (BSA) and gold nanorod monitored by fluorescence spectroscopy of the intrinsic tryptophans at pH 7.4. Gold nanorod–albumin solution gave an emission spectrum in the wavelength range 300–440 nm with emission maxima at 351 nm when excited at 280 nm. The magnitude of fluorescence intensity increased with increasing nanorod concentration. The interaction of BSA with these nanorods shows an enhancement of fluorescence with binding constants of 0.13 × 108 M−1 and 0.27 × 108 M−1 for nanorod of aspect ratio 3.0 and 8.0, respectively. On the other hand, the titration of BSA with 14 nm gold nanosphere shows a strong quenching of fluorescence with a binding constant of 1.7 × 108 M−1. The fluorescence enhancement is probably due to a direct contact of gold nanorod {1 1 1} face with the bovine serum albumin as determined by DLS, UV–vis and Zeta potential measurements. These results suggest that the technique of fluorescence enhancement can be used successfully to study the nanorod–albumin interaction.