Bovine serum albumin interactions with metallic nanoparticles

Metallic nanoparticles are considered as potential adjuvants for a growing list of pharmaceutical treatments. For such a purpose the nanoparticles would need to be introduced to tissues close to the pharmacological target. Frequently this involves an intravenous or intra‐arterial administration of the combination of the nanoparticles and the pharmacological agent. When foreign surfaces, however, come in contact with blood components they become coated with a variety of plasma proteins, including albumin. This protein binding could potentially alter the properties of the nanoparticles employed. In this study we explored the interactions of bovine serum albumin (BSA) with gold nanoparticles as a model of protein‐nanoparticle interactions. BSA (1μM final) was characterized spectrophotometrically while buffered by 20mM HEPES, 150mM NaCl, 2mM CaCl 2 , pH 7.40. It was characterized by a major intrinsic fluorescence excitation peak between 250nm to 310nm, and an emission peak from 290nm to 410nm. We examined the effects of nanoparticles on the intrinsic BSA fluorescence spectra. We observed a concentration dependent quenching effect on intrinsic BSA fluorescence with increasing gold nanoparticle levels. The BSA emission peaks were integrated from 310nm to 390nm and were found to be substantially quenched by increasing nanoparticle levels. Since this type of energy transfer is exquisitely dependent on the proximity of the emitting and quenching components it implies that the fluorescent protein (BSA) and the quenching surface (gold nanoparticles) had to be bound to one another.