P53 detection by fluorescence lifetime on a hybrid fluorescein isothiocyanate gold nanosensor

P53 is a tumor suppressor used as marker for early cancer diagnosis and prognosis. We have studied constructs based on gold nanoparticles (NPs) decorated with specific anti-p53 antibodies and with a fluoresceine derivative, FITC. The interaction of gold surface plasmons with fluorophores bound within few nanometers from the surface, likely induces changes in the fluorophore excited state lifetime. Indeed we find that this parameter follows linearly the p53 concentration in solutions (in vitro conditions) up to 200-400 pM, depending on the size of the NP, with a 5 pM uncertainty. We have then evaluated the nanosensor specificity for p53 by testing it in-vitro against a number of globular proteins: bovine serum albumin (BSA), beta-lactoglobulin and lysozyme. The experiments indicate that, apart from BSA, which is notoriously a sticky protein, the other globular proteins do not compete for the p53 recognition by the p53 antibody. The titration of total cell extracts from p53+/+ or p53-/- cells with the p53antibody decorated gold NPs, indicates that the fluorophore lifetime is highly sensitive to the presence of p53 in the cell extracts. The nanocostrcut discussed here can then be used to detect the presence of p53 in total cell extracts and it will be therefore a valuable tool also for in vivo screening.