Laser Heating of Gold Nanospheres Functionalized with Octreotide: In Vitro Effect on HeLa Cell Viability

Objective: The aim of this study was to assess the effect of laser heating a well-characterized gold nanoparticle (AuNP)-octreotide system on HeLa cell viability, to evaluate its potential as a suitable agent for plasmonic photothermal therapy. Background data: Octreotide is a synthetic peptide derivative of somatostatin with an effect on the survival of HeLa cells. Peptides bound to AuNPs are biocompatible and stable multimeric systems with target-specific molecular recognition. Methods: Octreotide was conjugated to AuNPs (similar to 20 nm) by spontaneous reaction with the thiol groups. The nanoconjugate was characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet visible spectroscopy (UV-Vis), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Irradiation experiments were conducted using an Nd:YAG laser pulsed for 5ns at 532nm with a repetition rate of 10Hz for up to 6min while delivering an average irradiance of 0.65W/cm(2). HeLa cells were incubated at 37 degrees C (1) with AuNP-citrate, (2) with AuNP-octreotide, or (3) without nanoparticles. Results: After laser irradiation, the presence of AuNP caused a significant increase in the temperature of the medium (48 degrees C vs. 38.3 degrees C of that without AuNP). The AuNP-octreotide system resulted in a significant decrease in cell viability of up to 6% compared with the AuNP-citrate system (15.8 +/- 2.1%). Two possible mechanisms could be at play: (1) octreotide alone exerts an effect on survival HeLa cells, or (2) the release of heat (similar to 727 degrees C per nanoparticle) in the membranes or cytoplasm of the cells caused by the interaction between AuNP-octreotide and somatostatin receptors reduced viability. Conclusions: The AuNP-octreotide system exhibited properties suitable for plasmonic photothermal therapy in the treatment of cervical cancer.