| Abstract [eng] |
Multifunctional nanomaterials, capable of simultaneously performing diagnostic and therapeu- tic functions, have high potential for cancer diagnosis and treatment. Gold nanoclusters (AuNC) pos- sess favourable optical properties, biocompatibility and potential for application in photodynamic therapy. Additional labelling of AuNC with technetium-99m (99mTc) enables the application of these systems for multimodal SPECT/CT and fluorescence imaging. The aim of this study was to investigate the properties of 99mTc-labelled bovine serum albumin- coated gold nanoclusters (99mTc-BSA-AuNC) and to evaluate their potential for multifunctional theranostic applications. BSA-AuNC were synthesized, radiolabelled with 99mTc and the physico- chemical and photophysical properties of the obtained complex were investigated. It was determined that dialysis significantly improved the homogeneity and long-term stability of BSA-AuNC by reducing aggregation and fluorescence quenching without altering the BSA-AuNC core structure. 99mTc-BSA-AuNC radiochemical purity reached 96 %, while the specific activity was 245,5 MBq/mg. It was also established that the greatest impact on the complex properties was caused by SnCl2 modification. Absorption and fluorescence studies demonstrated that SnCl2 and 99mTc mod- ifications did not alter the BSA-AuNC core structure significantly, however, SnCl2 increased surface charge, promoted aggregation and enhanced fluorescence quenching. Fluorescence lifetime and quan- tum yield measurements revealed the appearance of additional non-radiative relaxation pathways in modified samples. Photobleaching studies showed that BSA-AuNC fluorescence quenching followed a biexponential decay model and exhibited partial fluorescence recovery after irradiation. Intermittent irradiation reduced the extent of irreversible photochemical damage and helped maintain greater flu- orescence stability. It was also determined that both BSAAuNC and 99mTc-BSA-AuNC efficiently generated reactive oxygen species, while 99mTc incorporation did not alter ROS generation mecha- nism significantly. Intermittent irradiation increased ROS generation while simultaneously helping to preserve fluorescence stability. The obtained results demonstrated that 99mTc-BSA-AuNC retain optical properties, exhibit suf- ficient photostability and efficient ROS generation. Therefore 99mTc-BSA-AuNC may be considered a promising multifunctional system for fluorescence and SPECT/CT imaging as well as photody- namic therapy. |
