Core-shell type thermo-nanoparticles loaded with temozolomide combined with photothermal therapy in melanoma cells

A novel core-shell type thermo-nanoparticle (CSTNP) co-loaded with temozolomide (TMZ) and the fluorescein new indocyanine green dye IR820 (termed IT-CSTNPs) was designed and combined with a near-infrared (NIR) laser to realize its photothermal conversion. The IT-CSTNPs were prepared using a two-step synthesis method and comprised a thermosensitive shell and a biodegradable core. IR820 and TMZ were entrapped in the shell and the core, respectively. Dynamic light scattering results demonstrated that the average hydrodynamic size of the IT-CSTNPs was 196.4±3.1 nm with a ζ potential of −24.9±1.3 mV. The encapsulation efficiencies of TMZ and IR820 were 6.1 and 16.6%, respectively. Temperature increase curves under NIR laser irradiation indicated that the IT-CSTNPs exhibited the desired photothermal conversion efficiency. The in vitro drug release curves revealed a suitable release capability of IT-CSTNP under physiological conditions, whereas NIR laser irradiation accelerated the drug release. Inverted fluorescence microscopy and flow cytometry results revealed that the uptake of IT-CSTNPs by A375 melanoma cells occurred in a concentration-dependent manner. Confocal laser scanning microscopy results indicated that IT-CSTNPs entered tumour cells via endocytosis and were located in intercellular lysosomes. In summary, the present study explored the photothermal conversion capability, cellular uptake, and intracellular localization of IT-CSTNPs.