Gold nanorods@mSiO2 with a smart polymer shell responsive to heat/near-infrared light for chemo-photothermal therapy

Abstract

Novel composite nanoparticles based on poly(N-isopropylacrylamide-co-N-hydroxymethyl acrylamide) (P(NIPAM-co-NHMA)) layer coated gold nanorod@mesoporous silica (GNR@mSiO₂) has been successfully synthesized by precipitation polymerization. The composite nanoparticles exhibited a thermo/near-infrared (NIR) light sensitivity. The volume phase transition temperature (VPTT) could be precisely regulated by the content of NHMA in monomers and an excellent photothermal conversion effect was expressed due to the surface plasmon resonance of gold nanorods in the composite nanoparticles. Doxorubicin hydrochloride (DOX) was applied as a model drug and the drug storage/release behavior was investigated. The results demonstrated that DOX could be effectively loaded into the composite nanoparticles with 21% loading capacity. The cumulative release of DOX-loaded composite nanoparticles was temperature dependent and the release rate was significantly enhanced above the VPTT. Therefore, the composite nanoparticles applied as a drug delivery system could reduce the side effect of DOX to normal tissues as only a small fraction of DOX was released from the composite nanoparticles at 37 °C. In addition, the DOX-loaded composite nanoparticles demonstrated a synergistic effect, the therapeutic efficacy was improved significantly by the combination of photothermal therapy and traditional chemotherapy with low composite nanoparticle concentration and short laser irradiation time in an in vitro study.