MoS2/Au–Ag@PEG nanosheets with plasmonic coupling effect-enhanced NIR-II photothermal therapy and silver ion release for combined treatment of MRSA infection

Abstract

The evolution of bacterial resistance to antibiotics has resulted in a global public health crisis, necessitating the development of novel antibiotic-independent antimicrobial strategies. In this study, MoS₂/Au–Ag@PEG nanosheets (MAAP NSs) were prepared via sequential deposition of gold and silver nanoparticles onto MoS₂ nanosheets (MoS₂ NSs), which were then used for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections. Compared to MoS₂ NSs, MAAP NSs exhibit a significantly enhanced near-infrared region II (NIR-II) absorption at 1064 nm (a 7.51-fold increase), and the photothermal conversion efficiency improves by 50.7%, reaching 19.9%. Theoretical simulations reveal that the plasmonic coupling effect between adjacent Au–Ag nanoparticles (Au–Ag NPs) on the surface of MAAP NSs leads to the formation of hot spots and significantly enhances NIR-II light absorption, thereby improving the NIR-II photothermal performance. Moreover, the release of silver ions (Ag⁺) can be effectively controlled by NIR laser irradiation. In vitro experimental results show that, upon NIR-II laser (1064 nm) exposure, MAAP NSs can effectively eliminate established MRSA biofilms with a bacterial inactivation efficiency of 99.992%. Notably, benefiting from the superior tissue penetration of the NIR-II laser, MAAP NSs exhibit potent therapeutic efficacy against both superficial wound infection and subcutaneous implant-associated MRSA biofilm infection in mouse models. In vivo results demonstrate that, under NIR-II laser stimulation, MAAP NSs can not only effectively kill 99.95% of MRSA in infected wounds and accelerate wound healing, but also remove MRSA biofilms from subcutaneous implant surfaces, achieving a 99.92% bacterial reduction. This work presents a novel strategy for designing NIR-II responsive antibacterial nanoagents based on plasmonic coupling effects in two-dimensional (2D) nanosheets and provides a promising solution for the treatment of antibiotic-resistant bacterial infections.