Enzyme-responsive turn-on nanoprobes for in situ fluorescence imaging and localized photothermal treatment of multidrug-resistant bacterial infections.

Sensitive diagnosis and elimination of multidrug-resistant bacterial infections at an early stage remain paramount challenges. Herein, we present a gelatinase-responsive turn-on nanoprobe forin situnear-infrared (NIR) fluorescence imaging and localized photothermal treatment (PTT) ofin vivomethicillin-resistantStaphylococcus aureus(MRSA) infections. The designed nanoprobe (named AuNS-Apt-Cy) is based on gold nanostars functionalized with MRSA-identifiable aptamer and gelatinase-responsive heptapeptide linker (CPLGVRG)-cypate complexes. The AuNS-Apt-Cy nanoprobe is non-fluorescent in aqueous environments due to the fluorescence resonance energy transfer between the gold nanostar core and cypate dye. We demonstrate that the AuNS-Apt-Cy nanoprobe can achieve MRSA targeting and accumulation as well as gelatinase (overexpressed in MRSA environments)-responsive turn-on NIR fluorescence due to the cleavage of the CPLGVRG linker and localizedin vitroPTTviaa mechanism involving bacterial cell wall and membrane disruption.In vivoexperiments show that the AuNS-Apt-Cy nanoprobe can enable rapid (1 h post-administration) andin situturn-on NIR fluorescence imaging with high sensitivity (10(5)colony-forming units) in diabetic wound and implanted bone plate mouse models. Remarkably, the AuNS-Apt-Cy nanoprobe can afford efficient localized PTT of diabetic wound and implanted bone plate-associated MRSA infections under the guidance of turn-on NIR fluorescence imaging, showing robust capability for early diagnosis and treatment ofin vivoMRSA infections. In addition, the nanoprobe exhibits negligible damage to surrounding healthy tissues during PTT due to its targeted accumulation in the MRSA-infected site, guaranteeing its excellentin vivobiocompatibility and solving the main bottlenecks that hinder the clinical application of PTT-based antibacterial strategies.