Near-infrared light triggered upconversion nanocomposites with multifunction of enhanced antimicrobial photodynamic therapy and gas therapy for inflammation regulation.

Antibacterial photodynamic therapy (aPDT) is highly effective in killing bacteria, while the problem of hypoxia and limited light penetration in deep tissue has not been properly solved. In addition, few aPDT works take into account the regulation of inflammation, which is an important regulatory process after antimicrobial therapy and the final purpose of treatment. In this work, to address the above isssues, we have designed a multi-functional composite UCNPs-Ce6-Mn(CO)Br@Silane (referred to as UCM@Si), which consists of several key components: Up-conversion nanoparticles (UCNPs: NaErF:Tm@NaYF:Yb), Chlorin e6 (Ce6) and Manganese pentacarbonyl bromide (Mn(CO)Br). When exposed to near-infrared (NIR) light (980 nm), the UCNPs can emit strong red light at 655 nm which further trigger the aPDT of Ce6. The generated reactive oxygen (ROS) subsequently break the metal carbonyl bond of Mn(CO)Br, leading to the production of carbon monoxide (CO) molecules as well as manganese ions (Mn), which further decomposes hydrogen peroxide (HO) in the microenvironment to oxygen (O). Therefore, this simple nanocomposite not only provides substantial self-oxygen replenishment for enhanced aPDT, but also facilitates effective inflammation regulation via CO across a wide range of deep infections. This approach leverages the unique properties of these materials to combat bacterial infections by simultaneously killing bacteria, regulating inflammation, and enhancing the oxygen levels in the affected microenvironment. This O and CO gas based aPDT treatment system offers a promising approach to comprehensively address microbial-induced infectious diseases, particularly deep infections, holding the potential clinical applications.