Persistent Luminescence Nanoparticles For Photodynamic Antibacterial Therapy

The emergence of multidrug-resistant bacteria arising from the abuse of antibiotics urges researchers to develop advanced microbicides and antibacterial techniques.Antibiotic resistance is one of the global public health challenges now,but the development of new antibiotics is much slower than the emergence of resistant bacteria.Photodynamic therapy,which is widely used in tumor treatment,had been proposed to combat multidrug-resistant bacteria for its excellent characteristics of noninvasiveness and broad antibacterial spectrum.Photosensitizers(PSs)are excited by appropriate excitation sources to generate reactive oxygen species(ROS),which can damage a variety of biological molecules,such as proteins,lipids,and nucleic acids,and finally destroy microorganisms.However,most photodynamic antibacterial therapy requires the irradiation of light from specific equipment,and the short penetration depth in human tissue also limits the use of PDT.Hydrogels are promising wound dressing for their ability to maintain a moisture environment,three-dimensional cross-linked network,and fluid adsorb ability.Here we developed a sunlight-activated photodynamic hydrogel encapsulating PLNP and PS for the treatment of multidrug-resistant bacteria infected wound.We synthesized a persistent luminescence nanoparticle(PLNP)Zn3Ga2Ge2O10:0.5%,which could be irradiated by visible light and emit near-infrared light(NIR).The photosensitizer silicon phthalocyanine dichloride(SiPcCl2)was loaded on mesoporous SiO2 nanospheres(DMOS).NIR emited by PLNP excites SiPcCl2 and generates singlet oxygen(1O2),efficiently kills bacteria restricted in the range of ROS destruction.The hydrogel matrix is obtained by homogeneously mixing of C2/C3-dialdehyde-modifed rod-like cellulose nanocrystal(DACNC)suspension and carboxymethyl chitosan(CMC)solution.The amine group in CMC can react with the aldehyde group in DACNC to form a dynamic and reversible Schiff-base bond,which is easy to break and reform,enabling the selfhealing ability of the hydrogel.Upon being injected into wound bed,the hydrogel could mold into the irregular shape of the wound and capture the bacteria.The captured bacteria were killed by 1O2 generated from PLNP/SiPcCl2@DMOS photodynamic system.Significantly,by combining PLNP and photosensitizer,the hydrogel can achieve a synergistic bactericidal effect and reduce the risk of inflammation,resulting in rapid healing of infected wounds.In vitro and in vivo experiments showed that the hydrogel could effectively kill the drug-resistant bacteria MRSA,reduce the bacterial burden of the infected wound,and the dead bacteria were restricted in the hydrogel matrix,avoided the excessive inflammation.In conclusion,the current work proposed a new strategy for antibacterial photodynamic therapy.