Structure Regulation And Biomedical Applications Of Photo-responsive Noble Metal Nanozymes

Phototherapy is a therapeutic method that uses phototherapy agents to convert light energy into heat or chemical energy to achieve therapeutic purposes.According to the form of energy conversion,it can be divided into photothermal therapy and photodynamic therapy.Compared with traditional therapy methods,phototherapy has been applied to the treatment of a variety of diseases,including superficial cancer,microbial infections,and vascular diseases,due to its better tissue penetration depth,safety,and non-invasiveness.The most important component in phototherapy is the photothermal agents/photosensitizer.Inorganic nanomaterials are widely used as photothermal agents or photosensitizers in the field of phototherapy due to their unique optical properties,tunable structural compositions,and good stability.The types of inorganic nanomaterials are abundant,encompassing metal-based,transition metal oxygen/sulfur/nitride,carbon-based,and inorganic composites.In biomedical applications,noble metal-based nanomaterials have unique advantages in terms of safety and photoresponsiveness compared to other types of nanomaterials.However,there is still a lack of research on how to improve the reactivity of noble metal-based materials and clarify the mechanism of photo-controlled catalytic reactions.Therefore,it is of great significance to develop highly active photoresponsive noble metal-based nanomaterials and explore their photocontrol mechanisms to expand the biomedical applications of inorganic noble metal nanomaterials.In this paper,based on noble metal palladium nanosheets（Pd NSs）,the surface structure of Pd NSs was designed by lattice strain and single-atom construction,and the noble metal nanozymes with excellent enzyme-like activity and photoresponsiveness were developed.Its anti-tumor and antibacterial activities were explored.The main research contents of this paper are as follows:Firstly,based on the problem of chemical inertness of Pd NSs due to the exposure of their inactive crystal planes,this paper induces the surface remodeling of Pd NSs through strain engineering,so as to endow them with peroxidase-like and catalase-like catalytic activity and photodynamic properties.Density functional theory（DFT）calculations show that with the increase of strain strength,the surface energy and binding energy of Pd NSs to oxygen molecules increases,while the reaction energy of O-O bond cleavage in H₂O₂decreases,enabling the surface-reconstructed Pd NSs exhibit excellent chemical reactivity.Finally,through the construction of light-enhanced enzyme-catalyzed and phototherapy synergistic treatment system based on Pd NSs,efficient treatment of mouse breast cancer was achieved.To further improve the photo-responsiveness and enzyme-like catalytic activity of Pd NSs,a universal preparation method for single-atom alloy nanozymes was developed based on the electrochemical displacement strategy at room temperature.Through the introduction of single-atom Pt,the electronic structure of Pd NSs was optimized,which significantly enhanced its enzyme-like catalytic activity and photodynamic performance.Compared with Pd NSs,the affinity of Pt₁Pd single-atom alloy nanozyme（SAAzyme）for substrates is greatly improved,and the catalytic activity of its oxidase-like enzymes is increased by about 25 times.The results of cellular experiments showed that the IC₅₀value of Pt₁Pd SAAzyme was as low as 4.39 ug m L^-1under the stimulation of near-infrared light.In in vivo experiments,a 100%tumor suppression rate was achieved.In addition,due to the activated surface structure,Pt₁Pd SAAzyme exhibits biodegradable properties in physiological media,which is conducive to avoiding the systemic toxicity caused by the accumulation of nanomaterials in vivo.Finally,based on the unique physical structure,enzyme-like catalytic performance and photoactivity of Pd NSs,this paper used six common multidrug-resistant bacteria in clinical practice as research models to explore the potential of strained Pd NSs as broad-spectrum antimicrobial agents.The experimental results show that the layered structure of Pd NSs can play a role similar to that of nanoknives in the absence of light stimulation,promote the release of bacterial contents,and eventually lead to the death of bacteria.In vitro experiments revealed its physical bactericidal mechanism as a nanoknife and its light-enhanced broad-spectrum antimicrobial effect.Under near-infrared light stimulation,the photothermal and photodynamic properties of palladium nanosheets achieved a bacteriostatic rate of more than 99%against multidrug-resistant bacteria through synergistic enzyme activity.By establishing an animal-level multidrug-resistant bacteria wound infection model,its ability to treat multidrug-resistant bacteria wound infection and promote wound healing was further evaluated.Metabolomics and transcriptomics were used to analyze the antibacterial and pro-wound healing mechanisms.In summary,through the surface structure design of palladium nanosheets,a variety of noble metal light-responsive nanozymes were innovatively developed,and their enzyme-like catalytic activity and photoactivity were regulated.The constructed palladium-based nanozyme photocontrolled therapy system showed excellent anti-tumor and antibacterial therapeutic potential.These studies provide theoretical guidance for the development and application of light-responsive noble metal nanozymes.