Synthesis Of Upconversion Fluorescent Polymer Nanoparticles Based On Aggregation-induced Emission Characteristics And Their Application In Photodynamic Therapy

Photodynamic therapy(PDT)is a noninvasive therapy that produces reactive oxygen species(ROS)under irradiation.However,ROS has limited diffusion distances and short lifetime,greatly limiting their biomedical applications.Therefore,it is particularly important that the photosensitizers(PSs)transport to a specific site to improve the efficacy of photodynamic therapy.Mitochondria-targeted group,can guide the PSs to specifically target mitochondria,generate ROS in the specific locations,and further lead to mitochondrial collapse and cell apoptosis,which is beneficial to improve the effect of PDT treatment.Aggregation-induced emission(AIE)performs excellent fluorescence emission characteristics in the aggregated or solid state.A typical characteristic of AIE is opposite to aggregation-caused quenching(ACQ),which has attracted increasing attention of the researchers.The AIE luminogens(AIEgens)hardly emit light in solution,but in the aggregated state,the fluorescence intensity is greatly increased due to the restriction of intramolecular rotations and the prohibition of non-radiative energy dissipation.In recent years,AIEgens play a crucial role in the field of bioimaging.Some AIEgens produce ROS for PDT at specific wavelength of light.Thus,this AIEgens have broad application prospects in fluorescence bioimaging and photodynamic therapy.In this project,we synthesized a near-infrared laser-driven fluorescent polymer coated inorganic upconversion nanoparticles(UCNPs).Furthermore,this nanoparticle could target mitochondria.Simultaneously,upconversion luminescence imaging could be carried out upon the irradiation of 980 nm laser.Then,the nanoparticles have good biocompatibility in the dark,but produce cytotoxic ROS upon 980 nm excitation resulting in the death of cancer cells with only 10% cell viability.It is noteworthy that the nanoparticles are able to specifically target mitochondria and then generate ROS at specific sites,causing mitochondrial collapse and cells apoptosis.And the pH-responsive PEG layer increases anti-protein adsorption capacity of nanoparticles and prolongs their circulation time in the blood,greatly improving the PDT effect.The AIE characteristics of these nanoparticles,subcellular targeting delivery characteristics and near infrared light excitation characteristics and other advantages help to optimize the therapeutic effect,providing new opportunities for the biomedical application.