Construction Of Lipid Near-Infrared Nanoprobes And Imaging-Guided Photothermal Therapy

Currently,near-infrared region Ⅱ（NIR-Ⅱ）nanoprobes are widely used in cancer diagnosis and treatment research owing to their excellent photophysical properties.However,the inherent physiological barrier in the solid tumor region makes it difficult for the probes to reach the tumor tissue center where the most aggressive tumor cells exist.Consequently,developing novel tumor-enhanced delivery strategies and designing nanoprobes integrating accurate imaging and efficient treatment have become an urgent need to improve the cure rate and quality of life of cancer patients.Based on this,this paper presents a NO-enhanced delivery strategy by remodeling Tumor microenvironment（TME）.Quantum dots（QDs）with bright fluorescence in the NIR-Ⅱb（1,500-1,700 nm）window and high photothermal conversion efficiency were encapsulated into liposomes for imaging-guided photothermal therapy（PTT）of tumor.The fabrication of PEG and arginine-glycine-aspartate（RGD）peptide on liposomes ensured the prolonged circulation in vivo and active targeting to tumor related neovascularization and tumor cells.Meanwhile,the loading of a natural NO generator L-Arginine（L-Arg）in liposomes realized the continuous generation of NO in the acidic H₂O₂ TME,achieved degradation of extracellular matrix（ECM）furtherly,and accomplished highly-efficient delivery of liposomes.This TME remodeling strategy mediated by the release of NO favors the accumulation and distribution of liposomes in solid tumors and the accurate diagnosis and treatment of tumors.The research content is as follows:（1）The preparation method of RGD modified and L-Arg/QDs co-coated Arg/QDs@Lip-RGD probe by film-drying and high-pressure homogeneous-extrusion method was explored.The effects of drug lipid ratio,hydration temperature and freezing-cycle conditions on improving the co-coating efficiency were systematically investigated.Through the examination of morphology and stability,NIR fluorescence,photothermal and cell-targeting performance,it was confirmed that a tumor-specific NIR-Ⅱb imaging and photothermal therapy integrated probe has been constructed successfully.（2）NO generation in solution,cell and living body was detected.The sustained and slow release of NO in PBS solution with acidic H₂O₂ was verified by classical Griess method.NO response in 4T1 cells in vitro and tumor tissues in vivo was verified by DAF-FM DA probe without other exogenous stimulation.（3）High-resolution whole-body wide-field and tumor-targeting imaging was performed in NIR-Ⅱb window.The highest T/NT=47.3 at 4 h was observed.In vitro NIR frozen-section imaging showed highly-targeted liposomes accumulation and deep homogeneous distribution in the tumor area,which realized the enhanced delivery of liposomes.（4）This efficient delivery mechanism was proved to be NO-mediated TME remodeling through fluorescence imaging co-localization combined with WB experiment.Through the dual-channel imaging of collagen Ⅰ staining（visible region）and QDs fluorescence（NIR-Ⅱ region）of the same tumor,it was testified that ECM depletion caused uniform distribution of liposomes intratumorally.Combined with the increased expression of MMP-9 shown by WB,it was proved that NO could effectively activate MMP-9 to deplete ECM and improved the penetration of liposomes into the tumor center.Combined with this enhanced delivery strategy,we performed imaging-guided efficient PTT,and no obvious in vivo toxicity was observed.In summary,we proposed a NO-mediated tumor-enhanced delivery strategy to achieve NIR-Ⅱb imaging-guided efficient PTT with remarkable therapeutic efficacy.