Deformable Mesoporous Organosilica Nanoplatforms For Multimodal Imaging-guided Photothermal Immunotherapy In Pancreatic Cancer

BackgroundPancreatic cancer is insidious,progresses rapidly,and lacks apparent symptoms and signs in the early stage.The main clinical examination methods currently used,such as CT,MRI,and endoscopic ultrasonography,are based on the changes in the morphological and anatomical structure of the lesions.The detection of lesions smaller than 5 mm is challenging with these examinations.When a precise diagnosis can be made,most pancreatic cancers have invaded peripheral blood vessels,lymphatic vessels,nerves,and tissues such as fat and omentum around the pancreas and have distant metastasis.Previous studies showed that more than 75%of patients with pancreatic cancer had tumor invasion into surrounding tissues or distant metastases at diagnosis.Even a small number of pancreatic cancer patients can be detected at an early stage and undergo radical surgery.However,within 1-1.5 years after surgery,about 90%of patients will still experience disease recurrence and metastasis.The reason is that pancreatic cancer has a dense fibrotic stroma that makes it difficult for drugs to be delivered to target cells for their effects.It is also because pancreatic cancer has a unique tumor microenvironment—an immunosuppressive microenvironment.Monotherapies,such as previous treatments and emerging treatment strategies,are ineffective in treating pancreatic cancer.The effective superposition of treatment strategies is bound to positively impact the treatment of pancreatic cancer,which is of great value to the decision-making of clinical treatment of pancreatic cancer.ObjectivesA multifunctional nanoprobe capable of simultaneously loading photothermal agent(copper sulfide,CuS)and an immune checkpoint blocker(anti-PD-L1 antibodies,αPDL1 Ab)was prepared.The probe is used for photothermal therapy combined with immunotherapy for pancreatic cancer.Evaluate the efficacy of combination therapy and explore the mechanism of action.Methods1.Synthesis and characterization of probes:Deformable mesoporous organosilicon nanoparticles(DMONs)were synthesized by sol-gel chemistry and preferential etching.Copper sulfide nanoparticles(CuS)were synthesized by a simple solvothermal method.The synthesized CuS was connected to DMONs by electrostatic adsorption to prepare DMONs-CuS.In order to endow DMONs-CuS with imaging and immunotherapy capabilities,we further used amidation reaction and electrostatic adsorption to modify Cy5.5,Gd-DTPA and aPD-L1 Ab on DMONs-CuS to prepare DMONs-CuS-Cy5.5Gd-αPDLl(DCCGP).The particle size,potential,morphology,and imaging properties of DCCGP were also measured.2.Functional Verification of Probes:The biocompatibility of DCCGP was evaluated by CCK-8 assay,hemocompatibility assay,and in vivo toxicity assay.The ability of DCCGP to penetrate cells and spheroids under photothermal response was evaluated by cell uptake assay and 3D tumor spheroid penetration assay.In vitro,phototoxicity experiments were conducted to evaluate the killing ability of DCCGP under photothermal therapy under near-infrared laser irradiation.Furthermore,further explore the mechanism of DCCGP inducing tumor immunogenic cell death and activating DC cells in vitro.3.Evaluation of the efficacy of the probe:The in vivo distribution of DCCGP was clarified by MR imaging,NIFR imaging,and photothermal imaging in an orthotopic pancreatic cancer nude mouse model.By administering DCCGP to the bilateral subcutaneous tumor C57 mouse model,the volumes of the in situ and distal tumors were recorded.The survival was analyzed,and the pharmacodynamic mechanism was explored by TUNEL staining,hematoxylin-eosin(HE)staining,and flow analysis.Results1.DCCGP is spherical-like under the transmission electron microscope,with about 7080 nm diameter.The hydrodynamic diameter is 342.8 nm.The Zeta potential is 21.60±0.57 mV.In vitro imaging experiments show that the probe has good MR imaging,NIFR imaging,and photothermal imaging.Good photothermal conversion efficiency and good photothermal stability.2.Mild photothermal therapy can promote probe penetration into cells and 3D tumorsphere models.In vitro cytotoxicity and phototoxicity showed that the cell activity was more than 80%,while the co-incubation system was without laser irradiation.After laser irradiation,cell viability was 33.04%.In vivo and in vitro biocompatibility experiments showed that the probes had good biocompatibility.DC cells were matured by inducing ICD after DCCGP treatment.3.The imaging analysis of an orthotopic pancreatic cancer nude mouse model showed that DCCGP has good in vivo imaging ability.The efficacy analysis and survival analysis of the bilateral subcutaneous tumor C57 mouse model showed that after DCCGP treatment,the bilateral tumors of the mice were inhibited,and the survival period was prolonged.Flow analysis showed that photothermal synergistic immunotherapy played a major role in the treatment.Antigen-presenting cells were increased in tumor-draining lymph nodes,and the content of infiltrating cytotoxic T cells within the tumor was increased.ConclusionIn this study,a multimodal image-guided photothermal synergistic immunotherapy nanoprobe was prepared for the first time based on deformable mesoporous organosilica.Accurate photothermal therapy under the guidance of MR imaging,NIFR imaging and photothermal imaging visualization is achieved.At the same time,the ICD effect induced by photothermal therapy was used to relieve the immunosuppressive microenvironment of the tumor,and the mice were combined with αPD-L1 Ab for synergistic immunotherapy.Combining targeted photothermal therapy and immunotherapy effectively treats orthotopic and metastatic tumors in mice.