Construction Of Biomimetic Layered MoOx Nanosheet And Its Antitumor Effect

The development and application of two-dimensional(2D)nanomaterials with imaging,drug delivery,and photothermal therapy(PTT)functions had broad prospects in the biomedical field.In order to overcome the problems of low bioavailability of chemotherapy drugs and poor efficacy of single therapy,we constructed a multifunctional nano-preparation modified with phospholipids,coated with tumor cell membranes,and loaded with chemotherapy drug 7-ethyl-10-hydroxycamptothecin(SN38).This preparation with high photothermal absorption and biodegradability could achieve accurate delivery of tumor sites.The heat generated by MoOx under nearinfrared irradiation could cause local "burning" of tumor tissue and damage proteins and DNA,while inducing immunogenic cell death(ICD)to produce antigen and damage associated molecular patterns(DAMPs).Chemotherapy drug SN38 could not only induce ICD,synergistically induce DAMPs and dendritic cell(DC)maturation.It could also induce the production of type I interferon and activate the STING pathway,promoting the subsequent activation of various immune cells and alleviating the immunosuppressive environment of tumors.Firstly,molybdenum oxide was synthesized through hydrothermal method and peeled off into monolayer nanosheets under strong ultrasound.MoOx nanosheets were modified by egg yolk lecithin through rotary evaporation,and the phospholipid modification endowed strong hydrophobic nanosheets with good dispersibility and stability in aqueous media.Blank nanosheets were mixed and stirred with SN38 solution to obtain drug loaded nanosheets.Due to the large specific surface area of 2D nanomaterials,MoOx nanosheets had high loading capacity(42.5%)for hydrophobic drug SN38.Prepared 4T1 tumor cell membrane were mixed and stirred with lipid modified drug loaded nanosheets and obtain MoOx@M-SN38 through ultrasound.The immune escape and homologous targeting properties of the encapsulated 4T1 tumor cell membrane enabled SN38 to effectively accumulate at the tumor site.MoOx@M had a layered structure with particle size of 81 nm and zeta potential of-22.5 mV.MoOx@M nanosheets were dispersed and stable in aqueous media,and hemolysis rate was less than 5%at higher concentrations,indicating the stability and safety of in vivo injection.MoOx@M nanosheets had good photothermal heating performance,photothermal stability and photothermal repeatability and had a photothermal conversion efficiency of 27.2%,which indicated good photothermal performance.MoOx@M-SN38 degraded slowly in a neutral medium and relatively stable in acid medium.This property helped nanosheets accumulate in tumors and slowly release drugs.Meanwhile nanosheets that reach normal tissues could be metabolized quickly,reducing toxic side effects on non-targeted sites.4T1 breast cancer cells were used as the model to evaluate the anti-tumor effect of MoOx@M-SN38 in vitro.Cytotoxicity test,apoptosis,staining of living and dead cells and mitochondrial membrane potential test proved that MoOx@M-SN38+NIR had effective killing effect on cancer cells.The cell uptake experiment showed that the modification of tumor cell membrane in MoOx@M-SN38 enhanced its ability to target tumors.The cell cycle test results indicated that MoOx@M-SN38 had cell cycle blocking effect on S phase,inhibiting 4T1 tumor cell proliferation by inhibiting cell division.The results of CRT eversion and HMGB1 release experiments demonstrated that both the photothermal effect of MoOx and SN38 effectively induced ICD,activated immunity and alleviated tumor immune suppression.The combination of chemotherapy and photothermal therapy in the scratch experiment significantly inhibited tumor migration.In vivo anti-tumor research was conducted using 4T1 tumor bearing mice as model.Distribution experiment proved that MoOx@-IR780 had good tumor accumulation ability.In the in vivo photothermal experiment,MoOx@M nanosheets accumulated at the tumor site rapidly heated up to a maximum of 47℃ under laser,effectively leading to tumor thermal ablation.MoOx@M-SN38+NIR group showed significant inhibitory effects on primary tumors(with an inhibition rate of 88%)and lung metastasis.For the study of immune response,MoOx@M-SN38+NIR group had the highest maturity of DCs in lymph nodes(30%).Ths and CTLs infiltrating in the tumors and spleen significantly increased,while the proportion of M2 and Treg was significantly decreased.Meanwhile the fluorescence staining of MoOx@M-SN38+NIR group tumor sections showed significant upregulation of CRT and P-STING,indicating that activation of the ICD and STING pathways significantly alleviated immunosuppression.In summary,MoOx nanosheets coated with tumor cell membranes were constructed for tumor targeted delivery of SN38,achieving the combination of PTT and chemotherapy and having good application prospects.