| Background:The hypoxic zone of malignant tumor is one of the characteristics of tumor microenvironment.Because of the existence of hypoxic zone,the therapeutic effect of anti-tumor drugs is greatly limited,and even the tumor cells in the hypoxic zone can produce radioresistance,resulting in residual tumor cells after treatment.However,the hypoxic area of tumor is a suitable growth and reproduction environment for anaerobes,which can transport antitumor drugs to the hypoxic zone of tumor depending on the anaerobic targeting of anaerobes.Chemotherapy still plays a dominant role in cancer treatment.However,the inability of conventional chemotherapeutic drugs to reach the hypoxic zone of solid tumors significantly weakens their efficacy.Bacteria-mediated drug delivery systems can be an effective targeting strategy for improving the therapeutic outcomes in cancer.Anaerobic bacteria have the unique ability to selectively transport drug loads to the hypoxic regions of tumors.Methods and Results:The synthesis of methoxy polyethylene glycol-polycaprolactone（m PEG-PCL）was used methoxy polyethylene glycol（m PEG）andε-Caprolactone（ε-CL）under the catalysis of stannous octanoate（Sn（Oct）2）.Then,we used m PEG-PCL to wrap paclitaxel（PTX）to form PTX-NPs,and then wrapped a layer of adhesive polydopamine（PDA）on the surface of PTX-NPs to obtain PDA-PTX-NPs.Bif@PDA-PTX-NPs biohybrids Obtained by co-incubation of Bif and PDA-PTX-NPs.The successful combination of Bif and PDA-PTX-NPs was confirmed by morphology,UV-Vis,confocal laser scanning microscope and other studies.Our research is based on Bifidobacterium infantis（Bif）,which is not only anaerobic bacteria,but also probiotics.After the combination of PDA-PTX-NPs which has anti-tumor effect with Bif,Bif@PDA-PTX-NPs biohybrid can bring PDA-PTX-NPs to the hypoxic regions of tumor,increase the concentration of PTX in tumor tissue,and promote the therapeutic effect of anti-tumor nanoparticles.In vitro experiments,drug release experiment,cytotoxicity experiment,scratch experiment,cell uptake experiment,cell apoptosis experiment,and tumor microenvironment response experiment have confirmed the good anti-tumor effect of biohybrids,and the nanoparticles adhered on the surface of bacteria were not easy to fall off in the blood circulation.The anaerobic targeting of Bif was also confirmed by biological distribution and co-location fluorescence images in vivo.In vivo experiments,we evaluated the good anti-tumor effect of Bif@PDA-PTX-NPs biohybrids through tumor volume change curve,survival curve,18F-FDG PET/CT images,immunohistochemistry analysis and H&E staining analysis.Finally,in order to evaluate the safety of the drug delivery system,we carried out H&E staining analysis of important organs,hematology analysis,in vitro hemolysis test,blank carrier cytotoxicity test,and injected different concentrations of bacteria into mice with normal immune system.The results showed that the carrier,Bif and biohybrids were extraordinary safe.Therefore,the self-driven Bif@PDA-PTX-NPs biohybrids designed in this study,while maintaining the toxicity of paclitaxel,relying on Bifidobacterium infantis,paclitaxel was successfully targeted to the hypoxic area of tumor,and the drug concentration in the hypoxic area of tumor was increased.Conclusion:We constructed Bif@PDA-PTX-NPs biohybrids by conjugating PTX-NPs with Bif cells using PDA as the linker.The biohybrid can actively accumulate in the hypoxic regions of solid tumors by virtue of the anaerobic bacteria.Furthermore,the high GSH concentration and acidic conditions in the tumor environment led to the detachment of the PTX-NPs from the bacterial cells,which then released the drugs in-situ in a sustained manner,thereby inhibiting tumor cell proliferation and enhancing apoptosis.Thus,anaerobic-mediated biohybrids provide a new therapeutic strategy for targeted chemotherapy of solid tumors. |
