Study On Synthesis Of Bacterial Magnetosome Nanocarriers And Their Application In Tumor Photothermal-chemodynamic Synergistic Therapy

Objective:Magnetic nanoplatforms provide a promising avenue for tumor targeting,long effective,and combined therapy.The main drawbacks of magnetite nanoparticles based on inorganic synthesis are their instability,unattractive biocompatibility,and complicated synthesis.Therefore,a bio-based magnetic nanoplatform with bacterial magnetosome?MN?was proposed for antitumor application in this work.The design of magnetosome nanocarriers was carefully considered on the basis of their magnetic core and natural membrane structure.Controllable synthesis of bacterial magnetosome nanocarriers and their application in antitumor with synergistic effect were further explored,hence providing theoretical and technical supports for the development of novel biomedical nano-formulations and their applications for tumor synergetic therapy.Methods:Firstly,the biosynthesis of bacterial magnetosomes was investigated by transmission electron microscopy and magnetic sensitivity coefficient(C_mag)measuring instrument.The extraction,separation and purification of magnetosomes were achieved by multiple“ice water bath ultrasonic treatment-magnetic stand separation”.Then,Au-magnetosome nanoparticles?AMN?with controllable size were obtained by adjusting synthesis conditions such as the p H of the solution.The structure,photothermal/nanoenzyme/promoting Fenton-like reaction/imaging performance of AMN were further characterized by in vitro experiments.Subsequently,The tumor targeting abilities of AMN were evaluated by using fluorescence imaging,and the imaging abilities were evaluated by using photoacoustic and nuclear magnetic imaging.Finally,the antitumor effect of the process using AMN was investigated using both in vivo and in vitro model experiments.The corresponding mechanism of the synergistic effect in the process was explored using thermal imagers,tissue section analysis,etc.Results:The AMN has been successfully prepared in a controllable process at optimized conditions?Biosynthesis of MN,filling volume ratio of 75%and cultivation period of 72h;Purification of MN,“Ice water bath ultrasonic-magnetic stand separation”operation,20?25 times;Modification of MN,one/two-step growing process,p H control?.The purified MN indicated good biocompatibility.A middle-size Au-Magnetosome nanoparticle,which has been synthesized under one-step process,produced a high temperature of 65? and 0.33 mmol H₂O₂ within 30 minutes in the tests of photothermal process and chemodynamic process,respectively.When compared with photothermal therapy or chemical dynamic therapy,the AMN-mediated combination therapy significantly inhibited tumor cell growth in the in vitro model experiments of 4T1 cells?triple-negative breast cancer??p?27?0.01?and the inhibition ratio of the 4T1 cells reached 93.03%.Results of the in vivo experiments indicated that enhanced targeting abilities were carried out on the basis of magnetic manipulation and the tumor enrichment level increased by 2.51 times.The AMN indicated the abilities of magnetic resonance imaging and photoacoustic imaging.In the in vivo experiments of 4T1 mice model of triple-negative breast cancer,the survival periods of the mice were extended from 26 days in the control group to 31?43 days in the experiment groups by using photothermal and chemodynamic therapy alone.The AMN-mediated photothermal-chemodynamic combination treatment group with the magnetic manipulation indicated better tumor suppression effect?p?27?0.01?.Within 80days of the experimental period,the tumors of the mice almost completely disappeared,and all mice survived until the end of this experiment.There was no tumor bone and lung metastasis observed.The main pathological analysis of the viscera was normal in the mice after AMN injection,and no obvious damage and inflammation were observed.Conclusions:1.The size-controllable AMN nanocarriers have been successfully obtained on the basis of the bacterial biosynthesis of MN and one-step modification of nano-gold.2.The AMN nanocarriers indicated a good biocompatibility and had the abilities of magnetic resonance imaging and photoacoustic imaging.Enhanced targeting abilities were carried out on the basis of magnetic manipulation.In the in vivo experiments of 4T1 mice model of triple-negative breast cancer,the AMN-mediated photothermal-chemodynamic combination therapy has indicated excellent anti-tumor performance with synergistic effect.