Optimization Of Fermentation Conditions Of Thiobacillus Ferrooxidans And The Coupling Of Magnetosomes With Adriamycin

With the development of nanotechnology and macromolecular materials,targeted drug delivery for tumor treatment has become the focus of research,which can be directed to the targeted site to overcome the difficulty of cancer chemotherapy.Among the most of targeted drug carriers,nano-level Fe₃O₄ particles have become a research hotspot in the field of modern science due to their easy preparation and low price.Magnetosomes（MS）are natural nano-magnetic particles synthesized by magnetotactic bacteria and presenting the structure of biological nucleosomes,and their main composition is Fe₃O₄.Nano drug carrier with magnetic corpuscle targeted narrow distribution range,has the advantages of stable crystal structure,and to a certain extent,can be overcome through chemical or physical methods to obtain high purity of the existence of magnetic nanoparticles,uneven grain size,easy to gather,poor biocompatibility,and must carry out surface modification can be used to take medicine,but also can avoid the magnetic nanoparticles applied in targeting drug delivery low arising in the process of drug loading,easy to reunite the morphology,size is difficult to control.Although magnetosomes have great application value in the fields of biomedicine and biomaterials.However,most of the magnetosomes used for carrying drugs are separated from Magnetospirillum gryphiswaldense MSR-1 and Magnetospirillum magneticum AMB-1,the two magnetotactic bacteriums culture conditions are very harsh,low magnetosomes yield,difficult to produce in the industrial level of magnetosomes and other defects greatly limit the application of magnetosomes.Studies have shown that Acidithiobacillus ferrooxidans（At.ferrooxidans）can also synthesize the magnetosomes,and the culture conditions are simple,and the extraction method of magnetosomes is relatively easy,providing a possibility for the industrial development of magnetosomes.Based on single factor at the early stage of the laboratory research,the laboratory existing At.ferrooxidans,adopting air lift reactor for large-scale cultivation,through the response surface experiment,examine the effects of fermentation conditions on the production of magnetosomes,temperature,oxygen flux and glucose acid concentration to the corresponding variables,magnetosomes yield in the response value,and ultimately determine the At.ferrooxidans produces the best conditions of magnetosomes,when the temperature of 24℃,1.1vvm of oxygen flux,12 mmol of glucose acid concentration,it is predicted that the magnetic particle yield can reach 0.398 mg/L.The work was based on the cross-linking agent of genipin,coupling antineoplastic doxorubicin drugs and magnetosomes of At.ferrooxidans,use the single factor experiment,to explore the coupling of temperature,time of coupling,genipin,concentration of magnetosomes and concentration of doxorubicin.The influence of adopting variance analysis method can be concluded that the coupling time,concentration of doxorubicin concentration and genipin concentration influence,after using the response surface software,make test plan,by coupling time,genipin concentration and the concentration of doxorubicin as response variables,to drug loading,the envelopment rate and satisfaction function for the response value,at the time of the coupling,the concentration of genirapine was 2.4 mg/mL,and the concentration of doxorubicin was 0.9 mg/mL.At the time of the coupling,the drug loading and the encapsulation rate reached the optimal values of 41.3%and 91.1%,respectively.In this study,through the analysis of infrared light energy group and the comparison of particle size potential and the observation of its morphology by transmission electron microscope,the success of the coupling compound can be confirmed,and then its release property can be explored.The results showed that the complex of magnetosomes coupling with doxorubicin were surrounded by thick and fuzzy materials,and the average particle size increased to 83.98±7.5nm compared with the individual magnetic corpuscles（51.94±5.6 nm）.The potential of the magnetic corpuscles and the cross-linked doxorubicin magnetic corpuscles were-25.85±2.01mv and-34.42±6.13 mv,respectively.Through infrared spectrum analysis shows that the magnetic corpuscle doxorubicin magnetic coupling complexes and both have the same functional groups of carbonyl and hydroxyl corpuscle,and in 470 cm^-11 and have the same peak with doxorubicin.Through the drug release experiment of doxorubicin coupled magnetosomes complex,it can be found that At.ferrooxidans magnetosomes coupled compound was released rapidly at0-38 h,38 h after drug release tend to be slow,the drug release rate nearly 40%,proves that the coupling of stability and can release medicinal compounds.By semilog curves drawn on drug concentration-time,can judge the model belongs to the second chamber model,with the zero order kinetics and the first order kinetics and Higuchi equation fitting,the results show that the fitting Higuchi equation correlation（R²）is superior to the zero order release kinetics equation and release kinetics equation,Higuchi equation is closer to the experimental value,can better describe doxorubicin magnetic corpuscle complexes in artificial simulated gastric intestinal juice to release a quantity to the accumulation of the relationship with time.