Inactive Trojan Bacteria Drug Delivery System Basic Research In The Treatment Of Central Nervous System

The blood-brain barrier(BBB),a specialized barrier found in the tissues of human and other animal brains,protects the Central Nervous System(CNS)from peripheral blood circulation and guarantees that changes in the peripheral system do not affect the brain.It is crucial for preserving the internal environment of the CNS’s homeostasis.It is of great importance to maintain the homeostasis and normal function of the CNS.The complex cellular interactions of the BBB maintain its integrity and limit drug penetration,resulting in a relatively low success rate in the development of therapeutic agents for CNS diseases.Therefore,one of the greatest challenges in developing drugs for CNS disorders is achieving adequate BBB penetration.Bacteria have been widely used in cancer therapy due to their ability to target tumors,and many bacterial-nanohybrid systems have been developed for better application in the treatment of diseases.The ability of some bacteria to cross the BBB has been demonstrated in many studies,such as Neisseria,Streptococcus pneumoniae,Group B Streptococcus and Escherichia coli.However,the clinical development of live bacteria as therapeutic agents faces significant hurdles due to their potential infection-related toxicity.In this paper,Escherichia coli K1(EC-K1)was selected as a vector to cross the BBB,inactivated Trojan EC-K1 system was constructed,and the ability of the inactivated Trojan EC-K1 system to cross the BBB was investigated,as well as to achieve therapeutic use in mouse models of meningitis and glioblastoma.The main studies are as follows:Chapter 1:Firstly,the current status of research on BBB structure and delivery was systematically introduced;secondly,the application of bacteria in drug delivery and the progress of research on its mechanism of crossing the BBB were reviewed with emphasis;next,the development of silicon nanomaterials and their applications and research progress in the field of disease treatment were outlined.Based on this,the basis of this thesis,the significance of the research and the research content were discussed.Chapter 2:Firstly,MD-ICG-SiNPs were synthesized by loading Maltodextrin(MD)and Indocyanine Green(ICG)onto fluorescent silicon nanoparticles(SiNPs)via Schiff base reaction and electrostatic adsorption,respectively.MD-ICG-SiNPs were able to enter the interior of EC-K1 through the interaction of the attached MD with the ABC transport channel(ABC)on the surface of EC-K1 to construct Trojan EC-K1.Secondly,to subtract the toxicity of Trojan EC-K1,it was subjected to UV irradiation to construct the inactivated Trojan EC-K1 system.The coated plate and bacterial live-dead dye flow data showed that Trojan EC-K1 was able to reach a lethality rate close to 99%at 60 min of UV irradiation,and the inactivated Trojan EC-K1 system was successfully constructed.Next,in vivo imaging analysis of small animals showed that the system could carry ICG across the BBB in vitro and in vivo to reach the lesion site in the brain,and the dose of ICG delivered to the brain was about 3.0 times higher than that of ICG alone.Meanwhile,by observing their body weight changes their mortality rates,it was shown that all mice remained healthy after 14 days of intravenous injection of about 109 CFU of inactivated Trojan EC-K1.In contrast,injection of live Trojan EC-K1 caused 100%mortality within 5 days even at a low dose of～106 CFU.In addition,the inactivated Trojan EC-K1 system was shown to have a better safety profile by immune factor and blood biochemistry blood count data.Finally,the system was able to produce photothermal effects under 808 nm laser irradiation after effective BBB crossing to kill bacteria and achieve treatment of meningitis mice.Chapter 3:The inactivated Trojan EC-K1 system constructed based on Chapter 2 has the ability to cross the BBB in vitro and in vivo to achieve the treatment of meningitis mice.The application of this system and its application to the treatment of glioblastoma could further validate its treatment for CNS diseases.In an in vitro anti-tumor study,the inactivated Trojan EC-K1 system was able to produce photothermal effects under 808 nm laser,inhibit neovascularization in vitro,and kill tumor cells.In vivo,glioblastoma mouse model was constructed,and the inactivated Trojan EC-K1 system was able to reach the tumor location in the brain of mice,and its photothermal effect was able to inhibit the growth of glioblastoma.Chapter 4:The BBB crossing ability of the inactivated Trojan EC-K1 system constructed in this thesis and its application to the treatment of meningitis and glioblastoma were summarized,and the innovative points and shortcomings of the inactivated Trojan EC-K1 system were analyzed,and finally the improvement plan was proposed for its shortcomings.In summary,in this paper,inactivated Trojan EC-K1 system was constructed,loaded with MD-ICG-SiNPs,which inherited the ability to cross the BBB of live EC-K1 and could carry drugs to the brain lesion site.It was made to lose microbial viability and reduce its biotoxicity by UV treatment.And they were applied to the treatment of CNS diseases,including meningitis and glioblastoma.This paper was expected to provide new ideas for applied basic research in BBB delivery and treatment of CNS diseases.