Investigation On Interaction Between Nanodrug Carriers And Blood Brain Barrier Based On A Blood Brain Barrier Orgain-chip

Blood brain barrier(BBB)is a highly selective physiological barrier capable of protecting the brain by limiting entrance of neurotoxic substances into central nervous system(CNS).However,BBB also limits the entrance of most therapeutic drugs,leading to only a few neurological disorder drugs available for clinical treatment currently.Therefore,a variety of drug delivery methods have been developed to help drugs overcome the BBB.Nanocarrier-based drug delivery systems have attracted much attention because of their modifiable property and controllable structure.However,people still doubt about the safety and stability of nanodrug carriers,so it is necessary to conduct in-depth investigation on the interaction between nanodrug carriers and the BBB during their penetration,such as potential toxicity to BBB,changes of nanocarriers before and after penetration,and drug delivery efficiency.A reliable in vitro BBB model is necessary for investigation on the above issues so far.There are many methodological and ethical limitations in direct study of drug response on human beings,and the development and physiological activities of human diseases are very complex.Therefore,it is necessary to establish an in vitro BBB model that can accurately replicate human pathophysiological behaviors and respond to potential drugs,so as to improve the reliability of drug verification studies.At present,the commonly used in vitro BBB models mainly include Transwell system,animal model,organoid model and organ-on-a-chip model.The Transwell system is simple to construct in vitro BBB models,but it has few cell types and cannot reproduce key physiological parameters such as flow stimulation.For animal models,high-resolution in situ imaging in animal is also difficult,which is essential for the study of interactions between nanocarrier and BBB.For organoid models,the construction method is complex time-consuming,and the randomness of cell differentiation and assembly process is not conducive to the establishment of standardized models.Models based on microfluidic chips are capable of delivering a variety of physiological stimuli and can replicate the 3D BBB structure by designing different internal structures.Furthermore,it is easy for microfluidic chips to produce standardized and mass-produced structure,allowing construction of more uniform BBB in vitro models.More importantly,the in vitro model based on microfluidic chips is very convenient for collection of nanocarriers and high-resolution in situ observation of BBB,so it is more suitable for the study of the interaction between nanocarriers and BBB.The main works of this thesis are as follows:1.An in vitro BBB model based on microfluidic chips was constructed,which could reproduce the complex 3D structure and basic physiological functions of BBB.Using this model,we explored the interaction between gold nanoparticles(Au NPs)with different sizes and modification and found that Au NPs with smaller size and target molecular modification had stronger BBB penetrability and induced less BBB damage.In addition,we also found that the protein absorbed on Au NPs surface changed dynamically before and after BBB penetration,which reduced the stability of Au NPs during drug delivery.2.Based on the first work,we constructed an in vitro BBB model with direct cell to cell contact,which was closer to the real BBB structure,and the barrier function was further enhanced.Using this model,we explored the transport mechanism of three tumor-derived extracelluar vesicles(EVs),and found that the tumor metastasis ability was positively correlated with the BBB penetrability of EVs.In addition,the BBB permeability was regulated by mi RNA loaded in EVs.3.A BBB-Tumor model was constructed to study the BBB penetration process of drug-loaded EVs.We found that small molecule drugs encapsulated in EVs had higher BBB permeability,fewer side effects and better anti-tumor effect.However,some drugs leaked out from EVs in the process of ECs transport,resulting in BBB damage.Therefore,it is necessary to further improve the drug safety of drug-loaded EVs.4.The gut-brain axis model was initially constructed.The fluctuant structure of cell layer similar to the small intestinal villi,and the neural axis structure connecting the gut and brain were reproduced.This model provides a reliable in vitro model for the study of complex bidirectional regulation mechanism between gut and brain.