Study On Oral Absorption Properties Of Baicalin-berberine Nanocrystals

It is a key problem in the research of modern Chinese medicine to improve the bioavailability and efficiency of multiple components oral delivery.Drug nanocrystals is an important way to improve the oral absorption of insoluble components of traditional Chinese medicine,but it is difficult to design nanocrystals for co-delivery of insoluble multi-components of traditional Chinese medicine,and its absorption mechanism and fate in vivo need to be further studied.Scutellaria baicalensis Georgi and Coptis chinensis are common drug pairs,which are commonly used in Huanglian Jiedu Decoction,Gegen Qinlian Decoction and other prescriptions.Baicalin（BA）and berberine（BBR）have self-precipitation in the process of decocting.The carboxylic acid anion in BA and the quaternary ammonium cation in BBR interact easily to form compound salt.In this thesis,BA-BBR nanocrystals,the self-assembly product of nano BA and BBR,was studied by Caco-2 cell monolayer model,environmental responsive fluorescence probes,Ussing Chamber technique and small animal in vivo imaging technique,the oral absorption properties of BA-BBR nanocrystals were studied from three aspects of cell,tissue and animal.In this thesis,BA-BBR-TPE complex was prepared by aggregation induced emission（AIE）,and BA-BBR-TPE nanocrystals were prepared by high pressure homogenization.The relationship between solubility and fluorescence intensity was investigated to verify whether BA-BBR-TPE has AIE effect.The absorption properties of BA-BBR-TPE nanocrystals on Caco-2 cells were observed by laser confocal imaging microscope.The uptake experiment showed that the BA-BBR-TPE nanocrystals could be internalized into the cells and reached the peak at 5-7 h,and the fluorescence intensity of nanocrystals was higher than that of the complex at 5-7h.The fluorescence intensity of BA-BBR-TPE complex and nanocrystals decreased after7 h,and the fluorescence of nanocrystals was weaker than that of complex after 10 h.The results showed that BA-BBR nanocrystals exhibited better solubility and absorbability at the cellular level,and the decrease of particle size was more beneficial to endocytosis and drug absorption,and the BA-BBR nanocrystals showed the characteristic of"whole transport"at the cell level,which could be swallowed by the cell as a whole.Using Caco-2 cell monolayer model,the permeability coefficient of BA-BBR complex and nanocrystals transported from the inner side of intestinal cavity to the basal side was measured,and the transmembrane transport characteristics of BA-BBR complex and nanocrystals were evaluated.At the same time,P-gp inhibitor,verapamil was added and incubated with BA-BBR complex and nanocrystals to explore the effect of P-gp efflux on the transmembrane transport.The results showed that the P_app of BA and BBR in the complex were significantly lower than those in the physical mixture.Compared with the complex,the P_app of BA and BBR in nanocrystals were significantly increased by 1.3 times and 2.3 times,respectively.After the addition of verapamil,the P_app of BA and BBR in BA-BBR complex were significantly increased by 1.5 times and 2.0 times,respectively.Under the influence of verapamil,the P_app of BA and BBR in nanocrystals increased without significance.To sum up,BA-BBR complex is different from pure physical mixture.It has its own absorption characteristics,low permeability and is affected by P-gp efflux.Nanocrystals can significantly increase the permeability of BA-BBR complex in Caco-2 cell monolayer membrane and reduce the efflux effect.Taking Using Chamber technology,the absorption characteristics of BA-BBR complex and nanocrystals in different intestinal segments of rats were evaluated.The results showed that compared with the complex,the K_a of BBR in the nanocrystals was significantly increased by1.4 times,1.9 times and 1.9 times in the duodenum,jejunum and ileum,and the P_app was significantly increased by 1.30 times,1.34 times and 2.36 times,respectively.The K_a of BA in nanocrystals increased significantly by 2.2 times,2.4 times and 1.8 times in duodenum,jejunum and ileum,respectively;P_appincreased significantly by 2.58 times,3.17 times and 2.07 times respectively.Different from the complex,BA and BBR in the nanocrystals showed better absorption in the ileum.The results shows that BA-BBR nanocrystals can effectively improve the permeability of BA and BBR in isolated intestinal mucosa,significantly improve intestinal absorption,improve the absorption site of drugs in the intestine and promote the balanced release of drugs.The transport characteristics of BA-BBR complex and nanocrystals in rats were studied by fluorescence resonance energy transfer effect（FRET）and small animal in vivo imaging instrument.The results of in vivo imaging in rats showed that the fluorescence intensity of nanocrystals in small intestine was higher than that of complex.In vitro gastrointestinal imaging showed that the retention time in the stomach,enteral entry and absorption rate of the nanocrystals were better than those of the complex.The results of tissue distribution showed that fret effect did not appear at most time points,and no trace of complex and nanocrystals was found in the tissue.The results shows that in the gastrointestinal tract,nanocrystals still exist in the form of"whole particles",but with the absorption and transport in vivo,the drug crystal structure collapses,and nanocrystals cannot reach various tissues and organs in the form of whole particles.This paper preliminarily illustrates the process of BA-BBR complex nanocrystals promoting oral absorption through integral transport,synchronized release,which provides an important basis for further revealing the in vivo process of"compound decoction self precipitation"and explaining the material basis and pharmacodynamic characteristics of traditional Chinese medicine from the perspective of traditional Chinese medicine preparation.