PEGylated Polyamidoamine Dendrimers As Intestinal Absorption Promoters On TCM:Effects And Biosafety Evaluation

Background Polyamidoamine(PAMAM)dendrimers have been proven to have significant absorption-promoting effects on oral drugs,but also have severe cytotoxicity,which inhibits its further application.It was reported that the cytotoxicity of PAMAM is caused by the interaction between the amino groups and cell membrane,which could be improved by structural modification and the reduction of amino number.This research focused on studying the biosafety and ability to promote absorption of PAMAM dendrimers derivative after structural modification.Fourth generation PAMAM(G4.0-PAMAM)was decorated with different molecular weight polyethylene glycol(PEG 1000,2000,5000)to form a series of PAMAM-PEG(1000,2000,5000),which might be utilized to improve the intestinal absorption of oral drugs innocuously since the outer peg as a protective layer.The experiment results confirmed that the biosafety of PAMAM-PEG was significantly higher than PAMAM.Liquiritin is easily hydrolyzed by intestinal phloretin hydrolase because of the high molecular weight due to glycosyl linkage,and first-pass effect on liquiritin is obvious after oral administration;the evodiamine is almost insoluble in water and rapidly excreted and metabolized in vivo,and it could promote apoptosis or be rapidly accumulated by local organs,which leads to serious side effects;the jujuboside A has high molecular weight and the oral administration bioavailability is poor;all the three compounds belong to the Changbaishan active drug library established in the early stage of the research group,and have the same characteristics of strong biological activity but low bioavailability.In previous study,PAMAM and PAMAM-OEG(PAG),which was the co-dendrimer of PAMAM modified with oligoethylene glycols(OEG)dendron had been studied to promote the absorption of evodiamine,liquiritin and jujuboside A.In this study,PAMAM-PEG was aslo studied as absorption enhancer through exploring the biosafety and absorption promoting effects on evodiamine,liquiritin and jujuboside A,so that we could not only observe the modification effect of different molecular weight PEG on PAMAM,but also compare the experiment results with the previous research.Methods PAMAM and PEG was conjugated to obtain PAMAM-PEG,which had less amino content and larger volume than PAMAM.The biosecurity of PAMAM-PEG was determined by MTT assays on cells,LDH activity and total protein release assay in intestine of rats after administration.The effects of PAMAM-PEG with different molecular weight on the absorption of evodiamine,liquiritin and jujuboside A were studied by MDCK cell transport experiments and rat intestinal loop circulation experiments.Results From the experiment results,we could know that under the same concentration,PAMAM-PEG2000 showed better biosafety,and the cytotoxicity of the three kinds of PAMAM-PEG was concentration dependent and 0.05%(w/v)PAMAM-PEG2000 was less toxic and more suitable for follow-up experiments.Cell transport experiments confirmed that 0.05%(w/v)PAMAM-PEG2000,PAMAM-PEG 1000,and PAMAM-PEG5000 could increase the cumulative permeability of evodiamine by 1.32 times,1.28 times and 1.11 times;0.05%(w/v)PAMAM-PEG2000,PAMAM-PEG1000,PAMAM-PEG5000 could increase the cumulative permeability of liquiritin by 1.45 times,1.38 times,1.26 times;and 0.05%(w/v)PAMAM-PEG2000,PAMAM-PEG 1000,PAMAM-PEG5000 had no significant effect on the cumulative permeability of jujuboside A.In vivo rat intestinal loop circulation experiments showed that AUC value of drug concentration time curve of evodiamine,liquiritin with 0.1%(w/v)PAMAM-PEG2000 increased by 1.31 times,1.53 times,and had no significant enhancement on jujuboside A.Conclusions It was concluded that PAMAM-PEG2000 had good biosafety for cells and small intestine of rats.For drugs with low permeability and intestinal malabsorption,PAMAM-PEG2000 could be studied as a potentially safe and effective intestinal absorption enhancer.