通过甲基丙烯酰胺侧基迈克尔加成制备阳离子聚碳酸酯

CATIONIC POLYCARBONATES PREPARED VIA MICHAEL ADDITION OF AMINES ON THE PENDANT METHACRYLAMIDO GROUPS

针对高分子量的聚乙烯亚胺(PEI)作为基因载体效率高但毒性大,而低分子量的聚乙烯亚胺虽毒性低但对基因的结合能力差、转染效率低的矛盾,设计合成了主链可生物降解而侧链带有胺类化合物的阳离子聚碳酸酯.首先,2-氨基-1,3-丙二醇和甲基丙烯酰氯反应制得2-(甲基丙烯酰胺基)-1,3-丙二醇,再用氯甲酸乙酯在室温下用三乙胺作碱关环反应得到2-(甲基丙烯酰胺基)三亚甲基碳酸酯(MATC)单体.该单体在二氯甲烷溶液中在1,8-二氮杂二环[5.4.0]十一碳-7-烯(DBU)催化下开环聚合得到聚(2-(甲基丙烯酰胺基)三亚甲基碳酸酯)(PMATC).然后,利用侧基双键和乙二胺或者低分子量PEI的迈克尔加成反应分别制备了带有乙二胺侧基的阳离子聚碳酸酯PTMC-EDA以及带有PEI侧链的聚碳酸酯PTMC-PEI.凝胶色谱(GPC)法测得聚碳酸酯PMATC、阳离子聚碳酸酯PTMC-EDA和PTMC-PEI的重均分子量分别为6300、7400、15100,分子量分布指数分别为1.21、1.83和2.17.这类带有多胺侧基或侧链的阳离子聚碳酸酯在较低用量下即能与pDNA形成表面带正电的粒径200 nm左右的复合物.它们具有与不可降解的25 kDa PEI类似的对pDNA的优良结合能力,并且对细胞的毒性要低得多.

This paper reports the preparation and pDNA complexation characteristics of cationic polycarbonates with pendant ethylenediamino groups or low molecular PEI side chains.The polyamino pendant groups or side chains were introduced on the polycarbonate backbone via Michael addition with methacrylamido pendant groups.First,cyclic carbonate monomer,2-（methacrylamido）trimethylene carbonate（MATC） was prepared from 2-amino-1,3-prapanediol by a two-step reaction.Ring-opening polymerization of MATC using 1,8-diazabicycloundec-7-ene（DBU） as a catalyst afforded poly（2-metacrylamidotrimethylene carbonate）（PMATC）.Then,cationic polycarbonates PTMC-EDA and PTMC-PEI were prepared by Michael addition of ethylenediamine and 600 Da PEI,respectively,on the methacrylamido pedant groups.The weight average molecular weights measured by GPC of polymers PMATC,PTMC-EDA,and PTMC-PEI were 6300,7400,and 15100,and the polydispersity indexes were 1.21,1.83 and 2.17,respectively.Cationic polycarbonates could form stable complexes with plasmid DNA at low polymer/pDNA weight ratios.The average diameters of the complexes were around 200 nm.The zeta potentials of cationic polycarbonates and DNA complexes were about 30 mV.The characteristics of the cationic polycarbonates of forming polyplexes with pDNA were very similar to those of 25 kDa PEI.Their cytotoxicity measured by MTT assay,however,was very low.The excellent ability for DNA complexation and low toxicity suggest that the cationic polycarbonates might have a good potential for use as gene vectors.