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

Abstract

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.