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Synthesis of amine containing well-defined polymers via reversible addition-fragmentation chain transfer (RAFT) polymerization and their characterization
The aim of the study is to synthesize well-defined, spermine-like, amine containing polymers via reversible addition fragmentation chain transfer (RAFT) polymerization as a potential endosomal escaping agent for intracellular drug delivery applications. Tert-butyl (2-((tert-butoxycarbonyl) amino) ethyl)(2-hydroxyethyl)carbamate was first synthesized and then methacrylated to yield 2-((tert-butoxycarbonyl) (2- ((tert-butoxycarbonyl) amino) ethyl) amino) ethyl methacrylate, (BocAEAEMA). BocAEAEMA was then polymerized via RAFT polymerization. A series of RAFT polymerization kinetics experiments were performed in order to investigate the RAFTcontrolled character of polymerizations. The effect of [M]/[R] ratio at constant monomer (0.36 M, 0.72 M and 1.44 M) and initiator concentrations (3.6x10-3 M) on polymerization kinetics was first investigated. Linear proportionality between ln [M]0/[M] and polymerization time, and Mn and conversion, indicated the RAFTcontrolled polymerization of BocAEAEMA monomer under the conditions tested. Boc-AEAEMA polymers were deprotected to yield AEAEMA polymers prior to assays performed to determine cytotoxicity and proton sponge capacity of polymers. Proton sponge capacity of AEAEMA polymers (5.5 kDa and 8 kDa) and PEI (25 kDa and 60 kDa) was investigated via potentiometric titration using constant polymer (2.2 x10-5 M) or repeating unit (2.9 x10-5 M) concentrations. The proton sponge capacity of p(AEAEMA)was found to be comparable to those of PEIs at the same repeating unit concentration. AEAEMA polymers did not show cytotoxic effect on NIH 3T3 cells up to 1.6 M concentration, tested via a cell viability assay for 24h and 72 h.