Double Thermoresponsive Polybetaine-Based ABA Triblock Copolymers With Capability To Condense DNA

ABA type MPDSAHy-MEO2MAx-MPDSAHy with narrow polydispersity indexwas prepared by ATRP in the mixture of water/methanol with addition of sodiumchloride. The aqueous solution of copolymer was shown to exhibit UCST and LCSTbehaviors. The dual temperature sensitiveness was investigated via turbiditymeasurement, variable temperature 1H NMR as well as steady-state fluoresence. TheUCST was dependent upon the solution concentration and the block length ofMPDSAH. Micropolarity assay of pyrene revealed that in the selected lowtemperature region, the micropolarity of pyrene slightly increased due to weakinteraction of positive-negative interaction in diluted solution; while above LCST,pyrene experienced more hydrophobic milieu owing to the noticeable dehydration ofPMEO2MA. The analsysis of ethyidium bromide displacement suggeted the capabilityof MPDSAH homopolymer and copolymers to bind DNA. 99% EB could be replacedby MPDSAH homopolymer. MEO2MA moieties in copolymers weakened the bindingability of PMPDSAH to DNA, but 54-60% EB was replaced by copolymer at acritical complexing ratio. AFM confirmed that PMPDSAH and copolymers werecapable of condensing DNA to nanaoparticles at an appropriate complexing ratios.The temperature sensitiveness of polymer/DNA complex was investigated via cloudmeasurement. Complexing with DNA, UCST of solution vanished, but LCST wasslightly increased due to the enhanced hydrophilicity caused by liberation of negativecharges.