PDEGMA-b-PDMAEMA-b-PLMA triblock terpolymers and their cationic analogues: synthesis, stimuli responsive self-assembly and micelleplex formation

Abstract

In this study, the synthesis, chemical modification and self-assembly in aqueous media of novel temperature-responsive and pH-responsive triblock terpolymers of the type (poly(diethylene glycol methyl ether methacrylate)-b-poly(2-(dimethylamino)ethyl methacrylate)-b-poly(lauryl methacrylate)) (PDEGMA-b-PDMAEMA-b-PLMA) are reported. The triblock terpolymers were synthesized via RAFT polymerization and molecular characterization was achieved by SEC, ¹H-NMR and FTIR spectroscopy. Methyl iodide (CH₃I) was utilized for chemical modification of the PDMAEMA blocks to increase the overall solubility of the triblock terpolymers in aqueous media and to obtain permanent positive charges, converting them to temperature-responsive block polyelectrolytes. PDEGMA-b-PDMAEMA-b-PLMA triblock terpolymers and their quaternized analogs self-assemble in aqueous media forming spherical micellar structures consisting of a hydrophobic PLMA core and stimuli-responsive PDMAEMA and PDEGMA corona, as evidenced by light scattering measurements. The dimensions of the formed micelles were influenced noticeably by variations in the solution temperature and pH. Moreover, we examine the formation of micelleplexes between quaternized PDEGMA-b-QPDMAEMA-b-PLMA thermoresponsive micelles and DNA molecules. The complexation capability of the formed micelleplexes was investigated by ethidium bromide quenching assays utilizing fluorescence spectroscopy techniques and UV-vis spectroscopy. Light scattering techniques are utilized in order to determine the structural characteristics of the formed micelleplexes. The quaternized terpolymer micelles effectively interact with nucleic acid molecules with their surface charge and their size depending on the composition of block terpolymers, the N/P ratio, and the increase of temperature above the LCST value of the temperature responsive PDEGMA block.