Abstract
Well-defined novel, linear, biodegradable, amphiphilic thermo-responsive ABA-type triblock copolymers, poly[2-(2-methoxyethoxy) ethyl methacrylate-co-oligo(ethylene glycol) methacrylate]-b-poly(ε-caprolactone)-b-poly[2-(2-methoxyethoxy) ethyl methacrylate-co-oligo(ethylene glycol) methacrylate] [P(MEO2MA-co-OEGMA)-b-PCL-b-P(MEO2MA-co-OEGMA)] (tBPs), were synthesized via a combination of ring-opening polymerization (ROP) of ε-caprolactone (εCL) and reversible addition-fragmentation chain transfer polymerization (RAFT) of MEO2MA and OEGMA comonomers. The chemical structures and compositions of these copolymers were characterized using Fourier transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (1H NMR). The molecular weights of the copolymers were obtained using gel permeation chromatography (GPC) measurements. Thermo-responsive micelles were obtained by self-assembly of copolymers in aqueous medium. The temperature sensitivity and micelllization behavior of amphiphilic triblock copolymers solutions were studied by transmittance, fluorescence probe, surface tension, dynamic light scattering (DLS) and transmission electron microscopy (TEM). A hydrophobic drug, anethole, was encapsulated in micelles by using the dialysis method. The average particle sizes of drug-loaded micelles were determined by dynamic light scattering measurement. In vitro, the sustained release of the anethole was performed in pH 7.4 phosphate-buffered saline (PBS) at different temperatures. Results showed that the triblock copolymer’s micelles were quite effective in the encapsulation and controlled release of anethole. The vial inversion test demonstrated that the triblock copolymers could trigger the sol-gel transition which also depended on the temperature, and its sol-gel transition temperature gradually decreased with increasing concentration. The hydrogel system could also be used as a carrier of hydrophobic drugs in medicine.
Highlights
The synthesis of amphiphilic block copolymers by reversible addition-fragmentation chain transfer (RAFT) polymerization is the most convenient method [1,2]
PCL central block and two outer thermo-responsive P(MEO2 MA-co-oligo(ethylene glycol) methacrylate (OEGMA)) blocks were prepared by a combination of ring opening polymerization (ROP) and reversible addition-fragmentation chain transfer (RAFT) polymerization methods to solve the solubility of PCL (Scheme 1)
A series of ABA-type amphiphilic triblock copolymers composed of a biodegradable PCL central block and two outer thermo-responsive P(MEO2MA-co-OEGMA) blocks were prepared by a combination of ring opening polymerization (ROP) and reversible addition-fragmentation chain transfer (RAFT) polymerization methods to solve the solubility of PCL
Summary
The synthesis of amphiphilic block copolymers by reversible addition-fragmentation chain transfer (RAFT) polymerization is the most convenient method [1,2]. Thermo-responsive amphiphilic block copolymers based on poly (ε-caprolactone)/poly(N-isopropylacylamide) (PCL/PNIPAAm) copolymers are the most studied for biomedical applications [29,30,31] These amphiphilic polymers are soluble in water and self-assemble into micelles which usually have small sizes with low critical micelle concentration (CMC) allowing them to avoid the reticuloendothelial system uptake thereby promoting prolonged blood circulation [34]. PCL central block and two outer thermo-responsive P(MEO2 MA-co-OEGMA) blocks were prepared by a combination of ring opening polymerization (ROP) and reversible addition-fragmentation chain transfer (RAFT) polymerization methods to solve the solubility of PCL (Scheme 1). A series of ABA-type amphiphilic triblock copolymers composed of a biodegradable PCL central block and two outer thermo-responsive P(MEO2MA-co-OEGMA) blocks were prepared by a combination of ring opening polymerization (ROP) and reversible addition-fragmentation chain transfer (RAFT) polymerization methods to solve the solubility of PCL.
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