Abstract
pH-sensitive hydrophilic poly(methacrylic acid)-b-poly(ethylene glycol)-b-poly(methacrylic acid) (PMAA-b-PEG-b-PMAA) triblock copolymers were synthesized through atom transfer radical polymerization, and were characterized by FT-IR, 1H NMR, and GPC. The as-synthesized polymers can self-assemble into stable and almost spherical nanomicelles in aqueous solution with an average size range from 18 to 89 nm, depending on the micellar concentrations, while they assumed well-defined spherical morphologies in PBS solutions. The micellization behavior in different media was investigated by a fluorescence spectroscopy technique, UV–Vis transmittance, and dynamic light scattering measurements. The critical micelle concentration and size of the micelles decrease with the increasing the length or molecular weights of PEG and PMAA chains. A pH-dependent phase transition behavior produces at a pH value of about 5.2, and the stable pH micellization behavior varied within a narrow pH range from ca. 4.8 to 7.4. These triblock copolymers are generally low cytotoxicity at a micellar concentration below 400 mg L−1, as revealed by the MTT assay. The prednisone release and release kinetics studies disclosed that these pH-sensitive polymeric micelles are good carriers for the drug delivery.
Highlights
In the past decades, stimuli-responsive materials have attracted rapidly growing interest because of their potential biomedical and pharmaceutical applications [1,2,3]
Synthesis and characterization of PtBMA-b-Poly(ethylene glycol) (PEG)-b-PtBMA and poly(methylacrylic acid) (PMAA)-b-PEGb-PMAA triblock copolymers pH-responsive PMAA-b-PEG-b-PMAA triblock copolymers were achieved via hydrolysis of amphiphilic PtBMA-b-PEG-b-PtBMA triblock copolymers, while the latter was synthesized by atom transfer radical polymerization (ATRP) using haloid-tailed Br–PEG–Br as a macroinitiator and tBMA as monomer
After the reaction was conducted at 90 °C for 24 h, the monomer conversion was about 60 %.The macroinitiator, amphiphilic triblock copolymer and resulting copolymer were characterized by Fourier transform infrared (FT-IR), 1H nuclear magnetic resonance (1H NMR), and GPC
Summary
Stimuli-responsive materials have attracted rapidly growing interest because of their potential biomedical and pharmaceutical applications [1,2,3]. Since pHsensitive carriers can target drugs to deep organs or tumor tissues, PMAA-based amphiphilic block copolymer micelles have widely been investigated for these applications. Stimuli-responsive amphiphilic block copolymers as biomaterials may self-assemble and form micelles in organic or aqueous media and can be used to load the hydrophobic drug. These nanoparticles should circulate until they reach the target organs or tissues, either by specific targeting [20]. Scheme 1 Synthetic scheme of representative PMAA-b-PEG-b-PMAA triblock copolymer and 2-butanone, supplied by the Sinopharm Chemical Reagent Co., Ltd, were used as received. All other reagents such as tetrahydrofuran (THF) and dioxane, etc., are available from commercial markets
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