ABA triblock copolymer based hydrogels with thermo-sensitivity for biomedical applications
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ABA triblock copolymer based hydrogels with thermo-sensitivity for biomedical applications Lucile Tartivel1,2, Marc Behl1, Michael Schroeter1 and Andreas Lendlein1,2 1
Institute of Biomaterial Science and Berlin-Brandenburg Center for Regenerative Therapies (BCRT), Helmholtz-Zentrum Geesthacht, Kantstr. 55, 14513 Teltow, Germany. Institute of Chemistry, University of Potsdam, 14476 Potsdam, Germany.
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ABSTRACT Oligo(ethylene glycol)-oligo(propylene glycol)-oligo(ethylene glycol) (OEG-OPG-OEG) triblock copolymers are hydrogel forming and extensively investigated in the field of drug release due to their biocompatibility and thermo-sensitivity. Here the synthesis and characterization of OEG-OPG-OEG based polymer networks from methacrylated oligomers by photo-irradiation are reported. Two precursors were selected to have comparable hydrophilicity (80 wt% OEG content) but different molecular weights of Mn = 8400 g·mol-1 and 14600 g·mol-1. The precursor solutions were prepared in concentration 10 to 30 wt%. The resulting polymer networks prepared from high Mn precursors exhibited higher swellability at equilibrium (up to 3400%) and mechanical properties in the range of G’ ~ 0.1 to 1 kPa at 5 °C compared to networks based on low Mn precursors. A more significant thermo-sensitive behavior in terms of swellability, volumetric contraction and mechanical transition, starting at 30 °C could also be observed for the networks based on high Mn precursors, thus promoting future application in the field of drug release. INTRODUCTION Hydrogels are an emergent class of polymer materials especially because their properties such as swellability and mechanical properties, and function such as stimuli-sensitivity can be adjusted to the requirements of specific applications to mimic e.g. the extracellular matrix [1]. Hydrogels based on synthetic compounds such as poly(vinyl alcohol) or poly(ethylene glycol) or natural polymers such as gelatin have been extensively explored [2, 3] due to their biocompatibility. However, other polymers such as poly(N-isopropylacrylamide) (PNIPAm) or block copolymers such as ABA triblock copolymer based on oligo(ethylene glycol) segments A and an oligo(propylene glycol) segment B (OEG-OPG-OEG) exhibit thermal transition when in aqueous solution, creating a physical gel at higher temperatures. They have attracted strong interest for pharmaceutical technologies, because of their biocompatibility and thermo-sensitivity [4]. In particular, the micellization of a OEG-OPG-OEG monomer solution upon its critical micellization temperature (cmt) can induce a self-gelation [5]. In this context, a drug can be incorporated in a solution and injected at room temperature and form a physical gel at body temperature. However, such a gel based on physical crosslinks can quickly dissolve when surrounded by body fluids, which could cause a burst release of the active compounds. On the other hand, a covalently crosslinked hydrogel with thermo-sensitivity used as template for drug loading might induce a more gradual release of
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