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首页> 外文期刊>Acta biomaterialia >Modulating rheological and degradation properties of temperature-responsive gelling systems composed of blends of PCLA-PEG-PCLA triblock copolymers and their fully hexanoyl-capped derivatives
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Modulating rheological and degradation properties of temperature-responsive gelling systems composed of blends of PCLA-PEG-PCLA triblock copolymers and their fully hexanoyl-capped derivatives

机译：调节由PCLA-PEG-PCLA三嵌段共聚物及其完全己酸封端的衍生物组成的温度响应性胶凝体系的流变和降解性能

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In this study, the ability to modulate rheological and degradation properties of temperature-responsive gelling systems composed of aqueous blends of poly(-caprolactone-co-lactide)-b-poly(ethylene glycol)-b-poly(-caprolactone- co-lactide) (PCLA-PEG-PCLA) triblock copolymers (i.e. uncapped) and their fully capped derivatives was investigated. Uncapped and capped PCLA-PEG-PCLA triblock copolymers, abbreviated as degree of modification 0 and 2 (DM0 and DM2, respectively), were composed of identical PCLA and PEG blocks but different end groups: namely hydroxyl and hexanoyl end groups. DM0 was synthesized by ring opening polymerization of l-lactide and -caprolactone in toluene using PEG as initiator and tin(II) 2-ethylhexanoate as the catalyst. A portion of DM0 was subsequently reacted with an excess of hexanoyl chloride in solution to yield DM2. The cloud point and phase behaviour of DM0 and DM2 in buffer as well as that of their blends were determined by light scattering in a diluted state and by vial tilting and rheological measurements in a concentrated state. Degradation/dissolution properties of temperature-responsive gelling systems were studied in vitro at pH 7.4 and 37 °C. The cloud points of DM0/DM2 blends were ratio-dependent and could be tailored from 15 to 40 °C for blends containing 15 to 100 wt.% DM0. Vial tilting and rheological experiments showed that, with solid contents between 20 and 30 wt.%, DM0/DM2 blends (15/85 to 25/75 w/w) had a sol-to-gel transition temperature at 10-20 °C, whereas blends with less than 15 wt.% DM0 formed gels below 4 °C and the ones with more than 25 wt.% DM0 did not show a sol-to-gel transition up to 50 °C. Complete degradation of temperature-responsive gelling systems took ～100 days, independent of the DM0 fraction and the initial solid content. Analysis of residual gels in time by GPC and 1H-NMR showed no chemical polymer degradation, but indicated gel degradation by dissolution. Preferential dissolution of lactoyl-rich polymers induced enrichment of the residual gels in caproyl-rich polymers. To the best of our knowledge, degradation of temperature-responsive gelling systems by dissolution has not been reported or hypothesized as being the consequence of acylation of polymers. In conclusion, blending of PCLA-PEG-PCLA triblock polymers composed of identical backbones but different end groups provides for a straightforward preparation of temperature-responsive gelling systems with well-characterized rheological properties and potential in drug delivery. Furthermore, acylation of triblock copolymers may allow for the design of bioerodible systems with control over degradation by polymer dissolution.
机译：在这项研究中，具有调节由聚（己内酯-丙交酯）-b-聚乙二醇-b-聚（己内酯-co-丙交酯（PCLA-PEG-PCLA）三嵌段共聚物（即未封端）及其完全封端的衍生物进行了研究。未封端和封端的PCLA-PEG-PCLA三嵌段共聚物，分别缩写为0和2的修饰度（分别为DM0和DM2），由相同的PCLA和PEG嵌段组成，但端基不同：羟基和己酰基端基。 DM0是通过使用PEG作为引发剂和2-乙基己酸锡（II）作为催化剂，在甲苯中将1-丙交酯和-己内酯开环聚合而合成的。随后使一部分DM0与过量的己酰氯在溶液中反应以产生DM2。 DM0和DM2在缓冲液及其混合物中的浊点和相行为，是通过稀释状态下的光散射以及浓缩状态下的样品瓶倾斜和流变学测量来确定的。温度响应胶凝体系的降解/溶解特性在pH 7.4和37°C的体外进行了研究。 DM0 / DM2共混物的浊点取决于比率，对于包含15至100 wt。％DM0的共混物，其浊点可在15至40°C之间调整。样品瓶倾斜和流变实验表明，固含量为20至30 wt。％时，DM0 / DM2共混物（15/85至25/75 w / w）在10-20°C时具有溶胶-凝胶转变温度，而具有小于15重量％的DM0的共混物在4℃以下形成凝胶，而具有大于25重量％的DM0的那些在高达50℃下没有显示出溶胶-凝胶转变。温度响应性胶凝体系的完全降解需要约100天，而与DM0分数和初始固体含量无关。通过GPC和1H-NMR及时分析残留的凝胶显示没有化学聚合物降解，但是表明由于溶解而凝胶降解。富含乳酰基的聚合物的优先溶解诱导了富含己酰基的聚合物中残留凝胶的富集。据我们所知，尚未报道或假设由于溶解导致温度响应性胶凝体系的降解是聚合物酰化的结果。总之，共混由相同骨架但不同端基组成的PCLA-PEG-PCLA三嵌段聚合物可直接制备具有良好流变特性和潜在药物传递特性的温度响应性胶凝体系。此外，三嵌段共聚物的酰化可允许设计可生物蚀解的体系，并通过聚合物溶解来控制降解。

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