Sustained delivery of protein therapeutics is limited owing to the fragile nature of proteins. Despite its great potential, delivery of proteins without any loss of bioactivity remains a challenge in the use of protein therapeutics in the clinic. To surmount this shortcoming, we report a pH- and temperature-responsive in situ-forming injectable hydrogel based on comb-type polypeptide block copolymers for the controlled delivery of proteins. Polypeptide block copolymers, composed of hydrophilic polyethylene glycol (PEG), temperature-responsive poly(γ-benzyl-L-glutamate) (PBLG), and pH-responsive oligo(sulfamethazine) (OSM), exhibit pH- and temperature-induced sol-to-gel transition behavior in aqueous solutions. Polypeptide block copolymers were synthesized by combining N-carboxyanhydride-based ring-opening polymerization and post-functionalization of the chain-end using N-hydroxy succinimide ester activated OSM. The physical properties of polypeptide-based hydrogels were tuned by varying the composition of temperature- and pH-responsive PBLG and OSM in block copolymers. Polypeptide block copolymers were non-toxic to human embryonic kidney cells at high concentrations (2000 μg mL⁻¹). Subcutaneous administration of polypeptide block copolymer sols formed viscoelastic gel instantly at the back of Sprague-Dawley (SD) rats. The in vivo gels exhibited sustained degradation and were found to be bioresorbable in 6 weeks without any noticeable inflammation at the injection site. Anionic characteristics of hydrogels allow efficient loading of a cationic model protein, lysozyme, through electrostatic interaction. Lysozyme-loaded polypeptide block copolymer sols readily formed a viscoelastic gel in vivo and sustained lysozyme release for at least a week. Overall, the results demonstrate an elegant approach to control the release of certain charged proteins and open a myriad of therapeutic possibilities in protein therapeutics.

中文翻译：

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基于多肽嵌段共聚物的pH和温度响应型可生物吸收的可注射水凝胶，可在体内持续递送蛋白质

由于蛋白质的易碎性质，蛋白质治疗剂的持续递送受到限制。尽管具有巨大的潜力，但在临床中使用蛋白质治疗剂时，在不损失任何生物活性的情况下递送蛋白质仍然是一个挑战。为了克服这个缺点，我们报告了一种基于pH和温度响应的原位形成的可注射水凝胶，该水凝胶基于梳状多肽嵌段共聚物，用于蛋白质的可控递送。由亲水性聚乙二醇（PEG），温度响应性聚（γ-苄基-L-谷氨酸）（PBLG）和pH响应性低聚（磺胺二甲嘧啶）（OSM）组成的多肽嵌段共聚物表现出pH和温度诱导的溶胶在水溶液中从凝胶转变为凝胶的行为。通过结合N合成多肽嵌段共聚物-N-羟基琥珀酰亚胺酯活化的OSM，基于-羧酸酐的开环聚合和链端的后官能化。通过改变嵌段共聚物中温度和pH响应性PBLG和OSM的组成，可以调节基于多肽的水凝胶的物理性质。多肽嵌段共聚物在高浓度（2000μgmL ^-1）下对人胚胎肾细胞无毒。皮下注射多肽嵌段共聚物溶胶在Sprague-Dawley（SD）大鼠的背部立即形成粘弹性凝胶。在体内凝胶表现出持续的降解作用，并在6周内可生物吸收，注射部位无任何明显的炎症。水凝胶的阴离子特性允许通过静电相互作用有效加载阳离子模型蛋白溶菌酶。载有溶菌酶的多肽嵌段共聚物溶胶在体内容易形成粘弹性凝胶，并持续释放溶菌酶至少一周。总的来说，结果表明了一种控制某些带电蛋白质释放并在蛋白质治疗中开辟无数治疗可能性的绝妙方法。