Stimuli-responsive hydrogels, known as smart hydrogels, are three-dimensional amphiphilic or hydrophilic polymer networks that are able to change their volume or phase, and other properties, including viscosity, structure, and dimension, in response to change in pH, temperature, and magnetic or electric field. Highly swellable, dual-responsive bovine serum albumin (BSA)-based injectable hydrogels are here prepared by the chemical conjugation of pH- and temperature-responsive oligo(sulfamethazine acrylate-co-N-isopropyacrylamide) (oligo(SMA-co-NIPAM)) copolymers on the surface of BSA through carbodiimide-mediated chemistry. The pH- and temperature-responsive oligomer-bearing BSA conjugates show rapid sol-to-gel phase transition properties. Specifically, the free flowing conjugates at high pH (pH 8.4, 23 °C) are transformed to a viscoelastic gel at the physiological condition (pH 7.4, 37 °C). The swelling ratio, gel strength, and pore size of the BSA hydrogel was tuned by altering the conjugation ratio of various lengths and compositions of oligo(SMA-co-NIPAM) copolymers to BSA. Subcutaneously administered BSA conjugate sols into the dorsal region of Sprague-Dawley rats formed an in situ gel. When the oligo(NIPAM) content in the hydrogel was high, the degradation rate of BSA hydrogels was remarkably slow, and two weeks after in vivo administration, the hydrogels with high oligo(NIPAM) had swollen more than 4-fold. An in vivo biodegradation study demonstrated that no necrosis or hemorrhage was observed in the tissues with the hydrogels. The concurrent stimuli-responsivity at the physiological condition and high elasticity suggests that these smart hydrogels may open a new avenue for hydrogel applications.

中文翻译：

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工程性高度膨胀的基于双反应蛋白的可注射水凝胶：体内分子结构和组成的影响

刺激响应水凝胶，称为智能水凝胶，是三维两亲或亲水聚合物网络，能够根据pH，温度，和磁场或电场。通过化学缀合pH和温度响应性低聚物（丙烯酸磺胺二甲基丙烯酸酯-co-N-异丙基丙烯酰胺）（oligo（SMA-co-NIPAM） ）通过碳二亚胺介导的化学反应在BSA表面上形成共聚物。带有pH和温度响应的低聚物的BSA共轭物显示出快速的溶胶-凝胶相变特性。具体而言，在高pH（pH 8.4，23°C）在生理条件下（pH 7.4，37°C）转化为粘弹性凝胶。通过改变寡聚（SMA-co-NIPAM）共聚物与BSA的各种长度和组成的共轭比，可以调节BSA水凝胶的溶胀率，凝胶强度和孔径。在Sprague-Dawley大鼠的背部区域中皮下施用BSA缀合物溶胶形成原位凝胶。当水凝胶中的低聚（NIPAM）含量高时，BSA水凝胶的降解速度显着缓慢，并且在体内给药两周后，高低聚（NIPAM）的水凝胶溶胀了4倍以上。体内生物降解研究表明，在使用水凝胶的组织中未观察到坏死或出血。