临床研究证明患缺血性脑卒中(脑血栓)后降低人体温度至30-35℃,可有效缓解治疗中的脑部损害(亚低温治疗),且血栓附近呈弱酸性。作为脑血栓的唯一特效药,针对重组组织型纤溶酶原激活剂（rtPA）改性使其具有pH和温度双响应无疑是治疗的关键。但目前文献报道的蛋白修饰方法大多无法满足rtPA活性和安全性要求。申请人结合高分子化学与临床医学的工作实践,提出利用pH和温度两种响应高分子对蛋白进行修饰的方法。通过对rtPA表面氨基的修饰、精确调控pH和温度两种响应高分子配比、分子量、接枝率等手段,实现对rtPA生物活性从血栓周围弱酸性pH至人体正常生理pH、从亚低温治疗温度范围至人体正常温度的双重“开-关”式控制。本项目将重点对蛋白表面接枝反应、接枝数量的精确控制和高分子/蛋白复合体系结构-性能关系进行系统考察；同时建立治疗模型,明确此双响应复合物的溶栓过程和机制,为响应性溶栓制剂的应用提供材料基础。

Clinical studies have shown that lowering the body temperature down to 30-35℃ during the treatment of ischemic stroke can effectively reduce the damage to the brain caused by the thrombolytic process, namely, Hypothermia Treatment, and near the thrombus is weak acid pH. Modifying recombinant tissue plasminogen activator (rtPA), the only effective drug for treating stroke currently, to achieve the pH-temperature dual response is undoubtedly the key to the treatment. However, most of the protein modification methods reported in the literature cannot be met the protein thrombolytic activity and safety requirements in therapy. Applicant combines polymer chemistry and clinical practices to propose a “safe” protein modification strategy using pH and temperature two types of responsive polymers. This enables an effective dual “on-off” control of the rtPA biological activity from the hypothermia temperature range to normal body temperature, the weak acid pH to physiological pH, by modifying surface amino group of protein Lys residue, regulating the precise ratio of pH and temperature two type of responsive polymers, the molecular weight of polymer and the grafting rate. In this study, the protein surface grafting, precise control of the number of grafted polymers and the relationship between structure and performance of polymer/protein complex will be investigated. Therapy models will be established to ascertain the thrombolytic process and mechanisms of the pH-temperature dual responsive rtPA composite, which is expected to a reliable theoretical basis and material basis for the application of such dually responsive polymer-protein conjugates in the thrombolytic therapy.