单克隆抗体由于其良好的抗原特异性和亲和性，可通过靶向相关的肿瘤标志物在分子水平上实现早期癌变的可视化。双特异性抗体同时与肿瘤细胞表面多个受体或抗原结合，能在分子水平上提高检测的灵敏性和精准性，在肿瘤的早期诊断领域具有不可估量的发展潜力。通过化学修饰的手段直接构建抗体衍生物具有快速、简单、高效等优点，但是目前抗体的化学修饰方法存在诸多问题，如修饰位点不可控、偶联产率低、产物结构不确定等。近年来发展的生物正交反应和酶催化的连接方法具有反应速度快、位点选择性高、生理条件兼容性好等优点，已成功用于构建含有非天然成分的蛋白质分子。本项目拟在基于基因编码的非天然氨基酸嵌入的技术上，将转肽酶催化反应和“点击”生物正交反应这两种方法联用，发展一种简单、高效的构建结构确定的抗体衍生物的方法。我们希望该方法可以用于构建特异性肿瘤靶向的双靶点免疫探针，为恶性肿瘤的早期检测和诊断提供新的思路。

Due to the strong affinity and high specificity for its target, monoclonal antibody can be used for early cancer detection and diagnosis through targeting the corresponding cancer biomarkers. The use of bispecific antibodies targeting multiple cancerous molecular pathway of cancer has great potential for early detection and diagnosis of small malignant lesion. Chemical modification of protein is a useful tool for rapid, facile and efficient preparation of various antibody derivatives. However, current chemical modification methods lacking of site-specificity show low conjugation efficiency, and most importantly, cannot provide structurally defined products. Due to the fast kinetics, high site-selectivity, and good compatibility under physiological conditions, bioorthogonal reactions and enzyme-mediated ligations have been successfully applied to site-specific modification of proteins in recent years. Herein, based on the incorporation of unnatural amino acids, we aim to develop a novel chemoenzymatic method for rapid and facile preparation of structurally defined antibody derivatives. It is hoped that this method can be used for constructing dual-antigen targeting immunoprobes, which may ultimately lead to better diagnosis sensitivity and early detection and diagnosis of small malignant lesions.