胃腺癌核酸适配体的筛选与特异性研究

核酸适配体可作为分子探针应用于胃腺癌的早期诊断和治疗，具有广泛应用前景。本实验利用Serum-SELEX（Ser-SELEX）技术筛选胃腺癌核酸适配体。通过对候选适配体二级结构分析，其二级结构多为茎环结构。圆二色谱分析显示，7条候选核酸适配体呈右手螺旋特征。通过荧光定量核酸扩增检测系统（q-PCR）检测了候选核酸适配体对胃腺癌靶标的亲和力，表明候选核酸适配体浓度梯度与Ct值均呈正相关，亲和力常数为纳摩尔级别。利用q-PCR法、量子点法验证了候选核酸适配体识别靶标的特异性，结果均显示Apt-101对靶标亲和力更高，特异性更强，Apt-101的平衡解离常数（K_d值）为6.444±1.128nmol/L,特异性检测阳性率大于70%。

Screening and specificity of aptamer for gastric adenocarcinoma

Gastric Adenocarcinoma (GA) is the most common pathological classification of gastric cancer, accounting for about 95% of the total number of gastric cancer. At present, the pathogenesis of gastric adenocarcinoma is not clear. Patients usually have no obvious symptoms in the early stage, but have developed to the middle and late stage by the time of diagnosis, missing the best intervention and treatment stage. Aptamer can be used as a molecular probe for early diagnosis and treatment of gastric adenocarcinoma. In this study, serum-Selex (Ser-SELEX) technique was used to screen aptamers of gastric adenocarcinoma. By analyzing the secondary structure of the candidate adaptors, the secondary structure is mostly stem ring structure. The circular dichroism analysis showed that seven candidate aptamers were right-handed helical. The q-PCR method was used to detect the affinity of the candidate aptamer to the gastric adenocarcinoma target, indicating that the concentration gradient of the candidate aptamer was positively correlated with the Ct value, and the affinity constant was nanomolar level. The q-PCR method and quantum dot method were used to verify the specificity of the target recognition of candidate aptamers. The results showed that APT-101 had a higher affinity and specificity to the target. The equilibrium dissociation constant (Kd) of APT-101 was 6.444±1.128 nM, and the positive rate of specificity detection was more than 70%.