Abstract: Abstract Objective To explore the targeting binding characteristics of aptamer L4 and its application as a molecular probe for targeted imaging of colorectal cancer tissues in clinical patients, with the aim of providing a potential molecular tool for targeted diagnosis of metastatic colorectal cancer. Methods Flow cytometry was used to detect the binding specificity, affinity, thermal stability and cell selectivity of aptamer L4. Enzyme treatment experiments were conducted to clarify the nature of the target molecule bound by aptamer L4. Based on the principle of biotin-streptavidin binding, aptamer L4 was conjugated with quantum dots to form L4-QD probes, and their targeted imaging of colorectal cancer tissues in clinical patients was observed. The targeting specificity of the tissues and its correlation with the pathological characteristics of the patients were analyzed. Results Aptamer L4 specifically and strongly binds to HCT116 cells with a Kd value of 10.4±1.7 nM and shows good thermal stability. Aptamer L4 has binding specificity for tumor cells with metastatic potential, suggesting that its target molecule is a cell surface membrane protein. Clinical tissue imaging shows that L4-QD probes can achieve targeted imaging of colorectal cancer tissues, and the fluorescence intensity is significantly positively correlated with the AJCC clinical stage and poor survival prognosis of the patients. Conclusion Aptamer L4 has high specificity and affinity for metastatic colorectal cancer cells. Conjugation with quantum dots enables targeted imaging of colorectal cancer tissues and is expected to become a potential molecular probe for assessing the progression of colorectal cancer and a new tool for targeted diagnosis of metastatic colorectal cancer.

Key words: Metastatic colorectal cancer, Aptamer, Targeted imaging, Quantum dots