Abstract
Colorectal cancer is one of the common causes of malignant tumors in recent years, thus the discovery of potential compounds that detect the occurrence of colorectal cancer by efficient approaches is necessary. In this study, the method of systematic evolution of ligands by exponential enrichment (SELEX) was used for recognizing serum from colorectal cancer patients by a single-stranded DNA library of aptamers assisted by single-walled carbon nanotubes (SWCNTs) to remove single-stranded DNA with low affinity. Ten rounds of selection were applied using colorectal cancer serum as a target with the serum of healthy individuals as a control. As the result, we have successfully identified four candidate aptamers after high-throughput genome sequencing analysis, comparison analysis and secondary structure prediction. Among them, aptamer Seq-2 exhibited the highest affinity and the strongest selectivity with an equilibrium dissociation constant (Kd) of 11.31 ± 3.25 nM and a Ct difference value of 4.25 ± 0.38 between the colorectal cancer group and the healthy group. Moreover, with fifty negative control serum samples, the positive detection rate of fifty positive serum samples tested by aptamer Seq-2 was over 90%. In particular, aptamer Seq-2 can strongly bind the colorectal cancer serum, less strongly bind the non-colon cancer serum and hardly bind the healthy serum. Therefore, aptamer Seq-2 presents enormous potential for exploring as a tumor diagnostic kit and detecting unknown tumor markers in serum to reflect colorectal cancer.
Highlights
Colorectal cancer, as a common cause of malignancy in the digestive tract, can occur anywhere in the colon
With y serum samples from healthy persons as the negative control samples, all the positive rates of y serum samples from the colorectal cancer patients using these four enriched aptamers as the probe molecules are all over 80%, attributing to the highly speci c affinity of these aptamers to unknown tumor markers in the serum of the colorectal cancer patients
In the initial rounds of screening, a large amount of ssDNA library and the serum samples from colorectal cancer patients were used in order to obtain speci c ssDNA libraries for the serum samples mentioned above
Summary
Colorectal cancer, as a common cause of malignancy in the digestive tract, can occur anywhere in the colon. Colorectal cancer has relatively high incidence in North America and Western Europe, and its mortality ranks 2nd of all the malignant cancers in the United States. Its mortality ranks 5th or 6th of all the malignant cancers in most provinces in China, and keeps going up in recent years.[1,2]. Early diagnosis and treatment is the key to improve the survival rate of patients with colorectal cancer.[3]. The early diagnosis of colorectal cancer depends mainly on endoscopies and tumor markers in the serum. Given that serum is the best specimen for in vitro diagnosis of cancer, detection of tumor
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