肿瘤的早期诊断对提高生存率和减轻患者痛苦具有重要意义。对体液中的肿瘤标志物(如ctDNA、miRNA、蛋白质、外泌体等)进行敏感检测是早期肿瘤诊断的重要途径。然而，传统的肿瘤检测方法由于其成本高、时间长以及灵敏度低，已成为肿瘤诊疗领域亟需突破的技术瓶颈。源于细菌的适应性免疫系统的规则成簇间隔短回文重复序列(clustered regularly interspaced short palindromic repeats，CRISPR)及其相关蛋白质(CRISPR-associated protein，Cas)系统，已开发成为一种高效的分子诊断工具。近年来，通过结合便捷、高灵敏、响应速度快的电化学技术，CRISPR/Cas生物传感器在快速检测领域显示出巨大潜力。本文简要介绍了第Ⅱ类CRISPR/Cas系统单效应蛋白的原理及特点，重点综述了基于CRISPR/Cas电化学生物传感器的各种检测技术(包括阻抗法、伏安法、光电化学法和电化学发光法)在肿瘤诊断领域的应用，并讨论了CRISPR/Cas集成电化学生物传感器的优势与局限性、当前的挑战及未来的发展前景。
Application of CRISPR/Cas-based Electrochemical Biosensors for Tumor Detection
Tumors represent one of the primary threats to human life,with the dissemination of malignant tumors being a leading cause of mortality among cancer patients.Early diagnosis of tumors can reliably predict their progression,significantly reducing mortality rates.Tumor markers,including circulating tumor cells,exosomes,proteins,circulating tumor DNA,miRNAs and so on,generated during the tumor development process,have emerged as effective approach for early tumor diagnosis.Several methods are currently employed to detect tumor markers,such as polymerase chain reaction,Northern blotting,next-generation sequencing,flow cytometry,and enzyme-linked immunosorbent assay.However,these methods often suffer from time-consuming process,high costs,low sensitivity,and the requirement for specialized personnel.Therefore,a new rapid,sensitive,and specific tumor detection method is urgently needed.The clustered regularly interspaced short palindromic repeats(CRISPR)/CRISPR-associated protein(Cas)system,originating from the adaptive immune system of bacteria,has found extensive applications in gene editing and nucleic acid detection.Based on the structure and function of Cas proteins,the CRISPR/Cas system can be classified into two classes and six types.Class Ⅰ systems consist of multiple Cas protein complexes,including types Ⅰ,Ⅲ,and Ⅳ,while Class Ⅱ systems comprise single,multi-domain Cas proteins mediated by RNA,including types Ⅱ(Cas9),Ⅴ(Cas 12),and Ⅵ(Cas13).Class Ⅱ systems have been widely employed in the fields of biotechnology and nucleic acid diagnostics due to their efficient target binding and programmable RNA specificity.Currently,fluorescence method is the most common signal output technique in CRISPR/Cas-based biosensors.However,this method often requires the integration of signal amplification technologies to enhance sensitivity and involves expensive and complex fluorescence detectors.To enhance the detection performance of CRISPR/Cas-based biosensors,the integration of CRISPR/Cas with some alternative techniques can be considered.The CRISPR/Cas integrated electrochemical sensor(E-CRISPR)possesses advantages such as miniaturization,high sensitivity,high specificity,and fast response speed.E-CRISPR can convert the reactions between biomolecules and detecting components into electrical signals,rendering the detection signals more easily readable and reducing the impact of background values.Therefore,E-CRISPR enhances the accuracy of detection results.E-CRISPR has been applied in various fields,including medical and health,environmental monitoring,and food safety.Furthermore,E-CRISPR holds tremendous potential for advancing the detection levels of tumor markers.Among all types of Cas enzymes,the three most widely applied are Cas9,Casl2,and Casl3,along with their respective subtypes.In this work,we provided a brief overview of the principles and characteristics of Class Ⅱ CRISPR/Cas single-effector proteins.This paper focused on the various detection technologies based on E-CRISPR technique,including electrochemical impedance spectroscopy,voltammetry,photoelectrochemistry,and electrochemiluminescence.We also emphasized the applications of E-CRISPR in the field of tumor diagnosis,which mainly encompasses the detection of three typical tumor markers(ctDNA,miRNA,and proteins).Finally,we discussed the advantages and limitations of E-CRISPR,current challenges,and future development prospects.In summary,although E-CRISPR platform has made significant strides in tumor detection,certain challenges still need to be overcome for their widespread clinical application.Continuous optimization of the E-CRISPR platform holds the promise of achieving more accurate tumor subtyping diagnoses in clinical settings,which would be of significant importance for early patient diagnosis and prognosis assessment.
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