title: A versatile immobilization-free photoelectrochemical biosensor for ultrasensitive detection of cancer biomarker based on enzyme-free cascaded quadratic amplification strategy.
abstract: In this work, an ultrasensitive immobilization-free photoelectrochemical (PEC) biosensor was successfully developed for the first time based on a novel enzyme-free cascaded quadratic signal amplification strategy. This rationally designed homogeneous dual amplification strategy consists of a target-analog recycling circuit based on catalytic hairpin assembly (CHA) and a hybridization chain reaction (HCR) mediated amplification circuit. In the presence of carcinoembryonic antigen (CEA), a proof-of-concept target, target-analog is released to trigger the upstream CHA recycling circuit. The generated dsDNA complexes from CHA recycling could further induce the downstream HCR amplification, leading to the formation of numerous hemin/G-quadruplex DNAzymes. This would accordingly stimulate the biocatalytic precipitation of 4-chloro-1-naphthol, inducing a distinct decrease in the photocurrent signal due to the formed insoluble/insulating products on electrode surface. Under the optimal conditions, this PEC biosensor achieved ultrasensitive detection of CEA down to the atto-gram level. The introduction of this aptamer-based cascaded quadratic amplification strategy not only remarkably improves the selectivity and sensitivity of CEA assay, but also allows the ultrasensitive detection of other proteins by designing specific aptamers, providing a universal, isothermal and label-free PEC biosensing platform for ultrasensitive detection of different kinds of cancer biomarkers and holding a great potential for early-diagnosis of cancer.
authors.affiliation: College of Chemistry and Pharmaceutical Sciences, Qingdao Agricultural University, Qingdao, Shandong 266109, People's Republic of China.
authors.forename: Lei
authors.initials: L
authors.lastname: Ge
authors.affiliation: College of Chemistry and Pharmaceutical Sciences, Qingdao Agricultural University, Qingdao, Shandong 266109, People's Republic of China.
authors.forename: Wenxiao
authors.initials: W
authors.lastname: Wang
authors.affiliation: College of Chemistry and Pharmaceutical Sciences, Qingdao Agricultural University, Qingdao, Shandong 266109, People's Republic of China.
authors.forename: Ting
authors.initials: T
authors.lastname: Hou
authors.affiliation: College of Chemistry and Pharmaceutical Sciences, Qingdao Agricultural University, Qingdao, Shandong 266109, People's Republic of China. Electronic address: lifeng@qust.edu.cn.
authors.forename: Feng
authors.initials: F
authors.lastname: Li
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis*; D002272:Carcinoembryonic Antigen / Q000032:analysis*; D003217:Conductometry / Q000295:instrumentation*; D004247:DNA / Q000737:chemistry* / Q000235:genetics; D004798:Enzymes; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D021141:Nucleic Acid Amplification Techniques / Q000295:instrumentation*; D010783:Photometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D014408:Biomarkers, Tumor; D002272:Carcinoembryonic Antigen; D004798:Enzymes; D004247:DNA
keywords: Catalytic hairpin assembly; Catalytic precipitation; DNAzyme; Homogeneous photoelectrochemical assay; Hybridization chain reaction