title: Aptamer biosensor for sensitive detection of toxin A of Clostridium difficile using gold nanoparticles synthesized by Bacillus stearothermophilus.
abstract: A sensitive electrochemical biosensor was developed to detect toxin A (TOA) of Clostridium difficile based on an aptamer selected by the systematic evolution of ligands using exponential enrichment and gold nanoparticles (GNPS) synthesized by Bacillus stearothermophilus. The thiolated single-stranded DNA used as the capture probe (CP) was first self-assembled on a Nafion-thionine-GNPS-modified screen-printed electrode (SPE) through an Au-thiol interaction. The horseradish peroxidase (HRP)-labeled aptamer probe (AP) was then hybridized to the complementary oligonucleotide of CP to form an aptamer-DNA duplex. In the absence of TOA, the aptamer-DNA duplex modified the electrode surface with HRP, so that an amperometric response was induced based on the electrocatalytic properties of thionine. This was mediated by the electrons that were generated in the enzymatic reaction of hydrogen peroxide under HRP catalysis. After the specific recognition of TOA, an aptamer-TOA complex was produced rather than the aptamer-DNA duplex, forcing the HRP-labeled AP to dissociate from the electrode surface, which reduced the catalytic capacity of HRP and reduced the response current. The reduction in the response current correlated linearly with the concentration of TOA in the range of 0-200 ng/mL. The detection limit was shown to be 1 nM for TOA. This biosensor was applied to the analysis of TOA and showed good selectivity, reproducibility, stability, and accuracy.
authors.affiliation: Clinical Laboratory, The First Affiliated Hospital, Chongqing Medical University, Chongqing 400016, PR China. Electronic address: nclp261@163.com.
authors.forename: Peng
authors.initials: P
authors.lastname: Luo
authors.affiliation: Department of Medical Technique, Chongqing Medical and Pharmaceutical College, Chongqing 400030, PR China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Clinical Laboratory, The First Affiliated Hospital, Chongqing Medical University, Chongqing 400016, PR China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Xia
authors.affiliation: Clinical Laboratory, The First Affiliated Hospital, Chongqing Medical University, Chongqing 400016, PR China.
authors.forename: Huajian
authors.initials: H
authors.lastname: Xu
authors.affiliation: Key Laboratory of Medical Diagnostics of Ministry of Education, Chongqing Medical University, Chongqing 400016, PR China.
authors.forename: Guoming
authors.initials: G
authors.lastname: Xie
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry*; D001427:Bacterial Toxins / Q000032:analysis*; D015374:Biosensing Techniques / Q000379:methods*; D016360:Clostridioides difficile / Q000737:chemistry*; D004768:Enterotoxins / Q000032:analysis*; D001411:Geobacillus stearothermophilus / Q000737:chemistry; D006046:Gold / Q000737:chemistry*; D057230:Limit of Detection; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D015203:Reproducibility of Results
chemical_list: D052157:Aptamers, Nucleotide; D001427:Bacterial Toxins; D004768:Enterotoxins; C041348:tcdA protein, Clostridium difficile; D006046:Gold
keywords: Aptamer; Biosensor; Biosynthesis; Clostridium difficile; Nanoparticles; Toxin