ABSTRACT
The contamination of food by pathogens is a serious problem in global food safety, and current methods of detection are costly, time-consuming, and cumbersome. Therefore, it is necessary to develop rapid, portable, and sensitive assays for foodborne pathogens. In addition, assays for foodborne pathogens must be resistant to interference resulting from the complex food matrix to prevent false positives and negatives. In this study, hemin and reduced graphene oxide-MoS2 sheets (GMS) were used to design a near-infrared (NIR)-responsive photoelectrochemical (PEC) aptasensor with target-induced photocurrent polarity switching based on a hairpin aptamer (Hp) with a G-quadruplex motif. A ready-to-use analytical device was developed by immobilizing GMS on the surface of a commercial screen-printed electrode, followed by the attachment of the aptamer. In the presence of Escherichia coli O157:H7, the binding sites of Hp with the G-quadruplex motif were opened and exposed to hemin, leading to the formation of a G-quadruplex/hemin DNAzyme. Crucially, after binding to hemin, the charge transfer pathway of GMS changes, resulting in a switch of the photocurrent polarity. Further, G-quadruplex/hemin DNAzyme enhanced the cathodic photocurrent, and the proposed sensor exhibited a wide linear range ((25.0-1.0) × 107 CFU/mL), a low limit of detection (2.0 CFU/mL), and good anti-interference performance. These findings expand the applications of NIR-responsive PEC materials and provide versatile PEC methods for detecting biological analytes, especially for food safety testing.
Subject(s)
Aptamers, Nucleotide , Biosensing Techniques , DNA, Catalytic , Escherichia coli O157 , Escherichia coli O157/genetics , Escherichia coli O157/metabolism , DNA, Catalytic/chemistry , Hemin/chemistry , Biosensing Techniques/methods , Aptamers, Nucleotide/genetics , Aptamers, Nucleotide/chemistryABSTRACT
Portable, ultrasensitive, and simultaneously quantitative detection of the nucleic acids of multiple foodborne pathogens is critical to public health. However, the current testing methods depend on costly equipment and tedious amplification steps. In this study, we propose a photoelectrochemical (PEC) biosensor combined with recombinase polymerase amplification (RPA) technology (RPA-PEC) for the rapid detection of multiple foodborne pathogens under irradiation of 980 nm light. In particular, two working surfaces were designed on homemade three-dimensional screen-printed paper-based electrodes. The genomic DNAs of Escherichia coli O157:H7 and Staphylococcus aureus was initiated by RPA on the corresponding electrode surfaces, thus forming a lab-on-paper platform. Using the formed DNA-PEC signaler, photocurrents were achieved at 37 °C after only 20 min of RPA. The detection performance was superior to that of conventional agarose gel electrophoresis, with detection limits of 3.0 and 7.0 copies/µL for E. coli O157:H7 and S. aureus, respectively. Our study pioneers a new RPA-PEC method for foodborne pathogens and provides directions for the construction of lab-on-paper platforms for the portable detection of multiple nucleic acids.
Subject(s)
Escherichia coli O157 , Nucleic Acids , Recombinases , Staphylococcus aureus/genetics , Nucleotidyltransferases , Escherichia coli O157/genetics , Nucleic Acid Amplification Techniques/methods , Sensitivity and SpecificityABSTRACT
The photoelectric response is crucial for photocatalysis, having applications in solar cells and photoelectrochemical (PEC) sensors. In this study, we demonstrate improvements in the near-infrared (NIR)-light-driven PEC response via synergism between reduced graphene oxide (rGO) and MoS2. Intriguingly, rGO modulates the morphology of MoS2, facilitating carrier generation and migration, improving the PEC performance of the resultant rGO-MoS2 sheets (GMS), and yielding an approximately 8-fold increase in the photocurrent compared to that of the pure MoS2. Based on these findings, a NIR-responsive PEC immunosensing platform for the "turn-on" analysis of Escherichia coli O157:H7 on 980 nm light irradiation is reported. Specifically, the device is a three-dimensional magnetic screen-printed paper-based electrode assembled on a home-made PEC cell, and it enables integrated separation and detection. Using a sandwich-type immunocomplex bridged by E. coli O157:H7 and a GMS PEC probe, the immunosensing platform detected E. coli O157:H7 between 5.0 and 5.0 × 106 CFU mL-1, having an extremely low detection limit of 2.0 CFU mL-1. Further, the assay enables the direct analysis of E. coli O157:H7 in milk without the need for pretreatment. Our findings suggest directions for the development of NIR-responsive paper-based PEC materials for portable biomolecule sensing.
