In this study, based on the specific binding of nucleic acid aptamers (Apts) to 3,3′,4,4′-tetrachlorobiphenyl (PCB77), an ultrasensitive electrochemical aptasensor was constructed for the detection of PCB77. The Apts were captured by hairpin (HP) deoxyribonucleic acid capture probes through complementary base pairing. The large surface area of reduced graphene oxide (rGO) combined with Ag-Cu 2 O significantly improved the efficiency of electron transfer on the electrode surface and provided a large number of binding sites for HP capture probes. Streptavidin (SA)-modified CeO 2 /AuPt was used as signal-generating material to amplify electrical signals cooperatively with Ag-Cu 2 O/rGO, and it was also combined with biotin-modified nucleic acid Apts via the SA-biotin system to form signal labels, which significantly improved the sensitivity of the aptasensor. The morphology and size of the synthesized materials were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The internal structure and composition of the materials were further analyzed by x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy. The sensor assembly process was confirmed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Differential pulse voltammetry (DPV) was used to optimize the experimental conditions and evaluate the performance of the sensor. Under optimal conditions, the detection limit of the aptasensor was 0.069 ng/L, and the dynamic range was 0.1–10 3 ng/L, providing a high-quality platform for PCB77 detection. Graphical Abstract
Yue Guo,Hai Wang,Xiaowei Ma,Jing Jin,Wei Ji,Xu Wang,Wei Song,Bing Zhao,Chengyan He
Highly sensitive biosensors are essential in medical diagnostics, especially for monitoring the state of an individual’s disease. An ideal way to achieve this objective is to analyze human sweat secretions by noninvasive monitoring. Due to low concentrations of target analytes in human secretions, fabrication of ultrasensitive detection devices is a great challenge. In this work, Ag–Cu2O/reduced graphene oxide (rGO) nanocomposites were prepared by a facile two-step in situ reduction procedure at room temperature. Ag–Cu2O/rGO nanocomposites possess intrinsic peroxidase-like activity and rapidly catalyze oxidation of the peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2. On the basis of the excellent SERS properties and high peroxidase-like activity of the Ag–Cu2O/rGO nanocomposites, the catalytic oxidation of TMB can be monitored by SERS. This approach can detect H2O2 and glucose with high sensitivity and distinguish between diabetic and normal individuals using glucose levels in fingerprints. Our work provides direction for designing other SERS substrates with high catalytic activity and the potential for application in biosensing, forensic investigation, and medical diagnostics.
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