Fang Li

Construction of a nanomaterial-modified aptasensor for AFB ₁ detection and the principle behind its fluorescent signal changes.

Kanamycin (KANA) is a veterinary drug residue that is highly scrutinized in food safety testing. In this study, a metal-organic framework-based aptamer-nanoenzyme (NH₂-MIL-88B(Fe)/CDs-Apt) was introduced for the dual-mode detection of KANA. NH₂-MIL-88B(Fe) catalyzes the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H₂O₂ to form blue ox-TMB, thereby enabling colorimetric detection. As a fluorescence quencher, NH₂-MIL-88B(Fe) quenches the fluorescence of CDs via photogenerated electron transfer (PET) or fluorescence resonance energy transfer (FRET) mechanisms. The detection limits were 0.716 fM (fluorescent) and 0.709 fM (colorimetric), respectively. The proposed aptasensor was successfully applied to the detection of KANA in eggs, honey, and lake water. This aptasensor demonstrates high sensitivity and accuracy, as well as broad application potential.

Herein , an electrochemical/photoelectrochemical (EC/PEC) dual-mode sensing platform based on carbon dots/liquid exfoliated graphene (CDs/LEG) nanocomposites was developed in this work. The CDs/LEG heterogeneous effectively exploited the excellent photoelectric activity of CDs and the high conductivity of LEG. Ferrocene-labelled aptamer (Fc-Apt) and methylene blue-labelled complementary DNA (MB-cDNA) were introduced as dual-signal probes. Upon aflatoxin B1 (AFB₁) binding, it competitively displaced MB-cDNA, restoring Fc-Apt hairpin conformation and causing MB to move away from the electrode surface while Fc approached it. This conformational change significantly increased the I_Fc to I_MB peak current ratio (I_Fc/I_MB), enhancing the EC signals; meanwhile, the aptamer complex immobilized on the electrode surface reduced the PEC signals through spatial site-blocking and light-shielding effects. The dual-mode responded synergistically to form a unique self-validation mechanism, which showed excellent linearity over the AFB₁ concentration range of 0.01-100 ng/mL, with detection limits (LOD) of 1.356 pg/mL (EC mode) and 0.087 pg/mL (PEC mode). Graphical Abstract

As ubiquitous pollutants, heavy metal ions can accumulate in the food chain, increasing toxicity through synergistic effects and posing health risks to humans and other organisms. In this study, we successfully developed a dual-signal aptasensing interface for simultaneous detection of cadmium ions (Cd²⁺) and lead ions (Pb²⁺). The 2D layered Ti₃C₂ MXene and liquid exfoliated graphene (LEG) composite nanomaterials were employed as ITO electrode modification materials, which exhibited enhanced electrochemical properties. The Cd²⁺-specific aptamer labeled with Nile blue and Pb²⁺-specific aptamer labeled with ferrocene bind to their complementary strands immobilized on the electrode surface, resulting in a dual-signal interface. In the presence of target ions, the aptamers specifically recognized and captured the targets, subsequently detaching from the electrode surface, leading to changes in the dual-signals and thereby enabling simultaneous detection of Cd²⁺ and Pb²⁺. The limits of detection for Cd²⁺ and Pb²⁺ were determined to be 0.689 pM and 1.548 pM, with linear response ranges of 0.1 pM to 10 μM and 0.01 pM to 10 μM. The effectiveness of the proposed aptasensor in determining Cd²⁺ and Pb²⁺ simultaneously in water and vegetables has been demonstrated, providing substantial evidence for its potential application in food safety and environmental monitoring.

A self-assembly aptasensor based on a two-round signal amplification strategy for kanamycin trace detection was demonstrated by employing carbon dot decorated Ti₃C₂ MXene as electrode modification material and the complex of double-stranded DNA (dsDNA) and methylene blue as probes.

Quantitative detection of veterinary drug residues in animal-derived food is of great significance. In this work, a simple and label-free electrochemical aptasensor for the highly sensitive detection of chloramphenicol (CAP) in milk was successfully developed based on a new biosensing method, where the single- or few-layer Ti₃C₂ MXene nanosheets functionalized via the specific aptamer by self-assembly were used as electrode modifiers for a glassy carbon electrode (aptamer/Ti₃C₂ MXene/GCE). Differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), scanning electron microscopy (SEM), atomic force microscope (AFM), and so on were utilized for electrochemical and morphological characterization. Under the optimized conditions, the constructed aptasensor exhibited excellent performance with a wider linearity to CAP in the range from 10 fM to 1 μM and a low detection limit of 1 fM. Aptamer/Ti₃C₂ MXene/GCE demonstrated remarkable selectivity over other potentially interfering antibiotics, as well as exceptional reproducibility and stability. In addition, the aptasensor was successfully applied to determine CAP in milk with acceptable recovery values of 96.13% to 108.15% and relative standard deviations below 9%. Therefore, the proposed electrochemical aptasensor is an excellent alternative for determining CAP in food samples.