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.

Aptamer functionalized graphene field effect transistor (apta-GFET) is a versatile bio-sensing platform. However, the chemical inertness of graphene is still an obstacle for its large-scale applications and commercialization. In this work, reduced carboxyl-graphene oxide (rGO-COOH) is studied as a self-activated channel material in the screen-printed apta-GFETs for the first time. Examinations are carefully executed using lead-specific-aptamer as a proof-of-concept to demonstrate its functions in accommodating aptamer bio-probes and promoting the sensing reaction. The graphene-state, few-layer nano-structure, plenty of oxygen-containing groups and enhanced LSA immobilization of the rGO-COOH channel film are evidenced by X-ray photoelectron spectroscopy, Raman spectrum, UV-visible absorbance, atomic force microscopy and scanning electron microscope. Based on these characterizations, as well as a site-binding model based on solution-gated field effect transistor (SgFET) working principle, theoretical deductions for rGO-COOH enhanced apta-GFETs’ response are provided. Furthermore, detections for disturbing ions and real samples demonstrate the rGO-COOH channeled apta-GFET has a good specificity, a limit-of-detection of 0.001 ppb, and is in agreement with the conventional inductively coupled plasma mass spectrometry method. In conclusion, the careful examinations demonstrate rGO-COOH is a promising candidate as a self-activated channel material because of its merits of being independent of linking reagents, free from polymer residue and compatible with rapidly developed print-electronic technology.

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.