Visual Detection of Harmful Substances in Food

Dear Colleagues,

The rapid and reliable detection of harmful substances in food is paramount for ensuring public health and maintaining consumer trust in the food supply chain. Traditional laboratory-based methods, while accurate, are often time-consuming, expensive and require specialized equipment and personnel, making them unsuitable for rapid, on-site screening. This is where the advancement of visual detection technologies becomes critically important. By leveraging innovations in colorimetry, fluorescence and nanotechnology, these methods translate the presence of contaminants into immediate, observable signals such as color changes or visible light. This approach enables point-of-care testing for food safety, empowering regulators, food producers and even consumers to perform real-time assessments without complex instrumentation. The ability to visually confirm the presence of pesticide residues, heavy metals, foodborne pathogens, or adulterants dramatically accelerates decision-making, helps prevent contaminated goods from reaching the market and reduces the burden on centralized laboratories. Ultimately, developing sensitive, specific and user-friendly visual detection platforms is key to proactive food safety management and the minimization of foodborne health risks.

Sub-topics:

1. Lateral Flow Immunochromatographic Strips

Based on specific antigen–antibody binding, using labels such as gold nanoparticles to achieve naked-eye semi-quantitative detection of targets (e.g., veterinary drug residues, pathogenic bacteria). It is a mainstream technology for on-site rapid testing.

2. Microfluidic Paper-Based Analytical Devices

Constructing hydrophilic/hydrophobic microchannels on paper, combined with colorimetric/fluorescent probes, to achieve low-cost, parallel visual screening of multiple contaminants (e.g., heavy metal ions, pesticides).

3. Colorimetric Sensor Arrays

Mimicking the mammalian olfactory system, using cross-responsive sensing units (e.g., nanozymes, pH indicators) to generate unique color fingerprint patterns for complex components (e.g., food spoilage products, toxins).

4. Smartphone-Based Detection Platforms

Utilizing the phone's camera as a signal reader, combined with 3D-printed accessories or APP algorithms, to convert color changes from test strips, solutions, etc., into quantitative data, suitable for household or grassroots monitoring.

5. Fluorescence/Colorimetric Dual-Mode Probes

Designing a single probe (e.g., quantum dots, upconversion nanomaterials) that exhibits both fluorescence changes and visible color changes in the presence of the target, enabling complementarity between on-site screening and accurate laboratory quantification.

6. Functional Nucleic Acid Probes

Utilizing aptamers or DNAzymes to specifically recognize targets (e.g., mycotoxins, antibiotics), triggering DNA conformational changes or catalytic reactions and achieving color development through G-quadruplex/hemin mimetic enzyme catalysis.

7. Hydrogel-Encapsulated Visual Sensors

Embedding recognition elements (e.g., enzymes, nanomaterials) within transparent hydrogels, utilizing target diffusion, enrichment and in situ reactions to achieve color signal amplification and portable storage.

8. Plasmonic Nanoprobes

Based on the localized surface plasmon resonance properties of gold/silver nanoparticles, utilizing target-induced nanoparticle aggregation/dispersion to cause solution color changes (e.g., red to blue) for the detection of heavy metal ions or small molecules.

9. Aggregation-Induced Emission Fluorescent Probes

Leveraging the property of AIE molecules to be non-emissive in a dispersed state but strongly emissive upon aggregation. Target-induced probe aggregation enables "turn-on" visual detection with low background interference.

10. Portable Spectroscopy and Imaging Tools

Developing miniaturized, low-cost handheld spectrometers or hyperspectral imaging systems, combined with chemometric models, for visual, non-destructive detection of harmful components (e.g., pesticide residues, mold contamination) on or inside food surfaces.

Dr. Shengnan Zhan
Dr. Hong Duan
Guest Editors

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• visual signal readout
• nanobiosensors
• colorimetric-based dual-signal sensors
• food contaminant screening
• smartphone-based methods
• sensitive detection
• naked-eye semi-quantitative detection
• color fingerprint patterns signal amplification
• on-site rapid testing