Single-molecule detection of proteins and toxins in food using atomic force microscopy

Background: Food safety is vital in everyday life. Food toxins are small peptides or proteins that can cause disease by disrupting biological macromolecules such as enzymes or cellular receptors. Toxins are introduced either externally or from internal, spoilage-related pathogens. To keep these unsafe foods off the market, detection techniques for various toxins have been devised. Although many techniques serve this purpose well, challenges remain regarding sensitivity, specificity, and cost, especially for trace amounts of highly lethal proteinaceous toxins. Scope and approach: Atomic force microscopy (AFM) is a widely used nanotechnology for imaging and force measurement in biophysics and biology. Its high sensitivity in probing specific, single-molecule binding between molecules is applicable to food toxin detection. In this review, after a summary of the development of AFM, different detection operation modes are introduced along with examples of their applications. Key findings and conclusions: Cantilever sensing and recognition imaging are found to be the appropriate AFM techniques for detection. Their shared functionalization approaches are outlined for two categories of surfaces: silicon and gold. Recent progress in AFM biosensors and their applications to food toxin detection are discussed. Single-molecule sensitivity and ease of designing sensing schemes make these AFM techniques excellent candidates for real-world application. Existing challenges in designing sensing molecules and preventing the food matrix from confounding signals are not only applicable to AFM techniques but to most current biosensors. Through the collaboration among materials science, chemistry, and molecular biology, solving these issues will promote significant advancement in AFM-based food toxin detection.