Identifying pathogens in food and drinking water has always been an important task. Escherichia coli (E. coli) is one of these pathogens found in food and water samples. Although there are several traditional microbiological analysis methods, the most advanced methods are based on biochemistry and molecular biology. New nanotechnology methods based on optical methods provide cheaper, more reliable, faster, and more sensitive platforms for detecting E. coli in a given sample. Various optical methods are available for the detection of E. coli. The most recently developed strategies to develop sensors for detecting E. coli are fluorescence, colorimetric, surface-enhanced Raman spectroscopy, surface plasmon resonance, localized surface plasmon resonance, and chemiluminescence. In addition, optical detection of E. coli in smartphone, paper-based, and portable devices are also considered. It has been shown that these optical nanobiosensors have high sensitivity and low detection limits for E. coli detection.

Lead is a heavy metal with increasing public health concerns on its accumulation in the food chain and environment. Immunoassays for the quantitative measurement of environmental heavy metals offer numerous advantages over other traditional methods. ELISA and chemiluminescent enzyme immunoassay (CLEIA), based on the mAb we generated, were developed for the detection of lead (II). In total, 50% inhibitory concentrations (IC₅₀) of lead (II) were 9.4 ng/mL (ELISA) and 1.4 ng/mL (CLEIA); the limits of detection (LOD) were 0.7 ng/mL (ic-ELISA) and 0.1 ng/mL (ic-CLEIA), respectively. Cross-reactivities of the mAb toward other metal ions were less than 0.943%, indicating that the obtained mAb has high sensitivity and specificity. The recovery rates were 82.1%–108.3% (ic-ELISA) and 80.1%–98.8% (ic-CLEIA), respectively. The developed methods are feasible for the determination of trace lead (II) in various samples with high sensitivity, specificity, fastness, simplicity and accuracy.