Humans are affected by numerous diseases caused by bacteria like spp, Escherichia coli, Listeria monocytogenes, Bacillus anthracis, and Bacillus cereus. In most cases, humans encounter these pathogens via contaminated or spoiled milk, raw meat, seeds, and vegetables. Scientists have developed different types of biosensors to rapidly detect foodborne pathogens.
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Increase in Foodborne Diseases in the 21st Century
In the 21st century, controlling the occurrence of foodborne diseases proved to be challenging. The frequency of foodborne diseases and food safety-related poisoning incidents is high, regardless of the country. The infections caused by these foodborne pathogens are categorized into four groups, i.e., food poisoning, allergic diseases, infectious diseases (e.g., dysentery), and chronic toxicity.
The main difference between food poisoning and chronic toxicity is that the former occurs due to ingesting food contaminated with toxic substances, while the latter is caused by long-term consumption of a large amount of harmful substances.
Although it is difficult to estimate the global incidence of foodborne diseases, in 2011 the Centers for Disease Control and Prevention (CDC) estimated that one in every six Americans contract foodborne disease. The CDC further reported that around 128,000 individuals are hospitalized and 3000 die of foodborne diseases annually. Common pathogens that produce toxins causing foodborne diseases are Clostridium perfringens, Escherichia coli, Bacillus cereus, Vibrio cholerae, and Staphylococcus aureus.
The conventional methods to detect foodborne pathogens are biochemical reactions, selective and non-selective enrichment culture, plate separation, and serological assays. Since these techniques are time-consuming and tedious, they cannot be applied in the food industry, where rapid detection of foodborne pathogens is absolutely essential.
Rapidly detecting foodborne pathogens has been made possible with the advancements of biotechnology-based techniques, such as bacterial automatic identification systems, and point-of-care technologies. However, these techniques also have some limitations such as the requirement of purifying cultures of bacteria. Many times, more than one pathogen may be present in the food sample; therefore, there is a need for a method that targets more than one microorganism at the same time.
Rapid Detection of Foodborne Pathogens Using Biosensors
Compared to traditional methods, biosensing technology has many advantages, including high sensitivity, simple operation, and low detection limit. In addition, biosensors can rapidly detect pathogens in real-time.
Biosensors are analytical devices developed by combining biology and sensing technology. These devices convert a biological response into an electrical signal, and the intensity of the signal is directly proportional to the analyte concentration. Two main components of biosensors are a bio-receptor/bio-recognition component and a transducer. The first component identifies the target analyte and the transducer converts the recognized factor into a measurable electrical signal.
A bio-receptor could be microorganisms, enzymes, tissue, organelle, cell, nucleic acid, antibodies, bio-mimic, and bacteriophage. A transducer could be based on optical, magnetic, electrochemical, micromechanical, thermometric, piezoelectric, or a combination of one or more of these techniques.
Biosensors have been divided into three generations based on the level of integration. First-generation biosensors, e.g., electrochemical biosensors to detect glucose levels, are based on directly identifying the substrate and product of the enzymatic reaction. In the second-generation biosensors, the co-reactants/ enzymes are co-immobilized on the surface of the transducer. In third-generation biosensors, biocatalysts are directly bound to an electronic device that provides the output.
Rapid Detection of Foodborne Pathogens by Biosensors
Over the years, different types of biosensors have been developed to detect foodborne pathogens. Biosensors are used in different divisions of food industries, i.e., production to the retail unit, to limit wastage and provide high-quality food products to the consumers. Some of the common types of biosensors used in the food industry are discussed below:
Nanosensors can detect the pathogens, which cause food spoilage within minutes. In this context, an array of nanoparticles has been designed that fluoresce in different colors upon contact with food pathogens. These sensors can be placed directly into the packaging material, where they functions as an “electronic nose or tongue” to identify chemicals released due to food spoilage.
Nanosensors based on microfluidics can detect pathogens in real-time with high sensitivity. For instance, a commercially available Cyranose-320™ electronic nose system can detect S. typhimurium in inoculated beef samples. Blood- hound™ BH114 electronic nose unit is another commercially available electronic nose that can detect bacterial (B. cereus, Pseudomonas aureofaciens, and P. fluorescens) and yeast pathogens in skimmed milk media.
Microbial biosensors use microorganisms or microbial metabolites as a biological sensing unit with a transducer that can estimate the concentration of the analyte. Microbes produce various organic compounds (anaerobically or aerobically), such as ammonia and carbon dioxide, that can be detected and quantified by these biosensors.
These sensors are based on the presence of piezoelectric crystals, which vibrate at a specific frequency when an electrical signal of a specific frequency is applied. The oscillation frequency is dependent on the electrical frequency introduced to the crystals along with the total mass of crystals. Two key types of mass-based sensors are surface acoustic wave and quartz crystal microbalance biosensors. L. monocytogenes is detected using a quartz crystal microbalance biosensor. Piezoelectric antigen-antibody biosensors are used for the rapid detection of Salmonella in food samples.
An electrochemical biosensor can detect and quantify analytes using a biological recognition element and transducer. This technique is an extension of antibody-based enzyme immunoassays (ELISA). This biosensor can detect pH changes, ion formation, or oxygen consumption due to catalytic reactions. Amperometric biosensors are used for the rapid detection of E.coli, which is present in poorly cooked animal-based foods or foods washed with contaminated water.
Optical-based biosensors are based on reflection, absorption, refraction, Raman, fluorescence, dispersion, phosphorescence, and chemi-luminescence properties. These biosensors are highly sensitive and selective and are typically used to detect bacterial pathogens. The fiber-optic biosensors are used to detect L. monocytogenes at low concentrations in processed foods, such as meat, shellfish, vegetables, and unpasteurized milk.
References and Future Reading
Nnachi, C.R. et al. (2022) Biosensors for rapid detection of bacterial pathogens in water, food and environment. Environment International. 166, pp. 1-20. https://www.sciencedirect.com/science/article/pii/S0160412022002847?via%3Dihub
Zhang, Z. et al. (2019) Electrochemical Biosensors for Detection of Foodborne Pathogens. Micromachines (Basel). 10(4), p. 222. https://pubmed.ncbi.nlm.nih.gov/30925806/.
Choudhary, U. (2019) Biosensors for detection of food borne pathogens. The Pharma Innovation Journal. 8(4), pp. 386-396. https://www.thepharmajournal.com/archives/?year=2019&vol=8&issue=4&ArticleId=3263
Yamada, K. et al. (2015) Rapid detection of multiple foodborne pathogens using a nanoparticle-functionalized multi-junction biosensor. Biosensors and Bioelectronics. 77, pp. 137-143. https://www.sciencedirect.com/science/article/abs/pii/S0956566315304279?via%3Dihub
Poltronieri, P. et al. (2014) Biosensors for the Detection of Food Pathogens. Foods. 3(3), pp. 511-526. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5302249/