Microfluidic technology has been studied ever since the early 1990s, allowing researchers to study liquid transport rules on the micrometer and nanometer scales or process small amounts of fluidics using channels measuring from tens to hundreds of micrometers. Current advancements in microfluidic technology undoubtedly have enhanced its applications in life science and medical research, including food safety monitoring.
What Makes Microfluidics Outstanding?
Compared to traditional biochemical instruments that consume a large number of fluidic samples with large space occupied and complex operations, microinstruments based on biosensors and bioelectronics outperform traditional instruments with higher detection efficiency and improved accuracy. Micro total analysis systems and laboratory-on-a-chip systems are gradually applied in a wide range of biological analyses because microfluidic chips are featured with increasing sensitivity and miniaturization, high throughput, and low cost. Microfluidic rapid detection now has been used for in vitro diagnostics, and other outstanding microfluidic technologies have been embedded in the other fields.
Microfluidic Chip Technology in Food Safety Monitoring
Food safety accidents in recent years force people to pay much attention to chemical contents, including pesticide residues, heavy metals, and excessive additives, as well as microbial contamination such as Bacillus cereus, Listeria monocytogenes, Campylobacter jejuni, Sonne dysentery bacillus, E. coli, and Salmonella typhimurium. However, food issues involve production, processing, and delivery from farm to table, in which food safety is difficult to be thoroughly monitored and analyzed using conventional detection methods like mass spectroscopy (MS), high-performance liquid chromatography (HPLC), enzyme-linked immunosorbent assay (ELISA), gas chromatography (GC), and capillary electrophoresis (CE). Traditional instruments also have limitations in cost, cycle time, operations, sensitivity, etc.
Therefore, methods of food safety assays on microfluidic chips are developed to satisfy the needs of the on-site, real-time, rapid, and portable detection of food quality and safety. Food safety analysis based on microfluidic chip technology is able to integrate sample pretreatment, separation, and detection into a chip measured a few square centimeters by designing a proper size and curvature of the flow channel, micro-valves, and cavity.
Ultimately, the whole detection of food safety has become miniaturized and automatized and is now widely applied to detect pesticide residue, pathogenic bacteria, heavy metals, and additives in food.
Pesticide Residue Detection
Though the primary aim of pesticides is to protect crops and improve the yield, recent studies show that people are increasingly developing cancer by eating food containing pesticide residues.
As a result, researchers have to get dedicated to developing portable, highly automated, and low-cost pesticide residue detection equipment. Fortunately, obvious outcomes have been achieved, including paper chips using the inkjet printing technique to detect organophosphorus pesticide (OPS) residues in food and beverage, polydimethylsiloxane (PDMS) microfluidic immunosensor chips embedded with the gold interdigital array microelectrode (IDAM) and the anti-chlorpyrifos monoclonal antibodies, as well as multilayer paper chip based on enzyme inhibition and internal heating technique.
Pathogenic Bacteria Detection
More and more news reports that people are food poisoned after consuming foods with pathogenic bacteria, forcing scientists to develop methodologies to detect and quantify pathogenic bacteria in foods. Three of the most common pathogenic bacteria are Escherichia coli, Salmonella, and Listeria monocytogenes. Different microfluidic systems without complex concentration steps now have been developed to detect bacterial pathogens, such as a loop-mediated isothermal amplification (LAMP) combined system based on microfluidic chips with a carbon nanotube (CNT) multilayer biosensor to detect E. coli and an eight-chamber lab-on-a-chip (LOC) system integrated with magnetic bead-based sample preparation and LAMP to detect Salmonella species in food.
Heavy Metal Detection
It's widely known that accumulative heavy metal elements in the human body contribute to acute or subacute poisoning and chronic poisoning by making protein and various enzymes inactive.
To detect the content of heavy metals in food, a disposable paper-based sensor for the determination of copper and other metal ions is developed by researchers. Other paper-based microfluidic instruments for the detection of heavy metal in food include electrochemical chips based on square wave anodic stripping voltammetry, and devices based on fluorescently labeled single-stranded DNA (ssDNA) functionalized graphene oxide sensors, and so on.
Food Additives Detection
Microfluidic technology can also be used to analyze the food additives, especially pigments that can enhance or change the color of food. In that illegal and excessive food additives are teratogenic or carcinogenic, detection and analysis of pigments in food based on microfluidics are gradually put into practice with the development of paper-based microfluidic chips for the separation and detection of pigments.
The industrialization of microfluidic chips is trending for more in-depth basic research and more widely expanded the application fields.
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