# An Overview of the Public Health Challenges in Diagnosing and Controlling Human Foodborne Pathogens
## 4 Diagnostic Approaches of Foodborne Pathogens
### Methods Based on Nucleic Acids
#### 4.2.5 Detection Technology Based on Biosensors  
Biosensors are used as a tool for analysis that consists of two components: the biosensor and the transducer. Microbes can be identified primarily by their antigens (antibodies), sensitive enzymes, alkaloids and their gene sequences [190; 191; 192]. The materials being tested undergo biological reactions when they are in contact with these substances. By using signal transducers, these interactions can be converted into quantifiable electrical signals, which are then detected and read by amplifiers [193; 194]. A variety of types of biosensors can be classified as biosensors based on their operating principles, including optical, electrochemical, enzyme, physical and mechanical biosensors [195; 196; 197; 198]. There are two types of biosensors commonly used for the rapid detection of foodborne pathogens: optical biosensors and electrochemical biosensors [199; 200]. The rapid detection ability of optical biosensors, as well as their sensitivity and selectivity, make them extremely useful for identifying foodborne pathogens [201]. The most popular optical sensing technologies currently being used are chemiluminescence, calorimetry, fluorescence and surface plasmon resonance [202]. [PERSON] et al. [203] used silver nanoparticles that were functionalized with oligonucleotide for optical biosensing. With an effective pooling method and a complex matrix that ensured viable cells detection, they developed a novel method for simultaneously detecting _Salmonella_ species strains optically in complex matrices. Based on the results of the study, it was confirmed that the test was able to detect <10 CFU/mL of the target bacteria with a 100% specificity, thus making it highly sensitive to its target species. Using an electric control-based photocatalytic nanocomposite in conjunction with a nanophotonic structure, [PERSON] et al. [204] were able to detect foodborne pathogens without a label by using optical nanophotonic detection. Biosensors are capable of identifying _Escherichia coli_ at a concentration of 5000 CFU/mL, which is very high. In order to detect _Salmonella typhimurium_ lipopolysaccharideandide and _Salmonella_ bacteria in drinking water, [PERSON] et al. [205] used white light reflectance spectroscopy to develop an optical biosensor. The experiment took approximately 15 min to complete, and the detection limits for bacteria and lipopolysaccharideare determined to be 4 ng/mL and 320 CFU/mL, respectively. It has been shown that electrochemical biosensors undergo electrochemical reactions with target analytes on the electrode interface, resulting in changes in currents, potentials, inductances or permeability on the sensor surface [206; 207]. A biosensor is an electrochemical system that uses an electrode as a signal converter. There are three different functional porous pseudo-carbon paste electrodes that can be fabricated [208]. There is a linear correlation between the peak current of porous pseudo-carbon paste electrodes and the _Escherichia coli_ O157:H7 concentration between \(1.0\times 10^{3}\) and \(1.0\times 10^{7}\) cells /mL, with a limit of detection as low as \(8.0\times 10^{2}\) cells /mL when the porous pseudo-carbon paste electrode was used as the anodic stripping anode. The target analyte can be measured by keeping an eye on the fluctuations in these signals while they are being analyzed. As a method for developing a label-free and quick electrochemical biosensor for _Listeria monocytogenes_ detection, [PERSON] et al. [209] converted platinum and chitosan into a biomimetic nanostructure that responds to pH variations. Using a reduced graphene oxide-gold nanocomposite, [PERSON] et al. [210] developed an electrochemical sensor for detecting _Staphylococcus aureus_ using single-stranded DNA as an aptamer. By using ferri-/ferrocyanide as a redox probe, [PERSON] et al. [211] identified _Staphylococcus aureus_ using impedance spectroscopy by monitoring the change in resistance before and after _Staphylococcus aureus_ was immobilized on a gold electrode.