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Listeria monocytogenes (L. monocytogenes) are a common foodborne pathogen responsible for many foodborne illness outbreaks in recent years. Currently, Listeria contamination in food products is identified only through molecular tests conducted in diagnostic laboratories. No established phage-based diagnostic methods for L. monocytogenes during food production or processing are used. Here we report a potentially disruptive rapid diagnostic method based on electrochemical biosensing principles that use bacteriophages as bioreceptors for selective identification and quantification of L. monocytogenes. Electrochemical biosensors are good alternatives to molecular detection methods due to their ease of use, high specificity, sensitivity, and low cost. Bacteriophages can serve as excellent biorecognition elements in biosensors due to their robust stability in a range of environmental conditions and their ability to distinguish between live and dead bacterial cells. The impedimetric biosensing platform for L. monocytogenes detection was developed by immobilizing P100 bacteriophage onto quarternized polyethylenimine modified carbon nanotubes using an in-house developed molecular tethering method. The resulting sensor showed high selectivity and sensitivity toward L. monocytogenes with a limit of detection of 8.4 CFU/mL. Initial results demonstrate that the biosensing platform is highly reliable in its selectivity towards its target analyte, L. monocytogenes.

Foodborne pathogens are an important diagnostic target for the food, beverage, and health care industries due to their prevalence and the adverse effects they can cause to public health, food safety, and the economy. The standards that determine whether a given type of food is fit for consumption are set by governments and must be taken into account when designing a new diagnostic tool such as a biosensor platform. In order to meet these stringent detection limits, cost, and reliability standards, recent research has been focused on developing lab-on-a-chip-based approaches for detection devices that use microfluidic channels and platforms. The microfluidics-based devices are designed, developed, and used in different ways to achieve the established common standards for food pathogen testing that enable high throughput, rapid detection, low sample volume, and minimal pretreatment procedures. Combining microfluidic approaches with electrochemical biosensing could offer affordable, portable, and easy to use devices for food pathogen diagnostics. This review presents an analysis of the established common standards and the recent progress made in electrochemical sensors toward the development of future lab-on-a-chip devices that will aid ‘collection-to-detection’ using a single method and platform.

Titanium and titanium alloys are used in biomedical implants such as dental screws due to their excellent mechanical strength and high resistance to corrosion. The corrosion resistance of these alloys is largely due to the formation of a passive oxide layer on the titanium surface when in contact with oxygen. For the application of use in dental implants, titanium’s ability to withstand corrosion in the presence of oral bacteria is of utmost importance, specifically in the presence of Streptococcus mutans, the most common plaque causing oral bacteria. Previous literature has explored the effects of the formation of a S. mutans biofilm on the corrosion resistance of commercially pure titanium [1]. A decrease in corrosion resistance is observed following the formation of the biofilm, however this decrease in corrosion resistance does not invalidate the viability of titanium for use in orthodontic systems. Due to the electrochemical and material similarities between titanium and zirconium, including the formation of a passive oxide layer on the zirconium surface and high material strength, there is evidence to suggest zirconium and zirconium alloys may be a viable alternative to titanium for these applications [2]. Previous literature has explored the use of titanium-zirconium alloys in such applications and found no decrease in their ability to withstand colonization and microbiologically induced corrosion in the presence of Streptococci species relative to commercially available titanium [3]. The aim of this current research is to begin the exploration of the feasibility of zirconium based materials in orthodontic applications by investigating the microbiologically induced corrosion of commercially pure zirconium and a zirconium-niobium alloy in the presence of S. mutans and compare them against commercially pure titanium. References: [1] Souza, Júlio C.M., et al. “Corrosion Behaviour of Titanium in the Presence of Streptococcus Mutans.” Journal of Dentistry, vol. 41, no. 6, 2013, pp. 528–534., https://doi.org/10.1016/j.jdent.2013.03.008. [2] Renganathan, Gunarajulu, et al. “Orthopedical and Biomedical Applications of Titanium and Zirconium Metals.” Fundamental Biomaterials: Metals, 2018, pp. 211–241., https://doi.org/10.1016/b978-0-08-102205-4.00010-6. [3] Siddiqui, Danyal A., et al. “Evaluation of Oral Microbial Corrosion on the Surface Degradation of Dental Implant Materials.” Journal of Periodontology, vol. 90, no. 1, 2018, pp. 72–81., https://doi.org/10.1002/jper.18-0110.