Team:THIS-China/Description

Project Description

Dental plaque, a biofilm consisting of a syntrophic consortium of a variety of bacteria, can result in gum and dental diseases such as tooth decay [1]. It has an astonishingly high global prevalence, troubling billions of people, including many living in developed countries. For instance, in France, the prevalence of dental plaque exceeded 50% in 2017, despite the provision of reasonably priced and regular dental treatments for approximately 95% of the population [2].

Deposition of dental plaque on cervical margins and around the gumline is a major cause of tooth decay, which leads to severe pain that interferes with daily life. If left untreated, tooth decay may even develop into tooth abscess. The containing bacteria can cause swollen gums as well as facial swelling when there is perforation of abscess to surrounding muscular tissue.

Some of our team members’ daily life routines are subtly afflicted by dental plaque, mainly because the disease was not noticed at an early stage. This was the inspiration for us to design a device to solve this problem. In addition, the presence of the COVID-19 pandemic has brought about inconvenience for those wanting to request appointments and do regular dental checkups. Therefore, we decided to propound a novel and preventative method of performing the early detection of dental plaque utilizing synthetic biology.

Pertinent literature provided us with information that the anaerobic coccus Streptococcus mutans was the causative agent of plaque formation [3]. As one of the early colonizers growing inside salivary pellicles, this bacterium can survive and thrive under acidic pH. It also metabolizes sucrose into a sticky extracellular polysaccharide which coheres bacteria to form dental plaque more rapidly than other strains. Our team therefore opted for finding the means of fast and efficient early detection of S.mutans. Traditional identification methods mainly involve the usage of disclosing solution or explorer, which require highly precise calibration of indices according to surface area of plaque covering the patient’s teeth [4]. Implementing this assessment can be both time consuming and expensive. More advanced measures of higher specificity, such as MRI imaging and X-ray radiography, require computed apparatuses including cone beam CT machines, which are exclusive to hospitals and imaging centers and thus can be difficult to access during the current pandemic [5].

After participating in several discussions with our PI, conducting independent research, and browsing the wiki of iGEM17_CCU_Taiwan, we became aware that S.mutans is able to conduct quorum sensing via competence regulon. During this process, it secretes small-peptide pheromone named CSP (Competence-Stimulating Peptide) to drive other bacteria out and form a biofilm. CSP can be detected by the comED regulatory system in S.mutans. The pheromone first binds to comD kinase, and the comD-CSP complex attaches to comE membrane protein, which phosphorylates the latter and then activates downstream genes. We consequently designed a engineered cell using E.coli as the host, and incorporated the aforementioned two-component system into it. Moreover, a perusal of team UCL’s wiki in 2014 inspired us to substitute the downstream genes to the genes which express cotA, a polyphenol oxidase that degrades azo dyes when active. This allows the detection result—which comes in the form of color change—to be observed by the naked eye rather than microscopy if, for example, fluorescent proteins are used to demonstrate the presence of CSP.

In order to put our project into practical application, an oral rinse containing the genetically modified E.coli as the detection system is being created. Portable and user-friendly, this product enables easy recognition of dental caries at home, and using it on a daily basis prevents dental plaque from building up in the long run.

References

[1] Darby ML, Walsh MM (2010). Dental Hygiene Theory and Practice

[2] Mazevet ME, Garyga V, Pitts NB, Pennington MW. The highly controversial payment reform of dentists in France: seeking a new compromise after the 2017 strike.

[3] Friedman, J. Y. (2011). The Role of Streptococcus Mutans in the Formation of Dental Caries: An Ecological Perspective. The Science Journal of the Lander College of Arts and Sciences, 5(1).

[4] H. Loe, “The gingival index, the plaque index and the retention index systems,” J. Periodontol., 38 610 (1967).

[5] Lee, S., Oh, Si., Jo, J. et al. Deep learning for early dental caries detection in bitewing radiographs. Sci Rep 11, 16807 (2021). https://doi.org/10.1038/s41598-021-96368-7