Volume 9 • 2022 • Issue 3

Dr. Siqueira hopes that measuring the volume of saliva will become a routine part of dental examinations. And as health care becomes more personalized, testing saliva for certain proteins could become a key part of how dentists care for patients. than 100 peer‑reviewed scientific papers. Indeed, Dr. Siqueira is so enthusiastic about his research that his personalized licence plate reads “SALIVA.” A few years ago, Dr. Siqueira and his team developed a nanoparticle that adheres to teeth and has pH sensitivity. 4 It opens when the pH level in the mouth drops. When the nanoparticle opens, it releases a specialized protein that kills bacteria and protects tooth enamel. When the normal pH of the mouth is restored, the nanoparticle closes and saves some of the protein still inside for the next time the pH is low. “When we eat something or drink a sweetened coffee, the pH of our saliva falls and that is when our teeth are vulnerable,” says Dr. Siqueira. “Then, after 10 to 20 minutes, our saliva returns our mouths to a pH of about 6.8.” The nanoparticles provide protection during those moments when teeth need it most. One nanoparticle can remain in the mouth and cycle through the process for up to six hours. Dr. Siqueira says the potential applications for nanoparticle technology are promising. “I hope that one day it will be available as a mouthrinse, or a soft drink,” he says. “It could also be great for use in pets. The benefits that could come from strategically using proteins to change biofilms is exciting.” The technology has been tested in vitro and in the lab on mice and rats with successful outcomes. “Much of the oral health advice we give our patients is about trying to change human behaviour,” says Dr. Siqueira. “We can ask people to eat less sugar, but changing actual behaviours is hard. It’s good to have additional kinds of tools available.” Early research into saliva included measuring the flow rate of saliva; too little saliva can have significant negative impacts on oral health. “Hyposalivation is a side effect of many of the most common medications,” says Dr. Siqueira. Both over-the-counter and prescription medications cause dry mouth, from painkillers to antidepressants to high blood pressure medications. An estimated 1 in 4 older adults suffer from dry mouth. Saliva is also very difficult to synthesize, and, currently, there are no effective saliva substitutes for patients with severe dry mouth, although there are medications that increase natural production of saliva. Research moved into identifying electrolytes in saliva, then identifying proteins. “Proteomics, in which scientists identify and characterize proteins in living systems, has been very fruitful in the study of saliva. In the past decades, we went from identifying about 40 proteins in saliva to 4,000,” says Dr. Siqueira. “Each protein has a function in the mouth or in the body as a whole, it’s there to do something important.” 1 His research has shown that salivary proteins bond together to form a protective shield for teeth against bacteria. 2 In his lab, Dr. Siqueira and his team use a computer simulation to chart how existing proteins in saliva would evolve over time. These more evolved “super” proteins can then be synthesized to help protect against tooth decay or gum disease. Dr. Siqueira’s lab also analyzes proteins to find biomarkers for systemic diseases using saliva. “Saliva has many diagnostic applications,” he says. “Currently, we are working on a project to identify biomarkers for COVID-19 using proteomics in saliva, and our initial data is showing that the process is very robust and sensitive. We are detecting peptides created by the virus in saliva instead of the RNA of the virus.” 3 37 Issue 3 | 2022 | Issues and People