What’s So Great About Oral Diagnostics?
Well, a lot of things, but let’s start with the basics. In order to use a microfluidic device, you need some type of fluid right? Sure if you had some powder or fine material you could suspend it in a fluid, but for simplicity sake, let’s look at fluids as our test material. If you wanted to run a health-related diagnostic, you only have so many bodily fluids available before you have to get creative and very invasive:
- Blood
- Urine
- Saliva
- Sweat
- Mucus
- Tears
Out of all those fluids, blood (or serum) has been the preferred liquid. It is extremely rich in information and can expose a lot about a systemic condition or report on ailments located deep within the body. You have to filter it if you don’t want the blood cells in your sample, but it’s just a needle prick away. Other ‘fluids’ like mucus or saliva require a bit more work because of how thick and viscous they are, plus you need to filter out the debris floating around in your mouth. If blood is so great, why do we need anything else? Although blood is a great global fluid, sometimes you can get more detailed information by going closer to the source of the problem and choosing a more local fluid, but perhaps one of the greatest reasons is because the process to obtain the blood is still invasive. In the ideal microfluidics world of the future, we would need very small sample sizes and pin pricks wouldn’t be that bad. For now, spitting into a cup is still easier than and more enjoyable than getting stuck. Plus, exposed blood is always a health concern, and should definitely be avoided if possible.
Okay, so I guess you can see why you might want to investigate other fluids, but why saliva? Like I said before, there are some analytes from the blood present in saliva in lower concentrations, like C-Reactive Protein (CRP). In fact, tests have been proposed to monitor growth factors, drugs of abuse, steroids and infectious diseases using oral fluid. CRP is a possible indication of inflammation and is released in events like heart attacks. Detection of this protein along with others can be a good indication of an acute myocardial infarction, but you wouldn’t be able to use that alone. CRP may be present for other types of inflammation, especially a local one occurring in the mouth.
Tackling Periodontal Disease Early
But let’s not focus solely on detecting global diseases and problems. It’s still valuable to detect diseases in the mouth. Periodontal disease is a common oral infectious disease that is a leading cause of tooth loss in adults. Currently, clinical practices don’t have the capability to detect the onset of inflammation leading to periodontal disease and can’t identify the patients at the greatest risk for disease progression. A Point-of-Care device to detect this onset would permit earlier detection and could be utilized outside of the dentist’s office. Testing for periodontal disease can become much easier and widespread since you don’t need a highly trained professional to run the test, and it can be done in health care clinics or at home. There are many underserved communities that cannot afford to visit the dentist, but cheap, regular screening for disease can allow them to manage a disease before it gets out of hand. Additionally, preventing oral diseases can go a long way for the rest of the body, as periodontal disease has been connected to cardiovascular disease, stroke and osteoporosis.
Engaging Saliva in Pharmacogenomics
Finally, oral fluids can play a part in pharmacogenomics studies. Pharmacogenomics is the marriage of genetics and pharmacology. While we may think that we understand the processes of diseases, the diseases and their treatments can vary greatly from person to person depending on genetics. In an ideal world, every single drug and treatment we receive would be tailored specifically to our DNA. There is still a lot of work needed to find out which genes have greater effects on both the disease and treatment, but in order to learn more and to eventually provide tailored treatments, we need to understand our own DNA. Oral fluid can be a great source to obtain that DNA. The DNA we use can come from anywhere, so why not easily dislodge some cells in the mouth instead of pricking ourselves with needles?
There are many bodily fluids for us to choose from, but saliva has some key advantages. There are both important local and global diseases it can test. It certainly is less invasive than blood and does not require the same privacy (and planning) as urine collection. But there still needs to be work to determine the ideal biomarkers in the saliva and amplify their signals. There’s some good advice found in “Translational and Clinical Applications of Salivary Diagnostics” that not only applies to saliva POC devices, but to all their POC device brethren:
“While their analysis core is substantially smaller than that of benchtop alternatives, the network of macroscopic laboratory-based infrastructure required for sample processing, analyte detection, data processing, and reagent handling implies that these platforms are best described as ‘chips-in-a-lab’ rather than true ‘labs-on-a-chip’.”
No matter what fluid we’re using, or disease we’re screening, we need to design these devices with the clear motivation for them to be used outside our labs, and in the wild.
References
Giannobile, W., McDevitt, J., Niedbala, R., & Malamud, D. (2011). Translational and Clinical Applications of Salivary Diagnostics Advances in Dental Research, 23 (4), 375-380 DOI: 10.1177/0022034511420434
Hart, R., Mauk, M., Liu, C., Qiu, X., Thompson, J., Chen, D., Malamud, D., Abrams, W., & Bau, H. (2011). Point-of-care oral-based diagnostics Oral Diseases, 17 (8), 745-752 DOI: 10.1111/j.1601-0825.2011.01808.x