Squid Ink: A Periodontal Map Maker

Gourmet delicacies such as squid ink pasta, a recently rediscovered culinary specialty, are on the rise. Did you realize that such an epicurean meal could in fact benefit your oral hygiene?

Imagine entering the dentist’s office with severe oral discomfort. You are strapped to the chair and subjected to painful probing with sharp instruments to look for signs of gum disease. What if you could solve this problem with an aquatic-derived mouthwash instead?

The first step to grasping the role of squid ink in treating oral diseases is by understanding the specific condition. Gum disease, also referred to as periodontitis, is a chronic inflammatory disease that affects the soft and hard tissue surrounding the teeth. It occurs as a result of poor brushing and flossing, leading to the accumulation of plaque and harmful bacteria. It initially appears with inflamed gums (gingivitis), but if not treated, can lead to severe oral pain and tooth loss. It is even associated with certain systemic diseases such as cardiovascular disease, cancer and Alzheimer’s disease.

The conventional method for dentists to assess gum health is by using a periodontal probe, a metal “measuring stick” that is inserted between the teeth and gums to measure the extent of gingival attachment, or pocket depth. However, this measurement process can be time consuming, painful, and subjective, needing to be carried out individually for each tooth.

Recently, a new imaging technique was proposed by researchers at the University of California, San Diego to overcome these limitations. The study, titled “Photoacoustic imaging for monitoring periodontal health: a first human study”, was published in the imaging journal, Photoacoustics. The lead author, Colman Moore, is a Ph.D. candidate studying biomedical applications of nanoengineering in Dr. Jesse Jokerst’s Bio-Imaging Lab.

The technique is a continuation of prior lab work on new oral imaging methods and consists of two steps: 1) Applying a squid ink solution to the gums, and 2) Performing photoacoustic imaging.

Photoacoustic imaging is an alternate form of ultrasound imaging, an affordable and noninvasive imaging technology. In photoacoustic imaging, light is pulsed by a transducer and absorbed by the target tissue. On a molecular and nano- scale, the energy is converted to heat and released as a brief pressure wave detectable with ultrasound. This noninvasive approach can penetrate soft tissues at varying depths and generate cross-sectional images of each section.

In his research work exploring the use of squid ink in dentistry, Moore and his colleagues conceptualized an ultrasound technique: something affordable and accurate. The specific approach is called photoacoustic imaging, where light is absorbed directly by the target tissue and thermo-elastic expansion generates waves that exit out of it. This specific approach could penetrate soft tissue at varying depths and generate results for each section.

The squid is one particular organism whose ink has several known pharmacological properties like minimizing tumor growth, anti-hypertensive actions and antibacterial properties. What stood out in this case was the ink’s unique response to near-infrared light, caused by melanin nanoparticles that allow the ink to briefly expand upon optical excitation and generate photoacoustic signals. It is also unique in that it does not stain teeth when in use.

“UV light is only able to move through a small layer, less than a millimeter,” Moore explained, “On the other hand, the 600 to 1000 nanometer, or near-infrared light, is valuable because it can penetrate deeper through the tissue.”

Moore explains that when melanin nanoparticles from the squid ink solution fill gaps between the gum and tooth (the gingival sulcus), they can efficiently absorb the near-infrared light generated by the photoacoustic transducer. This generates imaging signals and allows the research team to ‘sketch’ out a map of deep pockets of soft tissue degeneration for each tooth.

The work was validated in pig jaws and a human case study, but further human trials are ongoing. The melanin amounts are safe in terms of pH and have good buffer ability, which means the substance is viable for human oral consumption and will not affect the taste of any other food or beverages that are eaten after the procedure. The salty taste caused by the ink could easily be masked with artificial flavoring agents.

When asked how he comes up with ideas for his research projects, Moore emphasized the collaborative nature of the work and Dr. Jokerst’s mentorship, also describing the process as an “iterative rationale to turn an introductory idea into a finished concept.” He drew parallels to a different project, using a light-scattering technology to precisely count amyloid-beta protein fibrils in Alzheimer’s disease. While the motivation for that idea was planted as an undergraduate intern in an Alzheimer’s research lab, he could only develop the concept after gaining further experience, perspective and scientific guidance as a graduate student.

Ultrasound devices, like the photoacoustic imaging technology tested by Dr. Moore in Dr. Jokerst’s lab, may soon be adopted in dental offices. Developing better predictive algorithms can eliminate error and account for logarithmic reductions in the complexity of the detection process. However, developing those algorithms can be its own challenge. Once those hurdles are overcome, a sea-animal byproduct may become a highly effective periodontal mapmaker.