When we cry, we say a lot more about the situation than we think. Useful and quantifiable biomarkers exist in our tears — including sodium ions, which can indicate glucose molecules, dry-eye disease, show how effective drug treatments may be, and even serve as an early diagnostic tool to detect diabetes.
This is why a new collaborative team has developed a fabrication method to forge a hydrogel contact lens for biomarker sensing, according to a blog post shared on Terasaki Institute's official website.
Next-gen contact lenses use tears as therapeutic biomarkers
Surprisingly, secretions like sweat, tears, and saliva are the best source of biomarkers — with concentrations not unlike those found in blood. Tears are sterile, easy to acquire, and less prone to damage or alteration from temperature shifts.
This is why the ability to collect tears effectively and measure their pH and biomarker levels in real-time is worthwhile. The team behind this new device includes a group from the Terasaki Institute for Biomedical Innovation — and they began via the optimization of hydrogel components, which yielded elastic features. This in turn enabled the engineers to make something with a smooth and malleable shape.
Next, the team put microchannels in the hydrogel — via a 3D printed mold. Lastly, the team bonded an additional layer of hydrogel onto the microchannel surface, to enclose them.
Once finished with the prototype, the device was tested rigorously for performance in channeling and amassing fluids (tears). The team measured flow rates of artificial tears in the enclosed channels — at varying levels of hydration, with zero flow measured at complete hydration, and full spontaneous flow viewed at full hydration, read the blog post.
Contact lens with biosensors may help diagnostic procedures
Notably, when the hydrogel was mildly hydrated, the flow of liquid in the channels came to a stop — but under the force of more rhythmic pressure, the flow recommenced. This was significant because it lends credibility to the idea that eye-blinking can also provide enough pressure to create additional hydration, when needed to enable tear flow within the contact lens and, by extension, the eye itself.
"In addition to our successful fabrication of microchannels in commercial contact lens hydrogels, we also found that eye-blinking pressure may facilitate tear exchange in the lens through these microchannels," said researcher Shiming Zhang of the Terasaki Institute, according to the blog post. "This is an exciting finding because it opens the possibility for the lenses to be a means of preventing dry eye disease, a condition commonly found in contact lens wearers."
"We aim to develop a patented contact lens that actively treats this condition by enhancing tear flow in the eye," Zhang added.
After this, the team developed prototype sensors to collect, test for, and measure pH levels in the artificial tears while flowing through the enclosed microchannels. Additionally, they tested sodium levels — which showed an acceptable and expected range of sodium detection for future diagnostic procedures.
Prototype contact lens opens new biosensing solutions
There are further goals for the team — including fine-tuning humidity, applied pressure order, and hydrogel hydration — to upgrade the flow rates, in addition to the biosensing contact lens' dynamics. The team even plans to experiment with smaller channels using thinner hydrogel films before the final contact lens design is decided upon.
"The production of the successful prototype described here and the continuing efforts to perfect its capabilities mark a significant advance in contact lens biosensing," said CEO and Director of the Terasaki Institute Ali Khademhosseini, in the blog post. "Such innovative work fits in well with our institute's mission to create solutions that restore or enhance the health of individuals."
We've seen technology track conventional biomarkers before — like heart rate and steps-per-day. The Apple Watch and associated apps offer similar biosensing capabilities — which existed long before the COVID-19 crisis. Of course, the contact lens biomarker device likely won't need the heavy tear flow that comes with sobs to work. But for those who have always preferred to cry their way to wellness, the answer will soon be among us.