Researchers at the University of Illinois (UI) have developed a gel laden with gold nanoparticles that changes color when it reacts with a teardrop containing ascorbic acid released from a wound to the eye.
The study has been newly published in the journal Biosensors and Bioelectronics.
The sensor, called OjoGel, can measure ascorbic acid levels, a key marker of eye injury in minutes.
A tiny teardrop is all that's needed to cause a color-change reaction in the OjoGel. The extent of the color change correlates to the concentration of ascorbic acid in the tear sample, shifting from pale yellow to a dark reddish-brown as the concentration increases.
The researchers did extensive testing to determine the concentrations associated with each degree of color change. They developed a color key and guidelines for using a mobile phone app, Pixel Picker, to precisely measure the concentration indicated by a reacted gel sample.
Previous research by UI researchers found that ascorbic acid concentration in tears is a good measure for determining extent of injury to the eye. Ascorbic acid normally has very low concentration in tears.
"Deep damage to the cornea from trauma or incisional surgery releases aqueous humor into the tear film, which increases the concentration of ascorbic acid in tears to a measurably higher level than that found in normal eyes," said study leader Dipanjan Pan, a UI professor of bioengineering and the Carle Illinois College of Medicine. "OjoGel offers a unique biosensing technique that provides an effective and simple method for testing ascorbic acid in a point-of-care delivery system."
In the next step, the researchers plan to continue refining OjoGel technology in hopes of producing a low-cost, easy-to-use clinical device. They also will perform clinical studies to determine whether OjoGel readings reliably evaluate eye damage.
