Vitamin C-detecting sensor could assess eye injuries on the spot

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The ascorbic acid-measuring OcuCheck sensor

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Although any eye injury can be painful and upsetting, those that involve damage to the inside of the eye are the most serious. For people like battlefield medics or rural physicians, however, it can be difficult to judge the extent of such injuries without the resources of a hospital. That's why scientists from the University of Illinois have created OcuCheck – it's a portable sensor that assesses eye injuries based on the amount of vitamin C in the patient's tears.

Normally, relatively low concentrations of vitamin C (aka ascorbic acid) are present in our ocular tear film, which is the liquid that coats our eyes. By contrast, the vitreous gel inside our eyes contains much more of the acid.

The sensor works by sampling a small amount of the patient's ocular tear film, and measuring its ascorbic acid content. If more than the normal amount is present, then it can be assumed that the excess is leaking out from within the eye. In fact, the severity of the injury can be ascertained by determining how much extra acid is present.

The device is made up of several stacked layers. These include a 1-nanometer-thick layer of graphene applied to a layer of filter paper; a polymer that interacts with the graphene; gold electrodes; and ascorbate oxidase, which is an enzyme that binds to ascorbic acid. When acid in the sample binds with the enzyme, it causes the polymer to be pulled away from the graphene, changing the electrical qualities of the sensor. The electrodes detect the amount of that change.

Lead scientists Prof. Dipanjan Pan (left), ophthalmologist Dr. Leanne Labriola, and postdoctoral researcher Santosh Misra

OcuCheck has so far been tested on tear samples from 16 patients undergoing eye surgery, and was found to be highly accurate at detecting ascorbic acid concentrations. It has yet to be tested on samples from trauma patients, although it will likely perform well, as it isn't affected by the presence of blood in samples.

The sensor is now being being commercially developed by spin-off company InnSight Technology, which is developing a portable housing and interface for it.

A paper on the research was recently published in the journal Scientific Reports.

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