Fabrication and Validation of a Handheld Non-Invasive, Optical Biosensor for Self-Monitoring of Glucose Using Saliva

We report the method for fabrication and validation of a standalone handheld optical biosensor for non-invasive monitoring of glucose using saliva. For this, a biodegradable, low-cost test strip for glucose was developed by co-immobilizing glucose oxidase enzyme and bromocresol purple pH sensitive dye. The enzymatic reaction produced pH change and, thus, a change in color of a filter paper strip, which was detected by a standalone electronic meter. The in-house developed meter consisted of an optically isolated region in the chassis for inserting the test strip along with the sample to avoid interferences from ambient wind and light. The developed biosensor had a wide detection range of detection between 32- and 516-mg/dL glucose concentration while the sensitivity of detection was 1.0 mg/dL/count at a limit of detection (LOD) of 32 mg/dL within a response time of 15 s. The device along with strips was validated on clinical samples while comparing salivary glucose level with that of blood glucose level using a commercial glucometer. A very good correlation was found for diabetic individuals (0.80), whereas it was less significant (0.53) for non-diabetic individuals. The device passed Clarke’s error grid analysis and hence should be medically acceptable. This simple and low-cost setup should be ideally suited for mass screening of diabetes, apart from being used as a self-monitoring device in a non-invasive and painless manner.