The Gupta group is developing universally applicable optical sensors that can be adapted to measure a range of analytes including small molecules, oligonucleotides and proteins. This is because the basic sensing principle is based on a universal property of analytes, refractive index. Refractive index has real and imaginary components, which are related to the speed of light and (absorption, scattering) losses in a medium respectively. The change in refractive index caused by the binding of an analyte to recognition species (e.g. antibodies, aptamers) is directly proportional to the concentration of the analyte in the sample, allowing quantitative measurements. These changes in refractive index are converted to a more easily measurable signal by a transducer.

We have been working on the following types of transducers – leaky waveguides, interferometers, gratings and Bragg reflectors. All our transducers are made of hydrogels, which (1) offer chemical diversity to tailor the immobilisation density of recognition elements, (2) allow solution-processed fabrication resulting in affordable devices and (3) are biocompatible. In addition to capillary and pressure driven sample delivery, we also use electric fields to transport and process samples.

The waveguides and interferometers are being developed to facilitate point-of-use chemical and biological sensing. The gratings and Bragg reflectors, on the other hand, offer significant potential to serve as wearable biosensors. Please follow the links below to learn more.