The research theme in Gupta group is polymeric optical sensors. We design internally referenced transducers and associated instrumentation to analyse species of interest in “real” samples and environmental conditions. A significant activity in the group is also focused on polymer design, engineering and characterisation. Additionally, we are developing (photo) chemistries for the fabrication of optical nanostructures for sensing using solution processing methods in a single step. We collaborate with researchers in clinical sciences and industry to exploit the application of our sensors in point-of-care/ point-of-use analysis.
The research in the group is broadly divided into three themes:
The primary sensing mechanism is based on change in refractive index caused by binding of analyte to recognition species attached to an optical transducer. Alternatively, the sensing mechanism relies on changes in absorption or fluorescence or scattering, which can be a result of analyte itself or its interaction with another species. The optical biosensors we are currently working on include waveguides and interferometers.
The sample preparation and delivery is achieved using microfluidic architectures integrated with the sensor. Techniques such as milling, injection moulding and photolithography are currently being used to make microfluidic structures, which range from a simple microchannel to 3D interconnected multichannel systems. The research in the group also includes integration of electroseparation techniques with optical sensors both to remove sample interferents and pre-concentrate analyte. By doing so, the limit of detection of sensors could be improved by about three orders of magnitude.
The members working in this theme are Hazel Dixon, Elisabetta Labella and Thomas Wensley. Other members co-supervised by Dr Gupta under this theme are Beverly Andrew and Nasser Alamrani at the University of Hull.
Photochemistry and photophysics
The research group has been investigating (photo) chemistries for the fabrication of optical nanostructures using solution processed methods to facilitate their mass manufacturing. We design chemical moieties (e.g. photocaged molecules) with required absorption spectrum, solubility and functional groups (so that they may be covalently attached to polymers). The light activated chemistries also allow us to control the spatial position of immobilised recognition species (such as antibodies and aptamers) in polymers to make array based sensors for multiplexed analysis.
Additionally, we study interaction of light with polymeric nanostructures to design holograms and photonic crystals capable of manipulating light. These structures are typically used as label-free optical sensors for applications in healthcare and environmental monitoring.
The members working in this theme are Firoj Ali and Anil Pal.
Polymers and hydrogels
We work with polymers because they offer chemical diversity that allow us to tailor their physiochemical properties. For example, by tailoring the relative concentration and reactivity rates of monomers, we are able to obtain co-polymers with required concentration of reactive groups. This in turn implies that recognition species can be immobilized with tailored density within the polymer matrix.
We are developing polymers with required: (1) pore size and connectivity, (2) optical transparency; (3) ability to respond to applied stimuli; and (4) withstand mechanical stresses. We use a combination of swelling, diffusion studies, electron microscopy, UV-Vis spectroscopy, compression and rheology tests to characterise the polymers.
The polymers and hydrogels that we have worked with so far includes silica sol-gel, polystyrene, polysaccharides, polyacrylamide and polyethylene glycol.
The members working in this theme are William Glover-Humphreys and Nicola Toole.