Prof. T P Radhakrishnan, School of Chemistry and Dr. N. Senthilnathan who completed Ph.D. in February 2021 under the supervision of Prof. T. P. Radhakrishnan have been granted a Patent titled DADQ Dye for Bio-imaging vide Patent no. 201741017444 dated 19-01-2024
Fluorescence-based imaging is a prominent tool for exploring the structure and function of biological systems. Challenges associated with cytotoxicity, photo-stability, and emission quenching have restricted the utilization of conventional fluorophores such as fluorescent proteins, quantum dots, and nanoparticles in bio-related applications. To address these challenges, small organic molecule-based fluorophores, namely, diaminodicyanoquinodimethanes (DADQs), were developed with strong fluorescence in the aggregated/solid states (popularly known as aggregation-induced emission enhancement), excellent photo-stability and bio-compatibility for bioimaging, specifically, stomatal imaging. Stomatal imaging is critical for morphological and epidermal studies of plant species, understanding the stimuli responsive dynamics of inner/outer guard cell walls and related signal transduction pathways.
This patent provides a facile staining method for imaging walls of guard cells and walls and nuclei of epidermal cells employing a DADQ derivative, 7,7-bis(piperazinium)-8,8-dicyanoquinodimethane bis(p-toluene sulfonate) (BT2) in aqueous medium. The method successfully stains the walls of guard cells as well as the walls and nuclei of epidermal cells at higher concentrations ranging from 2 – 5 mM, while lower doses of 0.02 – 2 mM can be used to stain the walls of guard cells specifically. The molecular interactions existing between BT2 and the stomatal cells that facilitate efficient staining were unraveled through experiments including isothermal titration calorimetry, various spectroscopy and microscopy.