A CONVENIENT APPROACH TO GLYCOAMPHIPHILES AS ACTIVE LAYERS OF LCD-BASED BIOSENSORS – SWEET-DISPLAY

Glycoconjugates, defined here as carbohydrates attached to a lipid or a protein, are ubiquitous in Nature. They are present on all cell membranes through a dense coating named Glycocalyx. They play critical roles in a wide variety of biological and pathological processes acting as signaling, recognition, and bacterial adhesion, etc. Consequently, major scientific and biotechnological interests in accessing glycoconjugates derive from the promise to use them as probes for biological research, as well as lead compounds for developing drugs, vaccines, and diagnostic tools. These endeavors are however complicated by a lack of general methods for the straightforward preparation of these key-enabling carbohydrate derivatives. This is a major scientific challenge for glycochemists worldwide.

The transdisciplinary (Chemistry/Biology/Nano-science/technology) SWEET-DISPLAY project aims at developing a new modular chemical platform based on barbituric acid, allowing direct access to a wide range of glyco-amphiphiles (GAs) or glycolipids analogues through Knoevenagel condensation on protecting group-free carbohydrates. These GAs will act as active recognition layers of pathogenic lectins in liquid crystal (LC) biosensors. In fact, Prof. N.L. Abbott’s group has pioneered, and successfully developed over the past two decades, the smart use of LCs to transduce and amplify molecular events at an aqueous/LC interface; allowing their detection though optical signals and images visible to the naked eye. This LC biosensor technology is capable of delivering a simple, high-sensitivity, and label-free detection without the requirement of complex instrumentations, making it well-suited for the primary screening assay of analytes performed away from central laboratories. LC biosensors have already been designed with many amphiphilic species (e.g. surfactants and lipids) to detect a hand full of biological analytes (e.g. including proteins, nucleic acids, viruses, endotoxins, and cells to name few) but never challenged till date for probing carbohydrate/pathogenic lectin (a carbohydrate-binding protein) interactions, pointing out toward the inherently innovative application of this Public Collaborative Research (PRC) exploratory project. Lectins such as LecA (galactophilic) and LecB (fucophilic) from Pseudomonas aeruginosa, a bacterium that have become a real concern in hospital-acquired infections will be first covered. Other biotargets of interests are RSL (fucophilic) from the plant pathogen Ralstonia solanacearum that leads to lethal wilt in many agricultural crops or its homolog BambL from human pathogen Burkholderia ambifaria that was identified in clinical isolates from cystic fibrosis patients.

SWEET-DISPLAY is a low TRL (1-3) PRC project grounded on the unification of cross-fertilizing knowledge and complementary expertise of two internationally recognized labs uniting for the first time under a PRC: CERMAV, in glycosciences, and SyMMES, in functional liquid crystals. Backed on preliminaries results, its core novelty lies in an original access to a large range of GAs characterized by hydrophobic tails that will penetrate into the hydrophobic LC phase while the hydrophilic carbohydrate heads will remain exposed to the aqueous phase, defining a functional self-assembled monolayer at the LC/GA/water interface. Pathogenic lectins will cause local disruptions of this sensing interface that will propagate through the bulk of LCs providing an optical readout through polarizing microscopy images (with nematic LCs-Generation 1). A 2nd generation, even more appealing and easy to implement, enabling a color-indicating assay (with cholesteric (chiral nematic LCs-Generation 2) will be proposed and will rely on the sensitivity of Bragg reflections (induced by the helical self-assembly of cholesteric LCs) to temperature and pathogen concentration when sense with a fiber optic-based UV-Vis-NIR spectrophotometer.