Functionalized Complex Colloids for Biomolecular Diagnostics

The aqueous interface between biomolecular analytes and transduction materials is critical to biosensing. We have been focused on complex multiphase colloidal materials and developing interfacial chemistry for the attachment of receptors to develop new assays. Multiphase liquid colloidal particles (emulsions) have been developed that behave as dynamic lens materials. Multivalent interactions cause a non-equilibrium alignment of these complex emulsions and associated optical changes that have been used to detect pathogenic bacteria. The detection methods make use transmitted and fluorescence light and have limits of detection for Listeria and Salmonella of 100 CFU/mL. In another method Pickering emulsion phases with polypyrrole nanoparticles stabilizing an oil-water interface. Polypyrrole is an insoluble polymer, and the fluidized nanoparticles allow for efficient bioconjugation to antibody and engineered protein receptors. As part of the conjugation chemistry sequence the polypyrrole is put in its undoped low-conductivity state for depositing on nitrocellulose membranes to create lateral flow assay sensors. Assays for inflammatory biomarkers CRP and IL-6 are produced and capture at the test line immobilizes oxidase enzymes that cause a doping of the polypyrrole and conductivity changes as high at 100,000% to create ultra-sensitive quantitative assays.