Molecular assembly of proteins and conjugated polymers: toward development of biosensors

A molecular assembly in which a conjugated polymer is interfaced with a photodynamic protein is described. The conjugated polymer, functionalized with biotin, is designed such that it can be physisorbed on or chemically grown off a glass surface. The streptavidin-derivatized protein is immobilized on the biotinylated polymer matrix through the strong biotin-streptavidin interactions. The assembly, built on the surface of an optical fiber or on the inside walls of a glass capillary, forms an integral part of a biosensor for the detection of environmental pollutants such as organophosphorus-based insecticides. The protein in the system can be replaced by any biological macromolecule of interest. We study one specific case, the inhibition of the enzyme alkaline phosphatase. The enzyme catalyzes a reaction producing an intermediate compound that chemiluminesces, and the chemiluminescence signal is monitored to detect and quantify insecticides such as paraoxon and methyl parathion. Preliminary results indicate ppb level detection with response time less than 1 minute