THIS GRANT IS A CONTINUATION OF N00014-14-1-0792 Developing pH Modulation Sensing for Novel Biosensor Assays

Under previous ONR funding (N000140810467 and N000141310276), the Principal Investigator used lipid-conjugated pH sensitive dye molecules as reporters for ion, small molecule, peptide, and protein interactions with planar supported lipid bilayers. The fluorescence level of the dyes is dictated by the surface potential at the lipid membrane/aqueous interface. Dyes that increase their fluorescence as the bulk solution is acidified act as 'turn on' sensors for negatively charged target analytes. Dyes that increase their fluorescence response at more basic pH values function in the opposite manner. The sensing technique is referred to as pH modulation sensing. The goal of the proposed research is to further advance this biosensor technology such that sensors developed using the approach are practical, portable devices that can operate under a broad range of conditions. First, the process will be made to withstand harsh operating environments and the presence of numerous interferents by combining pH modulation sensing with strategies for mechanically stabilizing planar supported bilayers. Next, fundamental studies on the dye molecules used in this assay will be performed in order to determine their quenching mechanism as a function of pH. Such studies are expected to help in the development of a wide range of dyes that can be fully turned on and off by subtle changes in the interfacial potential at the bilayer surface. Then, the assay will be converted into an inexpensive fluorescence imaging platform that costs on the order of a few hundred dollars to set up. Finally, the pH modulation platform will be used to gain a fundamental understanding of the interactions of antimicrobial peptides with lipid bilayers as a function of membrane chemistry. This has been of on-going interest to the Navy.