This presentation will highlight two platforms recently developed in the Sagle group which combine lipids and plasmonic nanoparticles. The first platform involves sandwiching a liposome between a planar gold surface and a gold colloid to generate a biocompatible, highly enhancing surface enhanced Raman spectroscopy (SERS) substrate. Our initial characterization of these novel substrates investigates substrate stability, temperature inside the liposome component, SERS activity inside the liposome, SERS mechanism and reproducibility. The substrates are shown to be stable to laser irradiation and exhibit a temperature increase of only 20 degrees Celsius inside the liposome component. The SERS enhancement of dye residing in the liposome component was found to be 8 x 106, higher than expected considering the dye molecules are at least 4 nm from either gold surface. Finite Difference Time Domain (FDTD) calculations reveal that the field enhancements inside the liposome are uniform with the major contributing factor being long range coupling between the gold nanoparticle and the mirror. Lastly, these substrates show greater reproducibility than typical SERS substrates in which dye is sandwiched between two metallic surfaces, and are expected to allow for the non-perturbative measurement of biological molecules in their native state, freely diffusing in solution. The second platform involves interfacing a gold nanodisc array with solid supported lipid bilayers for label-free biosensing of membrane-associated proteins. This platform is shown to have superior sensitivity due to elongated gold nanodics (exhibiting greater sensitivity than typical nanoparticle arrays) and an ultrathin silica layer above the nanodiscs, enabling the lipid bilayer to reside close to the nanoparticle surface. Further studies currently underway are using this platform with silver nanodiscs to carry out label-free SERS measurements of lipid components in the freely diffusing bilayer.
