Aggregation Control of Gold Nanoparticles and Surface-Enhanced Raman Scattering within Giant Unilamellar Vesicles

To detect trace molecules within giant unilamellar vesicles (GUVs), the effect of surface-enhanced Raman scattering within the vesicles was examined. Enhanced Raman spectra of a target molecule (bipyridine) within the GUVs were acquired through the encapsulation of gold nanoparticle aggregates and bipyridine. Furthermore, the introduction of gramicidin into the GUV membrane facilitated cation permeation through the lipid membrane, regulating the aggregation of gold nanoparticles. While the encapsulation of the gold nanoparticle dispersion in the GUV did not enhance the Raman signal, aggregation of gold nanoparticles, triggered by the influx of Na⁺ ions via gramicidin, amplified the Raman spectrum. This observation implies that molecules integrated into GUVs through vesicle fusion can aggregate with gold nanoparticles. These gold nanoparticle-encapsulated GUVs could serve as a new biosensor for detecting small amounts of molecules within the vesicles.