Metal Layered Shrink Wrap Makes Fluorescent Markers Glow Brighter

Close-up images of the new shrink wrap nanostructures taken with a scanning electron microscope (SEM). Each image depicts the shrink wrap’s surface with a fixed amount of nickel (5 nm) and different thicknesses of gold in the metal coating. Top: 10 nm thick. Middle: 20 nm thick. Bottom: 30 nm thick. The black arrows in the top image indicate a nanogap. Credit: Optical Materials Express.

Many current methods of detecting pathogens and biomarkers involve fluorescent particles that bind to their targets that then can be spotted using photodetectors while being in excited state. While this technique is continuing to revolutionize diagnostics and laboratory work, it’s often limited by the faintness of the fluorescence when small numbers of particles are being detected. One way to improve the sensitivity of fluorescent markers is to make them produce a stronger signal. Researchers at University of California, Irvine are reporting in journal Optical Materials Express the development of a new technique that significantly improves the brightness of fluorescing nanoparticles.

The technique involves applying layers of gold and nickel onto shrink wrap, the kind you have in your kitchen. When heated, the material wrinkles and compresses, creating a flower-like structure. Samples of goat anti-mouse immunoglobulin antibodies were tagged with fluorescent markers and placed on top of the new material. When tested in a laboratory setting, the resulting fluorescence in the near-infrared range was three orders of magnitude greater than without the metal enhanced fluorescence.

From the study abstract:

This is the first demonstration of leveraging the plasmons in such hybrid nanostructures by metal enhanced fluorescence (MEF) in the near-infrared wavelengths. We observed more than three orders of magnitude enhancement in the fluorescence signal of a single molecule of goat anti-mouse immunoglobulin G (IgG) antibody conjugated to fluorescein isothiocyanate, FITC, (FITC-IgG) by two-photon excitation with these structures. These large enhancements in the fluorescence signal at the nanoscale gaps between the composite wrinkles corresponded to shortened lifetimes due to localized surface plasmons. To characterize these structures, we combined fluctuation correlation spectroscopy (FCS), fluorescence lifetime imaging microscopy (FLIM), and two-photon microscopy to spatially and temporally map the hot spots with high resolution.

Study in Optical Materials Express: Enhanced emission of fluorophores on shrink-induced wrinkled composite structures…

Optical Society: Shrink Wrap Used to Enhance Detection of Infectious Disease Biomarkers…