UC Irvine

Routine surveillance for infectious diseases results in earlier detection and better prognosis. However, current diagnostic measures for infectious diseases are not directly translatable to low-resource settings as they are expensive, time-consuming, and require heavy medical infrastructure and trained personnel. The need for effective point-of-care (POC) diagnostics is critically important: the vast majority of deaths from infectious diseases occur in developing countries.

Here, a platform for producing enhanced fluorescence signals with applications in POC technology is presented. Dense multi-scale silica (SiO₂) structures are fabricated on pre-stressed polyolefin (PO) film and characterized. Linkage of fluorescent biomolecules on the SiO₂ structures results in far-field fluorescence signal enhancements (~116-fold with respect to a planar glass control and ~50-fold with respect to a flat unshrunk fluorescently conjugated polymer film) with increased signal-to-noise ratio (SNR) that are robust and reproducible. Optical characterization of the SiO₂ structures point to the concentration effect and optical scattering as the underlying mechanisms responsible for the far-field fluorescence signal enhancements.

Using the biotin-streptavidin hybridization as a model system, improved limits of detection (LOD) of the model target streptavidin were achieved on the SiO₂ structures relative to a flat glass control. Disease detection applications are demonstrated using the SiO₂ structures. Sandwich immunoassays for TNF-α and p24 antigen are performed on the SiO₂ structures and lower LODs are achieved (550 pg mL^-1 and 30 pg mL^-1 for TNF-α and p24 antigen, respectively). The SiO₂ structures demonstrate potential for POC applications as enhanced signal correlates to increased sensitivity.