Fluorescence lifetime and excitation-emission spectra of paper membranes used as substrates in diagnostics

Abstract

These data supplement a publication describing the auto-fluorescence of materials commonly used in paper-based microfluidics. The data presented include excitation-emission matrices of nitrocellulose, cellulose, and glass fiber manufactured by GE and Millipore, among others, and fluorescence lifetime data for Millipore HF120 nitrocellulose. The abstract of the publication follows: ------------------------------------------------------------- Porous media made of nitrocellulose and glass fiber are common “paper” substrates for lateral flow assays, microfluidic paper analytical devices, and other point-of-care diagnostic assays. Such assays commonly use optical labels such as gold nanoparticles, latex beads, or fluorescent nanoparticles to visualize the presence of analytes. Fluorescent labels are commonly used in bioassays to enhance sensitivity, but paper autoluminescence worsens signal-to-noise ratios of paper-based fluorescence assays. To date, there exists no systematic investigation of autoluminescence wavelengths or lifetimes of paper membranes. In response, we quantified the autoluminescence of commonly-used papers across the visible spectrum via excitation-emission spectroscopy and time-resolved fluorescence spectroscopy, and demonstrate that autoluminescence is solely due to autofluorescence with lifetimes of about 5 ns in the visible spectrum. Counterintuitively, we found that spectroscopy alone does not provide sufficient information to select candidate paper substrates for fluorophore-labeled assays. Therefore, we developed a simple quantitative framework to select a low-fluorescence substrate that minimizes both the overlap of paper and fluorophore emission spectra and the fluorescence intensity on an imaging system of interest (such as a gel imager). Use of this framework was shown to improve the limit of detection of an influenza A nucleoprotein immunoassay by over 50%. The tools developed in this manuscript may similarly enable other assay developers to screen appropriate, low-fluorescence paper substrates and enhance the sensitivity of paper-based fluorescence assays.