Fluorescing gel characteristics for use in biosecurity research

Disease transfer between surfaces is a biosecurity concern. Glogerm™ fluorescing material is a common tool for biosecurity education, with limited applications in research settings. The objective of this paper is to quantify the relationship between fluorescing gel area density (mass per unit area) applied to a surface and the resulting luminance, considering the influence of evaporation and surface type. Varying densities of Glogerm™ were applied to paper and plastic surfaces. Glogerm™ mass and digital images taken under ultraviolet light in a light-controlled environment were collected over one-hour periods. The measurements were replicated three times for each density and material combination. Digital images were analyzed for luminance (average gray value per unit area). Separate sets of tests focused on luminance and evaporation characteristics, and luminance as a function of density and surface type. Mixed model analyses considered fixed effects of fluorescing material density, surface type, and interactions, and the random block effect of three separate measurement periods. Repeated measures were considered in the analysis of luminance over time. The gel evaporated faster as density decreased. Evaporation was significantly faster (p = 0.0019) from the paper surface compared to the plastic surface. For paper and plastic surfaces, luminance did not change as the gel evaporated. Differences in luminance were driven by coverage area and surface material, decreasing as coverage area increased, and decreasing more rapidly on paper than plastic. For each material, luminance initially increased with increasing density. Luminance threshold values existed, after which the addition of more fluorescing gel mass per unit area did not change luminance. The thresholds for paper, plastic, and rubber surfaces were 0.018, 0.014, and 0.041 g cm^-2, respectively. The use of fluorescing gel has potential to quantify disease transfer risks in addition to education. This research shows limitations in equating mass transfer and luminance, but luminance threshold values can inform dosing for imaging purposes. More research in needed on accurate quantification of other fluorescing colors and substances.