We report methods for stabilizing cellulose-based immunoassays and using this platform to analyze human saliva. Stabilization treatments of immunoassays for matrix metalloproteinases (MMP)-8 and -9, biomarkers of periodontal disease, were conducted and compared, revealing that anti-MMP-8 and -9 capture antibodies could be stabilized with the addition of a 5% trehalose solution to the test zones, followed by drying in a vacuum oven. After stabilization, the paper devices retained equivalent binding activity to that of freshly prepared tests for 14 days-a time frame that enables US-based clinical testing of this diagnostic assay. A saliva pretreatment method was developed to remove viscous elements without reducing the concentration or binding activity of dissolved proteins. Immunoassays were stored in ziplock bags containing desiccant, and used to detect nanomolar concentrations of MMP-9 in human saliva across the relevant clinical concentration range. These methods and findings facilitate rapid, affordable validation studies of this and other biomarkers that are found in saliva using vertical flow immunoassays.
Keywords: diagnostics; low-cost; paper; periodontal disease; polymerization; protein stability; saliva.