Investigation of Reagent Delivery Formats and Implications for Higher-sensitivity Detection in Paper-based Diagnostics

Abstract

Millions of people in developing countries die from infectious diseases (e.g. malaria), yet many of these deaths can be prevented if given the tools for accurate diagnosis. Current diagnostic capabilities with the required clinical sensitivity are confined to laboratory settings due to cost, electrical, and personnel requirements. Current POC diagnostics targeting infectious diseases in low resource settings, lateral flow tests (LFTs), have the appropriate usability, but are confined to a single chemical step, and as a result lack the required sensitivity for clinical utility. A two-dimensional paper network (2DPN) is an inexpensive new technology based on the strengths of LFTs but allows complex chemical processes to be performed. Fluid control tools are essential for the success of a 2DPN in carrying out complex chemical processes in an automated fashion. Three versions of a 2DPN-based amplified assay in a malaria detection system are demonstrated using three fluid control tools: paper network geometry, dissolvable sucrose barriers, and cellulose-based delay shunts. Using the same system, assays based on two delivery formats, sequential delivery of analyte and colorimetric label and premixed one step delivery were characterized for reproducibility, sensitivity, and time to result. The sequential delivery format offers the potential for higher sensitivity detection compared to the premix delivery format used by conventional LFTs, but at the expense of additional time to result. Next steps for implementation of a high-sensitivity 2DPN using the sequential format are discussed.