Paper-based device for pre-concentration of target analytes

In this paper, we demonstrate proof-of-principle for a low cost paper-based chromatographic device capable of pre-concentrating a target analyte by a factor of three thousand fold (assessed using confocal laser scanning microscopy (LSCM)). The device consists of a capture zone and a passive pump. The capture zone was created by immobilizing biotinylated microgel particles onto a selected area of filter paper. Due to the presence of biotin on their surface, these particles have the ability to specifically bind streptavidin, which was the target analyte selected for this study. With the incorporation of a superabsorbent passive pump, created using cross-linked poly(acrylic acid), partial sodium salt-graft-poly(ethylene oxide), the paper-based device was able to process a volume of dilute solution much larger than that associated with paper porosity. Flow through the device, including the passive pump, could be modeled using Darcy's law. A simple equation was also developed to relate the concentration in the pre-concentration device to the concentration in the dilute sample. This type of device can be useful for sample pre-concentration before analysis using other methods, such as mass spectrometry.