Polymer modified paper - reducing sensitivity losses in paper-based analytical devices
Final Report Abstract
Paper is an ideal candidate for the development of new disposable diagnostic devices because it is a low-cost material, allows transport of the liquid on the device by capillary action, and is environmentally friendly. Today, colorimetric analysis is most often used as a detection method for rapid tests (test strips or lateral flow devices) but usually gives only qualitative results and is limited by a relatively high detection threshold. In this project we focus on some severe limitations current paper-based diagnostic devices have in common and that lead to a drastic reduction in the devices sensitivity. In 3 project parts we first focused on the understanding and prevention of analyte loss by non-specific adsorption of e.g. (model-)proteins on the paper fibers in the paper sheet pore space during the capillary transport. We can show that a modification of the paper fibers with a homogeneous thin coating of cross-linked polymer hydrogels can circumvent unspecific protein adsorption. In another part of the work we show that by controlling the swelling of the fibers during impregnation with the hydrogel-precursor polymers, one is capable to define how the hydrogel wraps around the fibers and how homogeneously the final coverage of the fiber with the hydrogel develops. In a final part, we focus on understanding a fluorescent read-out in paper based LFDs. Here we were able to show that paper-based fluorescence analysis allows for a better optical readout compared to that of nitrocellulose, which is currently the material of choice in colorimetric assays. In summary, fluorescence-based assays can produce highly sensitive and reproducible paper-based devices, thus posing an attractive alternative to commercial colorimetric assays. Crucial to this is that (a) the nonspecific adsorption of the biomolecules to be detected is prevented, e.g., by coating of the fibers with a surface-attached hydrogel, and (b) paper type and paper-intrinsic parameters such as grammage are carefully chosen for the problem at hand. All three parts have been published in separate manuscripts in peer-reviewed scientific journals to date.
Publications
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Accessibility of fiber surface sites for polymeric additives determines dry and wet tensile strength of paper sheets. Cellulose, 28(9), 5775-5791.
Schäfer, J.-L.; Schölch, S.; Prucker, O.; Brandstetter, T.; Rühe, J.; Stockert, A. Ritter v.; Meckel, T. & Biesalski, M.
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Reducing Unspecific Protein Adsorption in Microfluidic Papers Using Fiber-Attached Polymer Hydrogels. Sensors, 21(19), 6348.
von Stockert, Alexander Ritter; Luongo, Anna; Langhans, Markus; Brandstetter, Thomas; Rühe, Jürgen; Meckel, Tobias & Biesalski, Markus
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Controlling Fluorescent Readout in Paper-based Analytical Devices. ACS Biomaterials Science & Engineering, 9(11), 6379-6389.
Luongo, Anna; von Stockert, Alexander Ritter; Scherag, Frank D.; Brandstetter, Thomas; Biesalski, Markus & Rühe, Jürgen
