Reducing Unspecific Protein Adsorption in Microfluidic Papers Using Fiber-Attached Polymer Hydrogels

Abstract

Microfluidic paper combines pump-free water transport at low cost with a high degree of sustainability, as well as good availability of the paper-forming cellulosic material, thus making it an attractive candidate for point-of-care (POC) analytics and diagnostics. Although a number of interesting demonstrators for such paper devices have been reported to date, a number of challenges still exist, which limit a successful transfer into marketable applications. A strong limitation in this respect is the (unspecific) adsorption of protein analytes to the paper fibers during the lateral flow assay. This interaction may significantly reduce the amount of analyte that reaches the detection zone of the microfluidic paper-based analytical device (µPAD), thereby reducing its overall sensitivity. Here, we introduce a novel approach on reducing the nonspecific adsorption of proteins to lab-made paper sheets for the use in µPADs. To this, cotton linter fibers in lab-formed additive-free paper sheets are modified with a surrounding thin hydrogel layer generated from photo-crosslinked, benzophenone functionalized copolymers based on poly-(oligo-ethylene glycol methacrylate) (POEGMA) and poly-dimethyl acrylamide (PDMAA). This, as we show in tests similar to lateral flow assays, significantly reduces unspecific binding of model proteins. Furthermore, by evaporating the transport fluid during the microfluidic run at the end of the paper strip through local heating, model proteins can almost quantitatively be accumulated in that zone. The possibility of complete, almost quantitative protein transport in a µPAD opens up new opportunities to significantly improve the signal-to-noise (S/N) ratio of paper-based lateral flow assays.

NT-proBNP detection with a one-step magnetic lateral flow channel assay

“…In our assay, the reagents were dried on the sensor support, in direct contact to the PET surface. Within this hydrophobic environment, proteins might experience unfavorable conformational changes or irreversible adsorption, leading to compromised protein functionality and, consequently, hindering the overall sensor performance [ 51 – 53 ]. Moreover, it was crucial to enable fast rehydration and maintain the colloidal stability of the fluorescence–polystyrene nanoparticles and the MNPs.…”

Controlling Fluorescent Readout in Paper-based Analytical Devices

“…One of the main problems, when studying proteins, is the nonspecific adsorption of undesired proteins during analyte movement along the strip. In order to reduce this, paper samples were dip-coated with a hydrophilic copolymer containing benzophenone units, p­(DMAA-1%-MABP), which had been incorporated into the polymers through a standard free radical copolymerization procedure, as already discussed in previous work . The surface modification significantly reduces the nonspecific protein adsorption and allows molecules to reach the detection line, thanks to an entropic shielding effect. − p­(DMAA-1%-MABP) coatings also increase the wet strength properties, an important aspect for analytical device manufacturing. ,, It should be noted that in the studied wavelength range, the presence of benzophenone groups does not give rise to an additional background contribution to the signal intensity (see SI, Figure S11).…”

Fluorine-Labeled N-Boc-l-proline as a Marker for Solid-State NMR Characterization of Biofunctionalizations on Paper Substrates

“…We will further quantify this spin label by 19 F solid-state NMR and use it to inspect the local proton environment by the 1 H− 19 ■ EXPERIMENTAL SECTION General. The cotton linter paper substrate was prepared with a basis weight of 50 g/m 2 as described by Stockert et al 39 In brief, a HAAGE sheet former BB was used according to DIN 54358 and ISO 5269/2 to prepare paper samples with cotton linter fibers. [Median fiber length (length-weighted): 1.07 mm; curl: 33.8%; fibrillation degree: 1.6%; and fines content: 16.5%].…”