We suggested the paper-based ELISA using a streptavidin agarose resin-based immobilization. This method reduces assay times (∼2 h), provides strong binding, and retains good sensitivity and linearity.
Paper-based analytical devices (e.g. lateral flow assays) are highly advantageous as portable diagnostic systems owing to their low costs and ease of use. Because of their low sensitivity and detection limits for biomolecules, these devices have several limitations in applications for real-field diagnosis. Here, we demonstrate a paper-based preconcentration enhanced lateral flow assay using a commercial β-hCG-based test. Utilizing a simple 9 V battery operation with a low power consumption of approximately 81 μW, we acquire a 25-fold preconcentration factor, demonstrating a clear sensitivity enhancement in the colorimetric lateral flow assay; consequently, clear colors are observed in a rapid kit test line, which cannot be monitored without preconcentration. This device can also facilitate a semi-quantitative platform using the saturation value and/or color intensity in both paper-based colorimetric assays and smartphone-based diagnostics.
To overcome the hurdles of the ICP-based preconcentrator (i.e., instability and low efficiency) under physiological conditions, we proposed a novel approach by using a sequentially driven ICP process, showing a 13-fold preconcentration factor (PF) in human serum.
Ion concentration polarization (ICP) has been widely studied for collecting target analytes as it is a powerful preconcentrator method employed for charged molecules. Although the method is quite robust, simple, cheap, and yields a high preconcentration factor, a major hurdle to be addressed is extracting the preconcentrated samples without dispersing the plug. This study investigates a 3D folding-paper-based ICP preconcentrator for preconcentrated plug extraction without the dispersion effect. The ICP preconcentrator is printed on a cellulose paper with pre-patterned hydrophobic wax. To extract and isolate the preconcentration plug with minimal dispersion, a 3D pop-up structure is fabricated via water drain, and a preconcentration factor of 300-fold for 10 min is achieved. By optimizing factors such as the electric field, water drain, and sample volume, the technique was enhanced by facilitating sample preconcentration and isolation, thereby providing the possibility for extensive applications in analytical devices such as lateral flow assays and FTA R cards.
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