Simultaneous concentration and detection of biomarkers on paper

Abstract

The lateral-flow immunoassay (LFA) is an inexpensive point-of-care (POC) paper-based diagnostic device with the potential to rapidly detect disease biomarkers in resource-poor settings. Although LFA is inexpensive, easy to use, and requires no laboratory equipment, it is limited by its sensitivity, which remains inferior to that of gold standard laboratory-based assays. Our group is the only one to have previously utilized various aqueous two-phase systems (ATPSs) to enhance LFA detection. In those studies, the sample was concentrated by an ATPS in a test tube and could only be applied to LFA after it had been extracted manually. Here, we bypass the extraction step by seamlessly integrating a polyethylene glycol-potassium phosphate ATPS with downstream LFA detection in a simple, inexpensive, power-free, and portable all-in-one diagnostic device. We discovered a new phenomenon in which the target biomarkers simultaneously concentrate as the ATPS solution flows through the paper membranes, and our device features a 3-D paper well that was designed to exploit this phenomenon. Studies with this device, which were performed at room temperature in under 25 min, demonstrated a 10-fold improvement in the detection limit of a model protein, transferrin. Our next-generation LFA technology is rapid, affordable, easy-to-use, and can be applied to existing LFA products, thereby providing a new platform for revolutionizing the current state of disease diagnosis in resource-poor settings.

Improved LFIAs for highly sensitive detection of BNP at point-of-care

“…25 However, the existing LFAs are associated with the limitation of poor sensitivity. 11,26 Several methods have been developed to enhance the sensitivity of LFAs, such as sample concentration, [27][28][29][30] thermal contrast, 31 fluidic control, [32][33][34] temperature-humidity technique, 35 probe-based signal enhancement, 23,36 enzyme-based signal amplification 37,38 and electrochemical devices-based enhancement. 39 However, these approaches require either external equipment, 35 high-cost reagents 23,37 or complicated fabrication with multistep procedure, 32 limiting their application for POC testing.…”

Dispositivos de microfluídica basados en papel: orígenes, presente y perspectivas

“…Por esta razón cobra importancia la pre-concentración de la muestra, y diferentes mecanismos de pre-tratamiento están hoy bajo estudio (67). En particular se desea pre-concentrar en línea, es decir, en el propio dispositivo, para lo cual ya se están reportando ejemplos posibles (68). Pero un salto notable lo ha dado recientemente la pre-concentración en línea mediante isotacoforesis, al mostrar un incremento de la sensibilidad de dos órdenes de magnitud (69).…”

Paper-Based Systems for Point-of-Care Biosensing

“…Although the reason for this phenomenon is unclear, it is plausible that (1) the less viscous PEG-poor domains move ahead and coalesce quickly while the more viscous PEGrich domains remain behind and coalesce, and (2) the PEG molecules of the PEG-rich phase may have favorable interactions with the fibers of the paper, which further act to slow down the PEG-rich domains. 35 While the 1:1 solution showed noticeable separation on the paper strip, the phase separation for the 9:1 solution was less distinct. To further improve the phase separation, the authors implemented a 3D paper well consisting of layers of stacked paper (Fig.…”

“…In an attempt to reduce the extraction time as well as user interaction, the Kamei group investigated combining the two processes directly in paper. 35 Using the PEG-salt ATPS, the authors applied a well-mixed ATPS solution containing the DGNPs and Tf directly onto a paper strip. The authors experimented with both 1:1 and 9:1 volume ratios; as before, the Tf-bound DGNPs partitioned into the PEG-poor phase.…”

“…This all-in-one device allows the phase separation, concentration, and detection to simultaneously and seamlessly occur on paper, and this device was demonstrated to be able to achieve a 10-fold improvement in the detection limit of Tf in less than 25 min. 35 Aside from using an ATPS to concentrate biomolecules, other efforts have been made to develop electrochemical methods to concentrate analytes in paper. For instance, Rosenfeld and Bercovici 36 combined isotachophoresis (ITP) with assaybased diagnostic micropads to increase sensitivity.…”