Detection of an amphiphilic biosample in a paper microchannel based on length

Abstract

We developed a simple method to achieve semiquantitative detection of an amphiphilic biosample through measuring the length of flow on a microfluidic analytical device (μPAD) based on paper. When an amphiphilic sample was dripped into a straight microchannel defined with a printed wax barrier (hydrophobic) on filter paper (hydrophilic), the length of flow was affected by the reciprocal effect between the sample, the filter-paper channel and the wax barrier. The flow length decreased with increasing concentration of an amphiphilic sample because of adsorption of the sample on the hydrophobic barrier. Measurement of the flow length enabled a determination of the concentration of the amphiphilic sample. The several tested samples included surfactants (Tween 20 and Triton X-100), oligonucleotides (DNA), bovine serum albumin (BSA), human albumin, nitrite, glucose and low-density lipoprotein (LDL). The results show that the measurement of the flow length determined directly the concentration of an amphiphilic sample, whereas a non-amphiphilic sample was not amenable to this method. The proposed method features the advantages of small cost, simplicity, convenience, directness, rapidity (<5 min) and requirement of only a small volume (5 μL) of sample, with prospective applications in developing areas and sites near patients for testing at a point of care (POCT).

Distance versus Capillary Flow Dynamics‐Based Detection Methods on a Microfluidic Paper‐Based Analytical Device (μPAD)

“…Instead of quantifying the length of coloration, the flow distance has recently been utilized. Chen and Yang used the amphiphilic property of target . In their study, a sample solution containing amphiphilic target was placed into the hydrophilic channel.…”

“…The most promising method appropriate for POC diagnostics and field‐based assays is the distance‐based measurement on LFA or μPAD. In this method, the length of color development or final flow distance on a paper strip is measured to correlate it to the target concentration . In distance‐based methods, it is possible to implement different sensing modalities over multiple channels because only the distance is measured.…”

Paper-Based Microfluidic Devices: Emerging Themes and Applications

“…Distance-based detection that relies on reading a visual signal length linearly corresponding to analyte concentration is also popular. − Colored bands can be generated as analyte flows along a channel due to capillary force and reacts with predeposited reagents to form colored products that remain on the paper substrate, , or based on the flow stopping resulting from channel constriction as molecular binding to surface receptors occurs. , Cate et al created distance-based multiplexed paper sensors for simultaneous detection of Ni, Fe, and Cu in welding fumes based on complexation reactions between the metals and their corresponding chromogenic reagents . The paper devices were built with rulers printed next to the analysis channels to quickly quantify the colored region lengths and correlate these to the concentrations of the metals (Figure D).…”

Counting-based microfluidic paper-based devices capable of analyzing submicroliter sample volumes

“…Colorimetric readouts 4,16,[27][28][29][30][31][32] can be userfriendly, but quantification based on the color intensity requires the use of external devices, such as a camera and image processing software, or relies on visual detection from the naked eye, which can vary due to the perception of the user. 22 To avoid the drawbacks of color intensity measurements, distance-based 22,[33][34][35][36][37][38] and barcodebased or counting-based test readout [39][40][41][42][43][44][45][46][47] methods have been developed for μPADs. In the distance-based readout method, a colored band is developed along the flow path when the detection reagent interacts with the target analyte, and the length of the band correlates with how much of the analyte is present and provides a semiquantitative test result.…”