Microfluidic Paper-Based Sample Concentration Using Ion Concentration Polarization with Smartphone Detection.

Xue Li,Long Yi,Di Wu,Yunyi Chen,Yanan Niu,Xianbo Qiu

doi:10.3390/mi7110199

Abstract

A simple method for microfluidic paper-based sample concentration using ion concentration polarization (ICP) with smartphone detection is developed. The concise and low-cost microfluidic paper-based ICP analytical device, which consists of a black backing layer, a nitrocellulose membrane, and two absorbent pads, is fabricated with the simple lamination method which is widely used for lateral flow strips. Sample concentration on the nitrocellulose membrane is monitored in real time by a smartphone whose camera is used to collect the fluorescence images from the ICP device. A custom image processing algorithm running on the smartphone is used to track the concentrated sample and obtain its fluorescence signal intensity for quantitative analysis. Two different methods for Nafion coating are evaluated and their performances are compared. The characteristics of the ICP analytical device especially with intentionally adjusted physical properties are fully evaluated to optimize its performance as well as to extend its potential applications. Experimental results show that significant concentration enhancement with fluorescence dye sample is obtained with the developed ICP device when a fast depletion of fluorescent dye is observed. The platform based on the simply laminated ICP device with smartphone detection is desired for point-of-care testing in settings with poor resources.

Highlights

Ion concentration polarization (ICP) is an electrokinetic phenomenon caused by the transport of ions through ion-selective nanostructures [1]
We report a concise, fabricated, and easy-to-use microfluidic paper-based analytical device with an ion concentration polarization (ICP) effect for sample concentration
The developed paper-based ICP device consists of a sample channel made from nitrocellulose membrane with a thickness of 0.14 mm where a region coated with cation-selective nanoporous Nafion is developed at one end, and two buffer pools made from paper-based absorbent pads, and three of them are laminated with one another and fixed on a black backing layer (polyvinyl chloride (PVC)) with one sided tape (Figure 1A)

Summary

Introduction

Ion concentration polarization (ICP) is an electrokinetic phenomenon caused by the transport of ions through ion-selective nanostructures [1]. ICP can be adopted into an integrated analytical device for the detection of biomolecules by separating, and concentrating DNA or protein from the lysed cells [5]. Once the sample is applied onto the sample pad of the lateral flow strip, it will be captured by the immobilized protein on the test line area when it migrates along the strip because of the capillary force. With the lateral flow on a nitrocellulose membrane, because of the capillary force, much simpler detection can be obtained compared to most other analytical methods [10]. Similar to the lateral flow strip test, microfluidic paper-based analytical devices (μPADs) rely on the capillary force to drive sample or reagent without active pumping [11,12]. Because of the natural limitation of the assays implemented on μPADs, their detection sensitivity still needs to be increased to improve both accuracy and specificity

Methods

Results

Conclusion