Fabricating Cotton Analytical Devices

Summary

To investigate simple fabrication approaches for multiple assay needs, we created a fluid-absorbing channel system made of cotton material. This device was used to establish a multiple detection platform, and solve contamination issues that commonly affect lateral flow-based biomedical devices, for clinical urinalysis of nitrite, total protein, and urobilinogen.

Abstract

A robust, low-cost analytical device should be user-friendly, rapid, and affordable. Such devices should also be able to operate with scarce samples and provide information for follow-up treatment. Here, we demonstrate the development of a cotton-based urinalysis (i.e., nitrite, total protein, and urobilinogen assays) analytical device that employs a lateral flow-based format, and is inexpensive, easily fabricated, rapid, and can be used to conduct multiple tests without cross-contamination worries. Cotton is composed of cellulose fibers with natural absorptive properties that can be leveraged for flow-based analysis. The simple but elegant fabrication process of our cotton-based analytical device is described in this study. The arrangement of the cotton structure and test pad takes advantage of the hydrophobicity and absorptive strength of each material. Because of these physical characteristics, colorimetric results can persistently adhere to the test pad. This device enables physicians to receive clinical information in a timely manner and shows great potential as a tool for early intervention.

Introduction

The development of point-of-care (POC) diagnostic devices that are affordable, robust, and easily used is imperative for improving global health^1,2. In particular, devices composed of cellulose substrates (e.g., paper, thread, and cotton) provide promising analytical platforms for low-cost analysis because of their ubiquity, affordability, ease of use, robustness, and capacity to provide rapid results^3-7.

Here, we unveil the development of a cotton-based analytical device that uses a lateral flow-based format for urinalysis. This cotton-based analytical device provides an alternative detection approach with se....

Protocol

CAUTION: Proper laboratory hygiene practice is required. Gloves and universal precautions are required when using this POC device. Contamination of results or infection may occur if adequate sterilization procedures are not carried out properly.

1. Prepare Test Strip Devices

1. Determine the hydrophobicity of the exterior layer of the cleansing cotton by contact angle measurement⁸ (Figure 3).
2. Fabricate the cotton-based analytical device by cutting cleansing cotton into 5.5 cm x 1 cm pieces with a paper cutter (Figure 2A).
3. Drill holes (ø = 0.5 cm) in a standard sheet of lamination fil....

Results

We successfully demonstrated the development of cotton-based analytical devices by using commercially available cleansing cotton characterized by hydrophilic (inner portion) and hydrophobic (exterior portion) properties (Figure 1A). Figure 3 shows the results of contact angle measurement. The hydrophobic interface of exterior cotton was 127.35° ±  4.73°. From a user-friendly perspective, colorimetric assays employed here could be directly observed by the .......

Discussion

Critical steps in this protocol included determining the appropriate combination of cotton material (with varying hydrophobicity/hydrophilicity) and filter paper (chromatography filter paper or quantitative filter paper). A well-planned and executed device design renders the best performance attributes for colorimetric assays. From our colorimetric assay results, the cotton-based analytical device presented herein demonstrates great potential as a platform for multiple disease detection.

Most .......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
bovine serum albumin	Sigma-Aldrich, US	No. 9048468	≥ 99%
nitrite	Sigma-Aldrich, US	No. 7632000	≥ 99%
urobilinogen	Santa Cruz Bio, US	No. SC-296690
citrate	Sigma-Aldrich U.S	No. 6132043	≥ 99%
tetrabromophenol blue	Sigma-Aldrich U.S	No. 4430255	≥ 99%
sulfanilamide	Sigma-Aldrich U.S	No. 63741	≥ 99%
citric acid	Sigma-Aldrich U.S	No. 77929	≥ 99.5%
N-(1-naphthyl) ethylenediamine dihydrochloride	Sigma-Aldrich U.S	No. 1465254	≥ 98%
4-(Dimethylamine)benzaldehyde	AlfaAesar, U.S	No. A11712	≥ 98%
Methyl Red sodium salt	sigma, U.S	No. 114502	≥95%
Bromothyle blue	sigma, U.S	No. 114413	≥95%
Shiseido Cleansing Cotton	Shiseido, Japan	No. 79014
chromatography paper	GE Healthcare Whatman, Springfield Mill, UK	No. 30306132
plastic substrate	lamination film, MAS	A4	216 mm x 303 mm
scanner	microtek scanmaker	i2400
paper cutter	Life paper cutter	No.306
laminator	AURORA	LM4231H
laminator film	UNI LAMI	4A