Distance-Based Tear Lactoferrin Assay on Microfluidic Paper Device Using Interfacial Interactions on Surface-Modified Cellulose

Abstract

"Distance-based" detection motifs on microfluidic paper-based analytical devices (μPADs) allow quantitative analysis without using signal readout instruments in a similar manner to classical analogue thermometers. To realize a cost-effective and calibration-free distance-based assay of lactoferrin in human tear fluid on a μPAD not relying on antibodies or enzymes, we investigated the fluidic mobilities of the target protein and Tb(3+) cations used as the fluorescent detection reagent on surface-modified cellulosic filter papers. Chromatographic elution experiments in a tear-like sample matrix containing electrolytes and proteins revealed a collapse of attractive electrostatic interactions between lactoferrin or Tb(3+) and the cellulosic substrate, which was overcome by the modification of the paper surface with the sulfated polysaccharide ι-carrageenan. The resulting μPAD based on the fluorescence emission distance successfully analyzed 0-4 mg mL(-1) of lactoferrin in complex human tear matrix with a lower limit of detection of 0.1 mg mL(-1) by simple visual inspection. Assay results of 18 human tear samples including ocular disease patients and healthy volunteers showed good correlation to the reference ELISA method with a slope of 0.997 and a regression coefficient of 0.948. The distance-based quantitative signal and the good batch-to-batch fabrication reproducibility relying on printing methods enable quantitative analysis by simply reading out "concentration scale marks" printed on the μPAD without performing any calibration and using any signal readout instrument.

Microfluidic Paper-based Analytical Device for the Determination of Hexavalent Chromium by Photolithographic Fabrication Using a Photomask Printed with 3D Printer

“…Recently, microfluidic paper-based analytical devices (μPADs) have attracted a lot of attention and have been actively developed due to being simple, inexpensive, user-friendly, and disposable. [12][13][14][15][16] To date, μPADs have been used as elegant analytical tools for a variety of applications, including medical diagnosis, [17][18][19][20][21] food testing, 22 and environmental monitoring. [23][24][25][26][27][28][29] A lot of detection methods have been used for μPADs.…”

“…The most common detection method for μPADs is colorimetry because analysis is relatively simple. Moreover, there are various techniques of the fabrication of μPADs, such as wax printing, 23,26,27,[29][30][31][32] inkjet printing, 17 screen printing, 18,22 and photolithography. 24 With regard to Cr analysis using μPADs, several methods have been reported.…”

Highly Sensitive Paper-based Analytical Devices with the Introduction of a Large-Volume Sample via Continuous Flow

“…These techniques include time-based, [9][10][11][12] distancebased, [13][14][15][16] and titration-based detection. [17][18][19] Philips and coworkers demonstrated time-based detection using an enzymatic reaction wherein a color change took place at different times depending on the concentration of the analyte.…”

“…9,10 Conversely, some research groups have developed distance-based PADs that permit the quantitation of analytes without the use of either a scanner or a digital camera, since the amount of the analyte could be determined by reading the distance of the color bar evolving on the PAD. [13][14][15][16] Zhang and coworkers employed both the time and the number of the detection zones that changed color. 11,12,20 We also reported that titrimetric PADs where the endpoint is judged using only the naked eye to count the number of detection zones.…”

Microfluidic Paper-based Analytical Device for Quantification of Lead Using Reaction Band-length for Identification of Bullet Hole and Its Potential for Estimating Firing Distance

“…[19][20][21] The type and model of the optical recorder, as well as the ambient light condition, remain issues in achieving a reproducible and accurate quantitative assay. As a result, alternative ideas, such as utilizing the reaction band-length of the color zone, 17,[23][24][25] the number or position of colored regions 26 or measuring the time from sample introduction until the appearance of a particular phenomenon 27 have been proposed. The application of μPADs with detection of the reaction bandlength has been demonstrated for several classes of clinically or environmentally relevant analytes, including the determination of serum glucose and glutathione, 17 tear lactoferrin, 23 airborne metals (Ni, Cu, Fe) in welding fumes 24 and Cu ion in drinking water.…”