Distance-Based Paper Device for a Naked-Eye Albumin-to-Alkaline Phosphatase Ratio Assay

Abstract

The albumin-to-alkaline phosphatase ratio (AAPR) has been a cancer prognostic indicator. This paper presents the concept of a dual-color change distance-based paper device (dPAD) for albumin (Alb) and alkaline phosphatase (ALP) detection to evaluate this cancer prognostic index. Whereas Alb interacts with the bromocresol green (BCG) indicator to form a bluish-green complex, ALP hydrolyzes l-ascorbic acid-2-phosphate (AAP) to produce ascorbic acid (AA), which reacts with KIO3 to generate I2 and I–. I2/I– reacts with silver hexagonal nanoprisms (purple color) in the presence of Cu2+, resulting in a color change from purple to colorless. The distance of the color change from yellow to the bluish-green and purple to colorless correlates to Alb and ALP concentration, respectively. The angle index for the AAPR is then defined by drawing a straight line that connects the tops of the two changed band lengths in the detection area. The highest bluish-green color band length on the Alb region is the midpoint, which is the position set of the protractor at 0°, and the angle is measured using a simple protractor. The results indicate that an AAPR below 0.57 will have an angle greater than 40° and correlates with a risk factor for lung cancer. The naked-eye detection limits for Alb and ALP were found to be 0.8 g/L and 5 U/L (n = 10), respectively. The practical application of the developed dPAD was successfully demonstrated by Alb and ALP analysis in human serum and validated against standard methods. The proposed method does not require incubation conditions for the ALP assay, which strongly reduces the overall analysis steps and time. Moreover, our device provides a low-cost, simple, sensitive, selective, accurate, and precise determination of the AAPR.

A Simple Counting-Based Measurement for Paper Analytical Devices and Their Application

“…Distance-based paper analytical devices (dPADs) have recently become acceptable as a low-cost and instrument-free technique for analysis. Because their general processes rely on the length of color changes in the detection area, corresponding to the analyte level, the analyte solution can flow along the detection channel and then react with a deposited specific reagent that was predeposited. − The results show the changes in the color length on the dPADs, illustrating the need for an equipment-free detection system for onsite analysis. With these properties, it can be noticed that there were numerous developments of dPADs for various detections with different reactions including enzymatic, metal nanoparticle aggregation, and complexation reactions. − Therefore, dPAD sensors are more advantageous for point of care (POC) testing in resource-poor settings because they do not require external equipment to evaluate the data for quantification. − …”

Distance-based paper analytical device for multiplexed quantification of cytokine biomarkers using carbon dots integrated with molecularly imprinted polymer

“…The dPAD sensor for simultaneous CRP, TNF-α, and IL-6 detection utilizing CDs and MIP relies on the electronic transfer caused by fluorescence quenching after surface absorption of the target analyte. 23,24 CDs generally absorb UV energy through their free electrons, allowing them to become excited. As these excited electrons revert to their ground state, they emit blue fluorescence.…”

“…Furthermore, this technique can reduce errors that are common in colorimetric and fluorescence measurements from ambient lighting or background autofluorescence. 23,24 Previously, members of our group successfully developed a dPAD immunosensor for quantifying interleukin-6 (IL-6) in human samples utilizing methylene blue (MB) coated on the detection channel on paper. 7 The approach integrates microfluidic principles, microfabrication techniques, and immunological strategies to reduce the complexity and the time of the analysis procedure compared to traditional immunoassay methods.…”

Accuracy improvement via novel ratiometry design in distance-based microfluidic paper based analytical device: instrument-free point of care testing

“…35 Additionally, employing imaging soware to measure the length of colored bands yields fewer errors compared to using colorimetric detection alone. 36 One of the problems in paper-based devices in general and specially in distance based detection (DB-mPADs) that needs to be addressed is the leaching of the reagents from the detection zone towards the sampling zone, which results in systematic errors. Thus, eliminating this source of errors is crucial, and relevant corrections must be made.…”