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Global Health Technologies

Global Health Technologies - Poster Session D

Poster Y6 - Developing a Quantitative Multicolor Paper-Based Device by Combining the Lateral-Flow Immunoassay with Gold Nanorod Etching

Friday, October 25, 2024
3:30 PM – 4:30 PM EST
Location: Exhibit Hall E, F & G

Introduction:  Therapeutic drug monitoring is used to measure the concentrations of drugs, such as the cardiac medication digoxin, to ensure safe and effective dosages. Since many digoxin patients live in resource-limited areas, there is a need for an inexpensive, rapid diagnostic that can quantify this target molecule as the current gold standards require expensive equipment and trained personnel. The lateral-flow immunoassay (LFA) is a paper-based diagnostic but suffers from its inability to provide quantitative information. To address this, our lab previously combined LFAs with an H2O2 solution and gold nanorod (GNR) etching in suspension to yield easily distinguishable color hues that could be correlated to digoxin concentrations. However, this method required many liquid-handling steps that prevented its use at the point of care. This work expands upon our previous study to create a fully paper-based set-up combining LFAs with GNR etching on paper.

Materials and

Methods:  To achieve H2O2 degradation on paper, LFAs were first dipped into a human serum solution containing porous platinum-shell gold-core nanozyme probes (PtNPs). The LFA test line was then cut, followed by pipetting of an H2O2 solution onto the test line. After incubation on the test line, the solution was pipetted into a 96-well plate that contained necessary GNR etching reagents. To achieve GNR etching on paper, a GNR pad was made using a sol-gel precursor, GNRs, and horseradish peroxidase on fiberglass paper. Solutions with different concentrations of H2O2 were then pipetted onto the GNR pad to achieve GNR etching directly on paper.

Results, Conclusions, and Discussions: As shown in Figure 1, increasing the volume of PtNPs correlates with darker LFA test lines, which lead to more H2O2 degradation on paper and thus different GNR etching colors in suspension. This result therefore demonstrates that translating H2O2 degradation onto paper has the potential to correlate digoxin concentration, which affects the test line intensity, to different colors. In Figure 2, we developed GNR pads that were able to exhibit a variety of uniform colors based on different concentrations of H2O2, demonstrating that GNR etching on paper is indeed possible.

We have successfully improved upon our research group’s previous work by achieving H2O2 degradation on paper and developing novel GNR pads that utilize a sol-gel process to encapsulate GNRs and horseradish peroxidase in a paper matrix. With these GNR pads, a wide range of uniform colors were observed. Our overall strategy for determining digoxin concentration is beneficial as it is easier for the naked eye to see differences in color hue versus differences in intensity of a single color. We are currently working on designing and developing an all-in-one 3D-printed casing that houses both the LFA and GNR pad components to combine the H2O2 degradation and GNR etching steps. Such a user-friendly paper-based device that can provide a quantitative output will enable digoxin monitoring at home or in mobile clinics. Due to the modular design of the assay, this technology can also be easily applied to the quantitative detection of other medications that require therapeutic drug monitoring, expanding the possibilities for the quantification of target biomarkers in resource-limited settings.

Acknowledgements (Optional):  This project was supported by a seed grant provided by the Precise Advanced Technologies and Health Systems for Underserved Populations (PATHS-UP) Engineering Research Center (ERC) funded by the National Science Foundation (NSF) (Award No. 1648451).