Development of paper-based devices for point-of-need, bioanalytical applications
Date
2020
Authors
Noviana, Eka, author
Henry, Charles S., advisor
Reynolds, Melissa M., committee member
Chung, Jean, committee member
Geiss, Brian J., committee member
Journal Title
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Volume Title
Abstract
The growing demand for reliable analytical tools to perform testing at the point-of-need has necessitated the development of novel sensors that are low cost (USD 1-10), portable, sensitive, selective, easy to use, and rapid (i.e. provide results within minutes or a few hours). Miniaturization of the sensors into microfluidic platforms has become a promising approach to achieve these sensors. However, traditional microfluidics often require relatively expensive and complicated pumping mechanisms that increase the cost and limit the portability of the sensors. From a material perspective, cellulosic paper is an attractive substrate for constructing point-of-need sensors due to its affordability, vast availability, self-pumping ability via capillary action, and easy fabrication using various printing and patterning techniques. My dissertation research has been focused on developing paper-based devices to address several key gaps that exist between the current technologies and the desired properties of point-of-need sensors. Chapter 2 describes the development of a steady flow paper device that enabled a function similar to conventional flow injection analysis (FIA) without external pumps. Two-layer paper devices increased the attainable flow rate and reduced the analysis time to only a minute, compared with 10-20 min analysis time reported in previous paper-based FIA. Disposable Pt microwire electrodes were used as a detector in the electrochemical paper-based device (ePAD) and the proposed sensor has been used to detect the activity of β-galactosidase (a bacterial indicator for coliform detection and a common detection label in enzyme-linked immunosorbent assay). Similar enzyme kinetics to those reported in the literature was obtained using the proposed sensor, showing a great promise for semi-automation in bioanalysis. Implementing a similar flow ePAD, the goal has now expanded toward improving the detection sensitivity as well as reducing the cost of the sensors. In Chapter 3, low-cost (~1 USD) and reusable thermoplastic electrodes (TPEs) were fabricated by mixing carbon and a plastic binder and pressing the material into an acrylic mold. These TPEs showed an improved electrochemical activity over conventional carbon paste electrodes typically used in ePADs. In addition, electrode arrays can also be fabricated using the technique to improve detection sensitivity via a generation-collection experiment, where the first electrode in the array oxidizes the analyte, the second reduces it, and the process is repeated across the entire array to provide an enhanced cumulative signal. Nanomolar detection limits were achieved using TPEs in both single detector and detector arrays configurations. A 5× improved sensitivity was obtained by employing electrode arrays over the single detector. In Chapter 4, the dissertation shifts focus to a more specific application, detecting nucleic acid, an important biological analyte that has been largely targeted to diagnose various diseases including genetic disorders, cancer, neurodegenerative, and infectious diseases. This chapter describes the integration of nuclease protection assay (NPA), a highly specific hybridization-based technique, with a reader-free colorimetric detection via lateral flow assay (LFA). In NPA, the hybridization of an antisense probe to the target sequence is followed by single-strand nuclease digestion. The protected double-stranded target-probe hybrids are then captured on the LFA device, followed by the addition of a colorimetric enzyme-substrate pair for signal visualization. The proposed paper-based NPA can detect sub-femtomole (~108 copies) of target DNA with high specificity. While the paper-based NPA can serve a good screening tool for several types of chronic infection in which large copies of pathogen DNA is present in the samples, the high detection limit hinders the application of this method for early disease diagnosis and detecting pathogens in environmental samples. In Chapter 5, polymerase chain reaction (PCR), a nucleic acid amplification technique, was coupled to the colorimetric LFA to improve the detection limit and enable the detection of antimicrobial-resistant (AMR) genes and bacteria in environmental samples. Six orders of magnitude lower detection limit (i.e. 102 plasmid DNA copies) was achieved by the PCR-LFA. The proposed method can be applied for rapid detection (less than 3 h) of AMR bacteria in environmental samples. Several works presented in this dissertation provided different approaches to achieve viable paper-based sensors for point-of-need applications. Progress has been made in improving both analytical figures of merit (i.e. sensitivity and detection limit) and practical specifications of the paper sensors (i.e. reduced sensor cost, semi-automation via an external pump-free flow-based system, instrument-free colorimetric readout, and improved assay time).
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Subject
paper microfluidics
point-of-need
paper-based devices
bioanalytical sensors