Enabling robust quantitative readout in an equipment-free model of device development

Abstract

A critical constraint in the design of appropriate medical devices for the lowest-resource settings is the lack of access to maintenance or repair on instrumentation. There are numerous point-of-care applications for which quantitative readout would have clinical utility. Thus, a challenge to the device developer is to enable quantitative device readout in an equipment-free model that is appropriate for use in even the lowest-resource settings. Paper microfluidics has great potential for enabling equipment-free devices that are very low-cost, operable by minimally-trained users, and provide quantitative readout. The focus of this critical review is to describe the work, starting several decades ago and continuing to the present, to enable assays with quantitative readout in a fully-disposable device.

Biosensing with Paper-Based Miniaturized Printed Electrodes–A Modern Trend

“…In the near future, the translation of current research prototypes into commercial applications should mainly address challenges related with quality assurance [3]. One of the most critical aspects to be tackled is the achievement of reproducible quantitative results; this depends not only on the test’s performance and the capability of producing identical sensor batches but also on the environmental variables, which can affect the operating conditions and consequently, the signal output [8]. As such, POCTs are often more at risk of interferences than conventional laboratory assays [6].…”

“…The World Health Organization outlined other key words in the research and development of POCTs for the lowest-resource environments. Altogether, they constitute the ASSURED guidelines: Affordable, Sensitive, Specific, User-friendly, Rapid and Robust, Equipment-free and Deliverable to end-users [1,4,7,8]. However, regarding the use of POCTs in the developed world, some of these criteria are not quite relevant.…”

“…Moreover, patterning paper with hydrophilic channels delimited by hydrophobic walls allows samples to be dispensed into several spatially separated zones, which enables running multiple assays simultaneously, on a single device. All these characteristics are highly valuable for POCTs tailored not only for resource-limited settings but also for applications in developing regions, opening up a world of new applications for an older player, as paper is [1,6,8,11,12]. …”

Timing readout in paper device for quantitative point-of-use hemin/G-quadruplex DNAzyme-based bioassays

“…Key advantages include ease of fabrication (storage, transport and use), low reagent volume, porous structure that facilitates capillary flow, and simple signal readout. Several papers reviewed various fabrication methods and applications of the μPADs (Cate et al, 2014;Fu, 2014;Li et al, 2012;Martinez et al, 2010).…”

Paper and Fiber-Based Bio-Diagnostic Platforms: Current Challenges and Future Needs

“…Such strategies would reduce the cost of bio-diagnosis, while increasing the portability of the devices that do not require external readout instrumentation [141,142]. One approach to perform equipment-free analysis relies upon color intensity comparators using an external calibration or standard calibration integrated within the device [143,144].…”