Enhanced Sensitivity of Lateral Flow Tests Using a Two-Dimensional Paper Network Format

Abstract

Point-of-care diagnostic assays that are rapid, easy-to-use, and low-cost are needed for use in low-resource settings; the lateral flow test has become the standard bioassay format in such settings because it meets those criteria. However, for a number of analytes, conventional lateral flow tests lack the sensitivity needed to have clinical utility. To address this limitation, we are developing a paper network platform that extends the conventional lateral flow test to two dimensions. The two-dimensional structures allow incorporation of multi-step processes for improved sensitivity, while still retaining the positive aspects of conventional lateral flow tests. Here we create an easy-to-use, signal-amplified immunoassay based on a modified commercial strip test for human chorionic gonadotropin, the hormone used to detect pregnancy, and demonstrate an improved limit of detection compared to a conventional lateral flow assay. These results highlight the potential of the paper network platform to enhance access to high-quality diagnostic capabilities in low-resource settings in the developed and developing worlds.

Capillary microfluidics in microchannels: from microfluidic networks to capillaric circuits

“…26,74,108,111 Multi-step sequential liquid delivery may enable additional wash steps or chemical signal amplification to increase the signal-to-noise ratio of assay results. 26,112,113 Interestingly, sequential flow was also implemented in paper-based microfluidics using two-dimensional networks with varied flow path lengths. 112,114 As described in section 6, there are multiple approaches to achieving multi-step sequential liquid delivery in CCs including the use of capillaric elements such as retention valves, 5 RBVs, 26,44 capillary valves and vents, 74,108 and dissolvable barriers.…”

“…26,112,113 Interestingly, sequential flow was also implemented in paper-based microfluidics using two-dimensional networks with varied flow path lengths. 112,114 As described in section 6, there are multiple approaches to achieving multi-step sequential liquid delivery in CCs including the use of capillaric elements such as retention valves, 5 RBVs, 26,44 capillary valves and vents, 74,108 and dissolvable barriers. 71 For example, Safavieh and Juncker developed a CC that enabled not only precise metering of sample volume and incubation time, but also provided different flow rates for sample incubation (slow) and for rinsing (fast) by routing liquids through high and low resistance paths, respectively.…”

Programmed sample delivery on a pressurized paper

“…[1][2][3] Although the assays provide signals that are visible with the naked eye, further signal amplification can enhance the detection sensitivity. [4][5][6] However, such amplification process usually requires additional steps for the delivery of multiple reagents in a sequential manner for incubation and washing steps, which makes it difficult to design a device that can perform sequential delivery of real samples with a simple onestep procedure.…”

Point-of-Care Diagnostics

“…Other NP-based assay studies focused on improving the sensitivity of current lateral-flow tests by using paper network platforms. The 2D nitrocellulose-based networks enabled multistep processes to amplify the signal in immunoassays to improve the limit of detection [115,147]. These cards contained reagents stored dry and the assay was activated by wicking the sample in a single-user step.…”

“…1.2c), adopting folding techniques [119] and microplate paper platforms [120]. NP-based detection has been demonstrated with metabolites [109,111,113,117,121,147], bacterial agents [112] in disease diagnosis such as HIV [119], malaria [115], tuberculosis [120] and in environmental monitoring [114,118]. To multiplex the assay, monodisperse latex can be coupled with fluorescent and coloured dyes, and para/magnetic components.…”