Multiplexed Point-of-Care Testing - xPOCT

Abstract

Multiplexed point-of-care testing (xPOCT), which is simultaneous on-site detection of different analytes from a single specimen, has recently gained increasing importance for clinical diagnostics, with emerging applications in resource-limited settings (such as in the developing world, in doctors' offices, or directly at home). Nevertheless, only single-analyte approaches are typically considered as the major paradigm in many reviews of point-of-care testing. Here, we comprehensively review the present diagnostic systems and techniques for xPOCT applications. Different multiplexing technologies (e.g., bead- or array-based systems) are considered along with their detection methods (e.g., electrochemical or optical). We also address the unmet needs and challenges of xPOCT. Finally, we critically summarize the in-field applicability and the future perspectives of the presented approaches.

Keywords: lab-on-a-chip (LOC); microfluidics; multianalyte analysis; multiplexing; on-site testing; point-of-care testing (POCT).

Figure 1

Key Figure: Multiplexed Point-of-Care Testing (xPOCT) Requires Novel (Appropriate, Powerful, Low-Cost and Simple) Strategies for Sampling, Analysis and Data Interpretation. Therefore, it will pave the way for personalized therapies or on-site disease diagnostics in resource-limited settings in the future.

Figure 2

Schematic Description of the Microfluidic Paper-Based xPOCT Device for the Control of Liver Function. (A) Fabrication process describing the different assembly steps. (B) Measurement procedure. (C) Color readout guides for the multiplexed measurement of transaminase enzyme levels. Reproduced, with permission from AAAS, from . Abbreviations: ALT, alanine aminotransferase; AST, aspartate aminotransferase.

Figure 3

mChip Platform for Multiplexed On-Site Diagnostics. (A) Photo of the microfluidic polystyrene cassette with seven measurement units. (B) SEM image of channel cross-section (scale bar: 500 μm). (C) Transmitted light micrograph of a single detection site (scale bar: 1 mm). (D) Passive delivery of preloaded sequence of different reagents. (E) Schematics of assay reactions in different detection sites at different incubation steps. The on-chip signal detection is achieved by reduction of silver ions on secondary antibodies tagged with gold nanoparticles. (F) Measurement procedure and resulting optical density of a HIV-syphilis duplex test. Reproduced, with permission from Macmillan Publishers Ltd: Nature Medicine, from .

Figure 4

DxBox Integrated Microfluidic Card with Its Main Features. (A) Illustration of the pneumatic regulation for the fluid manipulation. (B) On-card volume metering and freeze-dried biomolecule storage. (C) Photograph of integrated microfluidic cartridge. (D) Schematics of the employed bath mixer for sample dilution and IgG removal. (E) Incubation procedure on the assay membrane. The application of an air vent and a valve removes the air between reagent deliveries, and the reagents itself between different incubation steps. (F) On-chip multianalyte detection of IgM antibodies against typhoid infection and malaria pfHRPII antigen from human plasma. Reproduced, with permission from The Royal Society of Chemistry, from . Abbreviations: E.C., endogenous control; P.C., process control.

Figure 5

Graphical Abstract Illustrating the Working Principle of ‘MultiLab’ Platform. (A) Schematics of the competitive enzyme-linked assay for the multianalyte antibiotic detection. For an easy and universally applicable ‘plug and play’ assay immobilization, antifluorescein antibodies are used as spacer and capture biomolecules. Glucose oxidase is employed as the labeling enzyme with glucose for its appropriate substrate. (B) CAD drawing of the microfluidic multiplexed biosensor. For the measurement, individual channel inlets are sealed with a PMMA piece and double-sided tape. (C) The subsequent electrochemical detection of hydrogen peroxide, generated by the competitive antibiotic assay, at the respective working electrode. (D) Stop-flow peaks from a simultaneous on-chip calibration measurement. (E) Resulting on single-chip calibration curve along with a four-parameter logistic fit. Reproduced, with permission from the American Chemical Society, from . Abbreviations: CAD, computer-aided design; PMMA, poly(methyl methacrylate).

Figure 6

Visual Overview of the Presented State-of-the-Art xPOCT Systems. Two important conceptual approaches are system complexity versus multiplexing performance. An ideal multiplexed on-site device needs to prove a high sensor performance at low system complexity. Abbreviations: LFAs, lateral flow assays; mLSI, microfluidic large-scale integration; μPADs, microfluidic paper-based analytical devices.