Point-of-care devices were originally designed to allow medical testing at or near the point of care by health-care professionals. Some point-of-care devices allow medical self-testing at home but ...cannot fully cover the growing diagnostic needs of eHealth systems that are under development in many countries. A number of easy-to-use, network-connected diagnostic devices for self-testing are needed to allow remote monitoring of patients’ health. This Outlook highlights the essential characteristics of diagnostic devices for eHealth settings and indicates point-of-care technologies that may lead to the development of new devices. It also describes the most representative examples of simple-to-use, point-of-care devices that have been used for analysis of untreated biological samples.
This paper describes an inexpensive, handheld device that couples the most common forms of electrochemical analysis directly to “the cloud” using any mobile phone, for use in resource-limited ...settings. The device is designed to operate with a wide range of electrode formats, performs on-board mixing of samples by vibration, and transmits data over voice using audio—an approach that guarantees broad compatibility with any available mobile phone (from low-end phones to smartphones) or cellular network (second, third, and fourth generation). The electrochemical methods that we demonstrate enable quantitative, broadly applicable, and inexpensive sensing with flexibility based on a wide variety of important electroanalytical techniques (chronoamperometry, cyclic voltammetry, differential pulse voltammetry, square wave voltammetry, and potentiometry), each with different uses. Four applications demonstrate the analytical performance of the device: these involve the detection of (i) glucose in the blood for personal health, (ii) trace heavy metals (lead, cadmium, and zinc) in water for in-field environmental monitoring, (iii) sodium in urine for clinical analysis, and (iv) a malarial antigen (Plasmodium falciparum histidine-rich protein 2) for clinical research. The combination of these electrochemical capabilities in an affordable, handheld format that is compatible with any mobile phone or network worldwide guarantees that sophisticated diagnostic testing can be performed by users with a broad spectrum of needs, resources, and levels of technical expertise.
Analytical tests/devices that are used outside laboratory settings are required to have a very simple analytical protocol to get clearance by regulatory authorities. This study describes sink/float ...magnetic immunoassays, a new type of rapid, mix‐and‐observe, instrument‐free tests for the detection of biomarkers in untreated biological samples that are very simple and might meet the simple‐to‐use criterion of authorities to be used in the field. These tests can tell whether an analyte is above or below a predetermined level within 25–45 minutes based on the sinking or floating of a mm‐sized sphere on the surface of which an immunoassay that uses reporter antibodies conjugated to superparamagnetic nanoparticles is performed. This manuscript describes the theory and proof‐of‐concept applications of sink/float magnetic immunoassays for the detection of C‐Reactive Protein, anti‐Treponema pallidum antibodies and E. coli bacteria.
Sink/float magnetic immunoassays detect proteins, antibodies, and bacteria in samples using a simple mix‐and‐observe protocol that uses a biofunctionalized small sphere, some liquid reagents and a small permanent magnet. A simple sink/float test of the sphere identifies if the analyte is above or below a predetermined level; the sphere sinks only if the analyte is above the concentration level.
Electrically Activated Paper Actuators Hamedi, Mahiar M.; Campbell, Victoria E.; Rothemund, Philipp ...
Advanced functional materials,
April 19, 2016, Volume:
26, Issue:
15
Journal Article
Peer reviewed
Open access
This paper describes the design and fabrication of electrically controlled paper actuators that operate based on the dimensional changes that occur in paper when the moisture absorbed on the surface ...of the cellulose fibers changes. These actuators are called “Hygroexpansive Electrothermal Paper Actuators” (HEPAs). The actuators are made from paper, conducting polymer, and adhesive tape. They are lightweight, inexpensive, and can be fabricated using simple printing techniques. The central element of the HEPAs is a porous conducting path (used to provide electrothermal heating) that changes the moisture content of the paper and causes actuation. This conducting path is made by embedding a conducting polymer (PEDOT:PSS) within the paper, and thus making a paper/polymer composite that retains the porosity and hydrophilicity of paper. Different types of HEPAs (straight, precurved, and creased) achieved different types of motions (e.g., bending motion, accordion type motion). A theoretical model for their behavior is proposed. These actuators have been used for the manipulation of liquids and for the fabrication of an optical shutter.
Hygroexpansive electrothermal paper actuators (HEPAs) are fabricated from paper, conducting polymer and adhesive tape, and operate based on the moisture‐induced dimensional changes of paper. The central element of the HEPAs is a porous conducting path (used to provide electrothermal heating). A theoretical model for their behavior is proposed. These actuators can be used for the manipulation of liquids and for the fabrication of an optical shutter.
...a) all channels and microchambers have been carefully designed to allow pump-free wicking of sweat and are all connected to channels that terminate at the exterior of the device to avoid any ...backpressure; (b) bursting pressure valves that have been incorporated into the network of microfluidic channels facilitate time-sequential sensing and analysis of sweat; (c) the interconnects of the biofuel-based cell have a serpentine shape to accommodate mechanical strains during bending of the device; and (d) a layer that has printed color reference charts is incorporated into the device to allow accurate color comparison of colored products during imaging regardless the lighting conditions. Several other ions (e.g., K+, Mg2 + , Ca2+, HCO3 , NH4+, Cu2+), amino acids (e.g., alanine, arginine, glycine, histidine), metabolites (e.g., glucose, lactate, creatinine, urea), proteins (e.g., cytokines), drugs (e.g., illicit drugs), and other small compounds (e.g., cortisol, ethanol) are also secreted with sweat, although they are not actively involved in sweat production; these ions, proteins, and small molecules diffuse from surrounding cells into the lumens of the eccrine gland secretory coils and duct (Fig. 1B) (4). ...the sweat rate influences the concentration ofbiomarkers in sweat. ...the sampling and analysis of sweat can greatly influence the accuracy of the results; for example, a typical problem of conventional sweat analysis methodologies is that sweat evaporation, contamination, or degradation may occur during the multistep processes of collection, storage, and transport of sweat affecting the accuracy of the results.
This paper demonstrates that, for applications in resource-limited environments, expensive microplate spectrophotometers that are used in many central laboratories for parallel measurement of ...absorbance of samples can be replaced by photometers based on inexpensive and ubiquitous, consumer electronic devices (e.g., scanners and cell-phone cameras). Two devices, (i) a flatbed scanner operating in transmittance mode and (ii) a camera-based photometer (constructed from a cell phone camera, a planar light source, and a cardboard box), demonstrate the concept. These devices illuminate samples in microtiter plates from one side and use the RGB-based imaging sensors of the scanner/camera to measure the light transmitted to the other side. The broadband absorbance of samples (RGB-resolved absorbance) can be calculated using the RGB color values of only three pixels per microwell. Rigorous theoretical analysis establishes a well-defined relationship between the absorbance spectrum of a sample and its corresponding RGB-resolved absorbance. The linearity and precision of measurements performed with these low-cost photometers on different dyes, which absorb across the range of the visible spectrum, and chromogenic products of assays (e.g., enzymatic, ELISA) demonstrate that these low-cost photometers can be used reliably in a broad range of chemical and biochemical analyses. The ability to perform accurate measurements of absorbance on liquid samples, in parallel and at low cost, would enable testing, typically reserved for well-equipped clinics and laboratories, to be performed in circumstances where resources and expertise are limited.
This work describes a device for electrochemical enzyme-linked immunosorbent assay (ELISA) designed for low-resource settings and diagnostics at the point of care. The device is fabricated entirely ...in hydrophobic paper, produced by silanization of paper with decyl trichlorosilane, and comprises two zones separated by a central crease: an embossed microwell, on the surface of which the antigen or antibody immobilization and recognition events occur, and a detection zone where the electrodes are printed. The two zones are brought in contact by folding the device along this central crease; the analytical signal is recorded from the folded configuration. Two proof-of-concept applications, an electrochemical direct ELISA for the detection of rabbit IgG as a model antigen in buffer and an electrochemical sandwich ELISA for the detection of malarial histidine-rich protein from Plasmodium falciparum (Pf HRP2) in spiked human serum, show the versatility of this device. The limit of detection of the electrochemical sandwich ELISA for the quantification of Pf HRP2 in spiked human serum was 4 ng mL–1 (102 pmol L–1), a value within the range of clinically relevant concentrations.
Regulatory authorities require analytical methods for bacteria detection to analyze large sample volumes (typically 100 mL). Currently only the Membrane Filtration and the Most Probable Number assays ...analyze such large volumes, while other assays for bacteria detection (ELISA, lateral flow assays, etc.) typically analyze volumes 1000 times smaller. This study describes flow-through direct immunoassays (FTDI), a new methodology for the targeted detection of bacteria in liquid samples of theoretically any volume. Flow-through direct immunoassays are performed in fluid-permeable microwells (e.g., wells of a filter well plate) that have a membrane on their bottom where the bacteria are trapped before their detection using a direct immunoassay. Two versions of FTDI assays for the detection of E. coli in 10 mL of sample were developed. A rapid FTDI assay that can be completed in less than 2.5 h can detect E. coli bacteria in levels down to 17 CFU/mL, and an ultrasensitive FTDI assay that employs an additional bacteria culturing step to boost the sensitivity can detect E. coli bacteria in levels lower than 1 CFU/mL in less than 5.5 h. All the steps of the assays, including the immunoassay steps, the culturing step, and the analytical signal measurement step are performed inside the well plate to decrease the chance of contamination and ensure a safe, easy process for the user. The assays were assessed and validated in tap water, river water, and apple juice samples, and the results suggests that the assays are robust, precise, and accurate. When the assays are performed in 96-well filter plates, a filter well plate vacuum manifold and a multichannel peristaltic pump are also used, so multiple samples can be analyzed in parallel to allow high-throughput analysis of samples.
Paper microfluidics and printed electronics have developed independently, and are incompatible in many aspects. Monolithic integration of microfluidics and electronics on paper is demonstrated. This ...integration makes it possible to print 2D and 3D fluidic, electrofluidic, and electrical components on paper, and to fabricate devices using them.
Diagnostic tests in resource-limited settings require technologies that are affordable and easy to use with minimal infrastructure. Colorimetric detection methods that produce results that are ...readable by eye, without reliance on specialized and expensive equipment, have great utility in these settings. We report a colorimetric method that integrates a paper-based immunoassay with a rapid, visible-light-induced polymerization to provide high visual contrast between a positive and a negative result. Using Plasmodium falciparum histidine-rich protein 2 as an example, we demonstrate that this method allows visual detection of proteins in complex matrices such as human serum and provides quantitative information regarding analyte levels when combined with cellphone-based imaging. It also allows the user to decouple the capture of analyte from signal amplification and visualization steps.
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