Cord-Based Microfluidic Chips as A Platform for ELISA and Glucose Assays.

This paper describes the development and application of microfluidic cord-based analytical devices (µCADs) in two enzyme-linked immunosorbent assays (ELISAs) and glucose assay. In this study, biotinylated goat anti-mouse immunoglobulin (IgG) antibody, rabbit IgG antibody, and glucose are quantitatively detected. In the ELISA systems, the antibody is spotted on the cord at the detection site and a series of washes, followed by streptavidin-alkaline phosphatase (Strep-ALP) or alkaline phosphatase (ALP)-conjugated secondary antibody and colorimetric substrate, completing the experiment. The devices are subsequently scanned and analyzed yielding a correlation between inverse yellow or inverse blue intensity and antibody concentration. For the first ELISA, a linear range of detection was observed at lower concentrations (2.50 × 10-4-1.75 × 10-3 mg/mL) of Strep-ALP with saturation of the enzyme achieved at higher concentrations (>2.50 × 10-4). For the second ELISA, the L50 was demonstrated to be 167.6 fmol/zone. The glucose assay consisted of spotting increasing concentrations of glucose on the analysis sites and transporting, via capillary action, a solution containing glucose oxidase (GOx), horseradish peroxidase (HRP), and potassium iodide (KI) to the detection sites realizing a yellow-brown color indicating oxidation of iodide to iodine. The device was then dried, scanned, and analyzed to show the correlation between yellow inverse intensity and glucose. Glucose in artificial urine showed good correlation using the devices.

Thread- paper, and fabric enzyme-linked immunosorbent assays (ELISA).

Enzyme-linked immunosorbent assay (ELISA) is an immunological assay commonly used to measure antibodies, antigens, proteins, and glycoproteins in biological samples. While the procedure is routine and straightforward, there are a number of variables (reagent selection, volume measurement, temperature, and time) that if not carefully considered, can affect the test outcome. Herein, we describe the development of microfluidic thread/paper-based analytical devices (µTPAD), microfluidic fabric-based analytical devices (µFAD), and microfluidic thread-based analytical devices (µTAD) as new platforms for ELISA. The quantitative detection of biotinylated goat anti-mouse IgG (system one) and rabbit IgG (system two) antibodies via colorimetric analysis is detailed. We explain the design and fabrication of the devices and the step-by-step protocol for the ELISA. A comparison between the techniques is described and the results obtained from them elucidated.

Enzyme-linked immunosorbent assays (ELISA) based on thread, paper, and fabric.

This paper describes enzyme-linked immunosorbent assays (ELISAs) utilizing microfluidic thread/paper-based analytical devices (µTPAD), microfluidic fabric-based analytical devices (µFAD), and microfluidic thread-based analytical devices (µTAD). Here, the quantitative detection of biotinylated goat anti-mouse IgG (system one) and rabbit IgG (system two) antibodies via colorimetric analysis is detailed. In both systems, antibody is spotted on the detection site and subjected to a series of washes, addition of streptavidin-alkaline phosphatase (Strep-ALP) (system 1) or alkaline phosphatase (ALP)-conjugated secondary antibody (system 2), and colorimetric substrate. The devices are scanned and analyzed yielding a correlation between inverse yellow (or purple) intensity. For system one, a linear range of detection at low concentrations of streptavidin-alkaline phosphatase (Strep-ALP) was observed befire the enzyme reached a Vmax . At higher concentrations of Strep-ALP, saturation is achieved for both the µTPAD and µFAD devices. For system two, the IC50 values obtained for the non-trifurcated and trifurcated µTADs were determined to be 180.2 fmol/zone and 133.8 fmol/zone, respectively. The IC50 value was demonstrated to be 1034 fmol/zone and 208.6 fmol/zone for the µTPADs and µFADs, respectively. For all devices the lowest concentration of Strep-ALP or rabbit IgG used in the assay was 3.75 × 10-4  mg/mL and 0.7 fmol/zone, respectively. The development of this technology should further facilitate the use of these platforms for ELISA to detect and quantitate antibodies.

Rapid detection of aortic occlusion with emergency ultrasonography.

The differential diagnosis of aortic emergencies includes abdominal aortic aneurysms and aortic dissection. Aortic occlusion is another rare yet deadly vascular emergency to be wary of. For acute occlusions, definitive management by embolectomy or aortofemoral bypass must be performed promptly. When suspected because of the history and physical examination results, bedside ultrasonography rapidly confirms the diagnosis. We describe 2 very different cases of aortic occlusion both initially detected with bedside ultrasonography in our emergency department.