Plasmon-enhanced near-infrared fluorescence detection of traumatic brain injury biomarker glial fibrillary acidic protein in blood plasma.

An ultrasensitive plasmonic near-infrared fluorescent biosensor substrate has been developed for detection of glial fibrillary acidic protein (GFAP) biomarker in blood plasma, an important protein biomarker of traumatic brain injury (TBI). To minimize the interference from blood plasma sample matrix, a near-infrared fluorophore in the first biological transparency window is used in the biosensor. To amplify the fluorescence signals, a plasmonic gold nanopyramid array has been coupled to the fluorophore. Finite-difference time-domain simulation reveals that the excitation enhancement is primarily responsible for the fluorescence enhancement owing to the intense local electric field excited on the corners and edges. As a result, this biosensor exhibits a lower limit of detection of 0.6 pg/mL toward detection of GFAP in blood plasma.

Trace analysis on chromium (VI) in water by pre-concentration using a superhydrophobic surface and rapid sensing using a chemical-responsive adhesive tape.

Heavy metal ions in water resources present great threats to human health. Chromium (Cr), as the frequently used heavy metal in industrial processes and everyday life, requires a low-cost, fast and effective means to determine its concentration, especially in drinking water. Conventional colorimetric paper-based analytical devices (PADs), due to the limited sensitivity, are unable to quantify the most harmful heavy metal ions to the drinking water standard. In this work, we present a method of using a superhydrophobic (SH) paper to concentrate Cr6+ from solutions of very low concentration to obtain the precipitated Cr6+ salt particulates. A known volume of Cr6+-containing solution was concentrated to "a spot" on the SH paper through drying, so that trace amount of Cr6+ can be quantified via the application of a specifically-designed chemical-responsive adhesive tape (CAT) sensor, loaded with Cr6+- specific indicator, on to the concentrated Cr6+ spot. The detection limit of the SH-CAT method for Cr6+ is 0.05 mg/L, which is the permitted maximum concentration in drinking water and is significantly lower than that of conventional PADs. The interference and the accuracy studies also show the reliability of this method for measuring trace amounts of analytes.

Three-dimensional microfluidic tape-paper-based sensing device for blood total bilirubin measurement in jaundiced neonates.

More than 60% newborns experience hyperbilirubinemia and jaundice within the initial week after birth due to the accumulation of total bilirubin in blood. Left untreated high levels of bilirubin may result in brain impairment. Simple, fast, accurate, low-cost and timely point-of-care (POC) analysis of total bilirubin is an unmet need especially in resource-limited areas. This work introduces a novel sensing device, named a "tape-paper sensor", capable of separating plasma from whole blood and measuring total bilirubin by a colorimetric diazotization method. The tape-paper sensing method overcomes non-homogeneous color distribution caused by the "coffee stain" effect, which improves the accuracy of colorimetric evaluation on paper-based analytical devices. The level of hemolysis in the plasma extracted by the device is evaluated, confirming no interference in the detection of total bilirubin. The accuracy of the tape-paper sensing approach for neonatal blood sample measurement is verified by comparison with the hospital pathology laboratory method. The small volume of samples and reagents, minimal equipment (an office scanner), fast detection (<10 min) and low fabrication cost (∼A$ 0.6) reveal the suitability of the device for POC use and in resource-limited settings. The tape-paper sensor is a low-cost, fast, and user-friendly device for measurement of blood total bilirubin levels in neonatal jaundice diagnostics.

Low-Cost Chemical-Responsive Adhesive Sensing Chips.

Chemical-responsive adhesive sensing chip is a new low-cost analytical platform that uses adhesive tape loaded with indicator reagents to detect or quantify the target analytes by directly sticking the tape to the samples of interest. The chemical-responsive adhesive sensing chips can be used with paper to analyze aqueous samples; they can also be used to detect and quantify solid, particulate, and powder analytes. The colorimetric indicators become immediately visible as the contact between the functionalized adhesives and target samples is made. The chemical-responsive adhesive sensing chip expands the capability of paper-based analytical devices to analyze solid, particulate, or powder materials via one-step operation. It is also a simpler alternative way, to the covalent chemical modification of paper, to eliminate indicator leaching from the dipstick-style paper sensors. Chemical-responsive adhesive chips can display analytical results in the form of colorimetric dot patterns, symbols, and texts, enabling clear understanding of assay results by even nonprofessional users. In this work, we demonstrate the analyses of heavy metal salts in silica powder matrix, heavy metal ions in water, and bovine serum albumin in an aqueous solution. The detection is one-step, specific, sensitive, and easy-to-operate.