Distance-based paper device using combined SYBR safe and gold nanoparticle probe LAMP assay to detect Leishmania among patients with HIV.

Asymptomatic visceral leishmaniasis cases increase continuously, particularly among patients with HIV who are at risk to develop further symptoms of leishmaniasis. A simple, sensitive and reliable diagnosis is crucially needed due to risk populations mostly residing in rural communities with limited resources of laboratory equipment. In this study, a highly sensitive and selective determination of Leishmania among asymptomatic patients with Leishmania/HIV co-infection was achieved to simultaneously interpret and semi-quantify using colorimetric precipitates (gold-nanoparticle probe; AuNP-probe) and fluorescence (SYBR safe dye and distance-based paper device; dPAD) in one-step loop-mediated isothermal amplification (LAMP) assay.

Distance-Based Paper Device for a Naked-Eye Albumin-to-Alkaline Phosphatase Ratio Assay.

The albumin-to-alkaline phosphatase ratio (AAPR) has been a cancer prognostic indicator. This paper presents the concept of a dual-color change distance-based paper device (dPAD) for albumin (Alb) and alkaline phosphatase (ALP) detection to evaluate this cancer prognostic index. Whereas Alb interacts with the bromocresol green (BCG) indicator to form a bluish-green complex, ALP hydrolyzes l-ascorbic acid-2-phosphate (AAP) to produce ascorbic acid (AA), which reacts with KIO to generate I and I.

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A paper-based method for heating preconcentration (PAD-HP) has been developed for the determination of Pb, Cd, Fe, and Ni. The design of our heating system was evaluated for dual quantification of ions using electrochemical and colorimetric methods simultaneously. The PAD-HP was used to detect Pb and Cd by anodic stripping voltammetry and to detect Fe and Ni by colorimetric reactions.

A paper-based conductive immunosensor for the determination of Salmonella Typhimurium.

We report for the first time a highly sensitive and rapid quantitative method for the detection of Salmonella Typhimurium (S. Typhimurium) using a conductive immunosensor on a paper-based device (PAD). S.

Sensitive distance-based paper-based quantification of mercury ions using carbon nanodots and heating-based preconcentration.

This article reports the first fluorescent distance-based paper device coupled with an evaporating preconcentration system for determining trace mercury ions (Hg) in water. The fluorescent nitrogen-doped carbon dots (NCDs) were synthesized by a one-step microwave method using citric acid and ethylenediamine. The fluorescence turn-off of the NCDs in the presence of Hg was visualized with a common black light, and the distance of the quenched fluorescence correlated to Hg concentration.

Distance-Based Paper Device Combined with Headspace Extraction for Determination of Cyanide.

We report for the first time a distance-based paper device based on gold/silver core shell nanoparticles (Au@Ag NPs) for a simple, inexpensive, instrument-free, and portable determination of cyanide by the naked eye. Au@Ag NPs immobilized on a paper channel were etched by cyanide ions so that a yellow color band length of Au@Ag NPs is proportional to a decrease in the cyanide concentration. Quantification is achieved by measuring color length, thus eliminating the need to differentiate hues and intensities by the user, and the processing data of each imaging device.

Cotton fiber-based assay with time-based microfluidic absorption sampling for point-of-care applications.

Time-based microfluidic absorption sampling was proposed using cotton fiber-based device made in swab stick. The assay was optimized and compared with conventional pipetted drop sampling using the same device. Reagents were integrated into cotton fiber device for assessing concentration of analytes by the colorimetric detection method through time-based absorption sampling microfluidic system.

Disposable Nonenzymatic Uric Acid and Creatinine Sensors Using PAD Coupled with Screen-Printed Reduced Graphene Oxide-Gold Nanocomposites.

Uric acid (UA) and creatinine are the imperative biological substance for clinical monitoring and diagnosis. Measuring the ratio between uric acid and creatinine in urine helps differentiate acute uric acid nephropathy from the hyperuricemia that secondarily occurs to renal failure. In general, the ratio is greater than 0.

A distance-based paper sensor for the determination of chloride ions using silver nanoparticles.

We report for the first time the development of a distance-based paper sensor for a simple, inexpensive, instrument-free, and portable determination of chloride ions. Our analysis reaction is based on the oxidative etching of silver nanoparticles (AgNPs) to form AgCl in the presence of Cl- and H2O2. H2O2 reacts with AgNPs in the channel of the paper device and Cl- in the sample forming a white precipitate (AgCl) where the white color band length is proportional to the Cl- concentration.

A Simple Paper-based Colorimetric Device for Rapid and Sensitive Urinary Oxalate Determinations.

In this work, a simple and inexpensive paper-based colorimetric device (cPAD) was developed for oxalate measurements. The colorimetric assay is based on the formation of formazan via the reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) by oxalate decarboxylase and formate dehydrogenase on the paper device. After the sample was spotted on the device, MTT changed color from yellow to purple, and the purple color intensity correlated with the oxalate concentration.

Highly sensitive colorimetric detection of lead using maleic acid functionalized gold nanoparticles.

Highly sensitive colorimetric detection for Pb(2+) has been developed using maleic acid (MA) functionalized GNP. The -COOH on MA was used to modify GNP surface whereas the other -COOH functional group have strong affinity to coordination behavior of Pb(2+) allowing the selective formation more than other ions. MA-GNPs solution changed from red to blue color after the addition of Pb(2+) due to nanoparticle aggregation.

Simple silver nanoparticle colorimetric sensing for copper by paper-based devices.

The first investigation of silver nanoparticle (AgNP) colorimetric sensing of Cu(2+) by paper-based analytical devices (PADs) is reported here. AgNP colorimetric sensing for the detection of Cu(2+) was first characterized by UV-visible spectroscopy. The -SH groups on homocysteine (Hcy) and dithiothreitol (DTT) were used to modify the AgNP surface whereas the -COOH and -NH(2) functional groups have strong affinity to Cu(2+) relative to other ions in solution.