On-site and low-cost detection of cyanide by simple colorimetric and fluorogenic sensors: Smartphone and test strip applications.

Cyanide is potentially hazardous and quickly acting chemical used in many fields of industry. Therefore, detection of cyanide is of main health concern due to its serious impacts on living organisms. In this context, we have developed rapid, low-cost and on-site sensory two molecules for the colorimetric and fluorogenic sensing of cyanide ion in aqueous samples and food samples. The prepared probes undergo distinct visual color change and exhibits selective fluorogenic turn-on or turn-off response towards cyanide. Competing anions have little or negligible effect on the detection of cyanide. The limit of detection for cyanide ion was calculated as low as 0.45 µM. Free receptors could be successfully regenerated by treating them with Ag+ ion. Moreover, a new visual colorimetric strip based on paper was fabricated with the pale yellow-to-pink color change signal. The fabricated test strips also demonstrated excellent selectivity towards cyanide ion without interfering possible fluoride and acetate ions. The smartphone-based technique which could directly read out the color value using a smartphone revealed an excellent potential for the cyanide detection without additional device.

A simple and cost effective method for preparing FL and LG solutions.

PURPOSE: The purpose of this study was to develop a clinically feasible method for obtaining dye concentrations of 2% fluorescein (FL) and 1% lissamine green (LG) by soaking commercially available dye impregnated strips in saline. METHODS: Calibration curves were established to related known concentrations of dye to prepared FL fluorescence and LG absorbance. To determine the optimum number of dye strips and soaking times (preliminary testing), 1, 2, 3 FL or LG strips were soaked in 200 µl commercially available saline for 0.5, 1, 2, 3, 4 and 5 min, using calibration curves to determine FL and LG concentrations. The best combination of number of dye strips and soaking time was soaking 3FL and 3LG strips for 5 min and these were finally tested in 2 ml centrifuge tubes, selected for ease of use in a clinical setting. RESULTS: Preliminary testing indicated that soaking 3 FL or 3 LG strips for 5 min in saline yielded an average (±standard deviation) of 2.0 ± 0.000% FL and 0.93 ± 0.010% LG. Final testing of FL in centrifuge tubes (strips soaked for 3-15 min) yielded an average of 1.99 ± 0.040% FL, with no significant difference among time periods or dye lots tested. However, LG showed more variable results with an average of 0.80 ± 0.160% LG (5-15 min), with significant differences among dye lots and times (2-way ANOVA, p < 0.05). CONCLUSIONS: This simple, reliable and relatively inexpensive method involves soaking 3 FL or LG strips in saline solution, yielding concentrations close to the 2%FL and 1%LG recommended for clinical trials, although LG showed more variability.

Point-of-care coagulation monitoring: first clinical experience using a paper-based lateral flow diagnostic device.

Vitamin K antagonists such as warfarin are the most widely used class of oral anticoagulants. Due to a narrow therapeutic window, patients on warfarin require regular monitoring. Self-testing using point-of-care (POC) diagnostic devices is available, but cost makes this monitoring method beyond reach for many. The main objective of this research was to assess the clinical utility of a low-cost, paper-based lateral flow POC diagnostic device developed for anticoagulation monitoring without the need for a separate electronic reader. Custom-fabricated lateral flow assay (LFA) test strips comprised of a glass fiber sample pad, a nitrocellulose analytical membrane, a cellulose wicking pad, and a plastic backing card were assembled in a plastic cassette. Healthy volunteers and patients on warfarin therapy were recruited for this prospective study. For each participant, a whole blood sample was collected via fingerstick to determine: (1) international normalized ratio (INR) using the CoaguChek® XS coagulometer, (2) hematocrit by centrifugation, and (3) red blood cell (RBC) travel distance on the experimental LFA device after 240 s using digital image analysis. RBC travel distance measured on the LFA device using blood samples obtained from warfarin patients positively correlated with increasing INR value and the LFA device had the capability to statistically distinguish between healthy volunteer INR values and those for patients groups with INR ≥ 2.6. From these data, it is predicted that this low-cost, paper-based LFA device can have clinical utility for identifying anticoagulated patients taking vitamin K antagonists who are outside of the desired therapeutic efficacy window.

Robust dipstick urinalysis using a low-cost, micro-volume slipping manifold and mobile phone platform.

We introduce a novel manifold and companion software for dipstick urinalysis that eliminate many of the aspects that are traditionally plagued by user error: precise sample delivery, accurate readout timing, and controlled lighting conditions. The proposed all-acrylic slipping manifold is reusable, reliable, and low in cost. A simple timing mechanism ensures results are read out at the appropriate time. Results are obtained by capturing videos using a mobile phone and by analyzing them using custom-designed software. We show that the results obtained with the proposed device are as accurate and consistent as a properly executed dip-and-wipe method, the industry gold-standard, suggesting the potential for this strategy to enable confident urinalysis testing in home environments.

Paper test cards for presumptive testing of very low quality antimalarial medications.

Carrying out chemical analysis of antimalarials to detect low-quality medications before they reach a patient is a costly venture. Here, we show that a library of chemical color tests embedded on a paper card can presumptively identify formulations corresponding to very low quality antimalarial drugs. The presence or absence of chloroquine (CQ), doxycycline (DOX), quinine, sulfadoxine, pyrimethamine, and primaquine antimalarial medications, in addition to fillers used in low-quality pharmaceuticals, are indicated by patterns of colors that are generated on the test cards. Test card sensitivity for detection of these pure components ranges from 90% to 100% with no false positives in the absence of pharmaceutical. The color intensities from reactions characteristic of CQ or DOX allowed visual detection of formulations of these medications cut with 60% or 100% filler, although samples cut with 30% filler could not be reliably detected colorimetrically. However, the addition of unexpected fillers, even in 30% quantities, or substitute pharmaceuticals, could sometimes be detected by other color reactions on the test cards. Tests are simple and inexpensive enough to be carried out in clinics, pharmacies, and ports of entry and could provide a screening method to presumptively indicate very low quality medicines throughout the supply chain.

Multiplex lateral-flow test strips fabricated by two-dimensional shaping.

We have fabricated paper- and nitrocellulose-based lateral-flow devices that are shaped in two dimensions by a computer-controlled knife. The resulting star, candelabra, and other structures are spotted with multiple bioassay reagents to produce multiplex lateral-flow assays. We have also fabricated laminar composites in which porous nitrocellulose media are sandwiched between vinyl and polyester plastic films. This minimizes evaporation, protects assay surfaces from contamination and dehydration, and eliminates the need for the conventional hard plastic cassette holders that are typically used to package commercial lateral-flow diagnostic strips. The reported fabrication method is novel, low-cost, and well-suited to (i) fabrication and adoption in resource-poor areas, (ii) prototype development, (iii) high-volume manufacturing, and (iii) improving rates of operator error.

Chemomorphic analysis of malathion in skin layers of the rat: implications for the use of dermatopharmacokinetic tape stripping in exposure assessment to pesticides.

The dermatopharmacokinetic (DPK) method of dermal tape stripping may prove to be a valuable addition to risk assessment protocols for toxic substances as it has been for the assessment of bioequivalence and bioavailability of topical dermatologic drugs. The measurement of drug penetration into stratum corneum (SC) with respect to time is thought to be comparable with drug distribution in underlying tissues. To examine this possibility, the dermal penetration and absorption characteristics of [(14)C]malathion in the Sprague-Dawley rat was examined by three analytical techniques. [(14)C]Malathion was applied in different vehicles for 30-min and 1-h periods of exposure. Penetration into the SC was assessed by tape stripping followed by instant electronic autoradiography (IEA). Also, the (14)C activity retained in three successive 16 microm sections of the skin application site was determined by IEA and malathion was identified by Fourier transform infrared microscopy (FTIR microscopy). Absorbed [(14)C]malathion was measured in selected tissues, organs, and the residual carcass by liquid scintillation counting (LSC). Penetration into the SC followed a linear trend. The capacity of the SC reservoir for malathion amounted to approximately 1% of the dermal dose, while approximately 6% of the dose was absorbed. Results from this study support the view that LSC remains the method of choice to efficiently and reliably quantify absorption of a radiolabeled test substance. IEA offers the ability of the user to visualize the extent and profile of dermal absorption. When IEA is combined with FTIR microscopy, an effectual tool for studying the penetration of chemicals into layers of the skin emerges. The combined use of the three analytical techniques can be used to test the validity of the DPK method in hazard evaluation and exposure assessment of the organophosphorus insecticides.