Simple Paper Strip Research Articles

Zn, Cd and Cu Coordination Polymers for Metronidazole Sensing and for Ullmann and Chan-Lam Coupling Reactions.

Five compounds, [Zn2(bpe)(BPTA)2(H2O)2] ⋅ 2H2O (1); [Zn(bpe)(BPTA)] (2); [Cd(bpe)(BPTA)H2O] (3); [Cd(BPTA) (bpmh)] ⋅ 2H2O (4); and Cu2(BPTA)2(bpmh)3(H2O)2] ⋅ 2H2O (5) were prepared employing 2,5-bis(prop-2-yn-1-yloxy)terephthalic acid (2, 5 BPTA) as the primary ligand and 1,2-di(pyridin-4-yl)ethane (4, 4' bpe) (1-3) and 1,2-bis(pyridin-3-ylmethylene)hydrazine (bpmh) (4-5) as the secondary ligands. Single crystal studies indicated that the compounds 1, 3 and 5 have two-dimensional layer structures and compounds 2 and 4 three-dimensional structures. The luminescence behaviour of the compounds 2 and 3 were explored for the sensing of metronidazole in aqueous medium. The studies indicated that the compounds can detect metronidazole in ppm level both in solution as well as simple paper strips. The Cu compound 5 was found to lose the coordinated water molecule at 100 °C without any structural change. The coordinatively unsaturated Cu-centre were examined towards the Lewis acidic character by carrying out the Ullmann type C-C homocoupling reaction of the aromatic halide compounds. The compounds, 4 and 5, also have the Lewis basic functionality arising out the =N-N=, aza groups. The bifunctional nature of the coordination polymers (CP) was explored towards the Chan-Lam coupling reaction between phenyl boronic acid and aniline derivatives in the ethanol medium. In both the catalytic reactions, good yields and recyclability were observed. The present studies illustrated the rich diversity that the transition metal containing compounds exhibit in extended framework structures.

Smartphone-Interfaced Serum Calcium-Level Quantification on a Simple Paper Strip Assay for Diagnostics at Extreme Point of Care

Due to its pivotal role in many physiological processes and calcium-depleting diseases like osteoporosis, accurate quantification of the concentration of calcium in blood serum is imperative in monitoring multifarious facets of human health and disease. Established laboratory-based protocols for serum calcium level detection are expensive, resource-intensive and functionally dependent on skilled technicians. Circumventing these constraints, here we innovate a novel adaptation of the Bradford’s assay as a decisive pre-processing step of a highly specific diagnostic test for serum calcium level detection. This ensures the binding of protein molecules to Coomassie dye under acidic conditions with a resulting alteration in its colour so as to quench out the possibilities of unwarranted side reactions with excess proteins abundantly present in patient samples. This specific adaptation renders the test to be implemented on a simple paper strip without deploying controlled laboratory-based procedure, obviating any adverse interference in the subsequent reaction of calcium in the serum with Arsenazo III, a metallochromic dye used for the final colorimetric detection step. The method is affordable, user-friendly and can be deployed by minimally trained personnel at the point of use in extreme harsh environments. By mapping the resulting colorimetric information quantitatively with the serum concentration level from a panel of training dataset pre-standardized via established laboratory-based gold standard examination, a simple smartphone-based readout system may be developed, bearing the potential of replacing the currently existing expensive, time-consuming and environmentally-restrictive diagnostic solutions.

Detection of tartrazine with fluorescence sensor from crayfish shell carbon quantum dots

As a typical water-soluble synthetic azo pigment, tartrazine is widely used in food products, and its abuse was harmful to our health. Hence, it is very important to establish a facile and economical method to detect the tartrazine content in food. In the current study, the crayfish shell carbon quantum dots (CS-CQDs) were prepared through a facile hydrothermal approach from crayfish shells. The CS-CQDs exhibited strong fluorescent emissions at 462 nm under the excitation wavelength of 380 nm. The CS-CQDs were demonstrated to react with the synthetic pigments tartrazine selectively and effectively with a limit of detection (LOD) of 0.48 μM in the linear range of 0-70 μM. The Stern-Volmer equation and thermodynamic analysis revealed that the fluorescence quenching was a spontaneous static quenching and mainly driven by van der Waals interactions and hydrogen bonds. Furthermore, the CS-CQDs sensor was applied in energy beverage and durian candy samples with acceptable recovery of 92.7% to 104.5% and low RSD. Finally, we successfully designed a fluorescent test strip using CS-CQDs and filter paper. The current CS-CQDs had the potential ability to construct a simple paper strip for the detection of tartrazine in the future, which was useful for the food industry.

One-step synthesis of a pH switched pyrene-based fluorescent probe for ratiometric detection of HS- in real water samples.

Only a few probes are suited for highly acidic environments and sensitive to pH values below 4. Thus, finding a solution for detecting strong acidic (pH value below 2) conditions is still challenging. Herein, we constructed and created a pH-switched fluorescent probe based on pyrene and a heteroatom containing pyridine unit. When exposed to acidic environments (pH 2.0), the probe's fluorescence redshifted with distinct colour and fluorescence changes owing to protonation on the nitrogen atom containing pyridine moiety, which could be deprotonated by HS- selectively compared to other competing analytes. Pyr can detect HS- with a rapid response within 5 s and showed very good quantum yield under acidic environments. The sensing mechanism was confirmed by Density Functional Theory (DFT) studies using the B3LYP and 6-31G+ (d) basis sets. Furthermore, the probe was utilized to monitor HS- in actual water samples and identify H2S gas by a simple paper strip test.

A handy and accessible tool for identification of Sn(II) in toothpaste

An easily accessible colorimetric probe, a carbazole–naphthaldehyde conjugate (CNP), was successfully prepared for the selective and sensitive recognition of Sn(II) in different commercially-available toothpaste and mouth wash samples. The binding mechanism of CNP for Sn2+ was confirmed by UV–Vis, 1H, and 13C NMR titrations. The proposed sensing mechanism was supported by quantum chemical calculations. Selective detection of Sn(II) in the nanomolar range (85 nM), among other interfering metal ions, makes it exclusive. Moreover, Sn2+ can be detected with a simple paper strip from toothpaste, which makes this method handy and easily accessible. The potential application of this system for monitoring Sn2+ can be used as an expedient tool for environmental and industrial purposes.

Carbazole-based chemosensor for highly sensitive and selective bioimaging identification of hydrazine in multiple model systems via ratiometric and colorimetric

Hydrazine (N2H4) is a widely used propellent in spacecraft propulsion, a chemical catalyst, a common precursor to several pharmaceuticals, and a big threat to human and animal health. Overexposure to it can cause a series of diseases, which underlies the importance of developing an effective probe for monitoring its levels. Herein, a carbazole-based novel ratiometric and colorimetric chemosensor, PCC-EC, was successfully developed and well-characterized. PCC-EC has demonstrated ratiometric blue-shifted fluorescent response to hydrazine, which induced naked-eye color and fluorescent color change, respectively. Besides, PCC-EC realized a highly sensitive and selective response to hydrazine in multiple model systems ranging from aqueous solutions, water samples, zebrafish, and mung bean sprouts, even imaging in choroidal melanoma cells of the human eye cells with a rapid response, good cell/tissue permeability, low cytotoxicity, and a wide pH-working range. We also created a simple paper strip system to facilitate the quick detection of hydrazine. The sensing mechanism of PCC-EC has been explored by DFT calculations and mass spectrometry. Overall, PCC-EC employs a rarely-reported strategy in sensing hydrazine and its successful application in multiple biological and environmental systems highlights its good application potential in the future.

Disposable Paper-on-CMOS Platform for Real-Time Simultaneous Detection of Metabolites.

Early stage diagnosis of sepsis without overburdening health services is essential to improving patient outcomes. A fast and simple-to-use platform that combines an integrated circuit with paper microfluidics for simultaneous detection of multiple-metabolites appropriate for diagnostics was presented. Paper based sensors are a primary candidate for widespread deployment of diagnostic or test devices. However, the majority of devices today use a simple paper strip to detect a single marker using the reflectance of light. However, for many diseases such as sepsis, one biomarker is not sufficient to make a unique diagnosis. In this work multiple measurements are made on patterned paper simultaneously. Using laser ablation to fabricate microfluidic channels on paper provides a flexible and direct approach for mass manufacture of disposable paper strips. A reusable photodiode array on a complementary metal oxide semiconductor chip is used as the transducer. The system measures changes in optical absorbance in the paper to achieve a cost-effective and easily implemented system that is capable of multiple simultaneous assays. Potential sepsis metabolite biomarkers glucose and lactate have been studied and quantified with the platform, achieving sensitivity within the physiological range in human serum. We have detailed a disposable paper-based CMOS photodiode sensor platform for real-time simultaneous detection of metabolites for diseases such as sepsis. A combination of a low-cost paper strip with microfluidic channels and a sensitive CMOS photodiode sensor array makes our platform a robust portable and inexpensive biosensing device for multiple diagnostic tests in many different applications.

A Haptic Model of Entanglement, Gauge Symmetries and Minimal Interaction Based on Knot Theory

The Heegaard splitting of S U ( 2 ) is a particularly useful representation for quantum phases of spin j-representation arising in the mapping S 1 → S 3, which can be related to ( 2 j , 2 ) torus knots in Hilbert space. We show that transitions to homotopically equivalent knots can be associated with gauge invariance, and that the same mechanism is at the heart of quantum entanglement. In other words, (minimal) interaction causes entanglement. Particle creation is related to cuts in the knot structure. We show that inner twists can be associated with operations with the quaternions ( I , J , K ), which are crucial to understand the Hopf mapping S 3 → S 2. We discuss the relationship between observables on the Bloch sphere S 2, and knots with inner twists in Hilbert space. As applications, we discuss selection rules in atomic physics, and the status of virtual particles arising in Feynman diagrams. Using a simple paper strip model revealing the knot structure of quantum phases in Hilbert space including inner twists, a h a p t i c model of entanglement and gauge symmetries is proposed, which may also be valid for physics education.

Chromogenic hydrazide Schiff base reagent: Spectrophotometric determination of CN- ion.

A Schiff base reagent, Picolinohydrazide-naphthol (HL), is used for trace level detection of toxic CN- selectively in presence of eighteen other anions (SCN-, OCN-, S2O32-, HPO42-, H2PO4-, I-, ClO4-, HSO4-, SO42-, AsO43-, NO2-, AsO2-, Cl-, F-, HF2-, NO3-, Br-, N3-) by visual color change, colorless to yellow, in DMSO/H2O (9:1, v/v) at pH, 7.2 (HEPES buffer) medium. The sensitivity of the probe shows that the limit of detection (LOD) is 7.08 μM. The probable mechanism for the sensing behavior involves the deprotonation of naphthol-OH by CN- that has been authenticated by 1H NMR titration and Mass spectra. The composition (1:1 mol ratio) is supported by Job's plot and binding constant (Ka, 1.5 × 104 M-1) is reported by Benesi-Hildebrand plot. Furthermore, a simple paper strip device is fabricated for the determination of CN- ion in water. DFT computation is carried out to explain the electronic spectral feature of the sensor.

A Haptic Model for the Quantum Phase of Fermions and Bosons in Hilbert Space Based on Knot Theory

A generalization of the famous Dirac belt trick opens up the way to a haptic model for quantum phases of fermions and bosons in Hilbert space based on knot theory. We introduce a simple paper strip model as an aid for visualization of the quantum phases before and after Hopf-mapping, which can be extended to arbitrary spin states with almost no mathematical formalism. Knot theory arises naturally, leading to the Jones polynomials derived from Artin’s braid group for fermionic knots and for bosonic links. The paper strip model explicitly illuminates the relation between these knots and links within the S U ( 2 ) -representation of spin-jstates in C 2 j + 1 before Hopf-mapping and the number p = 2 j of nodes in the stellar representation in C P 1 after Hopf mapping.

Rapid and selective visual detection of DCNP (nerve gas mimic) in sea water and soil with a simple paper strip

Nerve agents are extremely poisonous organophosphorus compounds. Due to their deadly activity towards the human and animal health, they are employed as chemical welfare agents; closely related compounds are used tremendously in the pesticide industry. Sea-dumping is considered as one of the conventional methods of disposal of these chemical weapons, but this may introduce a fatal consequence such as disruption of marine ecosystem and inclusion of these reactive and toxic substances into food chain. To detect the nerve gas we developed a very simple and low cost paper strip sensing method which can immediately recognize DCNP in visual range. A chemosensor, carbazole-salicylaldehyde based imine (CSI), has been introduced for selective detection and quantification of nerve gas (Tabun) mimic DCNP from sea water and soil in nanomolar range at neutral pH (pH 7.2, 10 mM Tris-HCl buffer).

Highly Selective Sub-ppm Naked-Eye Detection of Hydrazine with Conjugated-1,3-Diketo Probes: Imaging Hydrazine in Drosophila Larvae.

A pair of pyrene- and anthracene-based turn-on fluorescent probes (1 and 2, respectively) reported here can be easily synthesized in a single-step process and also exhibit outstanding sensing behavior toward hydrazine over various competing nucleophilic species and environmentally relevant ions. The probes display dramatic enhancements in the emission intensity with as high as 83- and 173-fold increases in the presence of hydrazine. Nitrogenous bases, thiols, and lanthanides do not interfere in the fluorometric detection. These probes enable the detection of hydrazine with the naked eye well below sub-ppm concentrations (ca. 30 ppb) with analytical detection limits of 5.4 ppb for 1 and 7.7 ppb for 2, which are far exceeded by the accepted lower limit for hydrazine (10 ppb) set by the US EPA. Simple paper strips based on these probes could be used for the detection of hydrazine even in the gas phase. Both of the probes could selectively detect hydrazine even in pond water samples efficiently. The probes were successfully applied to visualize, for the first time, accumulation of hydrazine in live fruit-fly larvae using epifluorescence microscopy. The novel and interesting detection mechanism, proposed on the basis of spectroscopic evidence and single crystal XRD results, indicates that the detection pathway proceeds via the initial step of a five-membered ring formation upon attack of the hydrazine, followed by a dehydration step for gaining aromaticity.

Paper Strip‐based Fluorometric Determination of Cyanide with an Internal Reference

The rapid, selective, and sensitive determination of cyanide anion (CN −) using a simple paper strip is highly attractive because cyanide is acutely lethal to living organisms via all routes of administration, including alcohol consumption and inhaling cigarette smoke. Here, a synthetic probe (1) was designed for the selective determination of cyanide. The probe displays rapid and large blue spectral change (Δλabs =148 nm, Δλem = 165 nm) with respect to target recognition. Probe 1 exhibits a strong push–pull electronic effect and comprises a dimethylaminoaryl group as a donor and malononitrile as an acceptor; the π‐conjugation system can be destroyed by the Michael‐type addition of cyanide at the electrophilic β‐positions of the nitrile groups, resulting in the marked emergence of a peak at λem = 515 nm. The developed probe was successfully applied to a paper test strip because of its noticeable optical changes upon reaction with cyanide. The fabricated dumbbell‐shaped paper strip with an internal reference allowed the cyanide detection, which is indispensable for quantitative analysis in point‐of‐care testing. The paper strip test showed selective response to cyanide, with a linear correlation in the range of 0–25 mM in a simple and cost‐effective manner.

The turn of the screw: An exercise in protein secondary structure

An exercise using simple paper strips to illustrate protein helical and sheet secondary structures is presented. Drawing on the rich historical context of the use of physical models in protein biochemistry by early practitioners, in particular Linus Pauling, the purpose of this activity is to cultivate in students a hands-on, intuitive sense of protein secondary structure and to complement the common computer-based structural portrayals often used in teaching biochemistry. As students fold these paper strips into model secondary structures, they will better grasp how intramolecular hydrogen bonds form in the folding of a polypeptide into secondary structure, and how these hydrogen bonds direct the overall shape of helical and sheet structures, including the handedness of the α-helix and the difference between right- and the left-handed twist.

Effects of a Tropical Cyclone on the Drinking‐Water Quality of a Remote Pacific Island

The effect of a cyclone (Ami, January 2003) on drinking-water quality on the island of Vanua Levu, Fiji was investigated. Following the cyclone nearly three-quarters of the samples analysed did not conform to World Health Organisation (WHO) guideline values for safe drinking-water in terms of chlorine residual, total and faecal coliforms, and turbidity. Turbidity and total coliform levels significantly increased (up 56 and 62 per cent, respectively) from pre-cyclone levels, which was likely due to the large amounts of silt and debris entering water-supply sources during the cyclone. The utility found it difficult to maintain a reliable supply of treated water in the aftermath of the disaster. Communities were unaware they were drinking water that had not been adequately treated. Circumstances permitted this cyclone to be used as a case study to assess whether a simple paper-strip water-quality test (the hydrogen sulphide, H(2)S) kit could be distributed and used for community-based monitoring following such a disaster event to better protect public health. The H(2)S test results correlated well with faecal and total coliform results as found in previous studies. A small percentage of samples (about 10 per cent) tested positive for faecal and total coliforms but did not test positive in the H(2)S test. It was concluded that the H(2)S test would be well suited to wider use, especially in the absence of water-quality monitoring capabilities for outer island groups as it is inexpensive and easy to use, thus enabling communities and community health workers with minimal training to test their own water supplies without outside assistance. The importance of public education before and after natural disasters is also discussed.

The use of a simple test for hypoglucosuria (uriglox) in the diagnosis of bacteriuria in pregnancy.

SummaryA simple paper strip test for hypoglucosuria (Uriglox) has been shown to be a reliable indicator of the presence of significant bacteriuria.

Paper strip urine test for checking the intake of isoniazid

A simple paper strip test for the detection of isoniazid metabolites in the urine is described. It is based on the colour reaction of isonicotinic acid and isonicotinoyl glycine with gaseous cyanogen chloride and benzidine. There was only one negative reaction among 74 patients treated with isoniazid and 2 erroneously positive reactions among 34 patients treated without isoniazid; both these patients were taking a vitamin preparation containing nicotinamide. On décrit un test simple pour déceler les produits du métabolisme de l'isoniazide dans l'urine, à l'aide d'une bande de papier. Le test est basé sur la réaction colorée que produit l'acide isonicotinique et l'isonicotinoyl glycine avec le chlorure de cyanogène gazeux et la benzidine. Il n'y eut qu'une réaction négative parmi 74 malades traités par l'isoniazide, et deux réactions faussement positives, parmi 34 malades non traités par l'isoniazide. Ces deux malades absorbaient une préparation de vitamines contenant de la nicotinamide. Se describe un test simple, en tira de papel, para detectar metabolitos de la isoniazida. Se basa en una reacción colot del ácido isonicotínico y del isonicotinoyl con cloruro de cianógeno gaseoso y benzidina. En 74 enfermos tratados con isoniazida hubo 1 sola reacción negativa, y en 34 enfermos no tratados con isoniazida hubo 2 falsos positivos, en pacientes que estaban tomando una vitamina que contenía nicotinamida.

A paper strip test for detection of cycloserine and pyrazinamide in urine

A simple paper strip test for the detection of cycloserine and pyrazinamide in the urine is described. It gives positive results with minimal concentrations of 20 μg./ml. cycloserine and 30 μg./ml. pyrazinamide respectively. Clinical trials revealed that after a single dose of 0·25 g. cycloserine the patient's urine gives a positive reaction within 1 to 6 hours after the drug was administered. Similarly, a dose of 0·5 g. pyrazinamide gives a positive reaction within 1 to 8 hours.