Nanotechnology-based Colorimetric Approaches for Pathogenic Virus Sensing: A Review.

Fast and inexpensive virus identification protocols are of paramount value to hinder the increase of pandemic diseases, minimize economic and social damages, and expedite proper clinical rehabilitation. Until now, various biosensors have been developed for the identification of pathogenic particles. But, they offer many limitations. Nanotechnology overcomes these difficulties and allows a direct identification of pathogenic species in real-time. Among them, nanomaterial based-colorimetric sensing approach for identifying pathogenic viruses by the naked eye has attracted much awareness because of their simplicity, speed, and low cost. In this review, the latest tendencies and advancements used in detecting pathogenic viruses using colorimetric concepts, are overviewed. We focus on and reconsider the use of distinctive nanomaterials such as metal nanoparticles, carbon nanotubes, graphene oxide, and conducting polymer for the formation of colorimetric pathogenic virus sensors.

A Review on Colorimetric Sensing of Tumor Markers Based on Enzyme-Mimicking Nanomaterials.

Nanomedicine is an arising field that exploits nanotechnology concepts for pioneered therapy and diagnostics. Colorimetric sensors for tumor markers have displayed interesting benefits compared to conventional systems in clinical laboratory diagnosis. Colorimetric immunoassay-based approaches show up-and-coming results since the goal cancer marker is determined with high sensitivity but without the utilization of advanced/- expensive techniques through an effortless optical color change. Also, colorimetric biosensor has the potential to detect proteins in biological fluids swiftly with high sensitivity, and they are anticipated to play a progressively serious role in tumor diagnosis. We reviewed (covering the period 2015-2020) various studies based on colorimetric sensing strategy using nanostructured materials (highly efficient enzyme mimics, artificial enzymes or nanozymes) to detect different tumor antigens in biological fluids. Specifically, we highlighted the recent progress and efforts in the construction of colorimetric immunosensors. Colorimetric immunosensors can be roughly divided into two main categories: transition metal nanozyme-based sensing and noble metal nanozyme-based sensing.

Electrochemical Immunosensors Based on Nanostructured Materials for Sensing of Prostate-Specific Antigen: A Review.

The prostate-specific antigen (PSA) has been considered a crucial serological marker for distinguishing prostate based cancer. This survey shows recent progress in the construction of nanomaterial-based electrochemical immunosensors for a PSA. This review (from 2015 to 2020) reports the latest progress in PSA sensing based on the employ of different types of nanostructured materials. The most popular used nanostructured materials are metal, metal oxide, carbon-based nanomaterials, and their hybrid architectures utilized for distinct amplification protocols. In this review, the electrochemical immunosensors for prostate-specific antigen sensing are classified into three categories such as sandwich type@labeled, label free@nonlabeled and aptamer-based electrochemical immunosensor.

Electrochemical and Electrochemiluminescence Dendrimer-based Nanostructured Immunosensors for Tumor Marker Detection: A Review.

The usage of dendrimers or cascade molecules in the biomedical area has recently attracted much attention worldwide. Furthermore, dendrimers are interesting in clinical and pre-clinical applications due to their unique characteristics. Cancer is one of the most widespread challenges and important diseases, which has the highest mortality rate. In this review, the recent advances and developments (from 2009 up to 2019) in the field of electrochemical and electroluminescence immunosensors for detection of the cancer markers are presented. Moreover, this review covers the basic fabrication principles and types of electrochemical and electrochemiluminescence dendrimer-based immunosensors. In this review, we have categorized the current dendrimer based-electrochemical/ electroluminescence immunosensors into five groups: dendrimer/ magnetic particles, dendrimer/ferrocene, dendrimer/metal nanoparticles, thiol-containing dendrimer, and dendrimer/quantum dots based-immunosensors.

Electrochemical immunosensors for the detection of cytokine tumor necrosis factor alpha: A review.

In this review, we focus on recent developments in nonlabeled@label-free and labeled@sandwich assay concepts of tumor necrosis factor-alpha (TNF-α) using numerous electrochemical approaches. The fundamental role of such nanostructured materials for the improvement of the analytical response and thus the analytical figures of merit of various TNF-α sensing operations were revealed. Also, this examination focused on recent developments in immuno-electrochemical cytokine TNF-α sensors based on nanostructured materials from 2006 to 2019.

Low-level Electrochemical Analysis of Ketoconazole by Sepiolite Nanoparticles Modified Sensor in Shampoo Sample.

In this study, the nano-sepiolite modified carbon paste electrode (CCPE) was prepared for the determination of ketoconazole (KC). The effects of pH, the proportion of the electrode modifier, deposition potential, and deposition time were investigated. Ketoconazole shows one irreversible oxidation peak at about the potential value of 0.6-0.7 V at different pH values. CV studies show that the modified electrode performed a catalytic effect on the peak signal of KC compared to the bare electrode. This catalytic behavior of CCPE was used for the development of a sensitive detection method. The impact of pH and scan rates on the anodic peak potentials and currents were examined, and the scan rate results show that the oxidation behavior of KC was controlled by the adsorption process at the CCPE surface. Therefore, adsorptive stripping differential pulse voltammetry (AdsDPV) and adsorptive stripping square wave voltammetry (AdsSWV) methods were developed for KC analysis. The two different linear ranges were obtained as (0.1?1.0) nM and (3.0?10.0) nM for AdsDPV, and (0.1-10.0) nM and (3.0-10.0) nM for AdsSWV, respectively. The detection (LOD) and quantification (LOQ) limits were found to be 0.017 nM and 0.056 nM for AdsDPV and 0.025 nM and 0.083 nM for AdsSWV, respectively. Besides, the proposed new sensor has obtained very high recovery values in the analysis of KC in the pharmaceutical shampoo.

Nanostructures for nonlabeled and labeled electrochemical immunosensors: Simultaneous electrochemical detection of cancer markers: A review.

The simultaneous electrochemical determination of multiple tumor antigens has attracted a great deal of attention, which can effectively enhance the capability and accuracy of the analysis. Nanostructured materials mostly played a key major role in the electrochemical immunosensors fabrication and operation improvement. This review focused mainly on the protocols for using nanostructures to fabricate electrochemical (nonlabeled@label-free and labeled@sandwich-type) immunosensors. Furthermore, this review has also described the diverse classes of electroactive nanospecies which are a complementary part of any immunosensor that assists to reach the selectivity for the target antigen. Finally, the important analytical characteristics of the published immunosensors were discussed (electrochemical detection technique, linear range, and detection limit). Studies published between the years 2009-2018 have been included in this review.

Magnetic nanostructures for preconcentration, speciation and determination of chromium ions: A review.

Magnetic nanoparticles based solid-phase extraction is a new analytical technique based on the use of magnetic sorbents for the preconcentration and quantification of different inorganic and organic species. The present review concentrates on recent developments that have been built in magnetic nanostructures-based solid phase extraction, speciation and quantification of chromium ions. Besides, a description of the preparation, characterization as well as applications of various types of magnetic nanostructures, either with an inorganic or organic coating of the magnetic core, is presented. In addition, the most important analytical characteristics such as preconcentration factor, linear range, and limits of detection were carefully reported and compared. On the other hand, the removal of the chromium ions by magnetic solid phase extraction was not discussed in the review.

Dextran modified magnetic nanoparticles based solid phase extraction coupled with linear sweep voltammetry for the speciation of Cr(VI) and Cr(III) in tea, coffee, and mineral water samples.

A simple and fast solid phase microextraction method using magnetic dextran (Sephadex G-150) as a sorbent was developed for the extraction, separation and speciation analysis of chromium ions. The retained Cr(VI) ions on the magnetic dextran sorbents were eluted and detected by linear sweep voltammetry at the gold nanoparticles modified screen- printed carbon electrode. The linear range, detection limit, quantification limit, and preconcentration factor of the established method for Cr(VI) and Cr(III) were calculated to be 0.5-10 µM, 0.01 µM, 0.1 µM, and 40, respectively. Chromium(III) concentration was determined after conversion of Cr(III) to Cr(VI) by H2O2 in alkaline media (NH4OH). The method was successfully applied to the speciation and determination of Cr(VI) and Cr(III) in artificial water and food samples using the standard addition method. The applicability of the method was confirmed by analysis of real food samples yielding good recovery values (92% and 102%).

A Nano-Sepiolite Clay Electrochemical Sensor for the Rapid Electro-Catalytic Detection of Hydroquinone in Cosmetic Products.

In this paper, a simple and sensitive electrochemical nano-sensor was developed for the analysis of hydroquinone based on sepiolite clay modified carbon paste sensor by using differential pulse adsorptive stripping voltammetry and square wave adsorptive stripping voltammetry. Surface morphology of sensors was characterized by using scanning electron microscopic technique, electrochemical impedance spectroscopy, and cyclic voltammetry. Electrochemical redox properties of hydroquinone were investigated by cyclic voltammetry. The oxidation peak current of hydroquinone in differential pulse and square wave adsorptive stripping voltammetry changes linearly in the concentration range of 0.01-700 µmolL-1 and 0.01-700 µmolL-1, respectively. Excellent limit of detection (LOD) and limit of quantification (LOQ) values were found as 0.01096 µmolL-1 and 0.03654 µmolL-1 for differential pulse, and 0.01031 µmolL-1 and 0.03438 µmolL-1 for square wave adsorptive stripping voltammetry, respectively. Additionally, the newly proposed sensor was applied to the analysis of hydroquinone in cosmetic cream with satisfying results.

Conducting polymer modified screen-printed carbon electrode coupled with magnetic solid phase microextraction for determination of caffeine.

In the current study, we introduce magnetic solid phase microextraction coupled with electrochemical detection of caffeine. A commercially available disposable screen-printed carbon electrodes modified with poly Alizarin Red S are employed as electrochemical sensors in the detection stage. However, the suitability of magnetic solid phase microextraction for electroanalytical methods such as square wave voltammetry has not been declared. With our optimised conditions in hand, the system response was linearly proportional to the concentration of caffeine in the range of 0.5-20µM with a correlation coefficient of about 0.9987. The detection limit of the sensing system was found to be 0.05µM (a signal-to-noise ratio of 3). At the end of the study, the suitability of this new procedure for the analysis of energy drink, soft drink, and chocolate milk samples was demonstrated.

Square-wave stripping voltammetric determination of caffeic acid on electrochemically reduced graphene oxide-Nafion composite film.

An electrochemical sensor composed of Nafion-graphene nanocomposite film for the voltammetric determination of caffeic acid (CA) was studied. A Nafion graphene oxide-modified glassy carbon electrode was fabricated by a simple drop-casting method and then graphene oxide was electrochemically reduced over the glassy carbon electrode. The electrochemical analysis method was based on the adsorption of caffeic acid on Nafion/ER-GO/GCE and then the oxidation of CA during the stripping step. The resulting electrode showed an excellent electrocatalytical response to the oxidation of caffeic acid (CA). The electrochemistry of caffeic acid on Nafion/ER-GO modified glassy carbon electrodes (GCEs) were studied by cyclic voltammetry and square-wave adsorption stripping voltammetry (SW-AdSV). At optimized test conditions, the calibration curve for CA showed two linear segments: the first linear segment increased from 0.1 to 1.5 and second linear segment increased up to 10 µM. The detection limit was determined as 9.1×10(-8) mol L(-1) using SW-AdSV. Finally, the proposed method was successfully used to determine CA in white wine samples.

Indirect fibre-optic colorimetric determination of ascorbic acid using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol and cloud point extraction.

A new method has been developed for the indirect determination of ascorbic acid (AA) in commercial syrup preparations based on cloud point extraction (CPE) separation and preconcentration, and determination by molecular absorption spectrometry. The colorimetric method was based on the reduction of Fe(III) to Fe(II) and complexation of Fe(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP), followed by its extraction into Triton X-114. Selectivity of the method was increased with the use of EDTA as a masking agent. The absorbance was measured at 742 nm. Various influencing factors on the separation and preconcentration of AA have been investigated systematically, and the optimized operation conditions were established. The proposed method allows the determination of AA in the range 5-200 µg L(-1) with a relative standard deviation of 3.0%. The detection limit was found to be 0.9 µg L(-1) for AA. This method has been applied to the determination of ascorbic acid in commercial pharmaceutical preparations.

Selective determination of catechin among phenolic antioxidants with the use of a novel optical fiber reflectance sensor based on indophenol dye formation on nano-sized TiO2.

The optical sensor for "tea catechins" was built by immobilizing 2,2'-(1,4-phenylenedivinylene)bis-8-hydroxyquinoline (PBHQ) on TiO2 nanoparticles (NPs). The sensor worked by "indophenol blue" dye formation on PBHQ-immobilized TiO2 NPs as a result of p-aminophenol (PAP) autoxidation with dissolved O2 at pH 10. Among quercetin, rutin, naringenin, naringin, gallic acid, caffeic acid, ferulic acid, p-coumaric acid, catechin, epicatechin, epicatechin gallate, epigallocatechin, epigallocatechin gallate, and trolox, only catechin group antioxidants delayed the color formation on NPs, as measured by the reflectance signal at 710 nm. For quantitative analysis, reflectance signal versus time was recorded, and the difference between the areas under curve (ΔAUC) in the presence and absence of catechin was correlated (r = 0.98) to catechin concentration. The selectivity of the sensor for catechins was shown in tea infusions compared to other plant extracts and was ascribed to the nonplanar structure of catechin interfering with the formation of perfectly conjugated indophenol blue on TiO2 surface.

Colourimetric solid-phase extraction coupled with fibre optic reflectance spectroscopy for determination of ascorbic acid in pharmaceutical formulations.

A redox colourimetric solid-phase extraction (C-SPE) procedure for the determination of ascorbic acid (AA) in pharmaceutical formulations was proposed. Iron (III)-2,2'-dipyridyl (Fe(III)-Bpy) reagent solution was used as a colouring reagent for AA and the immobilization of the redox product onto Amberlite XAD-16 resin was achieved. The analyte in the sample reacted with a solid sorbent loaded with the colourimetric reagent (Fe(III)-Bpy) and then quantified directly on the sorbent surface by using a fibre optic reflectance spectrometer (FORS). The amount of AA was reflectometrically determined in a few seconds with a total sample workup and readout time of ∼10 min using only 10-ml sample volumes. The limit of detection (LOD) and quantification (LOQ) values were 0.18 and 0.6 mg L(-1), respectively, and the linear dynamic range for AA extended up to 8.8 mg L(-1). The C-SPE for different extractions (n = 5) gave a relative standard deviation (RSD) of 2.9% at 5.28 mg L(-1) AA level.

A novel fiber optic spectrophotometric determination of nitrite using Safranin O and cloud point extraction.

A novel fiber optic spectrophotometric method for nitrite determination in different samples is suggested, based on the reaction of nitrite with Safranin O in acidic medium to form a diazo-safranin, which is subsequently coupled with pyrogallol in alkaline medium to form a highly stable, red azo dye, followed by cloud point extraction (CPE) using a mixed micelle of a nonionic surfactant, Triton X-114, with an anionic surfactant, sodium dodecyl sulphate (SDS). The reaction and extraction conditions (e.g., acidity for diazotization and alkalinity for pyrogallol coupling, and other reagent concentrations, time, and tolerance to other ions) were optimized. Linearity was obeyed in a concentration range up to 230 µg L(-1), and the detection limit of the method is 0.5 µg L(-1) of nitrite ion. The molar absorptivity for nitrite of the Safranin-diazonium salt (ɛ(610 nm) =4 × 10(3) L mol(-1)cm(-1)) existing in literature was greatly enhanced by pyrogallol coupling and CPE enrichment (ɛ(592 nm)=1.39 × 10(5) L mol(-1)cm(-1)). The method was applied to the determination of nitrite in tap water, lake water and milk samples with an optimal preconcentration factor of 20.

Rapid detection of nitroaromatic and nitramine explosives on chromatographic paper and their reflectometric sensing on PVC tablets.

Rapid and inexpensive sensing of explosive traces in soil and post-blast debris for environmental and criminological purposes with optical sensors has recently gained importance. The developed sensing method for nitro-aromatic and nitramine-based explosives is based on dropping an acetone solution of the analyte to an adsorbent surface, letting the solvent to dry, spraying an analytical reagent to produce a persistent spot, and indirectly measuring its reflectance by means of a miniature spectrometer. This method proved to be useful for on-site determination of nitro-aromatics (trinitrotoluene (TNT), 2,4,6-trinitrophenylmethylnitramine (tetryl) and dinitrotoluene (DNT)) and nitramines (1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)) pre-adsorbed on a poly vinyl chloride (PVC) surface, with the use of different spray reagents for each group of explosives producing different colors. The calibration equations of the tested compounds as reflectance vs. concentration showed excellent linearity (correlation coefficient: 0.998-0.999). The linear quantification interval in terms of absolute quantity of analyte was 0.1-0.5 µg. The developed method was successfully tested for the analysis of military explosives Comp B and Octol, and was validated against high performance liquid chromatography (HPLC). The reflectometric sensing method could also be used for qualitative identification of the nitrated explosives on a chromatographic paper. The reagent-impregnated paper could also serve as sensor, enabling semi-quantitative determinations of TNT and tetryl.

A sensitive method for determining total vanadium in water samples using colorimetric-solid-phase extraction-fiber optic reflectance spectroscopy.

A selective colorimetric-solid-phase extraction (C-SPE) method for the determination of total vanadium in water samples was developed. This method introduced a new variation of C-SPE. The colour reaction is based on the reaction of vanadium(V) ternary complex formed with 1-(2-Pyridylazo)-2-naphtol (PAN) in the presence hydrogen peroxide (H(2)O(2)). In this technique, the target analytes in samples are extracted onto solid matrix loaded with a colorimetric reagent and then quantified directly on the adsorbent surface by using a miniature fiber optic reflectance spectrometer. The measurements were carried out at a wavelength of 589.4 nm since it yielded the largest divergence different in reflectance spectra before and after reaction with the vanadium. The overall time required for the C-SPE procedure was approximately 20 min. The amount of concentrated V is then determined in a few seconds by using miniature reflectance spectrometer. At the optimal conditions, a calibration curve was constructed, revealing a linear range of 0.05-0.52 mg L(-1) and a detection limit as low as 0.01 mg L(-1) while the RSD lower than 2.8%. In order to verify the accuracy of the method, a certified reference water samples (TMDA) were analysed and the results obtained were in good agreement with the certified values. The proposed method was applied to the determination of vanadium in tap water, seawater samples with a recovery for the spiked samples in the range of 98-102%.

Selective cloud point extraction and graphite furnace atomic absorption spectrometric determination of molybdenum (VI) ion in seawater samples.

A cloud point extraction process using the nonionic surfactant Triton X-114 to extract molybdenum from aqueous solutions was investigated. The method is based on the complexation reaction of Mo(VI) with 1,2,5,8-tetrahydroxyanthracene-9,10-dione (quinalizarine: QA) and micelle-mediated extraction of the complex. The enriched analyte in the surfactant-rich phase was determined by graphite furnace atomic absorption spectrometry (GFAAS). The optimal extraction and reaction conditions (e.g. pH, reagent and surfactant concentrations, temperature, incubation and centrifugation times) were evaluated and optimized. Under the optimized experimental conditions, the limit of detection (LOD) for Mo(VI) was 7.0 ng L(-1) with an preconcentration factor of approximately 25 when 10 mL of sample solution was preconcentrated to 0.4 mL. The proposed method (with extraction) showed linear calibration within the range 0.03-0.6 microg L(-1). The relative standard deviation (RSD) was found to be 3.7% (C(Mo(VI))=0.05 microg L(-1), n=5) for pure standard solutions, whereas RSD for the recoveries from real samples ranged between 2 and 8% (mean RSD=3.9%). The method was applied to the determination of Mo(VI) in seawater and tap water samples with a recovery for the spiked samples in the range of 98-103%. The interference effect of some cations and anions was also studied. In the presence of foreign ions, no significant interference was observed. In order to verify the accuracy of the method, a certified reference water sample was analysed and the results obtained were in good agreement with the certified values.

Development of an optical fibre reflectance sensor for p-aminophenol detection based on immobilised bis-8-hydroxyquinoline.

2,2'-(1,4-Phenylenedivinylene)bis-8-hydroxyquinoline (PBHQ), a highly sensitive reagent used for the colorimetric determination of p-aminophenol (PAP), was successfully immobilised on XAD-7 and coupled with optical fibres to investigate a sensor-based approach for determining p-aminophenol. The solid-state sensor is based on the reaction of PAP with PBHQ in presence of an oxidant to produce an indophenol dye. The reflectance measurements were carried out at a wavelength of 647 nm since it yielded the largest divergence different in reflectance spectra before and after reaction with the analyte. The linear dynamic range of PAP was found within the concentration range of 0.1-2.18 mg l(-1) with its LOD of 0.02 mg l(-1). The sensor response from different probes (n=7) gave a R.S.D. of 4.4% at 1.09 mg l(-1) PAP concentration. The response time of the optical one-shot sensor was 5 min for a stable solution. As this PAP sensor is irreversible, a fresh sensor has to be used for each measurement. All the experimental parameters were optimized for the determination of PAP. Using the optical sensing probe, PAP in pharmaceutical wastewater and paracetamol was determined. The effect of potential interferences such as inorganic and organic compounds was also evaluated. Potential on-site determination of PAP with such sensors can indirectly aid detection of organo-phosphorus nerve agents and pesticides in the field by inhibition of acetylcholine esterase-catalyzed hydrolysis of p-aminophenyl acetate to p-aminophenol.