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A novel gold nanocluster surface molecularly imprinted polyisopropylacrylamide probe (AuNC@MIP) was synthesized for the specific detection of NO2−, using N-isopropylacrylamide (NIPAM) as the functional monomer, gold nanoclusters (AuNC) as the substrate, ethylene glycol dimethacrylate (EGDMA) as the cross-linking agent, and nitrosophenol (NPN) produced from sodium nitrite (NaNO2) and phenol (PN) as the template molecule, N,N-dimethylformamide (DMF) as the solvent, and azobisisobutyronitrile (AIBN) as the initiator. The nanoprobe was characterized using molecular spectroscopy, XPS, TEM, TGA, and zeta potential analysis. The probes revealed a prominent resonance Rayleigh scattering (RRS) peak at 370 nm. Upon addition of NO2−, the RRS intensity at 370 nm decreased due to the RRS energy transfer enhancing. The linear determination range is 0.125–1.50 nmol/L NO2−, with a limit of detection (LOD) of 0.085 nmol/L. The new RRS method was applied to determine NO2− in meat, dairy products, and water samples, with recovery of 96–107% also relative standard deviations (RSDs) of 1.1–8.0%. [ABSTRACT FROM AUTHOR]

Accurate monitoring of small molecules and precise characterization of the secretory ability of neurons are essential for effective diagnosis of neurological diseases. However, existing technologies for monitoring small molecules only provide approximate results. Plasmonic‐based biosensors are a potential solution in this biological application. Nevertheless, optical sensing nanoparticles require precise control of interparticle distance, particle shape and morphology, which can be challenging. This article discovers that the trapping of small molecules to aptamers induces a conformational change that alters the nanostructure of irregularly shaped Au nanoclusters (NCs) and aptamers due to the strong structure‐property relationships of Au NC‐aptamers. This change can be detected via resonance Rayleigh scattering (RRS) intensity in the dark‐field. This new technology overcomes the challenges of precise control of individual nanoparticles and the difficulty of small spectral peak shifts. The Au NC‐aptamers sensing device has a detection limit of 0.112 pm for dopamine, and this work detects 0.226 pm of dopamine surrounding a single epileptic neuron in polarization, which is more than those of healthy neurons. Overall, this easy‐to‐fabricate Au NC‐aptamers‐based technology has a high potential for monitoring small molecules and determining the secretory ability of single neurons, which is not possible using traditional technologies. [ABSTRACT FROM AUTHOR]

In this work, two validated approaches were used for estimating hydroxyzine HCl for the first time using resonance Rayleigh scattering (RRS) and spectrofluorimetric techniques. The suggested approaches relied on forming an association complex between hydroxyzine HCl and 2,4,5,7‐tetraiodofluorescein (erythrosin B) reagent in an acidic media. The quenching in the fluorescence intensity of 2,4,5,7‐tetraiodofluorescein by hydroxyzine at 551.5 nm (excitation = 527.5 nm) was used for determining the studied drug by the spectrofluorimetric technique. The RRS approach is based on amplifying the RRS spectrum at 348 nm upon the interaction of hydroxyzine HCl with 2,4,5,7‐tetraiodofluorescein. The spectrofluorimetric methodology and the RRS methodology produced linear results within ranges of 0.15–1.5 μg ml−1 and 0.1–1.2 μg ml−1, respectively. LOD values for these methods were determined to be 0.047 μg ml−1 and 0.033 μg ml−1, respectively. The content of hydroxyzine HCl in its pharmaceutical tablet was estimated using the developed procedures with acceptable recoveries. Additionally, the application of four greenness and whiteness algorithms shows that they are superior to the previously reported method in terms of sustainability, economics, analytical performance, and practicality. [ABSTRACT FROM AUTHOR]

In an acidic buffered solution, erythrosine B can react with amiodarone to form an association complex, which not only generates great enhancement in resonance Rayleigh scattering (RRS) spectrum of erythrosine B at 346.5 nm but also results in quenching of fluorescence spectra of erythrosine B at λemission = 550.4 nm/λexcitation = 528.5 nm. In addition, the formed erythrosine B–amiodarone complex produces a new absorbance peak at 555 nm. The spectral characteristics of the RRS, absorbance, and fluorescence spectra, as well as the optimum analytical conditions, were studied and investigated. As a result, new spectroscopic methods were developed to determine amiodarone by utilizing erythrosine B as a probe. Moreover, the ICH guidelines were used to validate the developed RRS, photometric, and fluorimetric methods. The enhancements in the absorbance and the RRS intensity and the decrease in the fluorescence intensity of the used probe were proportional to the concentration of amiodarone in ranges of 2.5–20.0, 0.2–2.5, and 0.25–1.75 μg/mL, respectively. Furthermore, limit of detection values were 0.52 ng/mL for the spectrophotometric method, 0.051 μg/mL for the RRS method, and 0.075 μg/mL for the fluorimetric method. Moreover, with good recoveries, the developed spectroscopic procedures were applied to analyze amiodarone in its commercial tablets. [ABSTRACT FROM AUTHOR]

Abstract The psychoanaleptic medication atomoxetine (ATX) is prescribed to cure attention-deficit hyperactivity syndrome. ATX works by selective prevention of norepinephrine reuptake. It acts by raising the brain’s natural level of norepinephrine, which is necessary for behavior regulation. In this study, a sensitive and practical experimental method was employed to analyze the presence of ATX. The approach utilized a green chemistry-compatible technique, known as a one-pot experiment. The main principle behind this method was the use of molecular-size-dependant resonance Rayleigh scattering (RRS) phenomenon, which occurred due to the interaction between the dual complex of Cilefa Pink B and ATX. When ATX medication and Cilefa Pink B were combined in an acidic environment, they formed an association complex, leading to an amplification of the RRS signal. This amplification directly correlated with the concentration of ATX, specifically within the range of 40-1250 ng/mL. The RRS signal was monitored at a wavelength of 352 nm. The sensitivity of the method was demonstrated by the determination of the limit of detection (LOD) at 12.9 ng/mL and the limit of quantitation (LOQ) at 39.2 ng/mL. The variables of the method were thoroughly investigated and optimized. To ensure the reliability of the method, it was validated according to the International Council for Harmonisation (ICH) guidelines. Furthermore, the method was successfully applied to analyze ATX in its prescribed dosage form. The achievement of using the established resonance Rayleigh scattering (RRS) technology to analyze the target drug in plasma and ensure content uniformity was a remarkable feat.

The psychoanaleptic medication atomoxetine (ATX) is prescribed to cure attention-deficit hyperactivity syndrome. ATX works by selective prevention of norepinephrine reuptake. It acts by raising the brain's natural level of norepinephrine, which is necessary for behavior regulation. In this study, a sensitive and practical experimental method was employed to analyze the presence of ATX. The approach utilized a green chemistry-compatible technique, known as a one-pot experiment. The main principle behind this method was the use of molecular-size-dependant resonance Rayleigh scattering (RRS) phenomenon, which occurred due to the interaction between the dual complex of Cilefa Pink B and ATX. When ATX medication and Cilefa Pink B were combined in an acidic environment, they formed an association complex, leading to an amplification of the RRS signal. This amplification directly correlated with the concentration of ATX, specifically within the range of 40-1250 ng/mL. The RRS signal was monitored at a wavelength of 352 nm. The sensitivity of the method was demonstrated by the determination of the limit of detection (LOD) at 12.9 ng/mL and the limit of quantitation (LOQ) at 39.2 ng/mL. The variables of the method were thoroughly investigated and optimized. To ensure the reliability of the method, it was validated according to the International Council for Harmonisation (ICH) guidelines. Furthermore, the method was successfully applied to analyze ATX in its prescribed dosage form. The achievement of using the established resonance Rayleigh scattering (RRS) technology to analyze the target drug in plasma and ensure content uniformity was a remarkable feat. [ABSTRACT FROM AUTHOR]

In this study, a resonance Rayleigh scattering technique-based sensing method for detecting Bentazone residual in water samples has been developed. This technique was carried out using chitosan-capped gold nanoparticles with a spectrofluorimetric method. Experimental results revealed that the developed method could allow the detection of Bentazone residual as low as a concentration of 0.02 ng mL−1 within 50-sec time. Overall results confirmed the very low detection limit for measuring the Bentazone. The chitosan-capped gold nanoparticles as an excellent sensor were applied to measure and analyze Bentazone in water samples. This article developed a resonance Rayleigh scattering technique-based sensing method for the detection of bentazone residual in water samples. This technique was carried out using chitosan-capped gold nanoparticles with spectrofluorimetric method. Because, Chitosan-capped AuNPs have exciting features, such as resonance Rayleigh scattering (RRS). Use of Chitosan-capped AuNPs sensor as an inexpensive valuable resource, and nontoxic. Chitosan has no toxicity, does not cause allergies and irritations, and is biodegradable and biocompatible. Chitosan-capped AuNPs have exciting features, such as resonance Rayleigh scattering (RRS). These properties are enhanced and modified by adding a hydrophilic polymer such as natural chitosan. [ABSTRACT FROM AUTHOR]

Naftidrofuryl is a vasodilator medication used for treating cerebral and peripheral vascular diseases. In this study, two spectroscopical techniques, spectrofluorimetric and resonance Rayleigh scattering (RRS), were utilized to quantify naftidrofuryl in its pharmaceutical samples. The developed methodologies in this study rely on a facile process of forming an association complex between erythrosine B reagent and naftidrofuryl under acidic conditions. The fluorimetric assay is based on the ability of naftidrofuryl to quench and decrease the native fluorescence intensity of the reagent when measured at λemis. = 550 nm (λexcit. = 526 nm). Under similar reaction conditions, the RRS method relies on the observed amplification in the RRS spectrum of the reagent at a wavelength of 577 nm following its interaction with naftidrofuryl. The methods exhibited linearity within the ranges 0.2–1.6 μg/ml (r2 = 0.999) and 0.1–1.4 μg/ml (r2 = 0.9994), with limit of quantitation values of 0.146 and 0.099 μg/ml, and limit of detection values of 0.048 and 0.032 μg/ml, for the fluorometric and the RRS methods, respectively. Moreover, the quenching between the dye and naftidrofuryl was studied using Stern–Volmer analysis, and the methodologies were experimentally optimized and validated. Additionally, acceptable recoveries were achieved when the procedures were applied to determine naftidrofuryl in pharmaceutical samples. [ABSTRACT FROM AUTHOR]

The modification of EGFR aptamer (Apt 1) and HER2 aptamer (Apt 2) with gold nanoparticles (AuNPs) is reported to obtain probe I (Apt 1-AuNPs) and probe II (Apt 2-AuNPs). Taking Eca109, KYSE510, and KYSE150 cells as models, the sandwich scattering system of probe I-cell-probe II was formed by the recognition of tumor markers by the aptamer modified probe, and the resonance Rayleigh scattering (RRS) spectra were investigated. The results showed that the scattering system can be used to quantitatively detect the Eca109 cell lines in the range 5.0×10 to 5.0×105 cells·mL−1 with a detection limit of 15 cells· mL−1.The system can also detect the KYSE510 cell lines in a linear range of 5.0×10 to 5.0×105 cells·mL−1 with a detection limit of 18 cells·mL−1 and the KYSE150 cell lines in a linear range of 3.0×10 to 5.0×105 cells·mL−1 with a detection limit of 12 cells·mL−1. To demonstrate the potential application of the RRS method for real sample analysis, cells were spiked into blank serum samples at concentrations from 1.0×102 to 1.0×105 cells·mL−1. The recovery was between 97.0% and 102.3%, and the RSD was between 1.1% and 4.9%, confirming the feasibility of the proposed method for ESCC cell determination. [ABSTRACT FROM AUTHOR]

Doxepin hydrochloride (DOX) is a tricyclic antidepressant drug. Three sensitive spectrofluorimetric methods, namely resonance Rayleigh scattering (RRS), frequency doubling scattering (FDS) and second‐order scattering (SOS), were developed and validated for their estimation of doxepin in spiked human plasma and formulation using liquid–liquid extraction method through the formation of an ion pair complex with eosin Y at a pH of 4.5. Various factors affecting fluorescence intensity were optimized, and the reaction kinetics was determined using the Arrhenius equation method. Different scattering methods such as RRS, FDS and SOS were developed at maximum scattering wavelengths λex/λem = 567/567 nm for RRS, 720/360 nm for SOS and 260/520 nm for FDS, respectively. The methods exhibited high sensitivities, and the detection limits for DOX were found to be 0.82, 1.20 and 1.03 ng/ml for RRS, FDS and SOS methods, respectively. The FDS method exhibited the highest sensitivity. The methods were validated using the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use guidelines and applied to determine DOX in capsule and spiked human plasma samples. [ABSTRACT FROM AUTHOR]

Levamisole is an anti-helminthic agent employed medically to treat worm-causative disease, also used as an immune system modifying agent in rheumatic arthritis and as assistant therapy for treating the cancers of the head, colorectal, and neck regions. The first innovative size-dependent approach for levamisole drug analysis is described in this study. It is both efficient and environmentally benign. The drug was evaluated and validated using a green, one-pot, and direct size-dependent technique in this approach. An instant complex was created by combining levamisole and Cilefa Pink B in a mildly acidic medium. The fluorimetric investigation was based on the augmentation effect of levamisole on the Rayleigh scattering response amplitude of a biological dye (Cilefa Pink B) at 424 nm. which was related to produced complex's molecular size. Linearity ranged from 0.08 to 2.0 µg mL−1, with sensitivity limits of 0.023 and 0.069 µg mL−1, respectively. Analytical modulation of Levamisole-Cilefa Pink B complexes was done for all system parameters. In addition, the system was found to meet ICH criteria. Moreover, this technique successfully recovered the substance in the prescribed medicinal dosage forms. The created fluorimetric technique was also successfully employed to track the drug of interest in human biofluids, which was a significant accomplishment. Finally, an eco-scale was applied to recognize the designed method's environmental friendliness.

[Display omitted] • A graphene oxide surface imprinted polymer probe was prepared by microwave irradiation. • The probe selectively recognized I 2. • A RRS analysis platform for iodine and iodate ions in salt samples was established. • The platform has simple, rapid and good selectivity. A new graphene oxide nanosurface molecularly imprinted polymer (GO@MIP) probe was synthesized by microwave irradiation, using graphene oxide (GO) as the carrier, iodine as the template molecule, acrylamide as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the crosslinking agent, azodiisobutyronitrile (AIBN) as the initiator, and acetonitrile as the pore forming agent. The nanoprobe recognizes the iodine, and exhibits significant resonance Rayleigh scattering energy transfer (RRS-ET) effect between iodine as the acceptor and the nanoprobe as donor. When iodine concentration was in the linear range of 0.02–0.5 mmol/L, the decreased RRS intensity was linear to the concentration. And it was used for the determination of iodine in water samples and iodate ions in salt samples. [ABSTRACT FROM AUTHOR]

It was demonstrated that the mechanism of the inner filter effect (IFE) can emerge well in the resonance Rayleigh scattering (RRS) technique and be utilized as a new analytical method in the design of innovative IFE-based sensors. To prove this process, silver nanocubes (Ag NCs) with tunable extinction spectra were selected as RRS probes, and three analytes, doxorubicin (DOX), sunitinib (SUN), and Alizarin Red S (ARS), were considered as the typical absorbers. In addition, in the presence of SUN as a typical analyte, the quenching of the RRS signal of Ag NCs, with λmax of 419 nm, was linear in the range 0.01 to 2.5 µM of SUN. The limit of detection (LOD) was 0.0025 µM. The introduced method was then used to develop a dual-signal assay for the ratiometric determination of Al3+ ions. The suggested dual-signal assay was based on the color changes of ARS caused by Al3+ and the IFE between ARS and Ag NCs. The obtained results showed that the two characteristics of response sensitivity and linear dynamic range are very satisfactory for sensing Al3+ ions. The findings of this study demonstrate that the newly developed IFE mechanism can be employed as an attractive and highly efficient analytical technique for measuring different analytes. [ABSTRACT FROM AUTHOR]

Two simple, sensitive, and low‐cost fluorescence spectroscopy methods for neomycin (NEO) detection were developed. Both methods were based on the interaction between NEO and Congo red (CR) in acidic buffer medium to form an ion‐association complex. The quenching effect of the formed ion‐association complex on the fluorescence of CR at 421 nm is a basic principle of fluorescence analysis, whilst the resonance Rayleigh scattering (RRS) method was used to enhance the resonance Rayleigh scattering spectrum at 384 nm by adding NEO. Experimental conditions such as pH, temperature, reaction time, CR concentration, and the ionic strength of the two methods were investigated and optimized. In addition, the effect of common coexisting substances on the method was tested and the results showed good selectivity. The composition of ion‐association complexes, the reaction mechanism, and reasons for the enhanced intensity of RRS are discussed. Under optimum conditions, the responses of the fluorescence spectrophotometry and RRS methods showed good linearity with NEO concentrations in the range 0.2–3.0 μg ml−1 and 0.1–3.0 μg ml−1, respectively. The detection limits of fluorescence spectrophotometry and RRS spectroscopy techniques were 0.02 μg ml−1 and 0.01 μg ml−1, respectively. Finally, the two methods were applied to the analysis of wastewater and the results were satisfactory. [ABSTRACT FROM AUTHOR]

A stable Au metal organic frameworks (AuMOF) nanosol was prepared. It was characterized by electron microscopy and molecular spectral techniques. In pH 6.8 PBS buffer solution, AuMOF nanoprobes exhibit a strong resonance Rayleigh scattering (RRS) peak at 330 nm. After basic fuchsin (BF) adsorbing on the surface of AuMOF, the RRS energy of the nanoprobe donor can be transferred to BF receptor, resulting in a decrease in the RRS intensity at 330 nm. Both sulfite and BF taken place an addition reaction to form a colorless product (SBF) that exhibit weak RRS energy transfer (RRS-ET) between AuMOF and SBF, resulting in the enhancement of the RRS peak. As the concentration of SO32–increases, the RRS peak is linearly enhanced. Thus, a new and sensitive RRS-ET method for the detection of SO32– (0.160–5.00 μmol/L) was developed accordingly using AuMOF as nanoprobes, with a detection limit of 0.0800 μmol/L. This new RRS method was applied to determination of SO32– in food and SO2 in air samples. The recoveries of food and air samples were 97.1–106% and 92.9–106%, and the relative standard deviation (RSD) was 2.10–4.80% and 2.10–4.50%, respectively.

[Display omitted] • A novel sort of macrocyclic CQDs sensor from HemiQ[6] has been developed. • The CQDs sensors exhibited a highly sensitive and real-time response to Pb2+. • The CQDs suggested a potential application for the efficient determination of Pb2+. A macrocyclic compound, hemicucurbit[6]uril (HemiQ[6]), is employed as the carbon source to produce a novel sort of carbon quantum dots (CQDs) with blue fluorescence in aqueous solution. The CQDs are fully identified by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Nuclear Magnetic Resonance (NMR), zeta potential, ultraviolet/visible (UV–vis) and photoluminescence spectroscopy (PL). The nanomaterial is developed for the analysis of Pb2+ in the light of the Resonance Rayleigh scattering (RRS) changes with the increasing Pb2+ concentration. The proposed probe emerges a high selectivity to Pb2+ and excellent sensitivity in the linear concentration range of 0–6 μM with a detection limit low to 0.42 μM, which is superior to the previous values of Pb2+ sensors, as well as the good anti-interference ability is confirmed by the specifical response to Pb2+ in the presence of other metal cations. Therefore, the proposed analysis of Pb2+ is explored for the application in real samples of tap water and lake water, in satisfied results of acceptable recoveries. [ABSTRACT FROM AUTHOR]

The interaction of venlafaxine hydrochloride (VLX) with erythrosine B was investigated using a resonance Rayleigh scattering (RRS) spectroscopic technique. In acetate buffer (pH 3.4), erythrosine B reacted with VLX to form a 1:1 ion‐pair complex with concomitant enhancement in RRS intensity that was measured at 330 nm. In addition, the stability constant and the change in free energy of the reaction were estimated. Based on this interaction a new method was developed for a sensitive VLX analysis using erythrosine B as a probe. The results indicated that this method had good selectivity in the presence of coexisting compounds. The scattering intensity (ΔIRRS) was linearly dependent on VLX concentration over the range 0.04–1.0 μg ml−1 with a determination coefficient (r) of 0.9998. The limit of detection and limit of quantitation were 0.01 and 0.03 μg ml−1, respectively. This method could be suitably used for analysis of VLX in pharmaceutical capsules and human plasma. [ABSTRACT FROM AUTHOR]

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In this work, a resonance Rayleigh scattering technique and a spectrofluorimetric technique were applied to the quantification of cyclobenzaprine through two validated methods. The suggested methods are based on a facile association complex formation between cyclobenzaprine and eosin Y reagent in the acidic medium. The resonance Rayleigh scattering method relied on the enhancement in the resonance Rayleigh scattering spectrum of eosin Y at 370 nm after the addition of cyclobenzaprine. On the other hand, the spectrofluorimetric quantification relied on the quenching effect of cyclobenzaprine on the fluorescence strength of the eosin Y reagent at 545 nm (excitation wavelength at 300 nm). The suggested methods were linear over the ranges of 0.07–1.75 μg/mL and 0.15–2.0 μg/mL with detection limit values of 0.023 μg/mL and 0.048 μg/mL for the resonance Rayleigh scattering method and the spectrofluorimetric method, respectively. All reaction conditions for cyclobenzaprine–eosin Y formation were experimentally evaluated and optimized. In addition, both methods were validated based on ICH rules. Furthermore, the developed methods were practically applied to the analysis of cyclobenzaprine in its commercial tablet dosage form with acceptable recoveries. Moreover, the content uniformity test of the commercial cyclobenzaprine tablets was successfully applied using the proposed spectroscopic methods based on USP rules.

Premature ejaculation is a male sexual problem that is marked by rapid ejaculation and quick attainment of orgasm. Dapoxetine belongs to the antidepressant category and modulates its action by preventing the reuptake of serotonin by neurons. Dapoxetine is marketed as an off‐label therapy for premature ejaculation. Here, two facile, sensitive, and green compatible approaches were established for dapoxetine assay. The approaches chemically rely on association complex formed between erythrosine‐B and dapoxetine in an acidic buffered medium. The quenching effect of the formed complex on the native erythrosine fluorescence at emission 553.5 nm is simply the main idea of spectrofluorimetric assay, while resonance Rayleigh scattering methodology uses augmentation of resonance Rayleigh scattering spectrum at 345 nm by the added dapoxetine. The current approaches exhibit linearity between response and dapoxetine concentration over 0.2–2.5 μg/ml and 0.3–3.0 μg/ml for spectrofluorimetric and resonance Rayleigh scattering (RRS) methods, respectively. All variables affecting methods and complex formation were studied and precisely optimized. The criteria of validation were performed by the directives provided by International Conference on Harmonization's (ICH) Guidelines and limits of detection were 0.06 and 0.05 μg/ml for spectrofluorimetric and RRS techniques, respectively. Finally, the approaches were applied with acceptable results for pharmaceutical formulation analysis. [ABSTRACT FROM AUTHOR]

Duloxetine is an antidepressant that exhibits its action by preventing the reuptake of serotonin and norepinephrine by neurons. In this analytical study, we developed two facile, sensitive methods for duloxetine analysis. Both methods rely on the formation of binary association complex between erythrosine-B and duloxetine in an acidic medium using spectrofluorimetric and resonance Rayleigh scattering (RRS) techniques. Spectrofluorimetric method simply uses the quenching property of the formed complex on the native fluorescence of erythrosine-B at an emission wavelength of 557.2 nm (λex = 528.6), while RRS is based on detecting the enhancement in the RRS signal at 357.2 nm. The proposed methods have been validated according to the International Conference on Harmonization guidelines. The approaches provide linear assay of duloxetine hydrochloride over 0.1–2.4 µg ml−1 and 0.2–2.0 µg ml−1 for spectrofluorimetric and RRS methods, respectively. Variables affecting methods and complex formation were studied and optimized. The limit of detection values were 0.03 and 0.056 µg ml−1 for spectrofluorimetric and RRS methods, respectively. Both approaches were applied with acceptable results for formulation analysis and evaluation of cymbatex capsule content uniformity.

In this study, rapid resonance Rayleigh scattering (RRS), spectrophotometric, and spectrofluorimetric methods were performed for facile quantitation of daclatasvir dihydrochloride without interference from sofosbuvir (a co‐formulated anti‐hepatitis C virus drug). The proposed approaches were based on forming a binary complex between daclatasvir dihydrochloride and merbromin reagent at pH 4.1. The binary complex was measured spectrophotometrically at λmax = 544 nm. The spectrofluorimetric approach relied on the quenching effect of daclatasvir dihydrochloride on the fluorescence strength of merbromin at λEmission = 545 nm. The RRS approach depended on augmentation in the merbromin RRS spectrum at 363 nm upon addition of daclatasvir dihydrochloride. The presented methodologies were linear over the concentration ranges 2.5−15.0, 0.2−1.6 and 0.15−3.0 μg ml−1 with detection limits of 0.45, 0.046, and 0.036 μg ml−1 for the spectrophotometric approach, the spectrofluorometric approach, and RRS approach, respectively. Current approaches were validated in compliance with International Council for Harmonisation guidelines and utilized practically to estimate daclatasvir dihydrochloride either in binary mixtures with sofosbuvir or in its commercial tablet dosage form with good results. Moreover, the test for content uniformity was applied successfully on commercial tablets using the current spectroscopic approaches. [ABSTRACT FROM AUTHOR]

A new gold nanosurface molecularly imprinted polymer spectral probe (AuNP-MIP) for the detection of 4-methylimidazole (MI) was synthesized by microwave irradiation, using AuNP as the nanosubstrate, the azo compound (AC) of MI as the template molecule and methacrylic acid (MAA) as the functional monomer. The probe was found to exhibit strong resonance Rayleigh scattering (RRS) effects and to specifically recognize AC. With the increase of MI concentration, the AC increased, the RRS energy transfer (RRS-ET) was enhanced, and the intensity of RRS signal at 370 nm decreased linearly. Accordingly, a new RRS-ET method was developed for the simple, sensitive and selective determination of MI, with the linear range of 0.0375–0.13125 μg/mL, and the detection limit of 0.0022 μg/mL MI. It was applied to analysis of MI in samples, with the recoveries of 91%–100% and relative standard deviations of 1.1%–8.5%. • A nanogold surface imprinted polymer was prepared by microwave method. • Gold nanoparticles-decorated molecularly imprinted polymers (AuNP-MIP) specifically recognized 4-Methylimidazole (MI). • A resonance Rayleigh scattering (RRS) analysis platform for trace MI was established. • The RRS platform has high sensitivity, high selectivity and high accuracy. [ABSTRACT FROM AUTHOR]

Sensitive and selective methods for the determination of urea in samples such as dairy products are important for quality control and health applications. Using ammonium ferric citrate as a precursor, Fe/N-codoped carbon dots (CDFeN) were prepared by a hydrothermal procedure and characterized in detail. CDFeN strongly catalyzes the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 to turn on an indicator molecular reaction, forming an oxidized tetramethylbenzidine (TMBox) probe with surface-enhanced Raman scattering, resonance Rayleigh scattering, and fluorescence (SERS, RRS, and FL) signals at 1,598 cm−1, 370 nm, and 405 nm, respectively. The urea aptamer (Apt) can turn off the indicator reaction to reduce the tri-signals, and the addition of urea turns on the indicator reaction to linearly enhance the SERS/RRS/FL intensity. Thus, a novel Apt turn-on tri-mode method was developed for the assay determination of ultra-trace urea with high sensitivity, good selectivity, and accuracy. Trace adenosine triphosphate and estradiol can also be determined by the Apt-CDFeN catalytic analytical platform.

Bisphenol A (BPA), as a typical endocrine disruptor, poses a serious threat to human health. Therefore, it is urgent to establish a rapid, sensitive, and simple method for the determination of BPA. In this paper, based on the aptamer-mediated single-atom Fe carbon dot catalyst (SAFe) catalyzing the HAuCl4-ethylene glycol (EG) nanoreaction, a new SERS/RRS di-mode detection method for BPA was established. The results show that SAFe exhibits a strong catalytic effect on the HAuCl4-EG nanoreaction, which could generate purple gold nanoparticles (AuNPs) with resonance Rayleigh scattering (RRS) signals and surface-enhanced Raman scattering (SERS) effects. After the addition of BPA aptamer (Apt), it could encapsulate SAFe through intermolecular interaction, thus inhibiting its catalytic action, resulting in the reduction of AuNPs generated and the decrease of RRS and SERS signals of the system. With the addition of BPA, Apt was specifically combined with BPA, and SAFe was re-released to restore the catalytic ability; the generated AuNPs increased. As a result of this RRS and SERS signals of the system recovered, and their increment was linear with the concentration of BPA. Thus, the quantification of 0.1–4.0 nM (RRS) and 0.1–12.0 nM (SERS) BPA was realized, and the detection limits were 0.08 nM and 0.03 nM, respectively. At the same time, we used molecular spectroscopy and electron microscopy to study the SAFe-HAuCl4-ethylene glycol indicator reaction, and proposed a reasonable SAFe catalytic reaction mechanism. [ABSTRACT FROM AUTHOR]

In this study, spectrofluorimetric and resonance Rayleigh scattering techniques were applied for the first time for determination of rupatadine through two validated methods. The proposed methods were based on a facile association complex formation between rupatadine and erythrosin B reagent in acidic medium. Spectrofluorimetric determination relied on the quenching effect of rupatadine on the fluorescence intensity of erythrosin B at 556 nm (excitation = 530 nm). Conversely, the resonance Rayleigh scattering (RRS) method relied on enhancement in the resonance Rayleigh scattering spectrum of erythrosin B at 344 nm after the addition of rupatadine. The developed methods produced linear results over ranges 0.15−2.0 μg/ml and 0.1−1.5 μg/ml, with detection limits of 0.030 μg/ml and 0.018 μg/ml for the spectrofluorimetric method and the RRS method, respectively. All reaction conditions for rupatadine–erythrosin B formation were optimized experimentally and both methods were validated according to International Council for Harmonisation guidelines. The developed methods were applied to estimate rupatadine content in its pharmaceutical tablet dosage form with acceptable recoveries. Furthermore, a content uniformity test for the commercial rupatadine tablets was successfully applied by the suggested spectroscopic methods according to United States Pharmacopeia guidelines. [ABSTRACT FROM AUTHOR]

Terbinafine hydrochloride is a potent antifungal drug indicated for oral and topical treatment of mycoses. A resonance Rayleigh scattering (RRS) method was developed for the determination of terbinafine hydrochloride through a feasible complexation reaction with erythrosine B. In a weakly acidic medium (acetate buffer, pH 5.0), terbinafine hydrochloride can react with erythrosine B through the electrostatic attraction and virtue of hydrophobic force to form an ion-association complex. The reaction resulted in the appearance of a new RRS peak at 369 nm. The RRS peak was increased by increasing the concentration of terbinafine hydrochloride in the linear range of 0.1–1.5 µg ml−1. All the reaction conditions (erythrosine B concentration, buffer volume, diluting solvent and pH) were optimized. The detection limit was 0.029 µg ml−1 while the quantitation limit was 0.089 µg ml−1. The suggested method after its validation was successfully applied for the determination of terbinafine hydrochloride in different pharmaceutical formulations (tablets and cream) with sufficient recovery.

This work described the use of a basic phenothiazine dye (toluidine blue, TB) as a resonance Rayleigh scattering (RRS) and colorimetric probe for the detection of perfluorooctane sulfonate (PFOS). Owing to the electrostatic interactions between TB and PFOS, TB in the presence of PFOS caused great enhancement of RRS signal at dual-wavelength (I345 nm and I506 nm) and the ratio changes of absorbance (A502 nm/A630 nm). The RRS enhancement was attributed to the absorption-rescattering resonance effect, the increase of the molecular size, and the enhancement of hydrophobicity. The analytical procedure was implemented by physically mixing TB, Britton-Robinson buffer solution, and PFOS solution (or sample solution) all-in-one, avoiding the tedious pre-derivatization or the preparation of nanoparticles. The whole approach was less than 8 min. Under the optimal conditions, the analytical performance was acquired. The linear ranges for RRS and colorimetry were 0.04–8.0 and 1.0–20 μmol/L, with detection limits of 4.2 nmol/L and 112 nmol/L, respectively. The RRS method was applied to the determination of PFOS in environmental water with recoveries of 93.2–106%. The dual-channel sensor is convenient, rapidly responsive, sensitive, and cost-effective, integrating the advantages of RRS and colorimetry. [ABSTRACT FROM AUTHOR]

A highly sensitive resonance light scattering method for detecting dopamine in urine was developed by using a novel probe based on lanthanide‐doped upconversion nanoparticles (UCNPs) linked to dopamine–quinone (DQ) by hydrogen bonding and electrostatic interactions. Adding dopamine to a solution containing UCNPs decreases their size and the intensity of their resonance light scattering signals. Based on the decrease, dopamine can be determined in Tris–HCl buffer and in urine samples spiked with analyte concentrations over the range 0–300 μM with a limit of detection of 1.62 μM. As‐prepared UD can thus provide an effective platform for biosensor development, drug discovery, and rapid diagnosis of Parkinson's and Alzheimer's disease, among other medical conditions. [ABSTRACT FROM AUTHOR]

In this work, two validated approaches were used for estimating hydroxyzine HCl for the first time using resonance Rayleigh scattering (RRS) and spectrofluorimetric techniques. The suggested approaches relied on forming an association complex between hydroxyzine HCl and 2,4,5,7-tetraiodofluorescein (erythrosin B) reagent in an acidic media. The quenching in the fluorescence intensity of 2,4,5,7-tetraiodofluorescein by hydroxyzine at 551.5 nm (excitation = 527.5 nm) was used for determining the studied drug by the spectrofluorimetric technique. The RRS approach is based on amplifying the RRS spectrum at 348 nm upon the interaction of hydroxyzine HCl with 2,4,5,7-tetraiodofluorescein. The spectrofluorimetric methodology and the RRS methodology produced linear results within ranges of 0.15-1.5 μg ml -1 and 0.1-1.2 μg ml -1 , respectively. LOD values for these methods were determined to be 0.047 μg ml -1 and 0.033 μg ml -1 , respectively. The content of hydroxyzine HCl in its pharmaceutical tablet was estimated using the developed procedures with acceptable recoveries. Additionally, the application of four greenness and whiteness algorithms shows that they are superior to the previously reported method in terms of sustainability, economics, analytical performance, and practicality., (© 2024 John Wiley & Sons Ltd.)

In an acidic buffered solution, erythrosine B can react with amiodarone to form an association complex, which not only generates great enhancement in resonance Rayleigh scattering (RRS) spectrum of erythrosine B at 346.5 nm but also results in quenching of fluorescence spectra of erythrosine B at λ emission  = 550.4 nm/λ excitation  = 528.5 nm. In addition, the formed erythrosine B-amiodarone complex produces a new absorbance peak at 555 nm. The spectral characteristics of the RRS, absorbance, and fluorescence spectra, as well as the optimum analytical conditions, were studied and investigated. As a result, new spectroscopic methods were developed to determine amiodarone by utilizing erythrosine B as a probe. Moreover, the ICH guidelines were used to validate the developed RRS, photometric, and fluorimetric methods. The enhancements in the absorbance and the RRS intensity and the decrease in the fluorescence intensity of the used probe were proportional to the concentration of amiodarone in ranges of 2.5-20.0, 0.2-2.5, and 0.25-1.75 μg/mL, respectively. Furthermore, limit of detection values were 0.52 ng/mL for the spectrophotometric method, 0.051 μg/mL for the RRS method, and 0.075 μg/mL for the fluorimetric method. Moreover, with good recoveries, the developed spectroscopic procedures were applied to analyze amiodarone in its commercial tablets., (© 2024 John Wiley & Sons Ltd.)

It remains a problem for direct detection of small inorganic nitrite ions using resonance Rayleigh scattering (RRS) method based on the direct dye-binding reaction. In the present study, a redox-derivatization reaction taking only 5 min was introduced prior to nitrite detection. In the redox-derivatization reaction, nitrite ions were reduced by excess iodine ions to generate triiodide ions (I3−), which were further derivatized with a cationic dye (basic violet 1, BV1) to form the ion associates of I3−-BV1. Therefore, the RRS signal was significantly enhanced, resulting from the increase of particle size and resonance-enhanced scattering effect. The analytical procedure was performed by just mixing nitrite, oxidant, acid, and dye all-in-one, avoiding the tediousness of a multi-step process or the preparation of nanoparticles. The whole detection process including the redox-derivatization reaction was less than 6 min. The reaction conditions such as concentration of hydrochloric acid, potassium iodide, and BV1, reaction time, and temperature were investigated. Under optimum conditions, the concentration of nitrite was linear with an RRS signal of I3−-BV1 ion associates at 320 nm in the range of 0.015–1.2 mg/L. The limit of detection (LOD) was calculated to be 3.0 μg/L. The RRS method was applied to the determination of nitrite in real samples such as pork sausage, milk powder, and water with recovery of 95.2–112%. With advantages of rapidness, high sensitivity, and high selectivity, the method indicates potential applicability for detection of nitrite in complex samples. The method also provides an instructive protocol for detection of analytes that generate no/weak RRS enhancement after the direct dye-binding reaction. [ABSTRACT FROM AUTHOR]

In 0.2 mol/L HCl–0.22 mol/L HNO 3 medium, trace Hg2+ catalyzed NaH 2 PO 2 reduction of HAuCl 4 to form gold nanoparticles (AuNPs), which exhibited a strong resonance Rayleigh scattering (RRS) effect at 370 nm. With increasing of [Hg2+], the RRS effect enhanced due to more AuNP generated from the catalytic reaction. Under the chosen conditions, the enhanced RRS intensity at 370 nm is linear to Hg2+ concentration in the range of 5.0–450 × 10−9 mol/L, with a detection limit of 0.1 nmol/L. This RRS method was applied for the determination of Hg in water samples, with high sensitivity and good selectivity, and its results were agreement with that of atomic fluorescence spectrometry. [ABSTRACT FROM AUTHOR]

In this research, a novel Resonance Rayleigh Scattering (RRS) aptasensor was developed for thrombin monitoring using in-situ synthesized and embedded Au nanoparticles (AuNPs) into poly vinyl alcohol –borax hydrogel (PBH). Thiolated-thrombin binding aptamer (thiolated-TBA) was attached to the surface of AuNPs embedded into PBH to design the PBH-aptasensor for thrombin detection (thiolated-TBA@AuNPs–PBH). To verify the characteristic and morphology of PBH nanocomposite, energy dispersive X-ray analysis, TEM, average particle size analizer and UV–Vis spectra were performed. The difference in RRS intensities in the absence and presence of thrombin was calculated and selected as the monitoring signal. Effect of different parameters on the RRS signal was investigated at excitation wavelength of 500 nm. Under the approved conditions, the linear detection range was validated over the concentration of 0.70 pM- 0.02 μM. The limit of detection based on 3S b was 0.10 pM. The relative standard deviation for 5.6 pM and 3.6 nM were 4.0 and 2.7% (n = 10), respectively. The proposed aptasensor was successfully applied as an experimental model for thrombin detection in serum samples of healthy volunteers with acceptable results. Image 1 • A new Resonance Rayleigh Scattering aptasensor has been designed for thrombin detection. • Au nanoparticles (AuNPs) were in situ synthesized into poly vinyl alcohol –borax hydrogel for the first time. • Thiolated-thrombin binding aptamer (thiolated-TBA) was attached to the surface of AuNPs. • The bio-sensing platform is selective and sensitive for thrombin detection. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A dual-signal responsive sensor was designed to detect GSH based on MnO 2 nanoflakes. • This sensor combined the advantages of RRS and colorimetry for the detection of GSH. • The sensor was successfully applied to detect GSH in the drug samples. • This work broadens the application of RRS technique in the analytical field. Abstract Glutathione (GSH) plays a critical role in the living system and its abnormalities are closely associated with numerous clinical diseases. Thus, monitoring and detecting the content of GSH in the living system is still of great importance. Herein, a novel dual-signal responsive optical sensor is developed by using resonance Rayleigh scattering (RRS) and colorimetry for sensitive detection of GSH. In this sensor, MnO 2 nanoflakes are used as both GSH recognizer and signal transducer of RRS and colorimetry. The solution of MnO 2 nanoflakes shows strong RRS and absorption signals because MnO 2 nanoflakes possess a large surface area and high molar extinction coefficient. However, MnO 2 can be reduced to Mn2+ and MnO 2 nanoflakes can be etched to small nanoparticles by GSH, causing both the RRS and absorption signals to decrease. Based on the change of RRS signal and absorbance of MnO 2 nanoflakes, a novel dual-signal responsive optical sensor is successfully constructed to detect the content of GSH. The as-developed optical sensor toward GSH presents a favorable sensitivity with a detection limit of 0.033 and 0.67 μM for RRS and colorimetry, respectively. Furthermore, the as-developed approach is straightforward, quickly responsive, free-label, and cost-effective. More significantly, this method combines the advantages of RRS and colorimetry for the detection of GSH. Beyond this, the proposed RRS method has also been successfully utilized to detect the content of GSH in glutathione injection samples. [ABSTRACT FROM AUTHOR]

Organotrialkoxysilanes like 3-aminopropyltrimethoxysilane (3-APTMS)-treated noble metal cations were rapidly converted into their respective nanoparticles in the presence of 3-glycidoxypropylytrimethoxysilane (3-GPTMS). The micellar activity of 3-APTMS also allowed us to replace 3-GPTMS with other suitable organic reagents (e.g., formaldehyde); this approach has significant advantages for preparing bimetallic and trimetallic analogs of noble metal nanoparticles that display efficient activity in many practical applications. The formation of monometallic gold, silver, and palladium nanoparticles, bimetallic Ag-Pd, and Au-Pd nanoparticles at various ratios of noble metal cations, and trimetallic Ag-Au-Pd nanoparticles were studied; their biocatalytic activity in non-enzymatic sensing of glucose based on monitoring synchronous fluorescence spectroscopy (SFS) was assessed. Of these nanoparticles, Au-Pd made with an 80:20 Au:Pd ratio displayed excellent catalytic activity for glucose sensing. These nanoparticles could also be homogenized with Nafion to enhance the resonance Rayleigh scattering (RRS) signal. In this study, the structural characterization of noble metal nanoparticles as well as bi- and tri-metallic nanoparticles in addition to their use in non-enzymatic sensing of glucose are reported.

Phospholipids in biological membranes establish a chemical equilibrium between free phospholipids in the aqueous phase (CMC) and self-assembled phospholipids in vesicles, keeping the CMC constant. The CMC is different for each phospholipid, depends on the amount of cholesterol, and, according to the lipid-chaperone hypothesis, controls the interaction between free phospholipids and amyloidogenic proteins (such as amylin, amyloid-β, and α-synuclein, all of which are, respectively, associated with a different proteinopathy), which governs the formation of a toxic complex between free lipids and proteins that leads to membrane destruction. Here, we provide quantitative measurements of CMCs and bilayer stability of pure phospholipids, lipid rafts, and their mixture with cholesterol by fluorescence methods (using pyrene as a probe) and light scattering techniques (resonance Rayleigh scattering and fixed-angle light scattering) performed on LUVs, as well as AFM to measure LUV dimensions. Also, we test the lipid-chaperone hypothesis on human IAPP interacting with different mixture of POPC cholesterol. Stated the importance of CMC in membrane stability and protein aggregation processes, these results could be a starting point for the development of a quantitative kinetic model for the lipid chaperone hypothesis., (© 2024 Wiley Periodicals LLC.)

A highly selectivity determination of epidermal growth factor receptor (EGFR) has been described in the article. Antibody immobilized cysteamine (Cys) functionalized gold nanoparticles (AuNP) were proposed as immunosensors, and resonance Rayleigh scattering (RRS) was used for detection. First, Cys stabilized AuNPs (Cys‐AuNP) were prepared by the reduction of chloroauric acid with sodium borohydride in the presence of Cys. Further, anti‐EGFR antibody (Cetuximab, C225) was covalently linked to the Cys‐AuNP by carbodiimide‐mediated amidation protocol to yield the C225‐AuNP immunoprobe. The prepared conjugations were characterized by ultraviolet‐visible (UV‐vis) spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared (FT‐IR) and sodium dodecyl sulphate‐polyacrylamide gel electrophoresis (SDS‐PAGE). Based on the specific binding of C225 to EGFR, an RRS method was established to determine the concentration of EGFR. Under the optimal conditions, the concentration of EGFR was related to the intensity of RRS in the range 30–130 ng ml−1 with a low detection limit of 4.0 ng ml−1. Meanwhile, the proposed immunosensor exhibited excellent selectivity and anti‐interference property. The method was applied to the determination of EGFR in human serum and cancer cell lysate samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (AuNPs) were modified by anti-epidermal growth factor receptor (EGFR) antibody (Ab) and EGFR aptamer (Apt) to obtain multifunctional Apt-AuNP-Ab nanoconjugate immunoprobe. The probe is specifically combined with EGFR to form large volume binding products that exhibited a remarkable enhancement of the resonance Rayleigh scattering (RRS) intensity, and to appear characteristic RRS peak at 312 nm. The scattering enhancement (Δ I ) is linear to the EGFR concentration in the range of 20∼100 ng mL −1 with limit of detection of 0.1 ng mL −1 . The immunoassay was successfully tested and validated by using esophageal squamous cell carcinoma (ESCC) cell Eca109 cell lysates, as well as human serum samples. The mechanism of selectivity and the reasons for RRS enhancement have been discussed. The experimental results reported in this article opened a new possibility of simple, rapid, selective and reliable determination of EGFR by measuring RRS intensity from multifuncition gold nanosystems. [ABSTRACT FROM AUTHOR]

A novel and simple method for simultaneous determination of chiral carnitine (CA) enantiomers was proposed. In this work, the rhodamine B (RhB) could react with D‐CA and L‐CA, and new resonance Rayleigh scattering (RRS) peaks were generated. According to the polarization experiments, it could be testified that scattering peak of this system was composed of resonance fluorescence and scattering light. The RRS intensity of the RhB could be enhanced with the addition of D‐ or L‐CA. However, The RRS signal with L‐CA had greater degree increased. So a useful assay program for the selective and simultaneous determination of CA enantiomers was built via the RRS signal differences of the two CA enantiomers responding to RhB. The results showing a good linear relationship and high correlation coefficient were obtained, and the detection limit was calculated as 0.086 μg·mL−1 (D‐CA) and 0.042 μg·mL−1 (CA). Here, new built RRS method with RhB as chiral probe could be applied to achieve selective analysis through this work. The applicability of the chiral recognition of CA enantiomers mixtures in samples had been demonstrated by its low cost, sensitivity, enantioselectivity, simplicity, and good availability of the materials. It was obvious from the left phone that single RhB had a certain grade of RRS intensities and appeared a characteristic peak, λex = λem = 566 nm, while the RRS intensities of single D‐CA or L‐CA were very weak without any characteristic peak. When RhB reacted with D‐CA and L‐CA, the RRS intensities were both remarkably enhanced. A more interesting phenomenon is that the RRS intensity of the RhB + L‐CA system was higher than that of RhB + D‐CA system (CRhB: 1.1 × 10−6 mol·L−1; CD‐CA: 25 μg·mL−1; CL‐CA: 25 μg·mL−1; 1‐mL HEPES buffer solution, pH = 7.6). The right graph was about the linear plots of the ΔIRRS of RhB corresponding to the concentration of D‐CA and L‐CA. (CRhB: 1.1 × 10−6 mol·L−1; 1 mL HEPES buffer solution, pH = 7.6). Based on this result, a novel RRS method for the selective analysis and simultaneous determination of carnitine enantiomers with RhB as an optical sensing and chiral probe could be proposed. [ABSTRACT FROM AUTHOR]