Visual colorimetric detection of berberine hydrochloride with silver nanoparticles

Post-synthetic modified luminescent metal-organic framework for the detection of berberine hydrochloride in a traditional Chinese herb

In this work, a novel fluorescence sensor UiO-66-PSM based on post-synthetic modified metal-organic frameworks was prepared for the detection of berberine hydrochloride (BBH) in the traditional Chinese herb Coptis. UiO-66-PSM was synthesized by a simple Schiff base reaction with UiO-66-NH2 and phthalaldehyde (PAD). The luminescence quenching can be attributed to the photo-induced electron transfer process from the ligand of UiO-66-PSM to BBH. The UiO-66-PSM sensor exhibited fast response time, low detection limit, and high selectivity to BBH. Moreover, the UiO-66-PSM sensor was successfully applied to the quantitative detection of BBH in the traditional Chinese herb Coptis, and the detection results obtained from the as-fabricated fluorescence sensing assay were consistent with those of high-performance liquid chromatography (HPLC), indicating that this work has potential applicability for the detection of BBH in traditional Chinese herbs.

Developing an analytical method for quantification of trientine based on modified silver nanoparticles

Trientine or (N,N´-bis(2-aminoethyl)-1,2-ethanediamine (TETA) is a copper chelator and used in Wilson's disease, is aliphatic amine that does not have UV absorbing groups. In this study, the modified silver nanoparticles (AgNPs) by sodium lauryl sulfate have been used to develop an analytical method for quantification of TETA. Different concentrations of TETA were added into a particular concentration of AgNPs and absorbance of each sample was measured at 397 nm under the optimal conditions which include pH, time, salt and AgNPs volume. It was optimized by a design of experiments using response surface methodology. Then, the calibration curve was obtained based on the concentrations of TETA solution versus decrease in the absorbance of AgNPs. Selectivity of the developed method was performed in plasma and presence of common cations i.e. copper, zinc and ferrous. Under optimum conditions, linear range of this method was between 10 and 40 ng.mL- 1 with correlation coefficient (R2) of 0.996 with limit of detection and quantification of 3 ng.mL- 1 and 10 ng.mL- 1, respectively. Selectivity of established method in presence of cations eliminated by diluting because of high sensitivity of the established analytical techniques based on AgNPs. This method is suitable and low costing for quantification of TETA and does not require high equipment.

Silver Nanoparticles Application as a Colorimetric Probe for the Spectrophotometric Determination of Hyoscine Butylbromide in Pharmaceutical Formulations

BACKGROUND

Hyoscine butylbromide is used as an antispasmodic in treating peptic ulcers, gastritis, and various disorders of the gastrointestinal tract that are characterized by spasms. It has also found employment for the relief of spasmodic conditions of the bile duct and urinary tract and for the treatment of dysmenorrhea.

OBJECTIVE

In this study, the application of silver nanoparticles (Ag NPs) as a colorimetric probe for the fast, selective, and simple determination of hyoscine butylbromide was described.

METHODS

The proposed method was based on the Ag NPs aggregation induced by their interaction with the cited drug. This interaction produced a color change from yellow to colorless measured at 405 nm.

RESULTS

The method linear concentration range was 0.10-50.0 µg/mL with a correlation equation (y = 0.0132 x + 0.3174), correlation coefficient of 0.9981, and quantification limits of 0.091 µg/mL. A thorough investigation was done to validate the method's analytical performance, and the findings were satisfactory. With great accuracy and precision, this approach was used to identify the medication in pharmaceutical tablet samples with recovery percentages ranging from 96.20 to 98.10%.

CONCLUSIONS

Since there are no critical reaction conditions or solvent extraction involved in the described method, it is distinguished by its simplicity. The results were quite consistent with those attained using the approved standard method.

HIGHLIGHTS

Simple, fast, and sensitive colorimetric probe developed for determination of hyoscine butylbromide in pharmaceutical formulations.

Tetraphenylethylene sulfonate derivative as turn-on fluorescent sensor for berberine chloride detection in aqueous solution

A negatively-charged tetraphenylethylene derivative (TPE-SE) was designed and synthesized as turn-on fluorescent sensor for berberine chloride (BBC) detection in aqueous solution. The fluorescent property and detection mechanism were elucidated by UV-vis absorption spectra, photoluminescence spectra, dynamic light scattering experiments. The results reveal that the BBC can lead to aggregation-induced emission of TPE-SE due to the electrostatic interactions, endowing TPE-SE with excellent turn-on detecting ability, high selectivity and sensitivity to BBC. The detection limit is as low as 6.58 × 10^-6M. These results should be applicable to fabricate special turn-on fluorescent sensors towards various antibiotics, and it is crucially important for achieving reasonable control and intake of small biomolecules.

One-step synthesis of red emission multifunctional carbon dots for label-free detection of berberine and curcumin and cell imaging

In this work, the red emission multifunctional carbon dots (R-CDs) were prepared via one-pot hydrothermal strategy of neutral red (NR) and ethylenediamine (EDA) for the label-free detection of berberine and curcumin, cell imaging, and fluorescent flexible film. The as-fabricated R-CDs not only possess good water dispersibility and excellent fluorescence stability, but also were successfully employed as a photoluminescent nanoprobe for label-free monitoring of berberine (BRH) and curcumin (Cur) based on dynamic quenching and internal filter effect (IFE), respectively. More importantly, as-proposed R-CDs displayed outstanding cellular permeability and lower cytotoxicity for cellular applications, which was consistent with the results of confocal fluorescence imaging and cell viability measurement of SMMC7721 cells. Thus, the multifunctional R-CDs may provide a rich tool library for biosensing and cellular imaging reagent applications. Interestingly, R-CDs were also used to manufacture R-CDs/PVA composites as fluorescent flexible films. To the best of our knowledge, this is the first demonstration of a label-free multifunctional fluorescent nanoprobe for berberine and curcumin based on red emission CDs.

A cationic quantum dot-based ratiometric fluorescent probe to visually detect berberine hydrochloride in human blood serums

Berberine hydrochloride (BH) is an isoquinoline alkaloid normally used as drug to treat diseases. Compared with the traditional detection methods, the carbon quantum dots (CQDs) have better selectivity, high sensitivity, easy operation, and is inexpensive which could be widely utilized as fluorescent nanoprobes to detect various compounds quantificationally. And ratiometric fluorescent sensors conspicuously increase sensitivity and precision detection and improve quantification. In this work, we use water-soluble and fluorescent cationic carbon dots cetylpyridinium chloride monohydrate (CPC)-CQDs to connect with pinacyanol chloride (PC) and sodium tetraphenylborate (ST) as the ratiometric fluorescent probe to detect BH. The ratiometric fluorescent probe has high sensitivity towards alkaloids and metal ions, photochemical stability (60 min), and pH stability (from 6.0 to 8.0), with the detection range from 0 to 200 μM, and limit was as low as 57.35 nM. The accuracy of the method was verified by spiked recovery experiment in different human blood serums which were drawn from healthy adult volunteers to explore the practicability. The recoveries were in the range 94.34 to 105.48% with relative standard deviations (RSD) of 0.80 to 2.92%. In addition, we could observe that the fluorescence was gradually darkened, and the color turned yellow to realize the visual detection. It is expected that this work would open up a new strategy for detecting BH in the environment and human blood serums.

Designing a two-stage colorimetric sensing strategy based on citrate reduced gold nanoparticles: Sequential detection of Sanguinarine (anticancer drug) and visual sensing of DNA

Distance dependent optical properties of colloidal gold nanoparticles offer designing of colorimetric sensing modalities for detection of a variety of analytes. Herein, we report a simple and facile colorimetric detection assay for an anti-cancer drug, Sanguinarine (SNG) and Calf Thymus DNA (Ct-DNA) based on citrate reduced gold nanoparticles (CI-Au NPs). The electrostatic interaction between SNG and CI-Au NPs induce aggregation of Au NPs accompanied with visible colour change of colloidal solution. The assay conditions like salt concentration, pH and reaction time had been adjusted to achieve highly sensitive and fast colorimetric response. Furthermore, the optimized CI-Au NPs/SNG sensing system is used for the detection of Ct-DNA based on the mechanism of anti-aggregation of CI-Au NPs. The simultaneous presence of SNG and Ct-DNA prevent aggregation of Au NPs owing to preferential formation of Ct-DNA-SNG intercalation complex and colour of the Au NPs solution tends to remain red, depending on the concentration of Ct-DNA in solution. The degree of aggregation and anti-aggregation of CI-Au NPs was monitored using Transmission electron microscopic (TEM) measurements and UV-Visible spectrophotometry by analysing the ratio of absorptions for aggregated and dispersed Au NPs. The intercalation mode of binding between SNG and Ct-DNA in CI-Au NPs/SNG sensing system was determined by Fluorescence spectral studies and UV-thermal melting studies. The absorption ratio (A₆₂₇/A₅₂₅) of Au NPs exhibited a linear correlation with SNG concentrations in the range from 0 to 0.9 μM with detection limit as 0.046 μM. This optical method can determine Ct-DNA as low as 0.36 μM and the calibration is linear for concentration range 0 to 5 μM. The proposed sensing strategy enables detection as well as quantification of SNG & Ct-DNA in real samples with satisfactory results and finds application in drug or DNA monitoring.

Design, characterization and catalytic evaluation of halometallic ionic liquid incorporated Nd2O3 nanoparticles ([smim][FeCl4]-@Nd2O3) for the synthesis of N-aryl indeno pyrrole derivatives

Silica modified imidazolium [smim] based halometallic ionic liquids, [smim][MCl₄] (M = Fe, Cu and Zn), were synthesized for the evaluation of acidic and catalytic properties. Among these ILs, [smim][FeCl₄]⁻ was used for the preparation of heterogeneous catalyst ([smim][FeCl₄]⁻@Nd₂O₃) by simple immobilization of IL on Nd₂O₃ nanoparticles. The structure of [smim][FeCl₄]⁻@Nd₂O₃ was established by various techniques including FTIR, Raman, UV-vis DRS, powder XRD, SEM/EDX, elemental mapping, TEM, TGA, EPR and XPS analyses. The stability of nano-catalyst, [smim][ FeCl₄]⁻@Nd₂O₃, was established with the help of zeta potential analysis which showed a value of −40.32 mV lying under the stability range. Potentiometric titration with n-butyl amine was used to evaluate the acidic properties of [smim][MCl₄] as well as [smim][FeCl₄]⁻@Nd₂O₃. The catalytic potential of the material was probed through the one pot synthesis of N-aryl indeno pyrrole derivatives. The results showed excellent performance of the material by producing a high yield (98%) of indeno pyrrole derivatives. A recyclability experiment revealed that the catalyst was efficient in up to five cycles with insignificant loss in catalytic activity. The evaluation of green metrics indicated the sustainability of the present protocol in terms of high atom economy and low E-factor.

Silica modified imidazolium based halometallic ionic liquids, [smim][MCl₄] and [smim][FeCl₄]⁻@Nd₂O₃ were synthesized for the evaluation of acidic and catalytic properties.

A fluorometric and colorimetric approach for the rapid detection of berberine hydrochloride based on an anionic polythiophene derivative

In this report, we develop a dual-output sensor with fluorometric and colorimetric responses, for the rapid and simple detection of berberine hydrochloride (BRH) in 100% aqueous solution based on an anionic polythiophene derivative, poly(2-(2-(4-methylthiophen-3-yloxy)-ethyl) malonic acid) (PTMA). The sensing performance and mechanism were carefully examined by absorption and emission spectra. It can be applied to quantitatively detect BRH in aqueous solution with a detection limit 0.27 μM. The appealing performance of the sensor was demonstrated to originate from the electrostatic and π-π interactions between PTMA and BRH, which promoted the conformational change and aggregation of the PTMA backbone. Moreover, this method allowed rapid detection of BRH in urine samples and BRH tablets with high accuracy.

Application of micro/nanomaterials in adsorption and sensing of active ingredients in traditional Chinese medicine

Traditional Chinese medicine (TCM) has been widely applied for the prevention and cure of various diseases for centuries. Ingredient with pharmacological activity is the key to the application of TCM. Hence, it is of significance to separate and detect active ingredients in TCM effectively. Micro/nanomaterial is the promising candidate for adsorption and sensing due to its unique physical and chemical properties. For years, many efforts have been made to develop functional micro/nanomaterials to realize the effective adsorption or sensing of bioactive compounds in TCM. In this review, we discussed recent progresses in the application of various functional micro/nanomaterials for adsorption or detection (electrochemical detection, fluorescent detection, and colorimetric detection) of active ingredients. Based on the kind of matrix materials, micro/nano-adsorbents or sensors can be classified into following categories: metal-based micro/nanomaterials, porous materials, carbon-based materials, graphene/graphite-liked micro/nanomaterials and hybrid micro/nanomaterials.

A highly fluorescent lanthanide metal-organic framework as dual-mode visual sensor for berberine hydrochloride and tetracycline

A microscale highly fluorescent Eu metal-organic framework (Eu-MOF) was synthesized with terephthalic acid and 1H-1,2,4-triazole-3,5-diamine by one-pot hydrothermal method. And it was characterized by scanning electron microscope, Fourier transform infrared spectroscopy, powder X-ray diffraction, fluorescence spectroscopy, thermogravimetric analysis, and energy dispersive X-ray mapping. The prepared Eu-MOF has high quantum yield of 30.99%, excellent water dispersibility, good fluorescence stability, and favorable thermal stability. Based on the distinctly different fluorescence responses of different emission, the prepared Eu-MOF was used as dual-mode visual sensor for the sensitive detection of berberine hydrochloride and tetracycline. The limits of detection are 78 nM and 17 nM, respectively. The sensing mechanism was also discussed. Moreover, a filter paper sensor has been designed for sensing tetracycline with a notable fluorescence color change from blue to red. The prepared Eu-MOF is promising to be developed as a multi-mode luminescent sensor for visual detection in biochemical analysis. Graphical abstract Illustration of the synthesis of Eu-MOF and its sensing applications for berberine hydrochloride and tetracycline.

Size-tunable Au@Ag nanoparticles for colorimetric and SERS dual-mode sensing of palmatine in traditional Chinese medicine

Palmatine is a protoberberine alkaloid separated from several plants and application as an anti-inflammatory and antibacterial agent in the therapy of gastrointestinal and genitourinary disorder. Thus, the fast quantification of palmatine is important in clinic medical assays. Herein, we report simple, fast and sensitive colorimetric visualization and surface-enhanced Raman spectroscopy (SERS) dual-mode detection of palmatine basing on bimetallic size tunable silver shell capped gold nanoparticles (Au@Ag NPs). Interesting, the best signals output for dual-mode sensing of palmatine were both 5 nm Ag shell thickness of Au@Ag NPs. Meanwhile, we found that the addition of NaHSO₄ significantly improves the aggregating sensitivity of Au@Ag NPs to trace palmatine. Upon exposure to 0.1 μM level palmatine, NaHSO₄-optimized Au@Ag NPs solution exhibits a highly sensitive color change from orange to green and rapid aggregation kinetics within the initial 5 min, which can directly be seen with the naked eye and monitored by UV-vis absorbance spectra. In addition, we measured palmatine by SERS with the excellent enhancement effect of Au@Ag NPs for further increase the sensitivity and selectivity. More importantly, other protoberberine alkaloids do not interfere with this dual-mode sensor due to the different interaction force between Au@Ag NPs and these alkaloids, and the applicability of the sensor is well demonstrated in real samples with satisfactory results. This provide a fast and simple assay for the rapid detection of palmatine in traditional Chinese medicine, the limit of detection (LOD) is 0.13 μM by the naked eye and 0.10 μM by UV-vis spectroscopy. Therefore, the size-tunable of NaHSO₄-optimized Au@Ag NPs can be used not only as a naked-eye sensor of palmatine, but also as a highly selective SERS probe.

An irreversible temperature indicator fabricated by citrate induced face-to-face assembly of silver triangular nanoplates

Assembly of anisotropic nanoparticles which need well controlling of assembly direction and spatial arrangement is more interesting than one-dimensional nanoparticles assemblies. As confirmed by observing of transmission electron microscopy images and analysis of plasmon resonance spectrum transformations, we found that silver triangular nanoplates (TNPs) without further modification could be face-to-face assembled by citrate. The face-to-face assembly of silver TNPs could be disassembled quickly by heating at a wide temperature range from 30 to 80 °C. In this process, an obvious localized surface plasmon resonance (LSPR) peak shift and a color change of solution from pink to purple could be observed. Moreover, the disassembled silver TNPs suspension is very stable that no significant peak shift of silver TNPs spectrum was observed in 8 h after removing of silver TNPs from a hearing area. Therefore, we fabricated an irreversible temperature indicator by measuring the relationship between the shift of LSPR peak and heating temperature, and by watching the color change of the solution in a certain environment. The irreversible temperature indicator has potential to develop a temperature label for revealing temperature history of a thermosensitive product which cannot expose to excessive temperature.

Determination of diclofenac sodium by resonance light scattering method using silver nanoparticles as probe

A sensitive, simple and novel method was developed to determine diclofenac sodium (DS) using silver nanoparticles (AgNPs) as probe by resonance light scattering (RLS) technique. It was found that DS could quench the RLS intensity of AgNPs. Moreover, the decrease in RLS intensity was linearly correlated to the concentration of DS over the range of 0.01-2.0μgmL^-1. DS can be measured in a short time (5min) without any complicated or time-consuming sample pretreatment process. Parameters that affect the RLS intensities such as pH, concentration of AgNPs, reaction time, electrolyte concentration, and coexisting substances were systematically investigated and optimized. The results showed that the method had a very good selectivity and could be used conveniently for the determination of DS. The limit of detection (LOD) was 2.85ngmL^-1 (3σ), and the relative standard deviation (RSD) was less than 3.6% (n=6). Possible mechanism for the RLS changes of AgNPs in the presence of DS was discussed and the method was successfully applied for the analysis of tablets and urine samples.

Surface plasmon resonance based selective and sensitive colorimetric determination of azithromycin using unmodified silver nanoparticles in pharmaceuticals and human plasma

In this article we report a novel method for colorimetric sensing and selective determination of a non-chromophoric drug-azithromycin, which lacks native absorbance in the UV-Visible region using unmodified silver nanoparticles (AgNPs). The citrate-capped AgNps dispersed in water afforded a bright yellow colour owing to the electrostatic repulsion between the particles due to the presence of negatively charged surface and showed surface plasmon resonance (SPR) band at 394nm. Addition of positively charged azithromycin at a concentration as low as 0.2μM induced rapid aggregation of AgNPs by neutralizing the negative charge on the particle surface. This phenomenon resulted in the colour change from bright yellow to purple which could be easily observed by the naked eye. This provided a simple platform for rapid determination of azithromycin based on colorimetric measurements. The factors affecting the colorimetric response like pH, volume of AgNPs suspension and incubation time were suitably optimized. The validated method was found to work efficiently in the established concentration range of 0.2-100.0μM using two different calibration models. The selectivity of the method was also evaluated by analysis of nanoparticles-aggregation response upon addition of several anions, cations and some commonly prescribed antibiotics. The method was successfully applied for the analysis of azithromycin in pharmaceuticals and spiked human plasma samples with good accuracy and precision. The simplicity, efficiency and cost-effectiveness of the method hold tremendous potential for the analysis of such non-chromophoric pharmaceuticals.

A simple, fast, and sensitive colorimetric assay for visual detection of berberine in human plasma by NaHSO4-optimized gold nanoparticles

Herein, we report a simple, fast and sensitive colorimetric visualization of berberine in human plasma using NaHSO₄-optimized gold nanoparticles. The LOD in human plasma is 0.24 μg mL⁻¹by the naked eye and 0.06 μg mL⁻¹by UV-vis spectroscopy.

Silver Nanoparticles Exhibit the Dose-Dependent Anti-Proliferative Effect against Human Squamous Carcinoma Cells Attenuated in the Presence of Berberine

The biological activity of nanosize silver particles towards oral epithelium-derived carcinoma seems to be still underinvestigated. We evaluated the influence of low doses of nanosize scale silver particles on the proliferation and viability of malignant oral epithelial keratinocytes in vitro, alone and in conjunction with the plant alkaloid berberine. Cells of human tongue squamous carcinoma SCC-25 (ATCC CRL-1628), cultivated with the mixture of Dulbecco's modified Eagle’s medium, were exposed to silver nanoparticles alone (AgNPs, concentrations from 0.31 to 10 μg/mL) and to a combination of AgNPs with berberine chloride (BER, 1/2 IC₅₀ concentration) during 24 h and 48 h. The cytotoxic activity of AgNPs with diameters of 10 nm ± 4 nm was measured by 3-(4,5-dimethyl-2-thiazyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Cell cycle analysis was performed by treating cells with propidium iodide followed by flow-activated cell sorting. RT-QPCR reaction was used to assess expression of anti-apoptotic proteins Bcl-2 and pro-apoptotic protein Bcl-2-associated X protein Bax genes expression. Monodisperse silver nanoparticles at a concentration of 10 μg/mL arrested SCC-25 cells cycle after 48 h at the G0/G1 phase in a dose- and time-dependent manner through disruption G0/G1 checkpoint, with increase of Bax/Bcl-2 ratio gene expression. AgNPs exhibit cytotoxic effects on SCC-25 malignant oral epithelial keratinocytes, which is diminished when combined with BER. The AgNPs concentration required to inhibit the growth of carcinoma cells by 50% (IC₅₀) after 48 h was estimated at 5.19 μg/mL. AgNPs combined with BER increased the expression of Bcl-2 while decreasing the ratio of Bax/Bcl-2 in SCC-25 cells. Silver particles at low doses therefore reduce the proliferation and viability of oral squamous cell carcinoma cells. SCC-25 cells are susceptible to damage from AgNPs-induced stress, which can be regulated by the natural alkaloid berberine, suggesting that nanoparticles may be potentially used in a chemoprevention/chemotherapy by augmentation of action of standard anti-cancer drugs.

Optical paper-based sensor for ascorbic acid quantification using silver nanoparticles

In this paper, we demonstrate for the first time the use of silver nanoparticles (AgNPs) for colorimetric ascorbic acid (AA) quantification in a paper-based sensor. This device is constituted by spot tests modified with AgNPs and silver ions bordered by a hydrophobic barrier which provides quantitative and fast analysis of AA. In addition, this device is employed as point-of-care monitoring using a unique drop of the sample. AgNPs paper-based sensor changed from light yellow to gray color after the addition of AA due to nanoparticle growth and clusters formation. The color intensities were altered as a function of AA concentration which were measured by either a scanner or a homemade portable transmittance colorimeter. Under the selected measurement conditions, results presented limit of detection which was comparable to analytical laboratory-based methodologies. In addition, the sensitivity of our sensor was comparable to the standard titration method when real samples were investigated.

Label-free silver nanoparticles for the naked eye detection of entecavir

A simple, rapid, field-portable colorimetric method for the detection of entecavir was proposed based on the color change caused by the aggregation of silver nanoparticles. Neutralization of the electrostatic repulsion from each silver nanoparticle resulted in the aggregation of AgNPs and a consequent color change of AgNPs from yellow to wine-red, which provided a platform for rapid and field-portable colorimetric detection of entecavir. The concentration of entecavir could be determined with naked eye or UV-vis spectrometer. The proposed method can be used to detect entecavir in human urine with a detection limit of 1.51μg mL(-1), within 25min by naked eye observation without the aid of any advanced instrument or complex pretreatment. Results from UV-vis spectra showed that the absorption ratio was linear with the concentration of entecavir in the range of 5.04-25.2μg mL(-1) and 1.01-5.04μg mL(-1) with linear coefficients of 0.9907 and 0.9955, respectively. The selectivity of AgNPs detection system for entecavir is excellent comparing with other ions and analytes. Due to its rapid, visible color changes, and excellent selectivity, the AgNPs synthesized in this study are suitable to be applied to on-site screening of entecavir in human urine.

Study on the interaction of β-cyclodextrin and berberine hydrochloride and its analytical application

The fluorescence enhancement of berberine hydrochloride (BBH) as a result of complex with β-cyclodextrin (β-CD) is investigated. The mechanism of the inclusion was studied and discussed by spectrofluoremetry and infrared spectrograms. The results showed that a 1∶1 (β-CD: BBH) complex was formed with an apparent association constant of 4.23×10² L/mol. Based on the enhancement of the fluorescent intensity of berberine hydrochloride, a new spectrofluorimetric method for the determination of BBH in the presence of β-CD was developed. The linear range was 1.00∼4.00 µg/mL with the detection limit of 5.54 ng/mL. The proposed method was successfully applied to the determination of BBH in tablets.

A highly sensitive dual-readout assay based on poly(A) and gold nanoparticles for palmatine hydrochloride

This report presents a highly sensitive, poly(A)-stabilized gold nanoparticle-based assay with dual readouts (resonance light scattering and colorimetric) for detecting palmatine hydrochloride (PaH) in real samples. The detection mechanism is based on the fact that palmatine hydrochloride has strong affinity to poly(A), which can stabilize gold nanoparticles at high ionic strength, and cause the aggregation of poly(A)-stabilized AuNPs, resulting in the enhanced resonance light scattering (RLS). At the same time, the color change of poly(A)-stabilized AuNPs solution is from red to blue via purple. Thus a highly sensitive RLS assay for PaH has been developed with a linear range of 0.023-2.5 μg/mL. The limit of detection (LOD, 3σ) is 2.3 ng/mL. In this work, the reaction mechanism of this system was investigated by scanning electron microscope (SEM), dark-field light scattering images (DLSI), dynamiclight scattering (DLS) and circular dichroism (CD). This proposed method was also applied successfully for the determination of PaH in pharmaceutical preparations and urine samples with RSD⩽4.0%. The results are in good agreement with those from the official method.

Highly selective and sensitive recognition of cobalt(II) ions directly in aqueous solution using carboxyl-functionalized CdS quantum dots as a naked eye colorimetric probe: applications to environmental analysis

Quantum dots (QDs) are usually used as fluorescent probe, and they are difficult to use in colorimetric detection. However, in this report carboxyl-functionalized CdS (COF-CdS) QDs were synthesized in aqueous solution for colorimetric detection following a classic method. On the basis of inducing the aggregation of COF-CdS QDs, a simple naked eye colorimetric method with high sensitivity and selectivity was developed for the sensing of Co(2+) ions in aqueous solutions. The Co(2+) ions induced COF-CdS QDs results in a marked enhancement of the UV-vis absorption spectra at 360 nm, and the process was accompanied by a visible color change from colorless to yellowish brown within 5 min, which proves a sensitive detection of Co(2+) ions. The sensing of Co(2+) ions can therefore be easily achieved by a UV-vis spectrophotometer or even by the naked eye. Under the optimized circumstances, this method yields excellent sensitivity (LOD = 0.23 μg mL(-1)) and selectivity toward Co(2+) ions. The calibration plot of (A - A(0)) at 360 nm against concentration of Co(2+) ions was linear over the range from 0.5 to 14 μg mL(-1) with a correlation coefficient of 0.9996. The accuracy and reliability of the method were further ascertained by recovery studies via standard addition method with percent recoveries in the range of 99.63-102.46%. The plausible mechanism for the color change reaction has also been discussed. Our attempt may provide a cost-effective, rapid, and simple solution for the inspection of Co(2+) ions in the presence of a complex matrix from environmental aqueous samples.

Application of silver nanoparticles and principal component-artificial neural network models for simultaneous determination of levodopa and benserazide hydrochloride by a kinetic spectrophotometric method

A multicomponent analysis method based on principal component analysis-artificial neural network model (PC-ANN) is proposed for the simultaneous determination of levodopa (LD) and benserazide hydrochloride (BH). The method is based on the reaction of levodopa and benserazide hydrochloride with silver nitrate as an oxidizing agent in the presence of PVP and formation of silver nanoparticles. The reaction monitored at analytical wavelength 440 nm related to surface plasmon resonance band of silver nanoparticles. Differences in the kinetic behavior of the levodopa and benserazide hydrochloride were exploited by using principal component analysis, an artificial neural network (PC-ANN) to resolve concentration of analytes in their mixture. After reducing the number of kinetic data using principal component analysis, an artificial neural network consisting of three layers of nodes was trained by applying a back-propagation learning rule. The optimized ANN allows the simultaneous determination of analytes in mixtures with relative standard errors of prediction in the region of 4.5 and 6.3 for levodopa and benserazide hydrochloride respectively. The results show that this method is an efficient method for prediction of these analytes.

Cooperative binding of bifunctionalized and click-synthesized silver nanoparticles for colorimetric co(2+) sensing

Bifunctionalized silver nanoparticles (triazole-carboxyl Ag NPs) were synthesized through a click reaction and have a cooperative effect on recognition of Co(2+), resulting in appreciable changes in color and absorption properties over other metal ions tested, including Fe(2+), Mn(2+), Hg(2+), Ni(2+), Cd(2+), Cu(2+), Zn(2+), Pb(2+), Li(+), Na(+), K(+), Cs(+). The functionalized silver nanoparticles became aggregated in solution in the present of Co(2+) through cooperative metal-ligand interaction. The colorimetric sensor allows a rapidly quantitive assay of Co(2+) down to the concentration of 7.0 x 10(-6) M. Moreover, the triazole-carboxyl AgNPs can be capable of evaluating the exceeding standard of Co(2+) in drinking water.