Spectrophotometric determination of L-cysteine by using polyvinylpyrrolidone-stabilized silver nanoparticles in the presence of barium ions

Synergistically Enhanced Oxidase-like Property of Core-Shell MOF Nanozymes by Decorating Au and Ag/AgCl Nanoparticles for l-Cysteine Colorimetric Sensing

Monitoring l-cysteine (l-Cys) is of importance for human health and food safety. Herein, we designed a novel strategy for bimetallic Au and Ag/AgCl anchoring on Ni-doped ZIF-67 to form core-shell nanocubes (Ni-ZIF-67/AuAg/AgCl) using the galvanic replacement processes. The unique properties of ZIF-67 nanocubes were conducive to generating strong synergistic catalytic effects with Au and Ag/AgCl, particularly when Ni-ZIF-67/AuAg/AgCl composites were employed as oxidase mimics for catalyzing the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). The Ni-ZIF-67/AuAg/AgCl composites displayed strong affinity toward TMB, displaying a lower Michaelis constant Km value of 0.25 mM and a higher maximum initial rate Vmax of 9 × 10-8 M s-1. By virtue of the nanozyme, the colorimetric sensor was constructed for l-Cys detection with a relatively low detection limit of 0.051 μM. The superior catalytic performance of the as-prepared Ni-ZIF-67/AuAg/AgCl composites can be ascribed to the core-shell structure, large specific surface area, and strong synergistic catalytic effects, which are beneficial for exposing more active sites and enhancing the conductivity to further boost their catalytic activity.

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.

Colorimetric and naked-eye detection of arsenic(iii) using a paper-based microfluidic device decorated with silver nanoparticles

Arsenic (As) as a metal ion has long-term toxicity and its presence in water poses a serious threat to the environment and human health. So, rapid and accurate recognition of traces of As is of particular importance in environmental and natural resources. In this study, a fast and sensitive colorimetric method was developed using silver nano prisms (Ag NPrs), cysteine-capped Ag NPrs, and methionine-capped Ag NPrs for accurate detection of arsenic-based on transforming the morphology of silver nanoparticles (AgNPs). The generated Ag atoms from the redox reaction of silver nitrate and As(iii) were deposited on the surface of Ag NPrs and their morphology changed to a circle. The morphological changes resulted in a change in the color of the nanoparticles from blue to purple, which was detectable by the naked eye. The rate of change was proportional to the concentration of arsenic. The changes were also confirmed using UV-Vis absorption spectra and showed a linear relationship between the change in adsorption peak and the concentration of arsenic in the range of 0.0005 to 1 ppm with a lower limit of quantification (LLOQ) of 0.0005 ppm. The proposed probes were successfully used to determine the amount of As(iii) in human urine samples. In addition, modified microfluidic substrates were fabricated with Ag NPrs, Cys-capped Ag NPrs, and methionine-capped Ag NPrs nanoparticles that are capable of arsenic detection in the long-time and can be used in the development of on-site As(iii) detection kits. In addition, silver nanowires (AgNWs) were used as a probe to detect arsenic, but good results were not obtained in human urine specimens and paper microfluidic platforms. In this study, for the first time, AgNPs were developed for optical colorimetric detection of arsenic using paper-based microfluidics. Ag NPrs performed best in both optical and colorimetric techniques. Therefore, they can be a promising option for the development of sensitive, inexpensive, and portable tools in the environmental and biomedical diagnosis of As(iii).

Citrate functionalized gold nanoparticles assisted micro extraction of L-cysteine in milk and water samples using Fourier transform infrared spectroscopy

This paper describes the sensing application of citrate functionalized gold nanoparticles (AuNPs) employing for the determination of L-cysteine in food and water samples. It is established with diffuse reflectance Fourier transform infrared (DRS-FTIR) spectroscopic analysis. The disappearance of the thiol (-SH) band in the FTIR spectra and the shift in the peaks of the amino group (NH₃⁺) and carboxylate group (-COO^-) indicated the Au-S interaction and the aggregation of the NPs. The signal intensity of L-cysteine was enhanced due to hot-spots formed by the aggregation of AuNPs producing the effective absorption of electromagnetic radiation in the IR region for molecular vibration. The relationship between AuNPs and L-cysteine was theoretically investigated by the Density Function Theory (DFT) based on LANL2DZ with the aid of the Gaussian 09 (C.01) software. Interaction between AuNPs and L-cysteine molecules resulted to a shift to higher wavelengths in the plasmon bands, further verified by transmission electron microscopes (TEM), which have indicated random aggregated particles. Further dynamic light scattering (DLS) measurements showed a relatively high degree of polydispersity confirming the aggregation of the particles. Under optimized conditions, the calibration curve showed a good linearity range from 20 to 150 μg mL^-1 with a correlation coefficient (R²) 0.990. The limit of detection and quantification were 1.04 and 3.44 μg mL^-1, respectively by DRS-FTIR. This modified AuNPs sample was used successfully in milk and water samples with adequate results to determine L-cysteine.

Colorimetric determination of L-cysteine in milk samples with surface functionalized silver nanoparticles

A simple, selective and sensitive method is proposed for determination of cysteine (Cys) in milk samples using ionic liquid functionalized silver nanoparticles (ILs-AgNPs) as a colorimetric probe. ILs-AgNPs was synthesized by simple reduction method using silver nitrate as a precursor and sodium borohydride as a reducing agent and functionalized with ILs to prevent particles from self-aggregation. The sensing mechanism has been dependent on the color change of ILs-AgNPs and red shift of absorption band from 395 nm to 560 nm in the visible region, which is found proportional to the concentration of target analyte in sample. ILs-AgNPs was characterized in absence and presence of Cys by UV-vis, Fourier transform-infrared (FTIR) spectroscopy, transmission electron microscope (TEM) and dynamic light scattering (DLS). The linear range was acquired in the range of 0-100 ng mL^-1, with correlation coefficient (R²) of 0.996 and limit of detection (LOD) of 4.0 nM. The binding mechanism and interactions between Cys and ILs-AgNPs was confirmed by calculating the binding constant and thermodynamic parameters such as enthalpy (∆H), entropy (∆S) and Gibb's free energy (∆G). The use of ILs-AgNPs exhibited high colorimetric selectivity for Cys in milk samples in presence of other amino acids. This proposed strategy possessed the advantages of simplicity and selectivity, hence is applied for analysis of Cys in milk samples.

Au–Ag core–shell composite nanoparticles as a selective and sensitive plasmonic chemical probe for l-cysteine detection in Lens culinaris (lentils)

The present work reported is a simple and selective method for the colorimetrical detection of l-cysteine in Lens culinaris (or lentils) using Au–Ag core–shell (Au core Ag shell) composite nanoparticles as a chemical probe.

The colorimetric and microfluidic paper-based detection of cysteine and homocysteine using 1,5-diphenylcarbazide-capped silver nanoparticles

We have prepared a microfluidic paper-based analytical device (μPAD) for the determination of cysteine and homocysteine based on 1,5-diphenylcarbazide-capped silver nanoparticles. The μPAD was developed to identify and quantify the levels of cysteine and homocysteine. The proposed μPAD enabled the detection of cysteine and homocysteine using a colorimetric reaction based on modified silver nanoparticles. The color of the modified AgNPs in the test zone immediately changed after the addition of cysteine and homocysteine. Based on this change, the quantification of these two amino acids was achieved using an RGB color model and ImageJ software. Under optimized conditions, the proposed device enabled the determination of cysteine in the 0.20–20.0 μM concentration range with a limit of detection (LOD) of 0.16 μM. In addition, the LOD of homocysteine was calculated to be 0.25 μM with a linear range of 0.50–20.0 μM. In this work, we focused on the use of the μPAD for the analysis of a series of human urine samples.

A simple and novel portable method for the quantitative measurement of cysteine and homocysteine in human urine samples is presented.

Colorimetric Sensor Based on β-Cyclodextrin-Functionalized Silver Nanoparticles for Zidovudine Sensitive Determination

Zidovudine (ZDV) is an antiviral drug against HIV that was approved by the FDA on March, 1987. It is a reverse transcriptase inhibitor. This type of drug stops the reproduction of DNA and decreases the amount of the virus in the patients' blood. Due to the ability of forming various molecular bonds, silver nanoparticles (AgNPs) are widely used for the detection of large range of agents, including drugs. In this study, we synthesized AgNP-modified β-cyclodextrin (β-CD) using green synthesis for the sensitive and selective zidovudine (ZDV) determination. Characterization of nanoparticles was done using different methods including infrared (IR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), and also, X-ray diffraction (XRD) patterns. The AgNP λ-max peak was at approximately 405 nm. In the presence of ZDV, yellow solution was turned to red color, and surface plasmon absorption band was dramatically centered at 560 nm. ZDV was determined in the range of 50-500 μM, and the detection limit value was obtained as 42 μM. The sensor was used to determine ZDV in tablets with good recovery.

Voltammetric Determination of Cysteine (2-amino-3-mercaptopropanoic acid, CySH) by Means of 4,4'-biphenol as a Homogeneous Mediator

In the present research, 4,4′-biphenol was used as a homogeneous mediator for determining cysteine (CySH) on a Glassy Carbon Electrode (GCE). To describe the electrochemical properties of 4,4′-biphenol and to examine its electrocatalytic impacts on cysteine oxidation, both Cyclic Voltammetry (CV) and Linear Sweep Voltammetry (LSV) were employed. Our findings revealed that 4,4′-biphenol could significantly accelerate the reactions related to electron transfer to CySH. Moreover, the diffusion coefficient of CySH and its reaction with the catalytic constant of 4,4′-diphenoquinone was estimated via chronoamperometry technique. The results showed that cysteine concentration range of 10-1000 μM led to linear increases in the oxidation peaks, thus to providing a detection of 0.99 μM with R² = 0.993. A Relative Standard Deviation (RSD) of 2.5% was achieved after performing 7 cysteine replicates (100 μM), and CySH was successfully determined in real serum samples through the proposed approach.

L-cysteine modified silver nanoparticles for selective and sensitive colorimetric detection of vitamin B1 in food and water samples

The use of L-cysteine modified silver nanoparticles (Cys-capped AgNPs) as a colorimetric probe for determination of vitamin B1 (thiamine) is described in the present work. This method is based on the measurement of red shift of localized surface plasmon resonance (LSPR) band of Cys-capped AgNPs in the region of 200–800 nm. The color of Cys-capped AgNPs was changed from yellow to colorless by the addition of vitamin B1. The mechanism for detection of vitamin B1 is based on the electrostatic interaction between positively charged vitamin B1, which causes the red shift of LSPR band from 390 nm to 580 nm. The interaction between Cys-capped AgNPs and vitamin B1 was theoretically explored by density function theory (DFT) using LANL2DZ basis sets with help of Gaussian 09 (C.01) program. The morphology, size distribution and optical properties of Cys-capped AgNPs were characterized by transmission electron microscope (TEM), UV-Visible spectrophotometry, Fourier transform infrared spectroscopy (FTIR) and dynamic light scattering (DLS) techniques. The method is linear in the range of 25–500 μg mL⁻¹ with correlation coefficient (R²) 0.992 and limit of detection of 7.0 μg mL⁻¹. The advantages of using Cys-capped AgNPs as a chemical sensor in colorimetry assay are being simple, low cost and selective for detection of vitamin B1 from food (peas, grapes and tomato) and environmental (river, sewage and pond) water samples.

Label-free colorimetric detection of serum cysteine using Ag-NP probes in the presence of Be2+ ions

Amino acids play a crucial role in a variety of significant metabolic processes and their homeostasis is essential for cell growth and survival.

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.

A selective colorimetric sensing strategy for cysteine based on an indicator-displacement mechanism

Rapid determination of cysteine in aqueous solution is important for the diagnosis and treatment of some diseases.

Determination of pyrophosphate and sulfate using polyhexamethylene guanidine hydrochloride-stabilized silver nanoparticles

Positively charged polyhexamethylene guanidine hydrochloride-stabilized silver nanoparticles (PHMG-AgNPs) were prepared and applied as a colorimetric probe for single-step determination of pyrophosphate and sulfate. The approach is based on the nanoparticles aggregation leading to change in their absorption spectra and color of the solution. Due to both electrostatic and steric stabilization these nanoparticles show decreased sensitivity relatively to many common anions, which allows for simple and rapid direct single-step determination of pyrophosphate and sulfate. Effects of different factors (time of interaction, pH, concentrations of anions and the nanoparticles) on aggregation of PHMG-AgNPs and analytical performance of the procedure were investigated. The method allows for the determination of pyrophosphate and sulfate in the range of 0.16-2μgmL^-1 and 20-80μgmL^-1 with RSD of 2-5%, respectively. The analysis can be performed using either spectrophotometry or naked-eye detection. Practical application of the method was shown by the example of pyrophosphate determination in baking powder sample.

Colorimetric detection of biothiols based on aggregation of chitosan-stabilized silver nanoparticles

We have described a simple and reliable colorimetric method for the sensing of biothiols such as cysteine, homocysteine, and glutathione in biological samples. The selective binding of chitosan capped silver nanoparticles to biothiols induced aggregation of the chitosan-Ag NPs. But the other amino acids that do not have thiol group cannot aggregate the chitosan-Ag NPs. Aggregation of chitosan-Ag NPs has been confirmed with UV-vis absorption spectra, zeta potential and transmission electron microscopy images. Under optimum conditions, good linear relationships existed between the absorption ratios (at A₅₀₀/A₄₁₅) and the concentrations of cysteine, homocysteine, and glutathione in the range of 0.1-10.0μM with detection limits of 15.0, 84.6 and 40.0nM, respectively. This probe was successfully applied to detect these biothiols in biological samples (urine and plasma).

A colorimetric sensor of cysteine based on self-assembly nanostructures of Fe3+-H2O2/Tetramethylbenzidine system with "On-Off" switching function

Many strategies have been explored for selectively and sensitively detecting cysteine in different samples. Here, a novel colorimetric sensor based on self-assembly nanostructures of Fe³⁺-H₂O₂/Tetramethylbenzidine system with dual-level logic gate function and colorimetric determination of cysteine were firstly explored. The proposed Fe³⁺-H₂O₂-TMB system provides a sensitive optical signal due to the selectively reductive ability of cysteine to the oxidized TMB and thus could be successfully applied to the construction of instant on-site visual detection method with a paper based test strip for cysteine determination in a sample solution as well as for a dual-level logic gate fabrication.

Thermal and optical characterization of biologically synthesized ZnS nanoparticles synthesized from an endophytic fungus Aspergillus flavus: A colorimetric probe in metal detection

Nanostructured semiconductor materials are of great importance for several technological applications due to their optical and thermal properties. The design and fabrication of metal sulfide nanoparticles with tunable properties for advanced applications have drawn a great deal of attention in the field of nanotechnology. ZnS is a potential II-IV group material which is used in hetero-junction solar cells, light emitting diodes, optoelectronic devices, electro luminescent devices and photovoltaic cells. Due to their multiple applications, there is a need to elucidate their thermal and optical properties. In the present study, thermal and optical properties of biologically synthesized ZnS nanoparticles are determined in detail with Thermal Gravimetric Analysis (TGA), Derivative Thermogravimetric Analysis (DTG), Differential Scanning Calorimeter (DSC), Diffuse Reflectance Spectroscopy (DRS), Photoluminescence (PL) and Raman spectroscopy. The results reveal that ZnS NPs exhibit a very strong quantum confinement with a significant increase in their optical band gap energy. These biologically synthesized ZnS NPs contain protein residues that can selectively bind with metal ions in aqueous solutions and can exhibit an aggregation-induced color change. This phenomenon is utilized to quantitatively measure the metal concentrations of Cu²⁺ and Mn²⁺ in this study. Further the stability of nanoparticles for the metal sensing process is accessed by UV-Vis spectrometer, zeta potential and cyclic voltammeter. The selectivity and sensitivity of ZnS NPs indicate its potential use as a sensor for metal detection in the ecosystem.