SERS study of classical and newly β-lactams-metal complexation based on in situ laser-induced coral reefs-like silver photomicroclusters: In vitro study of antibacterial activity

The influence of metal complexation of two polar β-lactam antibiotics was investigated using surface enhanced Raman spectroscopy (SERS) technique. SERS method was applied to track the structural changes and the degradation behaviour of the studied compounds upon Zinc (II) ions-complexation. In situ laser-induced coral reefs-like photomicroclusters have been utilized as a SERS platform. The produced coral reefs-like photomicroclusters were characterized using scanning electron microscopy (SEM) and transmission electron microscope (TEM). The antibacterial efficiency of the antibiotics was investigated and compared before and after metal complexation using two techniques; agar well diffusion and growth curve. To provide a detailed elucidation of the complexation reaction, mass fragmentation of metal- antibiotics complexes was investigated using liquid chromatography/mass spectrometric (LC/MS) technique. It was found that metal complexation of classical β-lactam antibiotic (Ticarcillin) promoted the rate of its degradation, leading to a decrease of the antibacterial efficiency. On the other side, the antibacterial activity of the newly developed β-lactam (Faropenem) has been greatly enhanced via metal-complexation reaction.

"Off/On" Fluorescent Probe based on Aggregation-Induced Quenching of ZnO-Quantum dots for Determination of Ara-C: Pharmacokinetic Applications, Adsorption Kinetics & Green Profile Assessment

Herein, a turn "Off/On" fluorescence probe based on ZnO quantum dots (ZnO-QDs) has been proposed and successfully utilized for the determination of Ara-C (cytarabine) using ceric ions (Ce4+) as quencher and ethylenediamine (ED) as a linker. The probe is based initially on the quenching effect of Ce4+ ions on the strong native fluorescence of ZnO-QDs forming the Turn Off system (Ce@ZnO-QDs) that believed to occur due to the aggregation-induced quenching (AIQ) mechanism. The second step is the addition of Ara-C in the presence of ethylenediamine (ED) that encourages the formation of Ara-C/ED/Ce4+ as well as the release of the free ZnO-QDs, leading to the recovery of the fluorescence intensity. The developed sensing platform shows a linear response towards Ara-C over the range of 10 to 1000 ng mL-1 giving a limit of detection (LOD) and limit of quantitation (LOQ) of 1.22 ng mL-1 and 3.70 ng mL-1, respectively. A dispersive magnetic solid phase micro-extraction (dMSPE) method was developed and optimized for the extraction of Ara-C in spiked human plasma using thiol-modified magnetite nanoparticles (S-MNPs). The proposed platform exhibits good sensitivity toward Ara-C in the presence of different interfering substances. Excellent recoveries are obtained after spiking different concentrations of Ara-C into rabbit plasma samples. The validated experimental parameters have been successfully applied to monitor the pharmacokinetic profile of Ara-C in rabbit plasma. A detailed adsorption kinetics study has been carried out to provide a deep insight into the adsorption behavior of Ara-C on the thiol-doped-magnetite nanoparticles. The greenness assessment of the proposed method was achieved and compared with other reported methods using two tools of greenness; the green analytical procedure index (GAPI) and the analytical greenness calculator AGREE.

NiFe-based Prussian blue analogue nanopolygons hybridized with functionalized glyoxal polymer as a voltammetric platform for the determination of amisulpride in biological samples

A novel voltammetric platform based on pencil graphite electrode (PGE) modification has been proposed, containing bimetallic (NiFe) Prussian blue analogue nanopolygons decorated with electro-polymerized glyoxal polymer nanocomposites (p-DPG NCs@NiFe PBA Ns/PGE). Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and square wave voltammetry (SWV) were utilized to investigate the electrochemical performance of the proposed sensor. The analytical response of p-DPG NCs@NiFe PBA Ns/PGE was evaluated through the quantity of amisulpride (AMS), one of the most common antipsychotic drugs. Under the optimized experimental and instrumental conditions, the method showed linearity over the range from 0.5 to 15 × 10-8 mol L-1 with a good correlation coefficient (R = 0.9995) and a low detection limit (LOD) reached, 1.5 nmol L-1, with excellent relative standard deviation for human plasma and urine samples. The interference effect of some potentially interfering substances was negligible, and the sensing platform demonstrated an outstanding reproducibility, stability, and reusability. As a first trial, the proposed electrode aimed to shed light on the AMS oxidation mechanism, where the oxidation mechanism was monitored and elucidated using the FTIR technique. It was also found that the prepared p-DPG NCs@NiFe PBA Ns/PGE platform had promising applications for the simultaneous determination of AMS in the presence of some co-administered COVID-19 drugs, which could be attributed to the large active surface area, and high conductivity of bimetallic nanopolygons.

Novel sublingual tablets of Atorvastatin calcium/Trimetazidine hydrochloride combination; HPTLC quantification, in vitro formulation and characterization

Background

Ischemic heart disorders and accumulation of lipids in blood vessels could contribute to angina pectoris. Therefore, the aim of this study was to formulate sublingual tablets containing a novel combination of Atorvastatin calcium (ATOR) and Trimetazidine HCl (TMZ) for efficient treatment of coronary heart disorders.

Methods

The dissolution rate of water-insoluble ATOR was enhanced via complexation with sulfobutyl ether-β-cyclodextrin (SBE-β-CD) and addition of soluplus as a polymeric solubilizer excipient. The solubilized ATOR and TMZ were compressed into a sublingual tablets by direct compression technique and evaluated for their tableting characteristics. In addition, a new validated method based on High Performance Thin Layer Chromatography (HPTLC) was developed for simultaneous determination of both drugs in pure forms and sublingual tablets.

Results

The developed HPTLC method showed LODs of 0.056 and 0.013 μg/band and LOQs of 0.17, 0.040 μg/band for TMZ and ATOR, respectively and proved to be linear, accurate, precise and robust. The optimum formulation containing mixture of superdisintegrants; Ac-Di-Sol and crospovidone (4.8% w/w, each) showed the shortest disintegration time (65 s) and enhanced release profiles of both drugs.

Conclusions

The prepared sublingual tablets combining ATOR and TMZ will be a promising dosage form for coronary heart disease patients with an instant action and improved patient compliance.

Enhancement effect of reduced graphene oxide and silver nanocomposite supported on poly brilliant blue platform for ultra-trace voltammetric analysis of rosuvastatin in tablets and human plasma

The enhancement effect of reduced graphene oxide (rGO) combined with silver nanocomposite supported on poly brilliant blue (PBB) platform was investigated for ultra-trace analysis of rosuvastatin (RS). Herein, in situ electrochemical deposition of the silver nanoparticles (AgNPs) and rGO hybrid was performed on the surface of the polymerized brilliant blue (PBB) platform. The developed (AgNPs–rGO/PBB) electrode showed an enhanced catalytic activity toward the oxidation of RS. The modified electrodes AgNPs–rGO/PBB and AgNPs/PBB required an overpotential of 0.68 and 1.06 V to achieve a current density of 10 mA cm⁻², and their corresponding Tafel slopes were calculated to be 70 and 105 mV dec⁻¹, respectively. Further, rGO and silver nanocomposites properties were characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV), square wave voltammetry (SWV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). Additionally, the formation of GO and AgNPs–rGO was confirmed by Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR). Under the optimized conditions, the electrochemical sensor showed a remarkable response for quantitation of RS over a wide range of concentrations 5 × 10⁻⁹ to 5 × 10⁻⁷ mol L⁻¹ (r = 0.9988), with a limit of detection 2.17 × 10⁻⁹ mol L⁻¹. The electrochemical performance of the studied electrode showed high reproducibility and suitability for tablets and human plasma.

In situ electrodeposition of AgNPs–rGO was carried out on PBB using CV, SWV methods were used for characterization, and the Tafel slope and overpotential were calculated.

A comparative study of different electrodeposited NiCo2O4 microspheres anchored on a reduced graphene oxide platform: electrochemical sensor for anti-depressant drug venlafaxine

Two different fabrication methods were performed and compared for preparation of binary metallic oxide microstructures supported on a reduced graphene oxide (rGO) modified graphite electrode. Nickel–Cobalt oxide microspheres (NiCo₂O₄ MSs) were prepared by two different deposition methods: wet chemical and in situ-electrical deposited methods. Different characterization methods were conducted, including cyclic voltammetry (CV), scanning emission microscopy (SEM), electrochemical impedance spectroscopy (EIS) and Raman spectroscopy. The deposition methods of NiCo₂O₄ MSs were found to affect the electrochemical behavior of the modified electrodes towards the oxidation of venlafaxine (VEN), an anti-depressant drug. The fabricated electrode showed linearity over the range 5–500 nmol L⁻¹ and an excellent sensitivity with a limit of detection (LOD) and limit of quantitation (LOQ) of 3.4 and 10.3 nmol L⁻¹, respectively. It was revealed that the wet-NiCo₂O₄@rGO modified electrode prepared by the wet chemical method showed an improved electrochemical behavior for determination of VEN in pharmaceuticals and human plasma with high recovery results in the range of 96.7–98.6% and 96.0–100.7%, respectively without any interference from the co-existing components.

Different electrodeposited NiCo₂O₄ microspheres supported on a reduced graphene oxide platform for electrochemical sensing of venlafaxine.

Structure elucidation and degradation kinetic study of Ofloxacin using surface enhanced Raman spectroscopy

A simple, fast and sensitive surface enhanced Raman spectroscopy (SERS) method for quantitative determination of fluoroquinolone antibiotic Ofloxacin (OFX) is presented. Also the stability behavior of OFX was investigated by monitoring the SERS spectra of OFX after various degradation processes. Acidic, basic and oxidative force degradation processes were applied at different time intervals. The forced degradation conditions were conducted and followed using SERS method utilizing silver nanoparticles (Ag NPs) as a SERS substrate. The Ag NPs colloids were prepared by reduction of silver nitrate using polyethyelene glycol (PEG) as a reducing and stabilizing agent. Validation tests were done in accordance with International Conference on Harmonization (ICH) guidelines. The calibration curve with a correlation coefficient (R=0.9992) was constructed as a relationship between the concentration range of OFX (100-500ng/ml) and SERS intensity at 1394cm^-1 band. LOD and LOQ values were calculated and found to be 23.5ng/ml and 72.6ng/ml, respectively. The developed method was applied successfully for quantitation of OFX in different pharmaceutical dosage forms. Kinetic parameters were calculated including rate constant of the degradation of the studied antibiotic.

A Localized Surface Plasmon Resonance Sensing Method for Simultaneous Determination of Atenolol and Amiloride in Pharmaceutical Dosage Forms and Urine Samples

This contribution describes a simple, fast, and sensitive application of localized surface plasmon resonance effect of silver nanoparticles for simultaneous determination of antihypertensive drugs' mixture atenolol and amiloride in both pharmaceutical dosage forms and in biological samples (urine). Silver nanoparticles were prepared by chemical reduction of silver nitrate using hydroxylamine HCL in an alkaline medium. Application of silver-hydroxylamine nanoparticles (SH NPs) provides many advantages including reproducibility, sensitivity, and cost effective way of analyte determination. Amiloride has four amino groups which act as attachment points on the surface of silver nanoparticles resulting in a synergistic effect on the absorption intensity of atenolol, leading to increase the sensitivity of the determination of both compounds. This method shows excellent advantages comparing with the previously reported methods, including accuracy, precision, and selectivity. The linear range of atenolol is 1 × 10^-5-1 × 10^-4 mol·L^-1 and of amiloride is 1 × 10^-6-1 × 10^-5 mol·L^-1. The limit of detection (LOD) values of atenolol and amiloride are 0.89 × 10^-5 and 0.42 × 10^-6 mol·L^-1, respectively.

Antibacterial effect of various shapes of silver nanoparticles monitored by SERS

A comparative evaluation of antimicrobial effect of synthesized silver nanoparticles (AgNPs) of different shapes using different methods was performed. Spherical, triangular and hexagonal AgNPs with an average size of 40 nm were chemically prepared and characterized by transmission electron microscope (TEM) and UV-visible spectroscopy. The antimicrobial effect of these different AgNPs against the gram negative bacterium Escherichia coli (E. coli) was studied by surface enhanced Raman spectroscopy (SERS), the evaluation of growth curves and inhibition zones. SERS proved to be sensitive to monitor the changes that occurred in the bacterial cells upon interaction with AgNPs, which qualitatively compared well with the data provided by the reference methods. However, as SERS is already sensitive to initial changes in the chemistry of bacteria due to the antibacterial effect of the AgNPs, fast and detailed information is provided by SERS as opposed to the classical reference methods based on the evaluation of growth curves and inhibition zones. The results of this work also demonstrate that hexagonal AgNPs display the highest antibacterial effect when compared to other NPs shapes, with triangular AgNPs exhibiting no antibacterial effect under the adopted conditions.