A novel mesna-based electrochemical sensor embellished with silver nanoparticles for ultrasensitive analysis of modafinil.

Modafinil (MOD) is a CNS stimulant used for the treatment of narcolepsy, shift work sleep disorder, excessive daytime sleepiness, and post-COVID 19 neurological symptoms. In the literature, there is no report of square wave voltammetric (SWV) methods being used for the determination of MOD. This study describes, for the first time, the construction and evaluation of the analytical performance of a novel sensor for ultrasensitive SWV detection of MOD. The sensor was constructed by integration of silver nanoparticles (AgNPs) on Mesna (MSN) layers over a pencil graphite electrode (PGE) surface. The interface and morphological characteristics of the fabricated AgNPs@MSN/PGE sensor were investigated via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). This sensor was found to enhance the electro-oxidation of MOD. The combination of AgNPs@MSN/PGE with SWV enabled the determination of MOD in its bulk form and in pharmaceutical and biological matrices at the nanomolar scale (LOD = 28.59 nM) with excellent recoveries. This study represents the first report describing an electrochemical procedure for MOD detection in human plasma. The established SWV method was also validated, and the results were consistent with ICH criteria. Finally, the presented SWV procedure provides a facile, sensitive, rapid, and cost-effective approach compared to other existing methods.

Enzymatic depletion of l-Met using an engineered human enzyme as a novel therapeutic strategy for melanoma.

Many cancers, including melanoma, have a higher requirement for l-methionine in comparison with noncancerous cells. In this study, we show that administration of an engineered human methionine-γ-lyase (hMGL) significantly reduced the survival of both human and mouse melanoma cells in vitro. A multiomics approach was utilized to identify global changes in gene expression and in metabolite levels with hMGL treatment in melanoma cells. There was considerable overlap in the perturbed pathways identified in the two data sets. Common pathways were flagged for further investigation to understand their mechanistic importance. In this regard, hMGL treatment induced S and G2 phase cell cycle arrest, decreased nucleotide levels, and increased DNA double-strand breaks suggesting an important role for replication stress in the mechanism of hMGL effects on melanoma cells. Further, hMGL treatment resulted in increased cellular reactive oxygen species levels and increased apoptosis as well as uncharged transfer RNA pathway upregulation. Finally, treatment with hMGL significantly inhibited the growth of both mouse and human melanoma cells in orthotopic tumor models in vivo. Overall, the results of this study provide a strong rationale for further mechanistic evaluation and clinical development of hMGL for the treatment of melanoma skin cancer and other cancers.

Combined experimental/computational aspects for the molecular interaction of empagliflozin with bovine serum albumin: Quantification and application to human plasma.

Empagliflozin (EMP) is an oral antihyperglycemic agent for type 2 diabetic patients. The molecular binding of EMP to bovine serum albumin (BSA) was elucidated by a combined experimental/computational approach to fulfil the pharmacokinetics and pharmacodynamics gaps of the cited drug for further development. Fluorescence, synchronous, and three-dimensional fluorescence spectroscopy verified that EMP quenched BSA native fluorescence through a dual static/dynamic mechanism that was further supported by FÓ§rster resonance energy transfer and ultraviolet absorption spectroscopy. Fourier transform infrared spectroscopy revealed the conformational variations in BSA secondary structure induced by EMP. Thermodynamic properties of the BSA-EMP complex were also investigated, and the hydrophobic interactions' role in the binding process was demonstrated by the computed enthalpy (ΔH = 6.558 kJ mol-1 ) and entropy (ΔS = 69.333 J mol-1  K-1 ). Gibbs free energy (ΔG) values were negative at three distinct temperatures, illuminating the spontaneity of this interaction. In addition, molecular docking studies depicted the optimal fitting of EMP to BSA on Site I (sub-domain IIA) through three hydrogen bonds. Additionally, and based on the quenching effect of EMP on BSA fluorescence, this study suggests a simple validated spectrofluorometric method for the quantitation of the studied drug in bulk form and human plasma samples with reasonable recoveries (96.99-103.10%).

Development and validation of a novel evaporation setup-assisted TLC method with fluorescence detection for determination of flibanserin in pharmaceutical and biological samples.

A specific and sensitive thin layer chromatographic method coupled with fluorescence detection for determination of flibanserin (FLN) that treats woman hypoactive sexual desire disorder was developed. The proposed method depends on the enhancement of FLN native fluorescence intensity via the exposure of the developed TLC plate to concentrated hydrochloric acid vapors. Herein, an evaporation setup needed for HCl vapors exposure step was designed for the first time to ensure a uniform distribution of the vapors throughout the developed bands on the plate. Chloroform: methanol (9.5: 0.5, v/v) was the optimum mobile phase that gave a compact band (Rf= 0.44 ± 0.02) using TLC aluminium plates precoated with silica gel G 60F254 as a stationary phase. After exposure of the developed TLC plate to HCl vapors, the FLN bands emission intensities were measured after excitation at 275 nm. Conferring ICH guidelines, the linearity range was 20.0 - 1500.0 ng/band with a good linear relationship (r= 0.9998). Detection and quantitation limits were 5.12 and 15.50 ng/band, respectively. Also, the method was validated for accuracy, precision, robustness, specificity and selectivity. Statistical analysis verified the suitability of the proposed method for estimation of FLN in tablets and in human plasma with acceptable recoveries (98.07-101.45%).

Towards understanding of the interaction of certain carbapenems with protein via combined experimental and theoretical approach.

The interactions of the recent carbapenems; ertapenem (ERP) and meropenem (MRP); with serum albumin (SA) were closely investigated by a combined spectrofluorometric experimental and theoretical approach. The approach is based on the quenching of fluorescence intensity of bovine serum albumin (BSA) upon binding with different carbapenems. The quenching was observed at λem 333-340 nm after excitation at 280 nm. Mechanism of interaction was found to be static quenching through hydrophobic and H-bonding interactions and confirmed with molecular docking using MOE software. Binding constant, binding number were estimated for both MRP and ERP. Thermodynamic parameters including entropy change (ΔS), enthalpy change (ΔH) and free energy change (ΔG) were calculated at three different temperatures. Moreover, BSA configuration during binding was investigated via synchronous and 3D spectrofluorimetry. Förster resonance energy transfer calculated (FRET), integration interval (J) and distance (ro) between BSA and the studied drugs were calculated to confirm the static quenching.

Poly (bromocresol green) flakes-decorated pencil graphite electrode for selective electrochemical sensing applications and pharmacokinetic studies.

A square wave voltammetric method for selective determination of meropenem (MRP) and ertapenem (ERP) was developed using pencil graphite electrode modified with poly (bromocresol green) (PGE/PBCG). The modified electrode film was characterized by scanning electron microscopy and electro-chemical impedance spectroscopy. Under the optimized conditions, the prepared electrode has good linearity over concentration range 1.0-60.0 and 0.3.0-75.0 µM for MRP and ERP, respectively. The developed method was validated according to ICH guidelines. In addition, the diffusion co-efficients of MRP and ERP were estimated to be 1.24 × 10-6 and 9.09 × 10-6 cm2 s-1, respectively using chronoamperometric technique. The developed method was highly sensitive and selective for the determination of MRP or ERP in the presence of their corresponding open beta-lactam ring degradation products. Consequently, it was successfully utilized for in-vitro and in-vivo applications in spiked and real plasma samples of healthy rabbits for their pharmacokinetic studies. Furthermore, the method was applied for the assay of the available dosage forms of both drugs.