Application of surface nitrogen-doped graphene quantum dots in the sensing of ferric ions and glutathione: Spectroscopic investigations and DFT calculations

Developing a sensing platform that can quickly and accurately measure glutathione (GSH) is crucial for the early detection of various human diseases. GQDs have shown great potential in many technological and biological applications. This study focused on synthesizing nitrogen-doped GQDs (NGQDs) with stable blue fluorescence using a simple and easy hydrothermal method in one step. The bamboo fiber was used as the green source for this synthesis. The NGQDs had a tiny particle size of 4.7 nm and emitted light at 405 nm when excited. They displayed a remarkable quantum yield of 40.36 % and were effectively used as fluorescent probe to specifically detect Fe3+. The energy transfer mechanism led to the NGQDs' fluorescence being deactivated by Fe3+ ions (turn- "off"). However, with the addition of GSH to the system, the fluorescence intensity of NGQDs was reactivated (turn- "on"). Thus, a fluorescence turn "off-on" system was developed for the sensitive detection of Fe3+ and GSH. Using density functional theory (DFT), it was theoretically calculated that the surface of the fabricated NGQDs possess lone pairs of electrons on oxygens and doped nitrogen causing a photo-induced electron transfer (PET) process to occur. This PET process was suppressed previously owing to complex formation between oxygen atoms of modeled structure and ferric ions. The sensing platform displayed a sensitive response to Fe3+ in the 1-1000 μM range with LOD of 34 nM and GSH in the range of 1-50 μM, with a detection limit of 45 nM. Furthermore, the NGQDs exhibited high selectivity towards Fe3+ and GSH over other electrolytes and biomolecules. Additionally, the probe exhibited non-cytotoxicity and was practically applicable for the detection of GSH in HeLa cells.

A comprehensive exploration of tartrazine detection in food products: Leveraging fluorescence nanomaterials and electrochemical sensors: Recent progress and future trends

Azo dyes are widely used as food coloring agents because of their affordability and stability. Examples include brilliant blue, carmoisine, sunset yellow, allura red, and tartrazine (Tar), etc. Notably, Tar is often utilized in hazardous food goods. They are frequently flavoured and combined with food items, raising the likelihood and danger of exposure. Therefore, detecting Tar in food is crucial to prevent health risks. Fluorescence nanomaterials and electrochemical sensors, known for their high sensitivity, affordability, simplicity, and speed, have been widely adopted by researchers for Tar detection. This comprehensive paper delves into the detection of Tar in food products. It extensively covers the utilization of advanced carbon-based nanomaterials, including CDs, doped CDs, and functionalized CDs, for sensitive Tar detection. Additionally, the paper explores the application of electrochemical sensors. The paper concludes by addressing current challenges and prospects, emphasizing efforts to enhance sensitivity, and selectivity for improved food safety.

Quality-by-design based fabrication of febuxostat-loaded nanoemulsion: Statistical optimization, characterizations, permeability, and bioavailability studies

The present work deals with QbD-based development of FEB-loaded nanoemulsion (FEB-NE) in order to enhance bioavailability and permeability. In the beginning, the risk assessment was performed on different experimental variables using the Ishikawa diagram followed by FMEA study in order to find critical process parameter (CPP) and critical material attributes (CMAs). To build quality in nanoemulsion, the quality target product profiles (QTPP) and critical quality attributes (CQAs) were determined. The different batches of FEB-NE were produced by the microemulsification-probe sonication method. Effect of varying levels of independent variables such as oil concentration (X₁), S_mix concentration (X₃), and amplitude (X₃) on responses such as globule size (Y₁), zeta potential (Y₂), and entrapment efficiency (Y₃) were studied using Box-Behnken design (BDD). FEB-NE formulation was optimized using a graphical and numerical method. The optimized formulation concentrations and their responses (CQAs) were located as design space in an overlay plot. The spherical shapes of globules were visualized by surface morphology using AFM and TEM. In vitro dissolution study showed 93.32% drug release from the optimized FEB-NE formulation. The drug release mechanism followed by the formulation was the Higuchi-matrix kinetics with a regression coefficient of 0.9236 (R²). FEB-NE showed enhanced permeability using PAMPA (artificial non-cell membrane) and everted gut sac model method. The developed optimized FEB-NE exhibited the enhancement of bioavailability by 2.48 fold as compared to FEB-suspension using Wistar rats suggesting improvement of solubility of a lipophilic drug. The optimized batch remained stable for 90 days at 4 °C and 25 °C. Thus, QbD-based development of FEB-NE can be useful for a better perspective on a commercial scale.

Discovery and Anticancer Activity of Novel 1,3,4-Thiadiazole- and Aziridine-Based Indolin-2-ones via In Silico Design Followed by Supramolecular Green Synthesis

Three crucial anticancer scaffolds, namely indolin-2-one, 1,3,4-thiadiazole, and aziridine, are explored to synthesize virtually screened target molecules based on the c-KIT kinase protein. The stem cell factor receptor c-KIT was selected as target because most U.S. FDA-approved receptor tyrosine kinase inhibitors bearing the indolin-2-one scaffold profoundly inhibit c-KIT. Molecular hybrids of indolin-2-one with 1,3,4-thiadiazole (IIIa-m) and aziridine (VIa and VIc) were afforded through a modified Schiff base green synthesis using β-cyclodextrin-SO₃H in water as a recyclable proton-donor catalyst. A computational study found that indolin-2,3-dione forms a supramolecular inclusion complex with β-cyclodextrin-SO₃H through noncovalent interactions. A molecular docking study of all the synthesized compounds was executed on the c-KIT kinase domain, and most compounds displayed binding affinities similar to that of Sunitinib. On the basis of the pharmacokinetic significance of the aryl thioether linkage in small molecules, 1,3,4-thiadiazole hybrids (IIIa-m) were extended to a new series of 3-((5-(phenylthio)-1,3,4-thiadiazol-2-yl)imino)indolin-2-ones (IVa-m) via thioetherification using bis(triphenylphosphine)palladium(II)dichloride as the catalyst for C-S bond formation. Target compounds were tested against NCI-60 human cancer cell lines for a single-dose concentration. Among all three series of indolin-2-ones, the majority of compounds demonstrated broad-spectrum activity toward various cancer cell lines. Compounds IVc and VIc were further evaluated for a five-dose anticancer study. Compound IVc showed a potent activity of IC₅₀ = 1.47 μM against a panel of breast cancer cell lines, whereas compound VIc exhibited the highest inhibition for a panel of colon cancer cell lines at IC₅₀ = 1.40 μM. In silico ADME property descriptors of all the target molecules are in an acceptable range. Machine learning algorithms were used to examine the metabolites and phase I and II regioselectivities of compounds IVc and VIc, and the results suggested that these two compounds could be potential leads for the treatment of cancer.

Quality by design (QbD)-based fabrication of atazanavir-loaded nanostructured lipid carriers for lymph targeting: bioavailability enhancement using chylomicron flow block model and toxicity studies

Atazanavir (ATV) is widely used as anti-HIV agent having poor aqueous solubility needs to modulate novel drug delivery system to enhance therapeutic efficiency and safety. The main objective of the present work was to fabricate ATV-loaded nanostructured lipid carriers (NLCs) employing quality by design (QbD) approach to address the challenges of bioavailability and their safety after oral administration. Herein, the main objective was to identify the influencing variables for the production of quality products. Considering this objective, quality target product profile (QTPP) was assigned and a systematic risk assessment study was performed to identify the critical material attributes (CMAs) and critical process parameter (CPP) having an influence on critical quality attributes (CQAs). Lipid concentrations, surfactant concentrations, and pressure of high-pressure homogenizer were identified as CMAs and CPP. ATV-NLCs were prepared by emulsification-high pressure homogenization method and further lyophilized to obtain solid-state NLCs. The effect of formulation variables (CMAs and CPP) on responses like particle size (Y₁), polydispersity index (Y₂), and zeta potential (Y₃) was observed by central composite rotatable design (CCRD). The data were statistically evaluated by ANOVA for confirmation of a significant level (p < 0.05). The optimal conditions of NLCs were obtained by generating design space and desirability value. The lyophilized ATV-NLCs were characterized by DSC, powder X-ray diffraction, and FT-IR analysis. The morphology of NLCs was revealed by TEM and FESEM. In vitro study suggested a sustained release pattern of drug (92.37 ± 1.03%) with a mechanism of Korsmeyer-Peppas model (r² = 0.925, and n = 0.63). In vivo evaluation in Wistar rats showed significantly higher (p < 0.001) plasma drug concentration of ATV-NLCs as compared to ATV-suspension using chylomicron flow block model. The relative bioavailability of ATV-NLCs was obtained to be 2.54 folds. Thus, a safe and promising drug targeting system was successfully developed to improve bioavailability and avoiding first-pass effect ensures to circumvent the acute-toxicity of liver.

Quantification and Validation of Stability-Indicating RP-HPLC Method for Efavirenz in Bulk and Tablet Dosage Form using Quality by Design (QbD): A Shifting Paradigm

The present study endeavors quality by design (QbD) assisted chromatographic method for the quantification of Efavirenz (ERZ) in bulk and tablet dosage form. Analytical QbD instigated with assignment of analytical target profile (ATP) and critical analytical attributes (CAAs). Risk assessment studies and factor screening studies facilitate to identify the critical method parameters (CMPs). Optimization was performed by employing 32 full factorial design using identified CMPs i.e., flow rate (X1) and pH of buffer (X2) at three different levels and evaluating selected CAAs i.e., retention time (Y1) and peak area (Y2). The individual and interactive influence of CMPs on CAAs were tested by statistical data and response surface plots. Analysis of variance (ANOVA) confirmed that method parameters are significant (P < 0.05). Chromatographic separation was achieved using methanol, 10 mM ammonium acetate buffer (70:30 v/v), pH adjusted at 3.1 with 0.05% ortho-phosphoric acid as a mobile phase at flow rate 1.0 mL/min, and a Nucleosil C18 (4.6 mm I.D. × 250 mm, 5 μm) column with UV detection at 247 nm. The method validation and subsequent stresses degradation studies according to ICH guidelines supported the method to be highly efficient for regular drug analysis and its degradation products. The proposed method was successfully demonstrated QbD based approach for the development of highly sensitive, reliable and suitable for routine analysis, and clinical applications.

Identification of potential Gly/NMDA receptor antagonists by cheminformatics approach: a combination of pharmacophore modelling, virtual screening and molecular docking studies

The Gly/NMDA receptor has become known as potential target for the management of neurodegenerative diseases. Discovery of Gly/NMDA antagonists has thus attracted much attention in recent years. In the present research, a cheminformatics approach has been used to determine structural requirements for Gly/NMDA antagonism and to identify potential antagonists. Here, 37 quinoxaline derivatives were selected to develop a significant pharmacophore model with good certainty. The selected model was validated by leave-one-out cross-validation, an external test set, decoy set and Y-randomization test. Applicability domain was verified by the standardization approach. The validated 3D-QSAR model was used to screen virtual hits from the ZINC database by pharmacophore mapping. Molecular docking was used for assessment of receptor-ligand binding modes and binding affinities. The GlideScore and molecular interactions with critical amino acids were considered as crucial features to identify final hits. Furthermore, hits were analysed for in silico pharmacokinetic parameters and Lipinski's rule of five, demonstrating their potential as drug-like candidates. The PubChem and SciFinder search tools were used to authenticate the novelty of leads retrieved. Finally, five different leads have been suggested as putative novel candidates for the exploration of potent Gly/NMDA receptor antagonists.

Development and Validation of HPTLC Method for Simultaneous Determination of Amlodipine Besylate and Metoprolol Succinate in Bulk and Tablets

A simple, selective, precise high-performance thin-layer chromatographic method for simultaneous determination of amlodipine besylate and metoprolol succinate in bulk and pharmaceutical combined dosage form was developed and validated. The method employed HPTLC aluminum plates precoated with silica gel 60F-254 (10×10) as the stationary phase. The solvent system consisted of toluene:ethyl acetate:methanol:triethylamine (4:1:1:0.4 v/v/v). The system was found to give a compact spot for amlodipine besylate (R(f) = 0.39±0.02) and metoprolol succinate (R(f) = 0.59±0.02). Densitometric analysis of amlodipine besylate and metoprolol succinate was carried out in the absorbance mode at 254 nm. Linear regression analysis data for the calibration plots showed good linear relationship with r(2) = 0.9990±0.0013 with respect to peak area in the concentration range 400-1400 ng per spot for amlodipine besylate and r(2) = 0.9993±0.0013 with respect to peak area in the concentration range 3800-13300 ng per spot for metoprolol succinate. The method was validated for precision, recovery and robustness. The limits of detection and quantitation were 39.99 and 121.20 ng per spot for amlodipine besylate and 234.31 and 710.03 ng per spot for metoprolol succinate, respectively. Statistical analysis proved that the method is selective, precise and accurate for the estimation of amlodipine and metoprolol.

2D, 3D-QSAR and docking studies of 1,2,3-thiadiazole thioacetanilides analogues as potent HIV-1 non-nucleoside reverse transcriptase inhibitors

Background

The discovery of clinically relevant inhibitors of HIV-RT for antiviral therapy has proven to be a challenging task. To identify novel and potent HIV-RT inhibitors, the quantitative structure–activity relationship (QSAR) approach became very useful and largely widespread technique forligand-based drug design.

Methods

We perform the two- and three-dimensional (2D and 3D) QSAR studies of a series of 1,2,3-thiadiazole thioacetanilides analogues to elucidate the structural properties required for HIV-RT inhibitory activity.

Results

The 2D-QSAR studies were performed using multiple linear regression method, giving r² = 0.97 and q² = 0.94. The 3D-QSAR studies were performed using the stepwise variable selection k-nearest neighbor molecular field analysis approach; a leave-one-out cross-validated correlation coefficient q² = 0.89 and a non-cross-validated correlation coefficient r² = 0.97 were obtained. Docking analysis suggests that the new series have comparable binding affinity with the standard compounds.

Conclusions

This approach showed that hydrophobic and electrostatic effects dominantly determine binding affinities which will further useful for development of new NNRTIs.

QSAR, docking studies and pharmacophore identification of phenylmethyl phenoxy propyl amino propanoic acid derivatives as leukotriene A4 hydrolase inhibitors

The enzyme leukotriene A4 (LTA4) plays an important role as precursor of slow reactive substances as LTC4, LTD4, and LTE4. It is an attractive target for molecular modeling and QSAR study. Our effort is mainly focused on exploring the SAR for inhibitors of the LTA4 hydrolase through docking study, pharmacophore modeling and molecular descriptor study. The binding of these small molecules on LTA4 hydrolase enzyme was described by the models developed on 2D molecular descriptors, with good predictive power (39 compounds, 6 descriptors, r2 0.98, SEE 0.167, F-value 268.53, q2 0.90, r2 adj 0.97, P-value < 0.0001, SD of residuals 0.15). Docking studies were employed to presume the probable binding conformation of these analogues and exploring the SAR for the compounds. The novel pharmacophore represents the ligand features that are involved in interactions with the target protein, as well as the space around the ligand occupied by the protein. The efforts are aimed to discover the SAR for the inhibitors of LTA4 hydrolase through techniques of QSAR, docking and pharmacophore.