Synthesis of cyclodextrin functionalized photoluminescent metal nanoclusters for chemoselective Fe3+ ion detection in aqueous medium and its applications of paper sensors and cell imaging

Four three-dimensional rare earth metal - organic framework fluorescent sensor for efficient detection of gentamicin sulfate and Fe3

Excessive use of gentamicin sulfate can cause severe nephrotoxicity and ototoxicity, abnormal levels of Fe3+ intake can also cause serious damage to body. Therefore, establishing a fast and accurate detection method for the above-mentioned substances is of great significance. However, traditional detection methods such as high-performance liquid chromatography still have certain problems such as high cost and complex operation. Fluorescent MOFs are favored by analysts due to their high specific surface area, high porosity, adjustable pore size, and good stability. In this paper, we have synthesized four rare earth MOFs based on the pyridinecarboxylic acid ligand (H2L), which are [Eu(L)1/2H2O]n, [Gd(L)1/2H2O]n, [Sm(L)1/2H2O]n, [Y(L)3/2H2O·DMF]n. The structures of four MOFs were confirmed by single crystal X-ray diffraction, which proved that MOF-1, MOF-2 and MOF-3 were isostructural, and all the four MOFs were three-dimensional structures. In the fluorescence test, gentamicin sulfate and Fe3+ can cause significant fluorescence quenching of MOF-1 and MOF-4 respectively, and show good selectivity and anti-interference performance, as well as low detection limit and wide detection range. This work may provide a possibility for the detection of gentamicin sulfate and iron ions in complex environments.

Oxadiazole Schiff Base as Fe3+ Ion Chemosensor: "Turn-off" Fluorescent, Biological and Computational Studies

Compound, (E)-5-(4-((thiophen-2-ylmethylene)amino)phenyl)-1,3,4-oxadiazole-2-thiol (3) was synthesized via condensation reaction of 5-(4-aminophenyl)-1,3,4-oxadiazole-2-thiol with thiophene-2-carbaldehyde in ethanol. For the synthesis and structural confirmation the FT-IR, ¹H, ¹³C-NMR, UV-visible spectroscopy, and mass spectrometry were carried out. The long-term stability of the probe (3) was validated by the experimental as well as theoretical studies. The sensing behaviour of the compound 3 was monitored with various metal ions (Ca²⁺, Cr³⁺, Fe³⁺, Co²⁺, Mg²⁺, Na⁺, Ni²⁺, K⁺) using UV- Vis. and fluorescence spectroscopy techniques by various methods (effect of pH and density functional theory) which showing the most potent sensing behaviour with iron. Job's plot analysis confirmed the binding stoichiometry ratio 1:1 of Fe³⁺ ion and compound 3. The limit of detection (LOD), the limit of quantification (LOQ), and association constant (K_a) were calculated as 0.113 µM, 0.375 µM, and 5.226 × 10⁵ respectively. The sensing behavior was further confirmed through spectroscopic techniques (FT-IR and ¹H-NMR) and DFT calculations. The intercalative mode of binding of oxadiazole derivative 3 with Ct-DNA was supported through UV-Vis spectroscopy, fluorescence spectroscopy, viscosity, cyclic voltammetry, and circular dichroism measurements. The binding constant, Gibb's free energy, and stern-volmer constant were find out as 1.24 × 10⁵, -29.057 kJ/mol, and 1.82 × 10⁵ respectively. The cleavage activity of pBR322 plasmid DNA was also observed at 3 × 10^-5 M concentration of compound 3. The computational binding score through molecular docking study was obtained as -7.4 kcal/mol. Additionally, the antifungal activity for compound 3 was also screened using broth dilution and disc diffusion method against C. albicans strain. The synthesized compound 3 showed good potential scavenging antioxidant activity against DPPH and H₂O₂ free radicals.

Multiple heteroatom dopant carbon dots as a novel photoluminescent probe for the sensitive detection of Cu2+ and Fe3+ ions in living cells and environmental sample analysis

Heavy metal ion pollution harms human health and the environment and continues to worsen. Here, we report the synthesis of boron (B), phosphorous (P), nitrogen (N), and sulfur (S) co-doped carbon dots (BP/NS-CDs) by a one-step facile hydrothermal process. The optimum synthetic parameters are of 180 °C temperature, 12 h reaction time and 15% of PBA mass. The as-synthesized BP/NS-CDs exhibits excellent water solubility, strong green photoluminescence (PL) at 510 nm, and a high quantum yield of 22.4%. Moreover, BP/NS-CDs presented high monodispersity (7.2 ± 0.45 nm), excitation-dependent emission, PL stability over large pH, and high ionic strength. FTIR, XRD, and XPS are used to confirm the successful B and P doping of BP/NS-CDs. BP/NS-CD photoluminescent probes are selectively quenched by Cu²⁺ and Fe³⁺ ions but showed no response to the presence of other metal cations. The PL emission of BP/NS-CDs exhibited a good linear correlation with Cu²⁺ and Fe³⁺ concentrations with detection limits of 0.18 μM and 0.27 μM for Cu²⁺ and Fe³⁺, respectively. Furthermore, the HCT116 survival cells kept at 99.4 ± 1.3% and cell imaging capability, when the BP/NS-CDs concentration is up to 300 μg/mL by MTT assay. The proposed sensor is potential applications for the detection of Cu²⁺ and Fe³⁺ ions in environmental water samples.

Cyclodextrin Inclusion Complexes and Their Application in Food Safety Analysis: Recent Developments and Future Prospects

Food safety issues are a major threat to public health and have attracted much attention. Therefore, exploring accurate, efficient, sensitive, and economical detection methods is necessary to ensure consumers' health. In this regard, cyclodextrins (CDs) are promising candidates because they are nontoxic and noncaloric. The main body of CDs is a ring structure with hydrophobic cavity and hydrophilic exterior wall. Due to the above characteristics, CDs can encapsulate small guest molecules into their cavities, enhance their stability, avoid agglomeration and oxidation, and, at the same time, interact through hydrogen bonding and electrostatic interactions. Additionally, they can selectively capture the target molecules to be detected and improve the sensitivity of food detection. This review highlights recent advances in CD inclusion technology in food safety analysis, covering various applications from small molecule and heavy metal sensing to amino acid and microbial sensing. Finally, challenges and prospects for CDs and their derivatives are presented. The current review can provide a reference and guidance for current research on CDs in the food industry and may inspire breakthroughs in this field.

SARS-CoV-2 main protease (3CLpro) interaction with acyclovir antiviral drug/methyl-β-cyclodextrin complex: Physiochemical characterization and molecular docking

During the current outbreak of the novel coronavirus disease 2019 (COVID-19), researchers have examined several antiviral drugs with the potential to inhibit the proliferation of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The antiviral drug acyclovir (AVR), which is used to treat COVID-19, in complex with methyl-β-cyclodextrin (Mβ-CD) was examined in the solution and solid phases. UV-visible and fluorescence spectroscopic analyses confirmed that the guest (AVR) was included inside the host (Mβ-CD) cavity. A solid inclusion complex of AVR was prepared by co-precipitation, physical mixing, kneading, and bath sonication methods at a 1:1 ratio of Mβ-CD:AVR. The prepared Mβ-CD:AVR inclusion complex was characterized using Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) analysis. Phase solubility studies indicated the Mβ-CD:AVR inclusion complex exhibited a higher stability constant and linear enhancement in AVR solubility with increasing Mβ-CD concentrations. In silico analysis of the Mβ-CD/AVR inclusion complex confirmed that AVR drugs show potential as inhibitors of SARS-CoV-2 3C-like protease (3CL^pro) receptors. Results obtained using the PatchDock and FireDock servers indicated that the most favorable docking ligand was Mβ-CD:AVR, which interacted with SARS-CoV-2 (3CL^Pro) protease inhibitors with high geometric shape complementarity scores (2522 and 5872) and atomic contact energy (-313.77 and -214.70 kcal mol^-1). Our results suggest that the Mβ-CD/AVR inclusion complex inhibits the main protease of SARS-CoV-2, although further wet-lab experiments are needed to verify these findings.

Fabrication and Characterization of Ag Nanoparticle-embedded κ-Carrageenan-Sodium Alginate Nanocomposite Hydrogels with Potential Antibacterial and Cytotoxic Activities

Hydrogel nanocomposites are attracting increasing attention in field of biology owing to their unique properties. The present work focuses on the fabrication and characterization of novel hydrogel nanocomposite systems in which silver nanoparticles (AgNPs) are embedded in a carrageenan (κ-CGN)-sodium alginate (SA) hydrogel. The performance of the prepared κ-CGN-SA hydrogel and κ-CGN-SA/AgNPs hydrogel nanocomposite was determined by UV-visible spectroscopy, FTIR, XRD, SEM, EDX spectrum, EDX mapping, and TEM analysis. Surface plasmon resonance at 428 nm confirmed the presence of AgNPs in the κ-CGN-SA hydrogel. The results indicate that AgNPs with an average diameter of 30 nm were uniformly dispersed in the κ-CGN-SA hydrogel matrix. The amount of Ag⁺ ion release kinetic from the κ-CGN-SA hydrogel matrix is very low, showing that AgNPs were well trapped within the κ-CGN-SA/AgNPs hydrogel nanocomposite. The high antibacterial activity of the κ-CGN-SA/AgNPs hydrogel nanocomposite was found to be 89.6 ± 1.4% and 91.4 ± 2.3% against the gram-positive S. aureus and the gram-negative E. coli, respectively. Moreover, the κ-CGN-SA/AgNPs hydrogel nanocomposite showed good biocompatibility by the MTT test. The novel κ-CGN-SA/AgNPs hydrogel nanocomposite low cytotoxicity and antibacterial efficacy is proposed as a potential candidate for biomedical applications.