Rapid Size-Focusing of Gold Nanoclusters with an Oxidant

Ceftriaxone-based Schiff base transition metal(II) complexes. Synthesis, characterization, bacterial toxicity, and DFT calculations. Enhanced antibacterial activity of a novel Zn(II) complex against S. aureus and E. coli

From the reaction of ceftriaxone 1 antibiotic with 2,6-diaminopyridine 2 a ceftriaxone-based Schiff base (H₂L,3) was obtained and its transition metal complexes were synthesized. Spectroscopic and physicochemical techniques, namely, UV-visible, FT-IR, ¹H NMR, EPR, mass spectrometry, molar conductance, magnetic susceptibility and density functional theory (DFT) calculations, together with elemental and thermal analyses, were used to find out the binding mode and composition of these complexes. The ceftriaxone-based Schiff base 3 behaves as a monoanionic tridentate N,N,O ligand. Spectral and magnetic data suggest an octahedral geometry for all complexes and the general formulae [M(HL)(OAc)(H₂O)₂] (M(II) = Mn²⁺4, Co²⁺5, Ni²⁺6, Cu²⁺7, Zn²⁺8), are proposed for them. All compounds were screened for antibacterial activity using both the agar disc diffusion method and the minimal inhibitory concentration (MIC). It was found that complex 8 exhibited the most promising bactericidal activity against S. aureus (MIC = 0.0048 μmol/ml) and E. coli (MIC = 0.0024 μmol/ml). It is more active than the free ligand 1 (MIC = 0.0560 μmol/ml for S. aureus and 0.0140 μmol/ml for E. coli). These MIC results were compared with those obtained using similar zinc(II) Schiff base complexes, and with the values obtained using ceftriaxone conjugated with silver and gold nanoparticles (NPs), using earlier published data. Synthesized metal complexes exhibited LC₅₀ values >1000 ppm indicating their nontoxicity against brine shrimp nauplii (Artemia Salina).

Rapid green synthesis of non-cytotoxic silver nanoparticles using aqueous extracts of 'Golden Delicious' apple pulp and cumin seeds with antibacterial and antioxidant activity

Abstract

A simple, facile and rapid microwave irradiated system was applied to synthesize silver nanoparticles using 'Golden Delicious' apple pulp (Malus domestica) and cumin (Cuminum cyminum) seed extracts. The phytosynthesized AgNPs were characterized by Ultraviolet–Visible Spectroscopy (UV–vis), Fourier transform infrared (FTIR), X-ray Diffraction (XRD) Transmission Electron Microscopy (TEM) and Zeta sizer analysis. In the study, the presence of face-centered cubic crystalline structured metallic silver in AgNPs from apple and cumin extracts and the monodisperse nature of AgNPs with the size distribution range of 5.46–20 nm and 1.84–20.57 nm were confirmed, respectively. This study established an efficient green synthesis approach that created so far, the smallest silver nanoparticles by using these two extracts. According to the results obtained, AgNPs synthesized using both extracts were non-toxic against L929 mouse fibroblast cells, while they were effective against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria with a greater effect on S. aureus. Moreover, AgNPs synthesized through cumin extract exhibited a higher ABTS scavenging ability (96.43 ± 0.78% at 160 μg/mL) in comparison to apple pulp extract mediated AgNPs, while both AgNPs showed lower activity for DPPH (27.84 ± 0.56% and 13.12 ± 0.32% from cumin seed and apple pulp extracts, respectively). In summary, our results suggest the green non-cytotoxic AgNPs synthesized in this study could be a promising template for further biological and clinical applications.

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