Selenium nanoparticles (Se NPs) were synthesized from Na₂SeO₃ using Foeniculum vulgare (fennel) seed extract as mild sustainable reductant, coated with chitosan (Ch), and loaded with Paclitaxel (PTX). The PTX release from the Se@Ch–PTX NPs and their cytotoxicity against MDA-MB-231 breast cancer cells was studied in view of an application as drug delivery platform. Thermogravimetric analysis (TGA) showed the thermal stability of the NPs up to 300 °C. UV–vis absorption and Fourier transform IR (FT-IR) spectroscopy allowed to trace surface species originating from the F. vulgare extract on the Se NPs, while the surface of the Se@Ch–PTX NPs is characterized from Ch and PTX functionalities. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed approximate spherical shaped NPs with sizes ranging from 10 to 40 nm. Zeta potential measurements showed a clear distinction between the −39 mV found the Se NPs and +57 mV for the Ch–PTX coated NPs. The NPs showed good biocompatibility with red blood cells (RBCs) in hemolytic activity assays, exhibiting no hemolytic effects at concentrations ranging from 50 to 400 µg/mL. In vitro release studies showed a sustained and pH-responsive release pattern with a maximum release of about 80% within 22 h for Se@Ch–PTX at pH = 3.5. The Se@Ch–PTX NPs showed high antiproliferative activity against MDA-MB-231 cells with an IC₅₀ value of 12.3 µg/mL compared to about 36 for PTX and 52 µg/mL for the Se NPs. The reactive oxygen species (ROS) activity as studied through DPPH scavenging showed higher values for the Se@Ch–PTX NPs compared to the Se NP.

A novel heterocyclic Schiff base ligand, {2,2′-((4-chloro-1,3-phenylene)-bis(oxy))bis-(N′-((E)-(1 H-benzo[1-3]-triazole-1-yl)methylene)acetohydrazide)}, was synthesized and coordinated with Co(II) and Zn(II) chlorides to yield two metal complexes. The ligand and complexes were analyzed using FT-IR, ¹H and ¹³C NMR, UV-visible spectroscopy, and mass spectrometry, which provided spectral shifts typical of coordination involving the imine nitrogen and amide carbonyl groups. DFT calculations (B3LYP/LanL2DZ) showed that complexation decreased the energy gap between HOMO and LUMO from 4.26 eV (free ligand) to 3.18 eV and 2.66 eV for Zn(II) and Co(II) complexes, respectively, showing increased chemical reactivity. Similarly, the electrophilicity index increased to 33.81 eV for the Zn complex and 40.97 eV for the Co complex, indicating increased electron-accepting ability and potential biological activity. Thermal decomposition of Zn and Co complexes yielded ZnO NPs (mean crystallite size 35.6 nm) and Co ₃ O ₄ NPs (33.8 nm), as evidenced by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Antibacterial activity against Gram-positive bacteria ( Staphylococcus aureus , Bacillus subtilis ) and Gram-negative bacteria ( Escherichia coli , Pseudomonas aeruginosa ) was found to show that ZnO NPs had the largest inhibition zones (up to 28 mm), followed by metal complexes [Zn(L)]Cl₂ and [Co(L)]Cl ₂ , whereas the free ligand had very poor activity (only inhibition zones of 11–13 mm).