Ciprofloxacin Metal Complexes–Silica Nanoparticles: Characterization, Spectroscopic Study, DNA Interaction and Biological Activity

Ciprofloxacin (CIPH) was classified as one of the most effective quinolone antibiotics, which is commonly used to cure a wide range of infections resulting from Gram-negative and Gram-positive microorganisms. The complexes which formed due to the interaction of Ni(II), Zn(II), Cu(II), Gd(III) and Sm(III) with ciprofloxacin were characterized by CHN% analysis, conductivity, FTIR, electronic spectra, fluorescence measurements, and magnetic susceptibility, besides studying the complex–DNA interaction. Meanwhile, the molar conductance values (0.001 mol·L⁻¹ in DMSO) revealed the electrolytic behavior of the complexes and could be designated with the A⁻B⁺ formula. In addition, the geometry of the compounds was confirmed from the electronic transitions as well as the μ_eff values as octahedral for all complexes. The postulated formula could be generally assigned as [M(CIP)_a(CIPH)_b(H₂O)_c](NO₃)(H₂O)_n(C₂H₅OH)_m. Moreover, the interaction between metal complexes and DNA revealed that the Cu complex had the highest binding constant. Nanotechnology was applied to synthesized compounds using silica nanoparticles (SiNPs), which were prepared using a sol–gel process. The silica nanoparticles were chemically functionalized for binding the ligand and its metal complexes; this enables the as-prepared compounds to enhance their features as a drug delivery platform. Meanwhile, the antimicrobial activity was tested for the free complexes and SiNPs composites. Collectively, Sm complex gave the largest zone of inhibition, while the Cu(II)–SiNPs composite showed the strongest potential to reduce the bacterial activity. Furthermore, the fluorescence data of CIPH, ligand–metal mixture and the effect of silica nanoparticles on them were studied.