Polymeric wound dressings embedded with a binuclear Cu(II) complex: physicochemical characterization and proof of antibacterial activity

The aim of the study was to produce polymeric films as a semi-solid matrix for the loading of a binuclear Cu(II) complex made by maleate and phenanthroline ligands complexed with Cu 2+ ions ([Cu 2 (Phen) 2 (Mal) 2 ]⋅2H 2 O⋅CH 3 OH), and to characterize the structural, optical, thermal, and biological properties of the obtained crystal-loaded films. The films were prepared by adding the synthesized polycrystal at concentrations of 0.5, 1, and 2% (m/V) in a polymeric solution composed of two polysaccharides (0.6% of sodium alginate and 0.6% of sodium carboxymethyl cellulose). To characterize the properties of the obtained crystal-loaded films, we used X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) and ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy, and differential scanning calorimetry (DSC). The diffractograms indicated the presence of crystalline material on the surface of the films, with a color similar to that of the [Cu 2 (Phen) 2 (Mal) 2 ]⋅2H 2 O⋅CH 3 OH crystal. According to SEM analysis, the surface morphology was governed by the concentration of [Cu 2 (Phen) 2 (Mal) 2 ]⋅2H 2 O⋅CH 3 OH dispersed in the polymeric matrix. FT-IR spectra showed characteristic modes of the complex and polymers, whereas UV-Vis spectra revealed that the films exhibit electronic transitions related to the crystalline material and the polymeric matrix. Heat flow analysis showed that the films kept their structural integrity and very high vaporization enthalpy values attributed to the polymeric chains. In bacterial inhibition tests, crystalline films were observed to inhibit the growth of Gram-positive ( S. aureus and E. faecalis ) and Gram-negative ( E. coli and P. aeruginosa ) bacteria, which are frequently associated with wound infections.