Fabrication and characterization of copper(II)-chitosan complexes as antibiotic-free antibacterial biomaterial

Abstract

We produced and characterized copper(II)-chitosan complexes fabricated via in-situ precipitation as antibiotic-free antibacterial biomaterials. Copper was bound to chitosan from a dilute acetic acid solution of chitosan and copper(II) chloride exploiting the ability of the polysaccharide to chelate metal ions. The influence of copper(II) ions on the morphology, structure and hydrophobicity of the complexes was evaluated using scanning electron microscopy, energy-dispersive X-ray spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy and static contact-angle measurements. To assess the biological response to the materials, cell viability and antibacterial assays were performed using mouse embryonic fibroblasts and both Gram-positive and -negative bacteria. Combined analysis of cell and bacterial studies identified a threshold concentration at which the material shows outstanding antibacterial properties without significantly affecting fibroblast viability. This key outcome sets copper(II)- chitosan as a promising biomaterial and encourages further investigation on similar systems toward the development of new antibiotic-free antibacterial technologies.

Polycaprolactone Electrospun Fiber Mats Prepared Using Benign Solvents: Blending with Copper(II)‐Chitosan Increases the Secretion of Vascular Endothelial Growth Factor in a Bone Marrow Stromal Cell Line

“…However, this increase is somewhat expected and can be explained as an effect of the higher molecular weight of the polymers used in this work compared to previous reports 51. The addition of copper could also have a part in changing the viscosity of the system30; however, this hypothesis was not further investigated.…”

“…In this context, our previous studies30 showed how chitosan, a widespread linear polysaccharide of natural origin,31 can be used as an efficient carrier for copper thanks to an intrinsic ability to chelate metal ions 32. The copper ions are successfully incorporated in the polysaccharide matrix and their release can be finely tailored by suitably changing the formulation of the material, as reported in a previous publication 33.…”

“…Polycaprolactone (v‐PCL, nominal molecular weight = 80 kDa) was purchased from Ashland Specialties Ireland Ltd. (Dublin, Ireland) and was guaranteed negligible solvent contamination of the final product thanks to its proprietary manufacturing process. Copper(II)‐chitosan was prepared according to a previously published protocol30 modifying medium molecular weight chitosan ( M w = 190‐310 kDa, DDA = 75‐85%; Sigma‐Aldrich, Germany). The amount of copper loaded in the polysaccharide matrix corresponded to a saturation of 12% of the amino groups of chitosan (CuChi12) 30.…”

“…Copper(II)‐chitosan was prepared according to a previously published protocol30 modifying medium molecular weight chitosan ( M w = 190‐310 kDa, DDA = 75‐85%; Sigma‐Aldrich, Germany). The amount of copper loaded in the polysaccharide matrix corresponded to a saturation of 12% of the amino groups of chitosan (CuChi12) 30. Benign (low‐toxicity) solvents (glacial acetic acid >99.85% and formic acid >94.5%; VWR, Germany) were of high purity analytical level and used without further purification.…”

“…The copper ions are successfully incorporated in the polysaccharide matrix and their release can be finely tailored by suitably changing the formulation of the material, as reported in a previous publication 33. Copper(II)‐chitosan has been effectively used as antibiotic‐free antibacterial material against both Gram positive and negative bacteria without significant cytotoxicity against fibroblasts 30. Further on, we hypothesized that copper(II)‐chitosan could be used not only as an antibacterial, but also as a component of tissue engineering scaffolds.…”