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.

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Porous composite scaffolds with decoupled ion release of copper and strontium were fabricated and characterized: a reproducible and cost-effective approach to obtain constructs with tailored release profiles and promising biological properties.

Biodegradable and bioresorbable polyesters (BBPEs) are a widespread class of aliphatic polymers with a plethora of applications in the medical field. Some reports speculate that these polymers have intrinsic antibacterial activity as a consequence of their acidic degradation by-products. The release of organic acids as a result of the hydrolytic degradation of BBPEs in vivo and the resulting pH drop could be an effective inhibitor of the growth of pathogens in the local environment adjacent to BBPE-based devices. However, there is no clear and conclusive evidence in the literature concerning the antibacterial activity of BBPE to support or refute this hypothesis. In this communication we address this point through an assessment of the antibacterial properties of six well-established commercially available BBPEs. Agar diffusion assays and optical density measurements at 600 nm were performed on all the polymer samples to characterize the growth of bacteria and any potential inhibition over an incubation period of 24 h. The results indicated that BBPEs do not possess an intrinsic and immediate antibacterial activity, which is consistent with the clear mismatch between the time-scales for bacterial growth and the rate of degradation of the polyesters.Graphical abstract

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Inducing the formation of new blood vessels (angiogenesis) is an essential requirement for successful tissue engineering. Approaches have been proposed to enhance angiogenesis using growth factors and other biomolecules; however, this approaches present drawbacks in terms of high cost and patient safety. Copper is known to effectively regulate angiogenesis and can offer a more cost‐effective alternative than the direct use of growth factors. With this study, a strategy to incorporate copper in electrospun fibrous scaffolds with pro‐angiogenic properties is presented. Polycaprolactone (PCL) and copper(II)‐chitosan are electrospun using benign solvents. The morphological and physicochemical properties of the fiber mats are investigated through scanning electron microscopy (SEM), static contact angle measurements, energy dispersive X‐ray, and Fourier‐transform infrared spectroscopies. Scaffold stability in phosphate buffered saline at 37 °C is monitored over 1 week. A bone marrow stromal cell line (ST‐2) is cultured for 7 days and its behavior is evaluated using SEM, fluorescence microscopy and a tetrazolium salt‐based colorimetric assay. Results confirm that PCL/copper(II)‐chitosan is suitable for electrospinning. The fiber mats are biocompatible and favor cell colonization and infiltration. Most notably, the angiogenic potential of PCL/copper(II)‐chitosan blends is confirmed by a three‐fold increase in VEGF secretion by ST‐2 cells in the presence of copper(II)‐chitosan.