Eco-friendly fabricated multibioactive Ca(II)-antibiotic coordination framework coating on zinc towards improved bone tissue regeneration

Zinc is a biodegradable candidate material for bone regeneration; however, concomitant implant-related infection and rejection require new solutions to raise the biomedical potential of zinc. Functionalization towards localized drug administration with bioactive frameworks can be a solution. It is herein reported for the first time an eco-friendly approach for coating zinc with multibioactive antibiotic coordination frameworks (ACF). ACF1, a new 1D framework with deprotonated nalidixic and salicylic acids, obtained by mechanochemistry, results from the coordination of Ca(II) centers to the organic acids anions. To maximize ACF1 loading and cells’ adhesion, the surface area was increased by creating a porous 3D Zn layer. A coverage of ∼70% of the surface with ACF1, achieved by electrophoretic deposition in an aqueous solution, preserved the desired Zn degradation as |Z| in the order of 103 Ω.cm2 is attained for both bare and coated samples in physiological conditions. The bioactivities of the ACF1 powder are a strong antibacterial activity against Escherichia coli (MIC of 1.95 µg/mL) and weaker against Staphylococcus aureus (MIC of 250 µg/mL), while osteoblasts’ cytocompatibility is achieved for concentration ranging between 10 and 100 μg/mL. In its coating form, the degradation of Zn coated with ACF1 results in nalidixic acid release, which may convey antibacterial activity to the implant. The osteoinduction observe over this new biomaterial relates to the precipitation of an apatite layer built from the Ca(II) of ACF1. The work described herein, where unexplored eco-friendly approaches were used, presents a new trend for the design of multibioactive coatings on bioresorbable metallic materials.