This study investigates a biomimetic method of deposition of bioactive calcium phosphate (CaP) layers on zirconium oxide substrates (ZrO2). The substrates contained polymer nanoparticles of poly(L-lactide-co-glycolide) (PLGA) obtained using the double emulsion method with solvent evaporation. Three antibiotics were encapsulated within the nanoparticles: bacitracin, gentamicin sulphate, and hydrophobic gentamicin, prepared with the use of the ion pairing method. Nanoparticles were immobilized on the substrates using the drop casting or the co‑deposition method. The microstructure of the layers and the distribution of the nanoparticles were assessed by scanning electron microscopy. The nanoparticles size and their zeta potential were measured using the dynamic light scattering method. The release of drugs over time was examined and the antibacterial properties were evaluated in contact with Staphylococcus aureus bacteria using the spectrophotometric method and the Kirby-Bauer test. The results show that the layer deposition method is effective and allows to obtain homogenous bioactive coatings. Nanoparticles were agglomerated on the surface or homogenously distributed in the CaP coating, depending on the process used to immobilize them. The drug release profile and antibacterial properties can also be modified by changing the process – the drop casting method allows to obtain a coating with a stronger antimicrobial effect and faster drug release.
Nanoparticles obtained by the double emulsion method with solvent evaporation have the required size to be immobilized between the CaP crystallites. Additionally, the encapsulation of drugs decreased the zeta potential of the nanoparticles, which was caused by the interaction of the drug and the polymer. Nanoparticles loaded with bacitracin showed weak antibacterial properties, as the growth inhibition zone in the Kirby-Bauer test was barely visible. Two other types of nanoparticles exhibited good antibacterial properties, exceptionally strong for those loaded with hydrophobic gentamicin.