Drug delivery systems based on calcium phosphate (CaP) coatings have been recently recognized as beneficial drug delivery systems in complex cases of bone diseases for admission of drugs in the localized area, simultaneously inducing osteoinduction because of the bioavailable Ca and P ions. However, micro-arc oxidation (MAO) deposition of CaP does not allow for the formation of a coating with sufficient interconnected porosity for drug delivery purposes. Here, we report on the method to deposit CaP-based coatings using a new hybrid ultrasound-assisted MAO (UMAOH) method for deposition of coatings for drug delivery that could carry various types of drugs, such as cytostatic, antibacterial, or immunomodulatory compositions. Application of UMAOH resulted in coatings with an Ra roughness equal to 3.5 µm, a thickness of 50–55 µm, and a combination of high values of internal and surface porosity, 39 and 28%, respectively. The coating is represented by the monetite phase that is distributed in the matrix of amorphous CaP. Optimal conditions of coating deposition have been determined and used for drug delivery by impregnation with Vancomycin, 5-Fluorouracil, and Interferon-α-2b. Cytotoxicity and antimicrobial activity of the manufactured drug-carrying coatings have been studied using the three different cell lines and methicillin-resistant S. aureus.

In addressing the challenge of enhancing orthopedic implants, 3D porous calcium phosphate (CaP) coatings on titanium (Ti) substrates modified with poly(lactic-co-glycolic acid) (PLGA) were proposed. CaP coatings on Ti were deposited using the ultrasonic-assisted micro-arc oxidation (UMAO) method, followed by modification with PLGA through a dip coating process at concentrations of 5%, 8%, and 10%. The addition of PLGA significantly improved adhesive–cohesive strength according to the scratch test, while PLGA to CaP adhesion was found to be not less than 8.1 ± 2.2 MPa according to the peel test. Tensile testing showed a typical fracture of CaP coatings and mechanisms of brittle fracture. Corrosion resistance, assessed via gravimetric and electrochemical methods in 0.9% NaCl and PBS solutions, revealed PLGA’s substantial reduction in corrosion rates, with the corrosion current decreasing by two orders of magnitude even for the 5% PLGA/CaP/Ti sample. Also, the PLGA layer significantly enhanced the impedance modulus by two orders of magnitude, indicating a robust barrier against corrosion at all PLGA concentrations. Higher PLGA concentrations offered even greater corrosion resistance and improved mechanical properties. This research underscores the potential of using CaP- and PLGA-modified coatings to extend the life and functionality of orthopedic implants, addressing a significant challenge in biomedical engineering.

The primary benefit of metamaterials is that their physical and mechanical properties can be controlled by changing the structure geometry. Numerical analysis tools used in this work offer a few advantages over full-scale testing, consisting of an automated process, as well as lower material and time costs. The investigation is concerned with the behavior of unit cells of the tetrachiral mechanical metamaterial under uniaxial compression. The base material is studied within an elastic mathematical model. The influence of topological defects of the unit cell on the metamaterial properties is studied for the first time. Defects, and especially topological defects, play a decisive role in the mechanical behavior of materials and structures. The unit cell without defects reveals orthotropy of properties. Torsion of a cell with a chiral structure is induced by the rotation of all tetrachiral walls, and therefore it is sensitive to the introduction of defects. There are cases of increased torsion as well as of no compression–torsion coupling effect. In the latter case, the unit cell experiences only shear. The effective Young’s modulus is calculated to vary in the range from 23 to 57 MPa for unit cells of different topologies. With the successive introduction of defects in two walls, the studied characteristics increase, correlating with each other. A further increase in the number of defects affects the characteristics in different ways. The introduction of two more defects in the walls decreases torsion and increases Young’s modulus, after which both characteristics decrease. The introduction of topological defects in all walls of the unit cell leads to the orthotropic behavior of the cell with the opposite sign of torsion.

The study of the influence of applied external ultrasound (US) field with varied power of 35 or 100 W during the micro-arc oxidation (MAO) processing on the thickness growth, surface roughness, porosity, sizes of structural elements and structural-phase states of the calcium phosphate (CaP) coatings on the titanium surface was performed. It was shown that the US transmittance through the electrolyte for 10 min of MAO processing had led to the increase of the coating thickness from 50 to 60 µm, the surface roughness from 3 to 4.5 µm, and the cross-section porosity from 27 to 40%. However, under the action of external US there was a destruction of structural elements (spheres with pores) on the coating surface and a filling of pores’ spaces by fragments. That led to the decrease of the surface porosity from 30 to 12%. It was revealed by X-ray diffraction (XRD) that all types of the CaP coatings deposited under external US field and without it were in X-ray amorphous state. However, applied US field had led to the increase of the coating crystallinity with incorporation of CaHPO₄ and β-Ca₂P₂O₇ phases.

The studies of the effect of applied ultrasound (US) field with varied power of 35 W or 100 W during the micro-arc oxidation (MAO) process on the morphology, porous structure and adhesion strength of the calcium phosphate (CaP) coatings on the titanium surface have been performed. The transmittance of US field through the electrolyte during the MAO process led to the increase of the coating thickness from 50 to 60 µm, roughness from 3 to 4.5 µm and internal porosity from 27 to 41 %, and to the decrease of the surface porosity from 25 to 12 %, and adhesion strength from 23 to 19 MPa. In addition, the applied US field led to the change of the surface and structure morphology of the coatings. There was a local destruction of the structure elements (spheres and pores) and filling the pore spaces on the coating surface. The local macropores of 15-40 µm in sizes were formed in the boundary to substrate layer.