New Insights into Biomaterials and Coatings

Global life expectancy is constantly rising throughout the world. The World Health Organization (WHO) predicts that the world population aged 80 years or over will triple by 2050 to reach 426 million [1]. The constant aging of the population implies an increasing demand for new solutions in bone tissue engineering [2,3]. Innovative biomaterials and bioactive coatings are constantly in development to produce new bone implants with better properties and an extended lifetime [4,5,6,7,8,9,10,11]. Biocompatibility and bioactivity are two major requirements for bone implants. Biocompatibility is the ability of a material to be in contact with a biological system without producing any adverse effects [12,13,14]. The bioactivity of bone implants defines their ability to develop a direct, adherent, and strong bonding with bone tissue [15,16,17,18,19]. This Special Issue on “Advanced Biomaterials and Coatings” gathers recent research articles dealing with the latest developments on this research topic [20].

The article by Ciobanu et al. describes an innovative chromium-doped hydroxyapatite coating deposited by the dip coating technique [21]. The low temperature of this deposition process allows the coating to be enriched with an antibiotic such as amoxicillin. The biocompatibility of the obtained coatings was studied in contact with bone cells (MG63 cell line) and the antibacterial activity of the coating was evaluated against Pseudomonas aeruginosa.

In another article, Alhotan et al. used 3D printing to produce a synthetic polymer material (polyamide 12) commonly used to reconstruct bony defects. To make its surface bioactive, the 3D-printed polymer was coated with hydroxyapatite using light-cured resin cement [22].

In their work, Kang et al. synthesized a composite material made of a glass ionomer cement named calcium fluoroaluminosilicate (CFAS) filled with nano-hydroxyapatite (nHA). This composite material shows enhanced cytocompatibility and histocompatibility, which make it suitable for dental repairs [23].

Dhiflaoui et al. developed a composite coating made of titanium oxide (TiO₂) and hydroxyapatite (HaP) deposited by spray pyrolysis on titanium alloy (Ti6Al4V). They studied the morphology, chemical composition, phase composition, and mechanical properties of this innovative composite coating. They used electrochemical impedance spectroscopy to show that the coating improves the corrosion resistance of Ti6Al4V in simulated body fluids [24].

In their article, Golubchikov et al. used precipitation to produce a bioceramic powder from an aqueous solution containing calcium, sodium, phosphate, and silicate ions. Different annealing temperatures were studied to crystallize and densify the precipitated bioceramic powder. The biocompatible and bioresorbable phases in the powder make it suitable for the treatment of bone defects [25].

In another article, Ferroni et al. developed a composite material made of polycaprolactone (PCL) combined with reduced graphene oxide (rGO). This innovative material is biocompatible, supports the adhesion and differentiation of human mesenchymal stem cells (MSCs), and shows good antibacterial properties [26].

Handral et al. studied the cytotoxic and genotoxic effects of nanoparticles of zinc oxide (ZnO), titanium dioxide (TiO₂), and silicon dioxide (SiO₂). These experiments were conducted with pluripotent human embryonic stem cell-derived fibroblasts (hESC-Fib) [27].

The article by Drevet et al. comprehensively reviews the electrophoretic deposition of bioactive glass coatings on metallic bone implants. Bioactive glasses are highly reactive materials in physiological environments. They are commonly used to support bone repair. The mechanisms involved in the electrophoretic deposition process are thoroughly described [28].

The contribution by Robert B. Heimann is a detailed review of the literature dealing with the physicochemical and biomedical properties of plasma-sprayed hydroxylapatite (HAp) coatings. These bioactive coatings are routinely deposited on the surface of metallic endoprosthetic and dental root implants [29].

Sergey V. Dorozhkin reviews preparation methods, properties, and applications of calcium orthophosphate (CaPO₄)-based bioceramics used for biomedical applications such as artificial bone grafting, bone augmentation, maxillofacial reconstruction, spinal fusion, periodontal disease repair, and bone filling after tumor surgery. Prospective future applications of calcium orthophosphate are also comprehensively discussed [30].