Hydroxyapatite (HA), the principal mineral of bone tissue, can be fabricated as an artificial calcium phosphate (CaP) ceramic and potentially used as bioceramic material for bone defect treatment. Nevertheless, the production method (including the applied sintering temperature) of synthetic hydroxyapatite directly affects its basic properties, such as its microstructure, mechanical parameters, bioabsorbability, and osteoconductivity, and in turn influences its biomedical potential as an implantable biomaterial. The wide application of HA in regenerative medicine makes it necessary to explain the validity of the selection of the sintering temperature. The main emphasis of this article is on the description and summarization of the key features of HA depending on the applied sintering temperature during the synthesis process. The review is mainly focused on the dependence between the HA sintering temperature and its microstructural features, mechanical properties, biodegradability/bioabsorbability, bioactivity, and biocompatibility.

Infections that occur during wound healing involve the most frequent complications in the field of wound care which not only inhibit the whole process but also lead to non-healing wound formation. The diversity of the skin microbiota and the wound microenvironment can favor the occurrence of skin infections, contributing to an increased level of morbidity and even mortality. As a consequence, immediate effective treatment is required to prevent such pathological conditions. Antimicrobial agents loaded into wound dressings have turned out to be a great option to reduce wound colonization and improve the healing process. In this review paper, the influence of bacterial infections on the wound-healing phases and promising modifications of dressing materials for accelerated healing of infected wounds are discussed. The review paper mainly focuses on the novel findings on the use of antibiotics, nanoparticles, cationic organic agents, and plant-derived natural compounds (essential oils and their components, polyphenols, and curcumin) to develop antimicrobial wound dressings. The review article was prepared on the basis of scientific contributions retrieved from the PubMed database (supported with Google Scholar searching) over the last 5 years.

Over the years, essential oils (EOs) and their compounds have gained growing interest due to their anti-inflammatory, antimicrobial, antioxidant, and immunomodulatory properties. The aim of this study was to evaluate the effect of eight commercially available EO-derived compounds ((R)-(+)-limonene, (S)-(−)-limonene, sabinene, carvacrol, thymol, alpha-pinene (α-pinene), beta-pinene (β-pinene), and cinnamaldehyde) on the bone formation process in vitro to select the most promising natural agents that could potentially be used in the prevention or treatment of osteoporosis. Within this study, evaluation of cytotoxicity, cell proliferation, and osteogenic differentiation was performed with the use of mouse primary calvarial preosteoblasts (MC3T3-E1). Moreover, extracellular matrix (ECM) mineralization was determined using MC3T3-E1 cells and dog adipose tissue-derived mesenchymal stem cells (ADSCs). The two highest non-toxic concentrations of each of the compounds were selected and used for testing other activities. The conducted study showed that cinnamaldehyde, thymol, and (R)-(+)-limonene significantly stimulated cell proliferation. In the case of cinnamaldehyde, the doubling time (DT) for MC3T3-E1 cells was significantly shortened to approx. 27 h compared to the control cells (DT = 38 h). In turn, cinnamaldehyde, carvacrol, (R)-(+)-limonene, (S)-(−)-limonene, sabinene, and α-pinene exhibited positive effects on either the synthesis of bone ECM or/and mineral deposition in ECM of the cells. Based on the conducted research, it can be assumed that cinnamaldehyde and (R)-(+)-limonene are the most promising among all tested EO-derived compounds and can be selected for further detailed research in order to confirm their biomedical potential in the chemoprevention or treatment of osteoporosis since they not only accelerated the proliferation of preosteoblasts, but also significantly enhanced osteocalcin (OC) synthesis by preosteoblasts (the OC level was approx. 1100–1200 ng/mg compared to approx. 650 ng/mg in control cells) and ECM calcification of both preosteoblasts and mesenchymal stem cells. Importantly, cinnamaldehyde treatment led to a three-fold increase in the mineral deposition in ADSCs, whereas (R)-(+)-limonene caused a two-fold increase in the ECM mineralization of both MC3T3-E1 cells and ADSCs.

Difficult-to-treat bone damage resulting from metabolic bone diseases, mechanical injuries, or tumor resection requires support in the form of biomaterials. The aim of this research was to optimize the concentration of individual components of polymer–ceramic nanocomposite granules (nanofilled polymer composites) for application in orthopedics and maxillofacial surgery to fill small bone defects and stimulate the regeneration process. Two types of granules were made using nanohydroxyapatite (nanoHA) and chitosan-based matrix (agarose/chitosan or curdlan/chitosan), which served as binder for ceramic nanopowder. Different concentrations of the components (nanoHA and curdlan), foaming agent (sodium bicarbonate—NaHCO₃), and chitosan solvent (acetic acid—CH₃COOH) were tested during the production process. Agarose and chitosan concentrations were fixed to be 5% w/v and 2% w/v, respectively, based on our previous research. Subsequently, the produced granules were subjected to cytotoxicity testing (indirect and direct contact methods), microhardness testing (Young’s modulus evaluation), and microstructure analysis (porosity, specific surface area, and surface roughness) in order to identify the biomaterial with the most favorable properties. The results demonstrated only slight differences among the resultant granules with respect to their microstructural, mechanical, and biological properties. All variants of the biomaterials were non-toxic to a mouse preosteoblast cell line (MC3T3-E1), supported cell growth on their surface, had high porosity (46–51%), and showed relatively high specific surface area (25–33 m²/g) and Young’s modulus values (2–10 GPa). Apart from biomaterials containing 8% w/v curdlan, all samples were predominantly characterized by mesoporosity. Nevertheless, materials with the greatest biomedical potential were obtained using 5% w/v agarose, 2% w/v chitosan, and 50% or 70% w/v nanoHA when the chitosan solvent/foaming agent ratio was equal to 2:2. In the case of the granules containing curdlan/chitosan matrix, the most optimal composition was as follows: 2% w/v chitosan, 4% w/v curdlan, and 30% w/v nanoHA. The obtained test results indicate that both manufactured types of granules are promising implantable biomaterials for filling small bone defects that can be used in maxillofacial surgery.

Zirconia is known as a strong and bioinert load-bearing material for dental implants. It typically exhibits no antibacterial activity. Inflammation is a crucial problem for dental implant surgery: about 3–5% of all dental implants experience inflammation. This study demonstrates that either fullerene C₆₀ films or a tribomechanical loading of zirconia without the fullerene C₆₀ coating can cause an improvement in antibacterial activity against Gram-positive Staphylococcus aureus. This moderate antibacterial activity is especially important, because a strong antibacterial effect could disturb the sensitive and beneficial oral bacterial biota. In the present study, different fullerene C₆₀ films were examined. In addition to fullerene C₆₀ film in an “as deposited” condition, treatment with nitrogen plasma as well as tribomechanical produced surface patterns with and without plasma post-treatment were tested. An 85.8% (log reduction 0.85) reduction in Gram-positive Staphylococcus aureus bacterial formation was observed on the zirconia with fullerene C₆₀ film. Plasma treatment of the C₆₀ film increases the antibacterial impact to 72.2% (log reduction 0.56) in comparison to zirconia without fullerene C₆₀ film. Also, tribomechanical loaded fullerene C₆₀ films suppress the growth of Gram-positive Staphylococcus aureus. The tribomechanical loading seems to compensate for the effect of the plasma treatment. ZrO₂ samples with fullerene C₆₀ film and tribomechanical loading achieve an increase in antibacterial impact of 83.36% (log reduction 0.78). Furthermore, surprisingly yttria-stabilized zirconia bioceramic without fullerene C₆₀ film also shows an improved antibacterial efficacy after a tribomechanical patterning procedure. The addition of surface patterning on the ZrO₂ by scratching microgroove arrangements with a diamond tip, increased the antibacterial effect against Gram-positive Staphylococcus aureus by 70.46% (log reduction 0.53).

Melanoma is the most aggressive and life-threatening form of skin cancer. Propolis possesses diverse biological activities and is considered a promising source of compounds for anticancer therapy. This study evaluated the cytotoxic effects of propolis from endemic regions of Nepal, Greece, Kazakhstan, Ukraine, and Georgia on melanoma cell lines (A375, SK-MEL-3) and normal human skin fibroblasts (BJ). Chemical characterization was performed using UHPLC-UV-ESI-qTOF-MS/MS. Total flavonoid and polyphenol contents, as well as antioxidant activity, were also determined. Biological effects were assessed by measuring cell viability, apoptosis (fluorescent staining and confocal microscopy), and caspase-6 activity (fluorometric assay). Most analyzed extracts contained markers characteristic of black poplar-type propolis, including chrysin, pinocembrin, galangin, pinobanksin-3-acetate, and caffeic acid monoesters such as caffeic acid phenethyl ester (CAPE) and isomers of the 1,1-dimethylallyl ester. Three propolis samples from Georgia showed the strongest anticancer activity against melanoma cells while exhibiting low toxicity toward normal fibroblasts (SI > 1). These extracts also displayed high antioxidant activity and elevated polyphenol content. Apoptosis predominated in A375 cells, whereas necrosis was more evident in SK-MEL-3 cells, consistent with increased caspase-6 activity in A375 cells. These results suggest that Georgian propolis may be a promising candidate for further investigation in melanoma therapy.