Investigating the surface reactivity of SiO2-TiO2-CaO-Na2O/SrO bioceramics as a function of structure and incubation time in simulated body fluid

Investigating the structure, solubility, and antibacterial properties of silver- and copper-doped hydroxyapatite

Hydroxyapatite (HA) powders were synthesized by the wet precipitation method in which two experimental compositions were synthesized (10 mol% Ag-HA and Cu-HA) where the CaNO₃ content was partially substituted with AgNO₃ and Cu(NO₃ )₂ . X-ray diffraction (XRD) was employed to characterize changes to the HA structure as the dopants (Cu²⁺ , Ag⁺ ) were incorporated into the materials structure. Energy-dispersive X-ray spectroscopy (EDS) determined confirmed the compositions and found that the Ca/P ratio was 1.63 for the control (HA) while Ag-HA and Cu-HA exhibited (X + Ca)/P ratios of 1.79 and 1.65, respectively. Antibacterial efficacies were evaluated against E. coli and S. aureus, as a function of surface area and incubation time. The more prominent antibacterial effects were observed with both Ag-HA and Cu-HA and the materials antibacterial influence was maintained with respect to time. Ion release studies of each HA composition (15, 30, and 45 days) showed that Cu-HA released significantly more Cu²⁺ (36.1 ± 5.1 mg/L) than Ag⁺ (2.9 ± 1.2 mg/L) from Ag-HA. Analysis of each composition incubated in simulated body fluid (SBF) exhibited surface depositions that are likely calcium phosphate (CaP). Cytocompatibility testing in MC 3T3 Osteoblasts showed slight reductions in cell viability when tested using MTT assay, however cell adhesion studies were positive for each composition.

Reshapable Osteogenic Biomaterials Combining Flexible Melt Electrowritten Organic Fibers with Inorganic Bioceramics

Ever-growing various applications, especially for tissue regeneration, cause a pressing need for novel methods to functionalize melt electrowritten (MEW) microfibrous scaffolds with unique nanomaterials. Here, two novel strategies are proposed to modify MEW polycaprolactone (PCL) grids with ZnO nanoparticles (ZP) or ZnO nanoflakes (ZF) to enhance osteogenic differentiation. The calcium mineralization levels of MC3T3 osteoblasts cultured on PCL/ZP 0.1 scaffolds are ∼3.91-fold higher than those cultured on nonmodified PCL scaffolds, respectively. Due to the nanotopography mimicking bone anatomy, the PCL/ZF scaffolds (∼2.60 times higher in ALP activity compared to PCL/ZP 1 and ∼2.17 times higher in mineralization compared to PCL/ZP 0.1) achieved superior results. Moreover, the flexible feature inherited from PCL grids makes it possible for them to act as a reshapable osteogenic bioscaffold. This study provides new strategies for synthesizing nanomaterials on microscale surfaces, opening up a new route for functionalizing MEW scaffolds to fulfill the growing demand of tissue engineering.

Investigating the effect of germanium on the structure of SiO2-ZnO-CaO-SrO-P2O5 glasses and the subsequent influence on glass polyalkenoate cement formation, solubility and bioactivity

A series of germanium (Ge)-containing glasses were synthesized based on a starting glass composition of SiO₂-ZnO-CaO-SrO-P₂O₅. Additions of GeO₂ (6 and 12 mol%) were incorporated at the expense of SiO_2, which retained the amorphous character, and each glass was processed to present similar particle size and surface area. Glass characterization using x-ray photoelectron spectroscopy (XPS) and magic angle spinning nuclear magnetic resonance (MAS-NMR) determined that the addition of GeO₂ increased the fraction of lower Q-speciation and subsequently the concentration of non-bridging oxygens (NBO). Glass Polyalkenoate Cements (GPC) were formulated from each glass with 40, 50 and 60 wt% PAA, and presented time dependent solubility profiles (1, 10, 100, 1000 h) for the release of Si⁴⁺ (4-140 mg/l), Ca²⁺ (1-8 mg/l), Zn²⁺ (<6 mg/l), Sr²⁺ (2-37 mg/l), PO₄^3- (2-43 mg/l) and Ge⁴⁺ (20-911 mg/l) and attained pH values close to 7.5 after 1000 h. Ge-GPCs containing 40 wt% polyacrylic acid (PAA) presented appropriate working time (T_w) and setting times (T_s), and the corresponding compressive strengths ranged from (14-30 MPa). The Ge-GPCs (40, 50 wt%) presented a linear increase (R²-0.99) with respect to time. Simulated Body Fluid (SBF) testing resulted in the Ge-GPCs encouraging the precipitation of crystalline hydroxyapatite on the GPC surface, more evidently after 100 and 1000 h incubation.

Multiple and Promising Applications of Strontium (Sr)-Containing Bioactive Glasses in Bone Tissue Engineering

Improving and accelerating bone repair still are partially unmet needs in bone regenerative therapies. In this regard, strontium (Sr)-containing bioactive glasses (BGs) are highly-promising materials to tackle this challenge. The positive impacts of Sr on the osteogenesis makes it routinely used in the form of strontium ranelate (SR) in the clinical setting, especially for patients suffering from osteoporosis. Therefore, a large number of silicate-, borate-, and phosphate-based BGs doped with Sr and produced in different shapes have been developed and characterized, in order to be used in the most advanced therapeutic strategies designed for the management of bone defects and injuries. Although the influence of Sr incorporation in the glass is debated regarding the obtained physicochemical and mechanical properties, the biological improvements have been found to be substantial both in vitro and in vivo. In the present study, we provide a comprehensive overview of Sr-containing glasses along with the current state of their clinical use. For this purpose, different types of Sr-doped BG systems are described, including composites, coatings and porous scaffolds, and their applications are discussed in the light of existing experimental data along with the significant challenges ahead.