CaSiO3-HAp Metal-Reinforced Biocomposite Ceramics for Bone Tissue Engineering.

Reconstructive and regenerative bone surgery is based on the use of high-tech biocompatible implants needed to restore the functions of the musculoskeletal system of patients. Ti6Al4V is one of the most widely used titanium alloys for a variety of applications where low density and excellent corrosion resistance are required, including biomechanical applications (implants and prostheses). Calcium silicate or wollastonite (CaSiO3) and calcium hydroxyapatite (HAp) is a bioceramic material used in biomedicine due to its bioactive properties, which can potentially be used for bone repair. In this regard, the research investigates the possibility of using spark plasma sintering technology to obtain new CaSiO3-HAp biocomposite ceramics reinforced with a Ti6Al4V titanium alloy matrix obtained by additive manufacturing. The phase and elemental compositions, structure, and morphology of the initial CaSiO3-HAp powder and its ceramic metal biocomposite were studied by X-ray fluorescence, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Brunauer-Emmett-Teller analysis methods. The spark plasma sintering technology was shown to be efficient for the consolidation of CaSiO3-HAp powder in volume with a Ti6Al4V reinforcing matrix to obtain a ceramic metal biocomposite of an integral form. Vickers microhardness values were determined for the alloy and bioceramics (~500 and 560 HV, respectively), as well as for their interface area (~640 HV). An assessment of the critical stress intensity factor KIc (crack resistance) was performed. The research result is new and represents a prospect for the creation of high-tech implant products for regenerative bone surgery.

Synthetic Calcium Silicate Biocomposite Based on Sea Urchin Skeleton for 5-Fluorouracil Cancer Delivery.

Synthetic calcium silicates and phosphates are promising compounds for targeted drug delivery for the effective treatment of cancerous tumors, and for minimizing toxic effects on the patient's entire body. This work presents an original synthesis of a composite based on crystalline wollastonite CaSiO3 and combeite Na4Ca4(Si6O18), using a sea urchin Mesocentrotus nudus skeleton by microwave heating under hydrothermal conditions. The phase and elemental composition and structure of the obtained composite were studied by XRF, REM, BET, and EDS methods, depending on the microwave heating time of 30 or 60 min, respectively, and the influence of thermo-oxidative post-treatment of samples. The role of the sea urchin skeleton in the synthesis was shown. First, it provides a raw material base (source of Ca2+) for the formation of the calcium silicate composite. Second, it is a matrix for the formation of its porous inorganic framework. The sorption capacity of the composite, with respect to 5-fluorouracil, was estimated, the value of which was 12.3 mg/L. The resulting composite is a promising carrier for the targeted delivery of chemotherapeutic drugs. The mechanism of drug release from an inorganic natural matrix was also evaluated by fitting its release profile to various mathematical models.

Moss-like Hierarchical Architecture Self-Assembled by Ultrathin Na2Ti3O7 Nanotubes: Synthesis, Electrical Conductivity, and Electrochemical Performance in Sodium-Ion Batteries.

Nanocrystalline layer-structured monoclinic Na2Ti3O7 is currently under consideration for usage in solid state electrolyte applications or electrochemical devices, including sodium-ion batteries, fuel cells, and sensors. Herein, a facile one-pot hydrothermal synthetic procedure is developed to prepare self-assembled moss-like hierarchical porous structure constructed by ultrathin Na2Ti3O7 nanotubes with an outer diameter of 6-9 nm, a wall thickness of 2-3 nm, and a length of several hundred nanometers. The phase and chemical transformations, optoelectronic, conductive, and electrochemical properties of as-prepared hierarchically-organized Na2Ti3O7 nanotubes have been studied. It is established that the obtained substance possesses an electrical conductivity of 3.34 × 10-4 S/cm at room temperature allowing faster motion of charge carriers. Besides, the unique hierarchical Na2Ti3O7 architecture exhibits promising cycling and rate performance as an anode material for sodium-ion batteries. In particular, after 50 charge/discharge cycles at the current loads of 50, 150, 350, and 800 mA/g, the reversible capacities of about 145, 120, 100, and 80 mA∙h/g, respectively, were achieved. Upon prolonged cycling at 350 mA/g, the capacity of approximately 95 mA∙h/g at the 200th cycle was observed with a Coulombic efficiency of almost 100% showing the retention as high as 95.0% initial storage. At last, it is found that residual water in the un-annealed nanotubular Na2Ti3O7 affects its electrochemical properties.

Enhancing Lithium and Sodium Storage Properties of TiO2(B) Nanobelts by Doping with Nickel and Zinc.

Nickel- and zinc-doped TiO2(B) nanobelts were synthesized using a hydrothermal technique. It was found that the incorporation of 5 at.% Ni into bronze TiO2 expanded the unit cell by 4%. Furthermore, Ni dopant induced the 3d energy levels within TiO2(B) band structure and oxygen defects, narrowing the band gap from 3.28 eV (undoped) to 2.70 eV. Oppositely, Zn entered restrictedly into TiO2(B), but nonetheless, improves its electronic properties (Eg is narrowed to 3.21 eV). The conductivity of nickel- (2.24 × 10-8 S·cm-1) and zinc-containing (3.29 × 10-9 S·cm-1) TiO2(B) exceeds that of unmodified TiO2(B) (1.05 × 10-10 S·cm-1). When tested for electrochemical storage, nickel-doped mesoporous TiO2(B) nanobelts exhibited improved electrochemical performance. For lithium batteries, a reversible capacity of 173 mAh·g-1 was reached after 100 cycles at the current load of 50 mA·g-1, whereas, for unmodified and Zn-doped samples, around 140 and 151 mAh·g-1 was obtained. Moreover, Ni doping enhanced the rate capability of TiO2(B) nanobelts (104 mAh·g-1 at a current density of 1.8 A·g-1). In terms of sodium storage, nickel-doped TiO2(B) nanobelts exhibited improved cycling with a stabilized reversible capacity of 97 mAh·g-1 over 50 cycles at the current load of 35 mA·g-1.