Structures and Dissolution Behaviors of Quaternary CaO-SrO-P2O5-TiO2 Glasses

Strain Engineering: Perfecting Freestanding Perovskite Oxide Fabrication

Freestanding oxide membranes provide a promising path for integrating devices on silicon and flexible platforms. To ensure optimal device performance, these membranes must be of high crystal quality, stoichiometric, and their morphology free from cracks and wrinkles. Often, layers transferred on substrates show wrinkles and cracks due to a lattice relaxation from an epitaxial mismatch. Doping the sacrificial layer of Sr3Al2O6 (SAO) with Ca or Ba offers a promising solution to overcome these challenges, yet its effects remain critically underexplored. A systematic study of doping Ca into SAO is presented, optimizing the pulsed laser deposition (PLD) conditions, and adjusting the supporting polymer type and thickness, demonstrating that strain engineering can effectively eliminate these imperfections. Using SrTiO3 as a case study, it is found that Ca1.5Sr1.5Al2O6 offers a near-perfect match and a defect-free freestanding membrane. This approach, using the water-soluble Bax/CaxSr3-xAl2O6 family, paves the way for producing high-quality, large freestanding membranes for functional oxide devices.

Development of bioinspired damage-tolerant calcium phosphate bulk materials

Improving the damage tolerance and reliability of ceramic artificial bone materials, such as sintered bodies of hydroxyapatite (HAp), that remain in vivo for long periods of time is of utmost importance. However, the intrinsic brittleness and low damage tolerance of ceramics make this challenging. This paper reports the synthesis of highly damage tolerant calcium phosphate-based materials with a bioinspired design for novel artificial bones. The heat treatment of isophthalate ion-containing octacalcium phosphate compacts in a nitrogen atmosphere at 1000°C for 24 h produced an HAp/β-tricalcium phosphate/pyrolytic carbon composite with a brick-and-mortar structure (similar to that of the nacreous layer). This composite exhibited excellent damage tolerance, with no brittle fracture upon nailing, likely attributable to the specific mechanical properties derived from its unique microstructure. Its maximum bending stress, maximum bending strain, Young's modulus, and Vickers hardness were 11.7 MPa, 2.8 × 10‒2, 5.3 GPa, and 11.7 kgf/mm2, respectively. The material exhibited a lower Young's modulus and higher fracture strain than that of HAp-sintered bodies and sintered-body samples prepared from pure octacalcium phosphate compacts. Additionally, the apatite-forming ability of the obtained material was confirmed in vitro, using a simulated body fluid. The proposed bioinspired material design could enable the fabrication of highly damage tolerant artificial bones that remain in vivo for long durations of time.

In Vitro Studies Demonstrate Antitumor Activity of Vanadium Ions from a CaO-P2O5-CaF2:V2O5 Glass System in Human Cancer Cell Lines A375, A2780, and Caco-2

In this research, we investigated the structural and biological properties of phosphate glasses (PGs) after the addition of V2O5. A xV2O5∙(100 − x)[CaF2∙3P2O5∙CaO] glass system with 0 ≤ x ≤ 16 mol% was synthesized via a conventional melt-quenching technique. Several analysis techniques (dissolution tests, pH, SEM-EDS, FT-IR, and EPR) were used to obtain new experimental data regarding the structural behavior of the system. In vitro tests were conducted to assess the antitumor character of V2O5-doped glass (x = 16 mol%) compared to the matrix (x = 0 mol%) and control (CTRL-) using several tumoral cell lines (A375, A2780, and Caco-2). The characterization of PGs showed an overall dissolution rate of over 90% for all vitreous samples (M and V1−V7) and the high reactivity of this system. EPR revealed a well-resolved hyperfine structure (hfs) typical of vanadyl ions in a C4v symmetry. FT-IR spectra showed the presence of all structural units expected for P2O5, as well as very clear depolymerization of the vitreous network induced by V2O5. The MTT assay indicated that the viability of tumor cells treated with V7-glass extract was reduced to 50% when the highest concentration was used (10 µg/mL) compared to the matrix treatment (which showed no cytotoxic effect at any concentration). Moreover, the matrix treatment (without V2O5) provided an optimal environment for tumor cell attachment and proliferation. In conclusion, the two types of treatment investigated herein were proven to be very different from a statistical point of view (p < 0.01), and the in vitro studies clearly underline the cytotoxic potential of vanadium ions from phosphate glass (V7) as an antitumor agent.