In vitro bioactivity evaluation, mechanical properties and microstructural characterization of Na₂O-CaO-B₂O₃-P₂O₅ glasses

Structural and impedance spectroscopic investigations of eco-friendly alkali phosphoborate glass-ceramics containing zirconium ion

Glass-ceramics with novel composition xZrO2.7P2O5.19CaO.24Na2O.(50-x)B2O3 (x = 0, 2, 4, 6, and 8 mol%) have been synthesized using melt quench technique. The synthesized compositions were characterized and analyzed by X-ray diffraction, field emission scanning electron microscopy, infrared absorption, and impedance spectroscopy. X-ray diffraction profiles of prepared samples confirm the existence of phases corresponding to Na3Ca6(PO4)5 crystal (with crystallite size ~ 23 nm). Infrared absorbance spectra reveal the presence of phosphate and borate units (PO3, PO4, BO3, BO4) in the glass matrix. Different dielectric parameters such as dielectric loss, electric modulus, and tangent loss were evaluated. Their variations with temperature and frequency confirm the non- Debye relaxation behavior of prepared samples. A phenomenal description of the capacitive behavior was studied by considering the circuit having a parallel combination of constant phase element and bulk resistance. The conduction is found to be governed by overlapping large polaron tunneling (OLPT) and follow OLPT model. The results indicate that ZrO2 substituted alkali phosphoborate glass-ceramics can be used as eco-friendly and safe dielectric materials.

High Boron Content Enhances Bioactive Glass Biodegradation

Derived Hench bioactive glass (BaG) containing boron (B) is explored in this work as it plays an important role in bone development and regeneration. B was also found to enhance BaG dissociation. However, it is only possible to incorporate a limited amount of B. To increase the amount of B in BaG, bioactive borosilicate glasses (BaG-B_x) were fabricated based on the use of the solution-gelation process (sol-gel). In this work, a high B content (20 wt.%) in BaG, respecting the conditions of bioactivity and biodegradability required by Hench, was achieved for the first time. The capability of BaG-B_x to form an apatite phase was assessed in vitro by immersion in simulated body fluid (SBF). Then, the chemical structure and the morphological changes in the fabricated BaG-B_x (x = 0, 5, 10 and 20) were studied. The formation of hydroxyapatite (HAp) layer was observed with X-ray diffraction (XRD) and infrared (IR) spectroscopy. The presence of HAp layer was confirmed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Enhanced bioactivity and chemical stability of BaG-B_x were evaluated with an ion exchange study based on Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) and energy dispersive spectroscopy (EDS). Results indicate that by increasing the concentration of B in BaG-Bx, the crystallization rate and the quality of the newly formed HAp layer on BaG-B_x surfaces can be improved. The presence of B also leads to enhanced degradation of BaGs in SBF. Accordingly, BAG-B_x can be used for bone regeneration, especially in children, because of its faster degradation as compared to B-free glass.

Influence of ZrO2 Addition on Structural and Biological Activity of Phosphate Glasses for Bone Regeneration

Zirconium doped calcium phosphate-based bioglasses are the most prominent bioactive materials for bone and dental repair and regeneration implants. In the present study, a 8ZnO–22Na₂O–(24 − x)CaO–46P₂O₅–xZrO₂ (0.1 ≤ x ≤ 0.7, all are in mol%) bioglass system was synthesized by the conventional melt-quenching process at 1100 °C. The glass-forming ability and thermal stability of the glasses were determined by measuring the glass transition temperature (T_g), crystallization temperature (T_c), and melting temperature (T_m), using differential thermal analysis (DTA). The biological activity of the prepared samples was identified by analyzing X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy-energy dispersive spectra (SEM-EDS), before and after immersion in simulated body fluid (SBF) for various intervals of 0, 1 and 5 days, along with the magnitude of pH and the degradation of glasses also evaluated. The obtained results revealed that the glass-forming ability and thermal stability of glasses increased with the increase in zirconia mol%. The XRD, FTIR, and SEM-EDS data confirmed a thin hydroxyapatite (HAp) layer over the sample surface after incubation in SBF for 1 and 5 days. Furthermore, the development of layer found to be increased with the increase of incubation time. The degradation of the glasses in SBF increased with incubation time and decreased gradually with the increase content of ZrO₂ mol% in the host glass matrix. A sudden rise in initial pH values of residual SBF for 1 day owing to ion leaching and increase of Ca²⁺ and PO₄³⁻ ions and then decreased. These findings confirmed the suitability of choosing material for bone-related applications.

Investigations on Physico-Mechanical and Spectral Studies of Zn2+ Doped P2O5-Based Bioglass System

ZnO incorporated phosphate based bioglasses with the composition xZnO–22Na2O–24CaO–(54-X)P2O5 (where X = 2, 4, 6, 8, 10 mol%) were developed by melt-quenching process. The physical, thermal and other structural properties of the glasses were studied in detail. By employing various characterization techniques such as X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) in addition to the energy dispersion spectroscopy (EDS), and Raman spectroscopy, the structural properties were analyzed. Interestingly, physical, thermal and mechanical properties were enhanced with the increasing content of zinc oxide up to 8 mol%, due to the presence of more ionic nature of P–O–Zn bonds than P–O–P bonds in the glass network. The FTIR and Raman analysis revealed the evolution of the phosphate network with increasing zinc concentration and leads to progressive depolymerisation of the glass network. The obtained results from the physical and structural properties of these zinc added calcium phosphate glasses support their potential to use as bone implant applications.

Investigation on the properties of borate bonding agents: Ti6Al4V-porcelain bonding, chemical durability and preliminary cytotoxicity

The purpose of this study was to investigate the properties of the borate bonding agents (BBAS) including chemical durability, biocompatibility and bonding characteristics of porcelain to Ti6Al4V. The bond strength was performed by the three-point bending test. And the chemical durability and ion release of BBAS were tested by chemical soaking and inductively coupled plasma optical emission spectrometry (ICP-OES), respectively. Moreover, cytotoxicity was evaluated by cell viability assay and cell adhesion using human osteosarcoma cells (MG-63) and cell counter kit-8 (CCK-8) assay. To investigate the influences of composition and microstructure changes on all the properties mentioned above, the ¹¹B and ²⁷Al spectra and infrared spectra of BBAS were measured by solid-state nuclear magnetic resonance (SSNMR) and Fourier transform infrared spectroscopy (FTIR), respectively. Combined with all these properties of BBAS, the optimal addition proportion of Al₂O₃ into BBAS is 20 mol%. The relative contents of [BO3], [BO4], [AlO4], [AlO5] and [AlO6] have great influences on these properties of BBAS. BBAS, possessing excellent chemical durability, good biocompatibility and low ion release and being an effective way to improve the Ti6Al4V-porcelain bond strength, have significant clinical potentials in porcelain fused to metal restorations.

Bioactive calcium phosphate-based glasses and ceramics and their biomedical applications: A review

An overview of the formation of calcium phosphate under in vitro environment on the surface of a range of bioactive materials (e.g. from silicate, borate, and phosphate glasses, glass-ceramics, bioceramics to metals) based on recent literature is presented in this review. The mechanism of bone-like calcium phosphate (i.e. hydroxyapatite) formation and the test protocols that are either already in use or currently being investigated for the evaluation of the bioactivity of biomaterials are discussed. This review also highlights the effect of chemical composition and surface charge of materials, types of medium (e.g. simulated body fluid, phosphate-buffered saline and cell culture medium) and test parameters on their bioactivity performance. Finally, a brief summary of the biomedical applications of these newly formed calcium phosphate (either in the form of amorphous or apatite) is presented.