Synthesis, characterization, bioactivity and biocompatibility of nanostructured materials based on the wollastonite-poly(ethylmethacrylate-co-vinylpyrrolidone) system

A Review on the Role of Wollastonite Biomaterial in Bone Tissue Engineering

Millions of people around the world have bone-tissue defects. Autologous and allogeneic bone grafting are frequent therapeutic techniques; however, none has produced the best therapeutic results. This has inspired researchers to investigate novel bone-regeneration technologies. In recent years, the development of bone tissue engineering (BTE) scaffolds has been at the forefront of this discipline. Due to their limitless supply and lack of disease transmission, engineered bone tissue has been advanced for the repair and reconstruction of bone deformities. Bone tissue is a highly vascularized, dynamic tissue that constantly remodels during an individual's lifetime. Bone tissue engineering is aimed at stimulating the creation of new, functional bone by combining biomaterials, cells, and factor treatment synergistically. This article provides a review of wollastonite's biomaterial application in bone tissue engineering. This work includes an explanation of wollastonite minerals including mining, raw materials for the synthesis of artificial wollastonite with various methods, its biocompatibility, and biomedical applications. Future perspectives are also addressed, along with topics like bone tissue engineering, the qualities optimal bone scaffolds must have, and the way a scaffold is designed can have a big impact on how the body reacts.

Size- and Shape-Controlled Synthesis of Calcium Silicate Particles Enables Self-Assembly and Enhanced Mechanical and Durability Properties

Calcium silicate (CS)-based materials are ubiquitous in diverse industries ranging from cementitious materials to bone tissue engineering and drug delivery. As a symbolic example, concrete is the most widely used synthetic material on the planet. This large consumption entails significant negative environmental footprint, which calls for innovative strategies to develop greener concrete with improved properties (to do more with less). Herein, we focus on the physicochemical properties of novel spherical calcium silicate particles with an extremely narrow size distribution and report their promising potential as fundamental building blocks. We demonstrate a scalable size- and shape-controlled synthesis protocol to yield highly spherical CS submicron particles, leading to favorable aggregation mechanisms and thus self-assembly of the bulk ensemble. This optimized kinetics-controlled synthesis is governed by suitable stoichiometric ratio of calcium over silicon, type and concentration of the surfactant, and molar ratio of the alkaline solution. Our extensive nano/micro/macro-characterization results show that the bulk ensemble exhibits many superior properties, such as improved strength, toughness, ductility, and durability, paving the path for bottom-up science-based engineering of concrete.

Synthesis and in Vitro Cytocompatibility of Segmented Poly(Ester-Urethane)s and Poly(Ester-Urea-Urethane)s for Bone Tissue Engineering

Two series of segmented polyurethanes were obtained and their mechanical and thermal properties as well as their biodegradability and cytotoxicity were evaluated. The chemical nature of the polyurethanes was varied by using either 1,4 butanediol (poly-ester-urethanes, PEUs) or l-lysine ethyl ester dihydrochloride (poly-ester-urea-urethanes, PEUUs) as chain extenders. Results showed that varying the hard segment influenced the thermal and mechanical properties of the obtained polymers. PEUs showed strain and hardness values of about 10⁻20 MPa and 10⁻65 MPa, respectively. These values were higher than the obtained values for the PEUUs due to the phase segregation and the higher crystallinity observed for the polyester-urethanes (PEUs); phase segregation was also observed and analyzed by XRD and DSC. Moreover, both series of polymers showed hydrolytic degradation when they were submerged in PBS until 90 days with 20% of weight loss. In vitro tests using a Human Osteoblastic cell line (Hob) showed an average of 80% of cell viability and good adhesion for both series of polymers.

Imaging of drug loading distributions in individual microspheres of calcium silicate hydrate--an X-ray spectromicroscopy study

Imaging is one of the most direct and ideal ways to track drug loading distributions in drug carriers on the molecular level, which will facilitate the optimization of drug carriers and drug loading capacities. Herein, we report the mapping of an individual mesoporous calcium silicate hydrate (CSH) microsphere before and after the loading of ibuprofen (IBU) and the interactions between drug carriers and drug molecules simultaneously by scanning transmission X-ray microscopy (STXM). Nanoscaled X-ray absorption near edge structure (XANES) spectroscopy clearly indicates that IBU is bonded to calcium and silicate sites via carboxylic acid groups. More importantly, STXM has been successfully used to determine the absolute thickness of IBU, revealing its distribution in the CSH microsphere.

Polyelectrolyte-mediated hierarchical mesoporous calcium silicates: a platform for drug delivery carrier with ultrahigh loading capacity and controlled release behavior

Hierarchical drug carrier: a facile method for polymer-assisted controlled synthesis of mesoporous calcium silicate hydrates with a large specific surface area and pore volume was developed.

Ultrathin calcium silicate hydrate nanosheets with large specific surface areas: synthesis, crystallization, layered self-assembly and applications as excellent adsorbents for drug, protein, and metal ions

A simple and low-cost solution synthesis is reported for low-crystalline 1.4 nm tobermorite-like calcium silicate hydrate (CSH) ultrathin nanosheets with a thickness of ~2.8 nm and with a large specific surface area (SSA), via a reaction-rate-controlled precipitation process. The BET SSA of the CSH ultrathin nanosheets can reach as high as 505 m(2) g(-1) . The CSH ultrathin nanosheets have little cytotoxicity and can be converted to anhydrous calcium silicate (ACS) ultrathin nanosheets with a well preserved morphology via a heat treatment process. The crystallinity of CSH ultrathin nanosheets can be improved by solvothermal treatment in water/ethanol binary solvents or a single solvent of water, producing well-crystalline 1.1 nm tobermorite-like CSH nanobelts or nanosheets. CSH ultrathin nanosheets acting as building blocks can self-assemble into layered nanostructures via three different routes. The CSH ultrathin nanosheets are investigated as promising adsorbents for protein (hemoglobin, Hb), drug (ibuprofen, IBU), and metal ions (Cr(3+) , Ni(2+) , Cu(2+) , Zn(2+) , Cd(2+) , Pb(2+) ). The highest adsorbed percentages of Hb and IBU are found to be 83% and 94%, respectively. The highest adsorption capacities of Hb and IBU are found to be as high as 878 milligram Hb per gram CSH and 2.2 gram IBU per gram CSH, respectively. The ppm level metal ions can be totally adsorbed from aqueous solution in just a few minutes. Thus, the CSH ultrathin nanosheets are a promising candidate as excellent adsorbents in the biomedical field and for waste water treatment. Several empirical laws are summarized based on the adsorption profiles of Hb and IBU using CSH ultrathin nanosheets as the adsorbent. Furthermore, the ACS ultrathin nanosheets as adsorbents for Hb protein and IBU drug are investigated.

Feasibility of ceramic-polymer composite cryogels as scaffolds for bone tissue engineering

The purpose of the current study was to investigate whether the cryopolymerization technique is capable of producing suitable scaffolds for bone tissue engineering. Cryopolymers made of 2-hydroxyethyl methacrylate and acrylic acid with (W1 and W20) and without (W0) wollastonite particles were prepared. The elastic modulus of the specimens rose one order of magnitude from W1 to W20. Total porosity reached 56% for W0, 72% for W1 and 36% for W20, with pore sizes of up to 2 mm, large interconnection sizes of up to 1 mm and small interconnection sizes of 50-80 µm on dry specimens. Cryogels swell up to 224 ± 17% for W0, 315 ± 18% for W1 and 231 ± 27% for W20 specimens, while maintaining the integrity of the bodies. Pore sizes > 5 mm can be observed for swollen specimens. The biocompatibility of the samples was tested using human mesenchymal stem cells isolated from bone marrow and adipose tissues. Both types of cells attached and grew on the three tested substrates, colonized their inner regions and organized an extracellular cell matrix. Fibronectin and osteopontin levels decreased in the media from cells cultured on W20 samples, likely due to increased binding on the ECM deposited by cells. The osteoprotegerin-to-receptor activator of nuclear factor-κB ligand secretion ratios increased with increasing wollastonite content. Altogether, these results indicate that an appropriate balance of surface properties and structure that favours stromal cell colonization in the porous cryogels can be achieved by modulating the amount of wollastonite.