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Applications of Biomaterials in Hard Tissue Replacement
Published in Yaser Dahman, Biomaterials Science and Technology, 2019
Bone apatite is one of the biological apatites that make up the mineral phase of calcified tissues in the body. The use of a synthetic compound similar to bone apatite is perceived as advantageous to the replacement of hard tissue compared to other synthetic materials. Consequently, there has been sustained interest over the past 20 years in hydroxyapatite (HAp, Ca10 (PO4)6(OH)2), which resembles bone apatite and is a member of the calcium phosphate family that is part of the bioceramic bio cyclic group. HAp has excellent biocompatibility and is an osteon conductor (Ladizesky et al., 1998). It has been clinically used alone as a bioactive material in the form of a powder, a porous structure, or a dense body (Hench, 1993). However, the most widespread success of HAp is its use as a bioactive coating on total hip prostheses. Another attractive member of the family of calcium phosphates for medical applications is tricalcium phosphate (TCP, Ca3 (PO4)2), which plays an important role as resorbable bioceramic. TCP was used for bone repair in the form of ceramic blocks, granules, or calcium phosphate cements (Bonner et al., 2002). HAp and TCP are weak biological ceramics and therefore cannot be used alone as major carrier implants in the human body.
Calcium Phosphate and Bioactive Glasses
Published in Vincenzo Guarino, Marco Antonio Alvarez-Pérez, Current Advances in Oral and Craniofacial Tissue Engineering, 2020
Osmar A. Chanes-Cuevas, José L. Barrera-Bernai, Iñigo Gaitán-S., David Masuoka
It has been known for more than 250 years that calcium phosphates are a component of the human body. Therefore, it was logical to assume that this material was thought of as a natural substitute for bone. Within calcium phosphates, one of the most used for this purpose is tricalcium phosphate (TCP). The first reported case of a tricalcium phosphate used as a graft dates back to 1920 by Albee who reported that a TCP graft promoted the formation of new bone tissue (Moed et al. 2003). Tricalcium phosphate is a bioceramics of formula Ca, (PO4)2, which is divided into two main groups, the form a and 13, both with the same Ca/P ratio of 1.5 but with different crystallographic, monoclinic and rhombohedral structures, respectively (Samavedi et al. 2013; Barrere et al. 2006; Jeong et al. 2019). This structure gives them different properties, since it depends on their stability, solubility, mechanical resistance and even their biological properties, and therefore their final applicability. The a form is generally obtained by two methods, the first is by means of a thermal transformation in which the temperature rises above 1125°C of some precursor with a Ca/P ratio of 1.5, such as hydroxyapatite deficient in calcium, amorphous calcium phosphate or the β-TCP form. The second method of obtaining it is by the so-called solid state reaction, in which precursors are mixed and the temperature is raised in the same way. Some authors recognize an α’ form that occurs only at temperatures greater than 1430°C and returns to the a form when cooled below its transition temperature, and therefore lacks clinical interest (Carrodeguas and De Aza 2011). In general, the α-TCP form is more soluble and less stable, and also has less mechanical resistance than the β-TCP form, so it is not used as a bone graft, but rather as cement, which can be accompanied by a polymer that functions as a vehicle for α-TCP particles. Colpo and collaborators developed an α-TCP cement using an acrylamide-based polymer as a vehicle, which was also used to release drugs in a controlled manner (Colpo et al. 2018). An and collaborators tested an α-TCP cement together with carboxymethylcellulose and hyaluronic acid, achieving values of up to 10 MPa, which shows that polymers also help improve their mechanical properties (An et al. 2016). The α-TCP cements set by a reaction in which three α-TCP molecules incorporate hydrogen from water to form an acidic phosphate, also adding a hydroxyl group to the resulting molecule (Gildenhaar et al. 2012).
Development of biomimetic electrospun polymeric biomaterials for bone tissue engineering. A review
Published in Journal of Biomaterials Science, Polymer Edition, 2019
Sugandha Chahal, Anuj Kumar, Fathima Shahitha Jahir Hussian
Bone extracellular matrix (ECM) is composed of organic constituents including collagen and non-collagenous proteins and inorganic minerals like nano-hydroxyapatite (nHA) [6–8]. The inorganic mineral of bone consists of calcium, phosphate, carbonate, and hydroxyl and minerals plays an important role for mechanical strength and osteoconductivity properties to bone [9]. The organic part of extracellular matrix contains interwoven collagen fibers within a hydrated network of glycosaminoglycan (GAG) chains. This structure serves as a frame, which can support tensile and compressive stresses by the fibrils and hydrated networks. The fibrillary and porous structure of ECM have a great influence on cellular functions; such as cell adhesion, migration and proliferation, which are responsible for tissue regeneration and repair [10,11]. For the past few decades, ceramics, many natural and synthetic polymers as well as composites have been extensively used for bone tissue engineering. Hydroxyapatite or tri-calcium phosphate (TCP) is widely used as bone scaffolds and highly bioactive and osteoconductive, but has some disadvantages like poor mechanical strength and slow degradation rate. Collagen, chitosan, and chitin are the most widely used natural polymers for bone tissue engineering applications.
Porous structure engineering of bioceramic hydroxyapatite-based scaffolds using PVA, PVP, and PEO as polymeric porogens
Published in Journal of Asian Ceramic Societies, 2019
Vicky Julius Mawuntu, Yusril Yusuf
The XRD results depicted in Figure 4 shows a low-intensity β-tricalcium phosphate (TCP) peak in addition to HAp. Tricalcium phosphate (TCP) is itself a tertiary calcium phosphate with high biocompatibility that can promote improvements in bone tissue [7,8].