Reaction kinetics of dual setting α-tricalcium phosphate cements

Abstract

Addition of ductile polymers to calcium-deficient hydroxyapatite (CDHA)-forming bone cements based on α-tricalcium phosphate (α-TCP) is a promising approach to improve the mechanical performance of α-TCP cements and extend their application to load-bearing defects, which is else impeded by the brittleness of the hardened cement. One suitable polymer is poly-(2-hydroxyethylmethacrylate) (p-HEMA), which forms during cement setting by radical polymerisation of the monomer. In this study the hydration kinetics and the mechanical performance of α-TCP cements modified with addition of different HEMA concentrations (0-50 wt% in the cement liquid) was investigated by quantitative in situ XRD and four-point bending tests. Morphology of CDHA crystals was monitored by scanning electron microscopy. The hydration of α-TCP to CDHA was increasingly impeded and the visible crystal size of CDHA increasingly reduced with increasing HEMA concentration. Modification of the cements by adding 50 wt% HEMA to the cement liquid changed the brittle performance of the hardened cement to a pseudoplastic behaviour, reduced the flexural modulus and increased the work of fracture, while lower HEMA concentrations had no significant effect on these parameters. In such a composite, the extent of CDHA formation was considerably reduced (34.0 ± 1.8 wt% CDHA with 50 % HEMA compared to 54.1 ± 2.4 wt% CDHA in the reference formed after 48 h), while the general reaction kinetics were not changed. In conclusion, while the extent of CDHA formation was decreased, the mechanical properties were noticeably improved by addition of HEMA. Hence, α-TCP/HEMA composites might be suitable for application in some load-bearing defects and have adequate properties for mechanical treatment after implantation, like insertion of screws.

Evaluation of cell binding to collagen and gelatin: a study of the effect of 2D and 3D architecture and surface chemistry

“…The addition of Gel to Col and the variation in crosslinking status can tailor many important material properties of resultant matrices. These include the dissolution resistance in different biological environments, the swelling characteristics and the mechanical strength [15, 25]. In conjunction with this data, the main objective of this research is to evaluate cell interaction with Col and Gel-based biomaterials with a particular focus on the chemical identity and availability of receptor recognition ligands for cell adhesion.…”

“…In our previous studies, we used UV irradiation and carbodiimide chemistry, based on the reaction with EDC (1-ethyl-3-(3-dimethylaminopropyl-carbodiimide hydrochloride) in the presence of NHS (N-hydroxy-succinimide), to tailor the physical characteristics of scaffolds [15, 25]. EDC crosslinking is a very effective method to increase the mechanical stability and the dissolution resistance of collagenous materials [28–31].…”

A Multimaterial Scaffold With Tunable Properties: Toward Bone Tissue Repair

“…The results from TGA analysis indicated that the addition of PLLA in PEEK decreased the thermal stability of scaffolds, as the starting decomposition temperature shifted to lower temperatures. In DSC curves, the endothermic peak at about 334 °C was attributed to the melting temperature of PEEK 27. Two endothermic peaks located at about 174 and 355 °C were attributed to the melting temperature and decomposition temperature of PLLA,28 respectively.…”

Development of a fast curing tissue adhesive for meniscus tear repair

“…Tissue adhesives are attractive biomaterials to be used for treating meniscus tears [4]. They are already employed in clinical practice for various applications.…”

“…Isocyanate-terminated polymers are of particular interest, since they have easily tuneable mechanical properties, they attach to the tissue via formation of strong covalent bonds and degrade to non-toxic products [4]. However, a drawback of this class of materials is the relatively long curing time: it can take up to several hours before the adhesive reaches maximum bonding strength.…”