Synergetic reinforcement of brushite cements by monetite/apatite whisker-like fibers and carboxymethylcellulose

Brushite-forming cements have attracted significant interest in bone tissue engineering due to their biocompatibility, resorbability, bioactivity, osteoconductivity, and self-setting characteristics. However, their poor mechanical properties and shorter setting time in comparison to apatite cements limit their clinical applications. The aim of this study was to develop a novel calcium phosphate (CaP) fiber-carboxymethylcellulose (CMC)-brushite composite with enhanced properties, and to investigate the effect of CaP fibers and CMC on the physicochemical, mechanical, and cellular properties. Biphasic monetite/hydroxyapatite fibers were synthesized by homogenous precipitation method and added to brushite and brushite-CMC composites (5, 10 or 20 wt.%). Characterization by XRD, FTIR, and SEM confirmed the formation of brushite crystals in all the samples and revealed that CaP fibers were covered with CMC and bonded to the matrix. The addition of CaP fibers decreased the initial and final setting time. The addition of CMC resulted in a rapid initial setting time but significantly prolonged the final setting time. The incorporation of biphasic CaP fibers increased the diametral tensile strength (DTS) by up to 1.85 MPa (an increase of 105%). The incorporation of CMC both increased the DTS by up to 3.29 MPa (an increase of 165%). Both CaP fibers and CMC have no adverse biological properties. The results showed that both CaP fibers and CMC can be effective additives to control the setting reaction and improve the mechanical and cellular properties of brushite cements.