Reinforcement of injectable premixed α-tricalcium phosphate cements with silk fibroin solutions

Abstract

Premixed injectable α-tricalcium phosphate (TCP)-based calcium phosphate cements (CPCs) attract significant interest due to their potential for use in minimally invasive procedures for bone filling and replacement. However, injectable α-TCP CPCs do not present adequate mechanical properties for most orthopedic applications as a higher incorporation of liquid is needed to obtain suitable injectability. A trivial number of studies have addressed this major difficulty in injectable systems and an even smaller fraction has successfully obtained applicable mechanical properties. Therefore, the aim of this study was to evaluate the premixing with SF of a α-TCP cement system as a means to develop a storable, injectable and reinforced CPC. All developed cement pastes showed storage stability for up to 22w and, after activation, transformation of the α-TCP to a biphasic CDHA/HAp-Cl material. Reinforced samples showed a 314% increase in compressive strength compared to the control sample, which demonstrates adequate coupling between the SF and the calcium phosphates (CPs). All samples incorporating SF exhibited a microstructure analogous to the mineral phase of bone, with nanosized needle-like crystals. Moreover, the addition of this polymeric phase contributed to reducing the dissolution of the material while immersed in PBS, and to increasing the deposition of bone-like apatite on the CPC’s surface when in simulated body fluid (SBF). The obtained composition did not affect the cell viability, maintaining adequate biocompatibility. Overall, injectable, biomimetic and biocompatible premixed CPCs with mechanical reinforcement through the addition of SF were successfully obtained, with the potential to be further evaluated as a material for bone regeneration.