Silanized-hydroxypropyl methylcellulose(Si-HPMC)/phase-transformed calcium phosphate (PTCP) composite cements were successfully prepared for application as novel injectable bone cements with enhanced biocompatibility. The crystal structure and chemical state of the synthesized PTCP and Si-HPMC powders as solid and liquid phases of the composite cements were determined via X-ray diffraction and Fourier transform infrared spectroscopy. The physical handling and mechanical properties of the Si-HPMC/PTCP composite calcium phosphate cements (CPCs) were measured via viscometric analysis, injectability tests, and using a universal testing machine. The cytotoxicity of the Si-HPMC/PTCP composite CPCs was evaluated and compared with that of Si-HPMC/alpha-TCP as a control. Analysis of the in-vitro mechanical properties of the Si-HPMC/PTCP composite CPCs showed that hardening was an inherent function of the cements after immersion in Hanks' balanced salt solution. The Si-HPMC/PTCP composite CPCs exhibited better biocompatibility and injectability than Si-HPMC/a-TCP; however, the Si-HPMC/PTCP composite CPCs have relatively lower mechanical properties than Si-HPMC/a-TCP. Therefore, these novel injectable cements can potentially be used as calcium phosphate cements for biomedical applications. (C) 2016 Published by Elsevier B.V.