The purpose of this study is to synthesize mesoporous calcium silicate (CS or wollastonite, CaSiO(3)) and evaluate its possible application in protein/drug delivery. First, calcium silicate was synthesized by wet chemical method and then mesoporosity was created by acid modification of the synthesized CS particle using hydrochloric acid at pH 7, 4.5, and 0.5. The results showed that a hydrated silica gel with abundant Si-OH functional group formed on the surface of calcium silicate due to acid modification. This surface layer had mesoporous structure, with pore diameter between 4 and 5 nm. BET specific average surface area increased to 221, 333, and 356 m(2) g(-1) due to acid modification at pH 7, 4.5, and 0.5, respectively, whereas the surface area for unmodified CS particles was 65 m(2) g(-1). Protein adsorption studies indicated that mesoporous CS has higher ability to adsorb bovine serum albumin and lysozyme compared to unmodified particles. The release kinetics showed that proteins on mesoporous CS released sequentially over one week, whereas the proteins on unmodified particle followed burst release kinetics within a few hours. Human osteoblast cell-material interaction study showed that these materials were biocompatible and promoted excellent bone cell proliferation. In summary, this work has demonstrated the potential to produce mesoporous CS as a carrier for protein/drug delivery for bone regeneration and other biomedical applications.