BACKGROUND: Both hydroxyapatites (HAp) and bacterial cellulose (BC) are excellent biomaterials. The former has outstanding osteoconductivity and bioactivity, while the latter has been proven to be a remarkably versatile biomaterial. By alkaline treatment, Ca2+ activation, and biomimetic mineralization, the nanocomposites (CaDHCAp/BC) consisting of calcium-deficient carbonate-containing hydroxyapatite (CaDHCAp) in the three-dimensional (3D) network of BC nanofibers were synthesized. RESULTS: The CaDHCAp/BC nanocomposites obtained were characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD). The results indicated that alkaline treatment improved the apatite nucleation ability of BC, and the apatite crystals deposited along BC nanofibers were partially substituted with calcium carbonate and the uniform spherical apatite particles were composed of squama-shaped nano-sized apatite crystals. The crystallite sizes of apatite crystals are below 10 nm and the crystallinities are below 1 %. The formation mechanism of CaDHCAp crystals along the BC fibers was described. CONCLUSION: Alkaline treatment was introduced before the biomimetic mineralization process. Compared with the results without alkaline treatment, the mineralization efficiency was obviously improved. The nanocomposites obtained may have potential application as an orthopedic biomaterial. (C) 2008 Society of Chemical Industry