(A) SEM (i), TEM bright-field (ii) and TEM dark-field (iii) micrographs of collagen fibrils mineralized with 450k-50 PAA solution for 7 days. Insert in Aii is the SAED pattern of the mineralized fibril shown in Aii and Aiii. Scale bar: 100nm. (B) ATR-FTIR spectra of collagen matrices mineralized for 7 days with 450k-10, 450k-50, 2k-10, 2k-50 PAA solutions and control pure type I collagen. Characteristic absorption bands of carbonated HAp are labeled. (C) XRD spectra of collagen matrices mineralized for 7 days with 2k-10, 450k-10 and 450k-50 PAA solutions. Characteristic peaks of HAp for the (002), (210), (211), (300), (310), (311) planes are labeled.