Bone models set for studying apatite mineralization tend to use excess of organic additives and a very low concentration of collagen in the light of those described in the biological tissue. However, the activity of soluble additives during mineral deposition is highly dependent on their concentration and confinement state, among others. Here, we investigate the role of concentration of organic additives described as key components in bone mineralization, i.e. the bioinspired synthetic

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... tate mimicking non-collagenous protein (NCP), citrate and collagen, on apatite formation. The precipitation set-up tends to mimic the acidic mineralization front in bone and was monitored by in situ Raman and ex situ solid-state nuclear magnetic resonance (ssNMR). This model helps to identify specific effects of organic additives on mineral formation. In particular, we show that the sequence of apatite precursors often described in vitro, i.e. amorphous calcium phosphate (ACP) and subsequent octacalciumphosphate (OCP) formation, is noticeably modified by varying the concentration of the additives. NCP and citrate are identified as either inhibitor or activator in the formation of calcium phosphate (CaP). Besides, collagen acts either as additives or as organic scaffold below and above the liquid-crystal threshold, respectively. This result highlights that confinement drives thermodynamically apatite formation by slowing down the kinetic formation of precursors, even at alkaline pH.