The phosphorylated noncollagenous proteins (NCPs) play a vital role in manipulating biomineralization, while the mechanism of phosphorylation of NCPs in intrafibrillar mineralization of collagen fibril has not been completely deciphered. Poly(vinylphosphonic acid) (PVPA) and sodium trimetaphosphate (STMP) as templating analogs of NCPs induce hierarchical mineralization in cooperation with indispensable sequestration analogs such as polyacrylic acid (PAA) via polymer-induced liquid-like precursor (PILP) process. Herein, STMP-Ca and PVPA-Ca complexes are proposed to achieve rapid intrafibrillar mineralization through polyelectrolyte-Ca complexes pre-precursor (PCCP) process. This strategy is further verified effectively for remineralization of demineralized dentin matrix both in vitro and in vivo. Although STMP micromolecule fails to stabilize amorphous calcium phosphate (ACP) precursor, STMP-Ca complexes facilely permeate into intrafibrillar interstices and trigger phase transition of ACP to hydroxyapatite within collagen. In contrast, PVPA-stabilized ACP precursors lack liquid-like characteristic and crystallize outside collagen due to rigid conformation of PVPA macromolecule, while PVPA-Ca complexes infiltrate into partial intrafibrillar intervals under electrostatic attraction and osmotic pressure as evidenced by intuitionistic 3D stochastic optical reconstruction microscopy (3D-STORM). The study not only extends the variety and size range of polyelectrolyte for PCCP process but also sheds light on the role of phosphorylation for NCPs in biomineralization.
Dental caries is a common oral disease and lacks an effective recovery method. The objective of the study was to investigate the remineralization efficiency of polyelectrolyte‑calcium complexes pre-precursor (PCCP) and polymer-induced liquid-like precursors (PILP) processes on mechanical and biochemical properties of dentin artificial caries lesions (ACLs) evaluated with micro-CT, SEM, TEM, ATR-FTIR, Raman spectra and nanoindentation. The human dentin ACLs were prepared with the depth of 100–120 μm. The intact dentin served as positive control and the dentin ACLs as negative control. The dentin ACLs were either incubated in poly-L-aspartic acid‑calcium suspension (PAsp-Ca, 4 g/L-5.44 M) followed by phosphate solution (0.325 M), and further incubated in artificial saliva serving as PCCP group, or in PAsp-stabilized amorphous calcium phosphate solution serving as PILP group. The micro-CT and SEM findings with EDX indicated that mineral contents of the dentin ACLs were dramatically increased in PCCP group, but, to some degree in PILP group. TEM and nanoindentation results showed that a heavy remineralization of dentin ACLs was obtained via PCCP process with an obvious recovery of mechanical properties while a poor remineralization via PILP process. In conclusion, the PCCP process is a promising strategy for functional remineralization of dentin caries lesions.
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