Polydopamine-assisted co-deposition of polyacrylic acid inducing dentin biomimetic mineralization for tooth-like structure repair in vitro

The aging of the global population has caused dentin exposure and root caries to become significant patient-management issues in clinical dentistry. Biomimetic remineralization, as a non-invasive therapeutic method, is of great significance to solve the problem. Herein, a novel biomimetic-mineralizing strategy to induce the self-healing of dentin defects with similar tooth structure was developed through the easy one-step polydopamine (PDA)-assisted co-deposition of polyacrylic acid (PAA) (denoted as PDA@PAA) in vitro. Immersing demineralized dentin into PAA and dopamine (DA) mixed solutions. Hereafter, the modified demineralized dentin was immersed in the supersaturated solution of calcium and phosphate at 37 °C at designated time. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and attenuated total reflection fourier transform infrared (ATR-FTIR) were performed to analyze the interaction and co-deposition between PDA and PAA. The remineralization of demineralized dentin was characterized by field emission scanning electron microscope (FE-SEM), TEM, X-ray diffraction (XRD), friction and wear test, nanoindentation, acid resistance. And the cytocompatibility of PDA@PAA was evaluated by cell counting kit-8 (CCK-8) and cell morphology observation. The results that PAA inhibited further PDA polymerization and aggregation, PDA@PAA were co-deposited onto the surface of demineralized dentin matrix. SEM and TEM showed that the demineralized-dentin modified with PDA@PAA was completely remineralized at 12 h, not only the dentin tubules were occluded, but more importantly, the demineralized dentin collagen matrix was remineralized. Moreover, after mineralization for 24 h, a dense mineral layer similar to enamel structure was regenerated on the surface of dentin and closely combined with dentin. The results of mechanical properties and acid resistance suggested that the mechanical properties of the regenerated enamel-like structure are close to that of enamel, and its acid resistance is better than that of enamel. This study demonstrated that the PDA-assisted co-deposition of PAA can offer an inexpensive, rapid, and efficient strategy for the management of illnesses related to exposed and demineralized dentin.