Effect of Polydopamine Nanoparticle-Induced Surface Modification on Demineralized Dentin for Enhanced Functional Remineralization.

Background: Development of biomimetic nanomaterials for remineralization therapy is an important strategy in minimally invasive dentistry. The size of the therapeutic agent has a great influence on bioavailability, penetration ability, and larger surface area for interaction in hard tissue remineralization through the nonclassical crystallization pathway. This study aimed to comparatively evaluate the remineralization-inducing potential of polydopamine (PDA) and polydopamine nanoparticles (nPDs) on artificially demineralized dentin. Methodology: nPDs were prepared using commercially procured dopamine hydrochloride by the wet precipitation method. Obtained particles were characterized using scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy, particle size analysis and zeta potential determination via dynamic light scattering with a laser particle analyser, X-ray diffraction, X-ray photoelectron spectroscopy, and attenuated total reflectance Fourier transform infrared spectroscopy. The cytocompatibility of nPD and PDA was assessed by (3-(4,5-dimethythiazol-2-yl) 2,5-diphenyl tetrazolium bromide) assay on human dental pulpal stem cell lines. A total of 66 demineralized dentin slabs of 3 mm × 3 mm × 1 mm dimension were immersed in 2 mg/ml of freshly prepared PDA and nPD solutions for 12 hours, followed by reimmersion in calcium and phosphate solution at 37°C days for 10 days. Samples immersed in deionized water were used as a control group. All the specimens were subjected to various remineralization testing methods using SEM-EDX, Vicker's microhardness, and micro-Raman spectroscopic analysis. The Shapiro-Wilk test was used to assess the normality of the distribution, followed by one-way ANOVA for intergroup analysis and Results: nPD exhibited a nanospherical morphology with positive zeta potential. nPD revealed the polymeric amorphous nature with characteristic functional groups and exhibited >80% relative cell viability. nPD promoted superior remineralization ability by the formation of hydroxyapatite closely mirroring the Ca/P ratio of natural dentin with a hardness value significantly closer to the baseline, which was further evidenced by higher-intensity peaks of phosphate, amide, and proline on micro-Raman spectroscopic analysis. Conclusion: Dentin remineralization is more strongly facilitated by nanometric PDA than PDA, which has an enhanced functional remineralization effect.