Magnetic guidance shape memory PLA/TBC/Fe₃O₄ microspheres for dentin tubule sealing

Shape memory polymer (SMP) microspheres possess controllable physicochemical properties, internal cavities capable of loading drugs or nanoparticles, and inherent intelligence, making them suitable for various biomedical applications. In this research, we utilized tri-n-butyl citrate (TBC) to lower the glass transition temperature of shape memory polylactic acid (PLA) to approximate oral temperature. Following this, we introduced oleic acid-modified Fe₃O₄ nanoparticles to confer magnetism to the material. Subsequently, SMP microspheres with a core–shell structure encapsulating Fe₃O₄ particles were prepared using the emulsion-solvent evaporation method, and we carefully controlled their particle size and morphology to match the diameter of dentinal tubules. Our investigation focused on applying these magnetically guided microspheres, which exhibited excellent shape memory performance, for sealing dentinal tubules. These microspheres displayed the ability to move directionally under the influence of a magnetic field. As a result, they could be attracted into the interior of dentinal tubules in their temporary shape and then revert to their initial shape upon heating at 40 °C, thereby achieving the closure of dentinal tubules effectively. The microsphere entry rate during the tubule closure process was found to be 93.33 ± 2.82 %, with a corresponding sealing rate of 85.41 ± 7.11 %. The successful demonstration of magnetic-guided movement and the utilization of the shape memory function for dentinal tubule sealing significantly expand the potential applications of SMP microspheres in the field of biomedical science.