Development Of PH Responsive Hollow Mesoporous Silica As Delivery Devices For PAA-ACP For Management Of Initial Caries

Objectives: Initial caries is one common side effect in orthodontic treatment,especially in patients with poor oral hygiene.The amorphous phosphate calcium(ACP),which could release calcium and phosphate ions,might enhance remineralization and inhibit the development of initial lesions.The objectives of the current study were to develop amine functionalization(AF)of large pore hollow mesoporous silica nanoparticles(AFLP-HMS)as the cargo to load ACP,and to test the effects of the composites on the remineralization of initial caries in-vitro.Methods: The hollow mesoporous silica nanoparticles(HMS)were synthesized through a selective etching strategy assisted by cationic surfactant with moderate modifications.1,3,5-trimethylbenzene(TMB)was employed as pore swollen to get large pore hollow mesoporous silica nanoparticles(LP–HMS).Amine groups were grafted on the surface of nanoparticles by a post-graft approach.Polyacrylic acidstabilized amorphous calcium phosphate(PAA-ACP)was developed by supersaturated solution method.Therefore,negatively charged PAA-ACP could be effectively loaded by positively charged AF-LP-HMS through electrostatic attraction(PAA-ACP @AFLP-HMS).In the oral cavity,since the local p H values could fluctuate from 7.0 to 4.0,the composites were immersed in the sodium chloride solution with p H values of 7.0,5.5 and 4.0 to investigate the release behavior of Ca and P ions.Results: The large pore hollow mesoporous silica nanoparticles were synthesized successfully through using TMB as pore swollen agent.Amine groups were successfully bonded to the surface of the LP-HMS to get positively charged nanoparticles by a post-graft approach,which facilitates the adsorption of negatively charged PAA-ACP.The release of Ca and P ions from PAA-ACP @AF-LP-HMS increased with the decrease in the external environment p H value through inductively coupled plasma-atomic emission spectroscopy(ICP-AES)analysis.And the SEM images and microhardness test confirmed the composites' capacity of enhancing remineralization.Conclusion: PAA-ACP@AF-LP-HMS could facilitate remineralization of initial caries through release of Ca and P ions in-vitro.And it was responsive to external environment p H,which indicated that the material released more Ca and P ions when local p H reduced.Hence,the novel material is promising in dental clinical practice and provided clinicians a new strategy for the management of incipient caries lesions formation.