Abstract:A pH-sensitive stimulus-response system for controlled drug release was prepared by modifying nano porous silica nanoparticles (NPSNPs) with poly(4-vinylpyridine) using a bismaleimide as linker. At physiological pH values, the polymer serves as gate keeper blocking the pore openings to prevent the release of cargo molecules. At acidic pH values as they can occur during a bacterial infection, the polymer strains become protonated and straighten up due to electrostatic repulsion. The pores are opened and the cargo is released. The drug chlorhexidine was loaded into the pores because of its excellent antibacterial properties and low tendency to form resistances. The release was performed in PBS and diluted hydrochloric acid, respectively. The results showed a considerably higher release in acidic media compared to neutral solvents. Reversibility of this pHdependent release was established. In vitro tests proved good cytocompatibility of the prepared nanoparticles. Antibacterial activity tests with Streptococcus mutans and Staphylococcus aureus revealed promising perspectives of the release system for biofilm prevention. The developed polymer-modified silica nanoparticles can serve as an efficient controlled drug release system for long-term delivery in biomedical applications, such as in treatment of biofilm-associated infections, and could, for example, be used as medical implant coating or as components in dental composite materials.

The objective of this study was to test whether nanoporous silica nanoparticles can be employed as fillers in dental composite materials to improve their mechanical properties. These nanoporous silica nanoparticles were synthesized using sol-gel methods, in part modified by silanization, and thoroughly characterized. The nanoporous nanoparticles were added to dental resins to form nanocomposites (resins impregnated with nanoparticles) and hybrid composites (containing in addition conventional microfillers). The incorporation of these nano porous nanoparticles in dental resins or composites was characterized by investigation of the complex viscosity and double bond conversion as well as by determination of flexural strength and Young's modulus. The dispersion of the nanofillers was examined by SEM and EDX imaging of fracture surfaces. Incorporation of small contents (1-3 wt%) of unmodified nanoporous particles leads to improved mechanical properties. However, the incorporation of larger contents results in particle agglomeration and declining mechanical properties. This effect is less pronounced when the surface of the particles is modified with methacrylate residues, resulting in a lower agglomeration tendency and a more homogeneous filler dispersion. Surface properties and, concomitantly, dispersibility of the nanoparticles have a strong influence on mechanical properties. But the incorporation of nanoporous instead of solid nanoparticles into dental composite materials is indeed a possibility to improve the mechanical behavior. However, modification of the surface is necessary and the key to achieving uniform dispersion and, thereby, improving mechanical properties.

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The objective of this study was to test whether nanoporous silica nanoparticles can be employed as fillers in dental composite materials to improve their mechanical properties. These nanoporous silica nanoparticles were synthesized using sol-gel methods, in part modified by silanization, and thoroughly characterized. The nanoporous nanoparticles were added to dental resins to form nanocomposites (resins impregnated with nanoparticles) and hybrid composites (containing in addition conventional microfillers). The incorporation of these nanoporous nanoparticles in dental resins or composites was characterized by investigation of the complex viscosity and double bond conversion as well as by determination of flexural strength and Young's modulus. The dispersion of the nanofillers was examined by SEM and EDX imaging of fracture surfaces. Incorporation of small contents (1-3 wt%) of unmodified nanoporous particles leads to improved mechanical properties. However, the incorporation of larger contents results in particle agglomeration and declining mechanical properties. This effect is less pronounced when the surface of the particles is modified with methacrylate residues, resulting in a lower agglomeration tendency and a more homogeneous filler dispersion. Surface properties and, concomitantly, dispersibility of the nanoparticles have a strong influence on mechanical properties. But the incorporation of nanoporous instead of solid nanoparticles into dental composite materials is indeed a possibility to improve the mechanical behavior. However, modification of the surface is necessary and the key to achieving uniform dispersion and, thereby, improving mechanical properties. Keywords: anisotropic shape; hybrid composite; mechanical properties; nanoparticles; nanocomposite; nanoporosity Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.

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