ABSTRACT
Silica nanoparticles were synthesized via a sol-gel method in which tetraethyl orthosilicate was hydrolyzed by the alkaline core of the nitroxide radical-containing nanoparticle (RNP). The silica nanoparticles were successively captured in the RNP core to obtain silica/RNP nanocomposite (siRNP). Alternatively, siRNP was prepared using commercially available silica nanoparticles. The amount of elemental Si present in the siRNPs was controlled from 3 wt% to 12 wt%. Notably, the obtained siRNPs were stable in acidic media, whereas the starting RNP disintegrated immediately. Crosslinking of the RNP by the entrapped silica might improve stability of the siRNPs under such acidic conditions. Rebamipide was found to be stably encapsulated in the cores of the prepared siRNPs even under acidic conditions, probably due to the both basic environment of the cores and absorption tendencies of the entrapped silica. Under neutral to alkaline conditions, release of the rebamipide is accelerated, which is probably due to the repulsion between the anionic silica surface and the anionic rebamipide. Rebamipide-loaded siRNPs (rebamipide@siRNP) were orally administered to mice, and the plasma level of rebamipide was checked at predetermined time intervals, showing a significantly higher uptake of rebamipide in the plasma when compared to orally-administered free rebamipide. Because siRNP possesses nitroxide radicals in the core, it is confirmed that dextran sodium sulfate-induced colon inflammation was effectively suppressed by the oral administration of rebamipide@siRNP in mice.
Subject(s)
Alanine/analogs & derivatives , Anti-Inflammatory Agents/administration & dosage , Colon/metabolism , Drug Carriers/chemistry , Nanoparticles/chemistry , Nitrogen Oxides/chemistry , Quinolones/administration & dosage , Silicon Dioxide/chemistry , Administration, Oral , Alanine/administration & dosage , Alanine/blood , Alanine/therapeutic use , Animals , Anti-Inflammatory Agents/blood , Anti-Inflammatory Agents/therapeutic use , Colitis/drug therapy , Colitis/metabolism , Colon/drug effects , Delayed-Action Preparations , Drug Carriers/chemical synthesis , Drug Compounding , Drug Liberation , Male , Mice, Inbred ICR , Oxidation-Reduction , Quinolones/blood , Quinolones/therapeutic useABSTRACT
A new approach to the preparation of PEGylated [PEG: poly(ethylene glycol)] SiO(2)/Au hybrid nanoparticles was investigated. The synthesis of a PEGylated nanogel containing SiO(2)/Au hybrid nanoparticles was performed using matrix-catalyzed hydrolysis of tetraethyl orthosilicate, followed by the reduction of HAuCl(4). UV-vis absorption of the prepared hybrid particles was obtained at 618 nm, which is a much longer wavelength than that of a nanogel containing only Au nanoparticles (523 nm). High-angle annular dark field images of the prepared particles observed using transmission electron microscopy and energy-dispersive X-ray spectroscopy confirmed the coexistence of Si and Au in the same particle. The presence of Si and Au in the prepared particles was also confirmed by inductively coupled plasma atomic emission spectroscopy. Dynamic light-scattering measurements of the particles in a highly ionic medium showed that they have high stability in both acidic and basic regions.
