Silica nanoparticle coated long-period grating for in situ monitoring of drug delivery thin films

摘要

Dielectric nanoparticle in integration with the long-period grating (LPG) is explored and its effect on the sensitivity is evaluated in the in situ monitoring of the deposition of drug delivery thin film. SiNPs were immobilized on the LPG via layer-by-layer self-assembly using poly allylamine hydrochloride (PAH). Theoretical calculation reveals that the SiNPs coating increases the evanescent field overlap in the surrounding of the LPG thus enhances its sensitivity. The increased total surface for the following thin film deposition also contributes to the enhancement of the sensitivity. Its unique capability for the in-situ monitoring of drug delivery thin film [chitosan (CHI) / Poly arylic acid (PAA) / Gentamicin sulfate (GS) /PAA]n through layer-by-layer assembly (LbL) was demonstrated with a sensitivity of 8.1 nm shift/tetralayer for LPG with 1 layer of SiNPs with 50 nm in diameter. The sensitivity enhancement of the LPG also depends heavily on the layer numbers and sizes of the SiNPs. The LPG with SiNPs of 8 layer numbers exhibits a sensitivity of only 1.2 nm shift/tetralayer. Control experiment of LPG without the SiNPs for the monitoring of [CHI/PAA/GS/PAA]_n shows a sensitivity of 2.4 nm shift/tetralayer. This investigation suggests that SiNPs are effective in fine tune the optical property of the LPG. SiNPs coating thick enough can be used as an effective insulation for LPG from outer species. This investigation sets up the foundation for the development of SiNPs enabled optical fiber LPG sensor for the in-situ study of drug delivery LbL thin film.