6.4 Experimental Methods


6.4.1 Nanocapsule Synthesis

 Synthesis of the core-shell nanocapsules was carried out according to the previous work

reported by our group.226 OTMS (0.09 g, Gelest Inc.), lecithin (0.05 g, Alfa Aesar), and Tween-

80 (2.8 g, Aldrich Chemical Co.) were used as the surfactants, and ethyl butyrate (0.4 g, Aldrich

Chemical Co.) was used as the hydrophobic oil phase. Microemulsion formation was carried out

by adding those four chemicals in saline solution (9 wt % NaCl aqueous solution, 26 mL) under

heating (70 oC) with vigorous stirring for at least 8 h. OTMS polycondensation was carried out at

pH = 3 using a 0.5 M HCI aqueous solution and by vigorous stirring for 30 min. The shell

thickness was controlled by reacting various amounts of TMOS (0.02 g-0.26 g, Gelest Inc.) with

the unreacted silanol groups of the OTMS molecules present at the microemulsion surface. This

last step was carried out after the pH of the nanocapsule solution was increased to neutral

conditions (pH 7.4) with 0.5 M NaOH and 0.5 M HEPES-buffered solutions. To remove

unreacted OTMS and TMOS, free Tween-80, and lecithin, extensive dialysis was performed

using Spectra/Por molecular porous membrane tubing with a molecular weight cutoff of 6-8000

Da.

6.4.2 Transmission Electron Microscopy

 For the TEM experiments, the nanocapsule core was doped with 1-dodecene (Aldrich

Chemical Co.). After deposition of a droplet on a carbon-coated nickel grid (Electron

Microscopy Sciences) and evaporation of the water in a desiccator, the nanocapsule core was

stained by exposure to OsO4 vapors (Aldrich Chemical Co.) in a closed container for at least 4 h.

All TEM images were obtained using a Hitachi H1-7000 instrument at 75 kV.