Photophysical characteristics of green fluorescent proteins embedded in mesoporous silica hosts

The influences of host-guest interactions on the emission properties of enhanced green fluorescent protein (EGFP) embedded in mesoporous silica particles are studied in detail by fluorescence spectroscopy and microscopy. Silica particles from the MCM-41, ASNCs and SBA-15 families that all possess nanometer-sized (3-8 nm in diameter) channels but different particle geometry and pore sizes (distribution) are employed to host EGFPs in order to study the confinement effects. We find that it is necessary to first functionalize the surfaces of the silica particles with an amino-silane for effective encapsulation of EGFP. The spatial distributions of the EGFPs are studied by confocal laser scanning microscopy (CLSM) and N₂ sorption measurements. The embedded EGFP in MCM-41 displays an increase in the steady-state fluorescence emission anisotropy and a decrease in the fluorescence lifetime compared to solution values, clearly demonstrating a confinement effect due to the silica surroundings. This inorganic-protein host-guest system may also lead to composite materials with novel optical properties.