Materials Chemistry and Physics, Vol.220, 201-207, 2018
Synthesis on aggregation of colloidal solutions of ICG-active silica nanoparticles and their application in in-vivo fluorescence imaging
This study reports two findings. The first is a method for preparing a colloidal solution of silica (SiO2) nanoparticles activated with fluorescent dye or fluorescent dye-active SiO2 nanoparticles. Preparation of a colloid solution of spherical SiO2 nanoparticles with an average size of 109.4 +/- 8.6 nm was performed using the sol-gel method at 35 degrees C using 0.2 M tetraethylorthosilicate, 25 M H2O, and 0.01 M NaOH in ethanol. Two kinds of cationic chemicals (poly-diallyldimethylammonium chloride (PDADMAC) and (3-aminopropyl) triethoxysilane (APES) were examined for surface-modification or surface-cationization of the SiO2 nanoparticles (SiO2/PDADMAC and SiO2/APES). To activate the SiO2 nanoparticles with fluorescent dye, indocyanine green (ICG) molecules were fixed on the surface-modified SiO2 nanoparticles by mixing ICG dissolved in albumin aqueous solution and the surface-modified SiO2 nanoparticle colloid solution (SiO2/PDADMAC/ICG and SiO2/APES/ICG) through electrostatic aggregation. The second finding is the verification of the fluorescence ability of the ICGactive SiO2 nanoparticle colloid solutions. Both the ICG-active SiO2 nanoparticle colloid solutions exerted fluorescence even at high ICG concentrations. Mouse tissues could be imaged by injecting the ICG-immobilized SiO2 nanoparticle colloid solution into the tail vein of the mouse and measuring the emitted fluorescence intensity. Pulmonary embolism was avoided in the SiO2/APES/ICG particle colloid solution-injected group, in which the particles reached the tissues more efficiently than in the SiO2/PDADMAC/ICG nanoparticles-injected group.