  Aminopropyl modified mesoporous SiO2 nanoparticles, MCM-41 type, have been
synthesized by the co-condensation method from tetraethylorthosilicate (TEOS)
and aminopropyltriethoxysilane (APTES). By means of modifying TEOS/APTES ratio
we have carried out an in-depth characterization of the nanoparticles as a
function of APTES content. Surface charge and nanoparticles morphology were
strongly influenced by the amount of APTES and particles changed from hexagonal
to bean-like morphology insofar APTES increased. Besides, the porous structure
was also affected, showing a contraction of the lattice parameter and pore
size, while increasing the wall thickness. These results bring about new
insights about the nanoparticles formation during the co-condensation process.
The model proposed herein considers that different interactions stablished
between TEOS and APTES with the structure directing agent have consequences on
pore size, wall thickness and particle morphology. Finally, APTES is an
excellent linker to covalently attach active targeting agents such as folate
groups. We have hypothesized that APTES could also play a role in the
biological behavior of the nanoparticles. So, the internalization efficiency of
the nanoparticles has been tested with cancerous LNCaP and non-cancerous
preosteoblast-like MC3T3-E1 cells. The results indicate a cooperative effect
between aminopropylsilane presence and folic acid, only for the cancerous LNCaP
cell line.
