Development and hazard assessment of nanoparticles

A series of highly monodisperse silicon nanoparticles (Si NP) with either
positively (amine), neutral (azide) or negatively (carboxylic acid) charged
covalently attached organic monolayers were synthesized and investigated for
their cytotoxicity. Infrared data confirmed the presence of these covalently
attached surface groups. The Si NP were characterized by absorption and
fluorescence spectroscopy. The cytotoxicity was investigated in Caco -2 cells by
determining the cell viability and proliferation. The EC50 values for the Si NP
ranged from 20 μg/l for the amine-terminated Si NP, via 550–850 μg/l for the
azide-terminated Si NP to non-toxic (no measureable EC50) for the carboxylic acid -
terminated Si NP. These results indicated a trend in cytotoxicity, depending on
surface charge, i.e. that positively charged Si NP we re more cytotoxic than
negatively charged Si NP. Interestingly, it appeared that the cytotoxicity of the
amine terminated Si NP (Si NP-NH2) depended strongly on the presence of fetal calf
serum (FCS) in the medium.