Silica-Based Nanoparticles for Intracellular Drug Delivery - Intracellular Delivery: Fundamentals and Applications - page 341

Taken together, these data suggest that silica nanoparticles impact on cell viability
is three-fold: (1) surface interaction, (2) internalization and (3) solubility.
Considering the first point, detrimental interactions exist between surface silanol
groups and cell membrane, that can lead to cell damage via oxidative stress and
even cell lysis. As a result, for plain silica nanoparticles, toxicity increases with
decreasing particle size. For mesoporous materials, these interactions decrease
with increasing porosity. Interestingly, a recent study showed that the mesoporosity
of some silica particles tends to collapse with time, increasing the plain surface of
the colloid and therefore its toxicity. Along the same lines, grafting the particle
surface with cationic groups (such as amino) or neutral hydrophilic groups (such
as PEG) or preparing hybrid particles incorporating cationic polymers (such as
chitosan) decreases the observed toxicity. Indeed, all these effects were shown to
be dose- and cell-dependent (Fig. 2 ).
Considering the second point, internalization processes will be discussed to a
large extent in the Sect. 4 . At this stage, it is just important to emphasize that no
Fig. 2 Analysis of silica nanoparticles (15 nm) toxicity via global DNA methylation in HaCaT
cells: ( a ) Anti-5-methylcytosine (5-mC) immunofluorescence ( green ). Nuclei were counterstained
with DAPI ( blue ), ( b ) Quantitative representation of fluorescence of 5-mC (Reprinted from (Gong
et al. 2010 ), Copyright (2010), with permission from Elsevier)