  The design of drug delivery systems needs to consider biocompatibility and
host body recognition for an adequate actuation. In this work, mesoporous
silica nanoparticles (MSNs) surfaces were successfully modified with two silane
molecules to provide mixed-charge brushes (-NH3/-PO3) and well evaluated in
terms of surface properties, low-fouling capability and cell uptake in
comparison to PEGylated MSNs. The modification process consists in the
simultaneous direct-grafting of hydrolysable short chain amino (aminopropyl
silanetriol, APST) and phosphonate-based
(trihydroxy-silyl-propyl-methyl-phosphonate, THSPMP) silane molecules able to
provide a pseudo-zwitterionic nature under physiological pH conditions. Results
confirmed that both mixed-charged pseudo-zwitterionic MSNs (ZMSN) and PEG-MSN
display a significant reduction of serum protein adhesion and macrophages
uptake with respect to pristine MSNs. In the case of ZMSNs, his reduction is up
to a 70-90% for protein adsorption and c.a. 60% for cellular uptake. This
pseudo-zwitterionic modification has been focused on the aim of local treatment
of bacterial infections through the synergistic effect between the capability
of the nanocarriers to transport and deliver specific drugs and the
electrostatic interactions between the mixed-charge systems and bacteria. These
findings open promising future expectations for the effective treatment of
bacterial infections through the use mixed-charge pseudo-zwitterionic MSNs
furtive to macrophages and with antimicrobial properties.
