  Novel materials, based on Mesoporous Bioactive Glasses (MBGs) in the ternary
system SiO2-CaO-P2O5, decorated with (3-aminopropyl)triethoxysilane (APTES) and
subsequently with amino acid Lysine (Lys), by post-grafting method on the
external surface of the glasses (named MBG-NH2 and MBG-Lys), are reported. The
surface functionalization with organic groups did not damage the mesoporous
network and their structural and textural properties were also preserved
despite the high solubility of MBG matrices. The incorporation of Lys confers a
zwitterionic nature to these MBG materials due to the presence of adjacent
amine and carboxylic groups in the external surface. At physiologic pH, this
coexistence of basic amine and carboxilic acid groups from anchored Lys
provided zero surface charge named zwitterionic effect. This behaviour could
give rise to potential applications of antibacterial adhesion. Therefore, in
order to assess the influence of zwitterionic nature in in vitro bacterial
adhesion, studies were carried out with Staphylococcus aureus. It was
demonstrated that the efficient interaction of these zwitterionic pairs onto
the MBG surfaces reduced bacterial adhesion up to 99.9% compared to bare MBGs.
In order to test the suitability of zwitterionic MBGs materials as bone grafts,
their cytocompatibility was investigated in vitro with MC3T3-E1 preosteoblasts.
These findings suggested that the proposed surface functionalization strategy
provided MBG materials with notable antibacterial adhesion properties, hence
making these materials promising candidates for local bone infection therapy.
