One-dimensional titanate nanotubes (TiONTs) were subjected to systematic ion exchange
to determine the impact of these modifications on biological activities. Ion exchanged
TiONTs (with Ag, Mg, Bi, Sb, Ca, K, Sr, Fe, and Cu ions) were successfully synthesized
and the presence of the substituted ions was verified by energy dispersive X-ray spectroscopy
(EDS). A complex screening was carried out to reveal differences in toxicity to human
cells, as well as in antibacterial, antifungal, and antiviral activities between the
various modified nanotubes. Our results demonstrated that Ag ion exchanged TiONTs
exerted potent antibacterial and antifungal effects against all examined microbial
species but were ineffective on viruses. Surprisingly, the antibacterial activity
of Cu/TiONTs was restricted to Micrococcus luteus. Most ion exchanged TiONTs did not
show antimicrobial activity against the tested bacterial and fungal species. Incorporation
of various ions into nanotube architectures lead to mild, moderate, or even to a massive
loss of human cell viability; therefore, this type of biological effect exerted by
TiONTs can be greatly modulated by ion exchange. These findings further emphasize
the contribution of ion exchange in determining not only the physical and chemical
characteristics but also the bioactivity of TiONT against different types of living
cells.
