he resulting silica nanomaterials.
3.6. Potential Applications of the HSNs. Hollow
nanomaterials are of great interest for applications in drug
delivery and catalysis. To investigate potential applications of
the developed hollow nanomaterials, the HSSNs were selected
as an example to study its drug-carrying ability. In this work, we
studied whether drugs could maintain their activity after being
encapsulated in the HSNs.
Polymyxin B, a well-known drug for its biocidal activity on a
number of bacteria, was chosen as a model drug. The
antimicrobial efficacy of the polymyxin B-doped HSNs was
examined against Gram-negative E. coli bacteria, which has been
used as a model bacterial system for various antimicrobial tests.
Without the addition of polymyxin B-doped HSNs, a full
bacterial layer on the surface was observed (Figures 1, 6, and
11). However, in the dish with the highest concentration of
polymyxin B-doped HSNs (Figures 2 and 11), the dish surface
was completely free from bacteria. As the concentration of the
polymyxin B-doped HSSNs decreased, bacterial colonies
gradually increased (Figures 3−5 and 11).
We further quantitatively evaluated the antibacterial activity
of the polymyxin B-doped HSSNs by studying the growth
kinetics of bacteria in a LB liquid medium. The bacterial
proliferation was measured using OD600 based on the turbidity
of the cell suspension within 24 h. The growth curve showed a
typical concentration-dependent antibacterial effect of the
polymyxin B-doped HSSNs (Figure 12). The bacteria growth
curves in the presence of polymyxin B-doped HSSNs were
significantly different from the ones in the two control media
(H2O and pure HSSNs) in the first 8 h, suggesting strong
inhibition of proliferation of E. coli. Complete inhibition of E.
coli growth during the whole 24 h was observed when 0.100
mg/mL polymyxin B-doped HSSNs were used. These data
strongly suggest a long-term antibacterial activity of polymyxin
B after being doped in the HSSNs.