Trojan Horse Antibiotic Nanocarriers
of macrophages was ~88%, and there was no significant dif-
ference in cell viability as compared to the control experiment
(cells incubated in growth medium only), indicating that CD-
MAN-ERY possesses no significant cytotoxicity to RAW
264.7 macrophages. In addition to murine 3T3 fibroblasts
and RAW 264.7 macrophages, human NCM460 colonic ep-
ithelial and HEK 293T embryonic kidney cells were also used
for the evaluation of cytotoxicity of CD-MAN-ERY with
Tali™ scan analysis. As shown in Fig. S5, more than 85%
of NCM460 and HEK 293T cells remained viable after
incubation with 5 to 400 mg/L of free ERY for 24 h.
Similarly, more than 80% of NCM460 and HEK 293T cells
remained viable after incubation with CD-MAN-ERY, even
at a very high dosage (2000 mg/L, containing 300 mg/L of
ERY, corresponding to ~16 times of MIC for P. aeruginosa
PAO1) for 24 h. These findings are very similar to those ob-
tained from the MTT assay, and confirm that the CD-MAN-
ERY has no significant cytotoxicity to mammalian cells over
the concentration range tested.
authors would also like to thank Dr. Rong Wang from the
Department of Chemical & Biomolecular Engineering,
National University of Singapore for his assistance in the an-
tibiotic resistance assay.
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CONCLUSIONS
Mannose and glucose molecules were grafted on modified β-
cyclodextrin via alkyne-azide click reaction. The resultant CD-
MAN and CD-GLU were used as nanocarriers for loading
hydrophobic antibiotics (ERY, RIF and CIP) and delivering
these antibiotics into Gram-positive (S. aureus including MRSA)
and Gram-negative (E. coli, P. aeruginosa and A. baumannii) bac-
teria. These sugar-modified nanocarriers enhanced the deliv-
ery and accumulation of the loaded antibiotic in the bacterial
cells, and as a result, the minimum inhibitory concentration of
the loaded antibiotics against the tested bacteria were reduced
by a factor ranging from 3 to >100 compared to the free
antibiotics. In addition, the CD-MAN-antibiotic complex is
able to inhibit the development of antibiotic resistance of
S. aureus and E. coli, and prolong the stability of the loaded
antibiotic and its activity to inhibit bacterial growth. In view
of the paucity of new antibiotics in the pipeline, it is highly
advantageous that these non-cytotoxic sugar-modfied
nanocarriers can potentiate the activity of existing antibiotics,
especially against multidrug-resistant bacteria. However, in vivo
evaluation of the performance of these sugar-modified
nanocarriers is necessary since the in vitro assays cannot dupli-
cate the complicated biological environment, and the perfor-
mance of these carriers in oral or intravenous applications may
be very different from that in topical application.
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ACKNOWLEDGMENTS AND DISCLOSURES
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This work was financially supported by the National
University of Singapore Grant R-279-000-359-731. The