<p>Pathogenic bacteria present a
critical threat to modern medicine. Therapeutic strategies to target and
eliminate resilient bacteria are not advancing at the same rate as the
emergence of bacterial resistance. An associated urgent concern regarding antibiotic resistance is
the existence and proliferation of intracellular bacteria, which find refuge
from bactericidal mechanisms by hiding within mammalian cells. Therefore, many once-successful
antibiotics become ineffective through the development of resistance, or through
failure to reach intracellular locations in therapeutic concentration. To
overcome these challenges, the covalent combination of a conventional
antibiotic with an antibiotic, cell-penetrating peptide was explored to develop
dual-action antibiotic conjugates. </p>
<p>Herein, we utilized a strategy in conjugating the antibiotics
by a cleavable linkage to cationic amphiphilic polyproline helices (CAPHs) to
improve vancomycin and linezolid antibiotics. This approach enables the
conjugate to penetrate cells and deliver two potent monomeric antimicrobial
drugs. The vancomycin-CAPH conjugate, <b>VanP14S</b>, showed enhanced mammalian
cell uptake compared to vancomycin, a poor mammalian cell-penetrating agent; and
<b>VanP14S</b> was capable of cleaving and releasing two antibiotics under mimicked
physiological conditions. Enhanced antibacterial activity was observed against
a spectrum of Gram-positive and Gram-negative pathogens, including drug-resistant
strains. Further investigation revealed that this conjugate’s bactericidal
activity was not entirely the result of significant membrane perturbation such
as a lytic mode of action. Mammalian cell toxicity and red blood cell lysis were
insignificant at relevant bactericidal concentrations below 20 µM. The current results suggest an
enhanced binding to the peptidoglycan of bacteria, the target of vancomycin,
although more work is needed to justify this claim. Preliminary results on <b>VanP14GAPS</b>,
a conjugate with a more rigid CAPH, convey similar activity to <b>VanP14S; </b>however,<b>
</b>moderate increases in red blood cell lysis and cytotoxicity were observed. </p>
<p>Regarding the <b>LnzP14</b> conjugate, preliminary data reveal
that the conjugate has Gram-negative activity against <i>Escherichia coli</i>,
whereas linezolid is ineffective in killing Gram-negative bacteria. This
conjugate showed significant enhancement in cellular uptake compared to the CAPH,
and the release of linezolid and CAPH in physiological conditions was confirmed.
Overall, arming a conventional antibiotic with an antimicrobial,
cell-penetrating peptide appears to be a powerful strategy in providing novel
antibiotic conjugates with the propensity to overcome the limitations in treating
challenging pathogens.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/14484477 |
| Date | 26 April 2021 |
| Creators | Samantha Mae Zeiders (10010291) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/EXPLORING_ANTIBIOTIC_CONJUGATION_TO_CATIONIC_AMPHIPHILIC_POLYPROLINE_HELICES/14484477 |
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