Nontoxic Antimicrobial Cationic Peptide Nanoconstructs with Bacteria-Displaceable Polymeric Counteranions.

Antimicrobial peptides that target the integrity of bacterial envelopes can eradicate pathogens with little development of resistance, but they often inflict nonselective toxicity toward mammalian cells. The prevailing approach to optimize the selectivity of cationic peptides has been to modify their composition. Instead, we invent a new generation of broad-spectrum antibacterial nanoconstructs with negligible mammalian cell toxicity through a competitive displacement of counter polyanions from the complementary polycations. The nanoconstruct, which has a highly cationic Au nanoparticles (NPs) core shielded by polymeric counterions, is inert in nonbacterial environments. When exposed to negatively charged bacterial envelopes, this construct sheds its polyanions, triggering a cationic Au NP/bacterial membrane interaction that rapidly kills Gram-positive and Gram-negative bacteria. The anionic charge and hydrophilicity of the polyanion provides charge neutralization for the peptide-decorated Au NP core, but it is also bacteria-displaceable. These results provide a foundation for the development of other cationic particles and polymeric counterion combinations with potent antimicrobial activity without toxicity.

Cationic Glycosylated Block Co-ß-peptide Acts on the Cell Wall of Gram-Positive Bacteria as Anti-biofilm Agents.

Antimicrobial resistance is a global threat. In addition to the emergence of resistance to last resort drugs, bacteria escape antibiotics killing by forming complex biofilms. Strategies to tackle antibiotic resistance as well as biofilms are urgently needed. Wall teichoic acid (WTA), a generic anionic glycopolymer present on the cell surface of many Gram-positive bacteria, has been proposed as a possible therapeutic target, but its druggability remains to be demonstrated. Here we report a cationic glycosylated block co-ß-peptide that binds to WTA. By doing so, the co-ß-peptide not only inhibits biofilm formation, it also disperses preformed biofilms in several Gram-positive bacteria and resensitizes methicillin-resistant Staphylococcus aureus to oxacillin. The cationic block of the co-ß-peptide physically interacts with the anionic WTA within the cell envelope, whereas the glycosylated block forms a nonfouling corona around the bacteria. This reduces physical interaction between bacteria-substrate and bacteria-biofilm matrix, leading to biofilm inhibition and dispersal. The WTA-targeting co-ß-peptide is a promising lead for the future development of broad-spectrum anti-biofilm strategies against Gram-positive bacteria.

Mixed-charge pseudo-zwitterionic copolymer brush as broad spectrum antibiofilm coating.

Zwitterionic polymers are classical antifouling polymers but they require specialized monomers that have cationic and anionic charges integrated into a single monomer. Herein, we show that pseudo-zwitterionic copolymers synthesized from a mixture of 2 monomers each having a single opposite polarity has excellent antibiofilm efficacy. We have discovered a new mixed-charge copolymer brush (#1-A) synthesized from 2 oppositely charged monomers, the anionic SPM (3-Sulfopropyl methacrylate) and the cationic AMPTMA ((3-Acrylamidopropyl) trimethylammonium chloride), that achieves broad spectrum in vitro antibiofilm effect of greater than 99% reductions against all six Gram-positive and Gram-negative bacteria tested. In the murine subcutaneous wound catheter infection models, the #1-A has good long-term anti-biofilm efficacy against MRSA and Pseudomonas aeruginosa of 3.41 and 3.19 orders respectively, outperforming previous mixed-charge copolymer coatings. We discovered a new method to choose the cationic/anionic pair combination to form the best antibiofilm copolymer brush coating by exploiting the solution polymerization kinetics disparity between the cationic and anionic monomers. We also showed that #1-A is softer and has higher hydration than the classical zwitterionic polymer. This study shows the possibility of achieving potent antibiofilm efficacy by combining readily available opposite singly charged monomers.

Enantiomeric glycosylated cationic block co-beta-peptides eradicate Staphylococcus aureus biofilms and antibiotic-tolerant persisters.

The treatment of bacterial infections is hindered by the presence of biofilms and metabolically inactive persisters. Here, we report the synthesis of an enantiomeric block co-beta-peptide, poly(amido-D-glucose)-block-poly(beta-L-lysine), with high yield and purity by one-shot one-pot anionic-ring opening (co)polymerization. The co-beta-peptide is bactericidal against methicillin-resistant Staphylococcus aureus (MRSA), including replicating, biofilm and persister bacterial cells, and also disperses biofilm biomass. It is active towards community-acquired and hospital-associated MRSA strains which are resistant to multiple drugs including vancomycin and daptomycin. Its antibacterial activity is superior to that of vancomycin in MRSA mouse and human ex vivo skin infection models, with no acute in vivo toxicity in repeated dosing in mice at above therapeutic levels. The copolymer displays bacteria-activated surfactant-like properties, resulting from contact with the bacterial envelope. Our results indicate that this class of non-toxic molecule, effective against different bacterial sub-populations, has promising potential for the treatment of S. aureus infections.