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Haktaniyan M, Sharma R, Bradley M. Size-Controlled Ammonium-Based Homopolymers as Broad-Spectrum Antibacterials. Antibiotics (Basel) 2023; 12:1320. [PMID: 37627740 PMCID: PMC10452032 DOI: 10.3390/antibiotics12081320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 08/08/2023] [Accepted: 08/14/2023] [Indexed: 08/27/2023] Open
Abstract
Ammonium group containing polymers possess inherent antimicrobial properties, effectively eliminating or preventing infections caused by harmful microorganisms. Here, homopolymers based on monomers containing ammonium groups were synthesized via Reversible Addition Fragmentation Chain Transfer Polymerization (RAFT) and evaluated as potential antibacterial agents. The antimicrobial activity was evaluated against Gram-positive (M. luteus and B. subtilis) and Gram-negative bacteria (E. coli and S. typhimurium). Three polymers, poly(diallyl dimethyl ammonium chloride), poly([2-(methacryloyloxy)ethyl]trimethylammonium chloride), and poly(vinyl benzyl trimethylammonium chloride), were examined to explore the effect of molecular weight (10 kDa, 20 kDa, and 40 kDa) on their antimicrobial activity and toxicity to mammalian cells. The mechanisms of action of the polymers were investigated with dye-based assays, while Scanning Electron Microscopy (SEM) showed collapsed and fused bacterial morphologies due to the interactions between the polymers and components of the bacterial cell envelope, with some polymers proving to be bactericidal and others bacteriostatic, while being non-hemolytic. Among all the homopolymers, the most active, non-Gram-specific polymer was poly([2-(methacryloyloxy)ethyl]trimethylammonium chloride), with a molecular weight of 40 kDa, with minimum inhibitory concentrations between 16 and 64 µg/mL, showing a bactericidal mode of action mediated by disruption of the cytoplasmic membrane. This homopolymer could be useful in biomedical applications such as surface dressings and in areas such as eye infections.
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Affiliation(s)
- Meltem Haktaniyan
- EaStCHEM, School of Chemistry, University of Edinburgh, Joseph Black Building, West Mains Road, Edinburgh EH9 3FJ, UK; (M.H.); (R.S.)
| | - Richa Sharma
- EaStCHEM, School of Chemistry, University of Edinburgh, Joseph Black Building, West Mains Road, Edinburgh EH9 3FJ, UK; (M.H.); (R.S.)
| | - Mark Bradley
- EaStCHEM, School of Chemistry, University of Edinburgh, Joseph Black Building, West Mains Road, Edinburgh EH9 3FJ, UK; (M.H.); (R.S.)
- Precision Healthcare University Research Institute, Queen Mary University of London, Whitechapel, Empire House, London E1 1HH, UK
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Affiliation(s)
- Phuong Pham
- Centre for Advanced Macromolecular Design and Australian Centre for NanoMedicine School of Chemical Engineering The University of New South Wales Sydney NSW 2052 Australia
| | - Susan Oliver
- Centre for Advanced Macromolecular Design and Australian Centre for NanoMedicine School of Chemical Engineering The University of New South Wales Sydney NSW 2052 Australia
| | - Cyrille Boyer
- Centre for Advanced Macromolecular Design and Australian Centre for NanoMedicine School of Chemical Engineering The University of New South Wales Sydney NSW 2052 Australia
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Shao Z, Wulandari E, Lin RCY, Xu J, Liang K, Wong EHH. Two plus One: Combination Therapy Tri-systems Involving Two Membrane-Disrupting Antimicrobial Macromolecules and Antibiotics. ACS Infect Dis 2022; 8:1480-1490. [PMID: 35771275 DOI: 10.1021/acsinfecdis.2c00087] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The escalating issue of multidrug-resistant (MDR) bacteria indicates the urgent need for new and effective strategies to combat this global health challenge. Here, we describe a new combinatorial approach that can be put forward for experimental therapy application against MDR bacteria. Specifically, we have developed a tri-system that includes the coadministration of two different membrane-disrupting-type antimicrobial agents─a synthetic antimicrobial polymer P and an antimicrobial peptide (AMP) colistin methanesulfonate (Col)─in conjunction with an antibiotic [doxycycline (Dox), rifampicin (Rif), or azithromycin (Azi)]. Traditionally, the administration of membrane-disrupting antimicrobial agents causes toxicity, but, in comparison, we demonstrated synergy and biocompatibility using this combinatorial approach. Checkerboard assays showed the occurrence of synergistic interactions in Col-Dox-P, Col-Rif-P, and Col-Azi-P tri-systems against wild-type and MDR Pseudomonas aeruginosa, with the Col-Dox-P system being the most effective. The ability to synergize thus enables the use of a lower dosage in combinations compared to the standalone agents. The tri-systems not only demonstrated bacteriostatic activity but were also bactericidal. For example, the Col-Dox-P system (at 8, 4, and 8 μg mL-1, respectively) and the Col-Rif-P system (at 4, 8, and 16 μg mL-1, respectively) were able to kill >99.999% of planktonic P. aeruginosa cells within 3 h of treatment. More importantly, an improvement of the therapeutic/selectivity index was achieved via combination therapy. Taking the Col-Dox-P system as an example, its biocompatibility with murine embryonic fibroblast cells was found to be comparable to that of polymer P alone despite the synergistic enhancement in antimicrobial activity of the combination. This resulted in a significant increase in selectivity by 16-fold for the Col-Dox-P combination system compared to P alone. Furthermore, the broad applicability of this tri-system strategy was demonstrated via the successful application of the AMP melittin in place of Col or P. Overall, this study sheds new insights on the application of membrane-disrupting antimicrobial agents in combination therapy and their potential for safer clinical use. Additionally, the information gathered in this study could inform the development of future combination therapy systems involving the simultaneous employment of multiple AMPs with antibiotics.
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Affiliation(s)
- Zeyu Shao
- Australian Centre for NanoMedicine (ACN), School of Chemical Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Erna Wulandari
- Australian Centre for NanoMedicine (ACN), School of Chemical Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Ruby C Y Lin
- Sydney Medical School, University of Sydney, Sydney, New South Wales 2006, Australia.,Centre for Infectious Diseases and Microbiology, Westmead Institute for Medical Research, Westmead, New South Wales 2145, Australia.,School of Medical Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Jiangtao Xu
- Australian Centre for NanoMedicine (ACN), School of Chemical Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Kang Liang
- Australian Centre for NanoMedicine (ACN), School of Chemical Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia.,Graduate School of Biomedical Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Edgar H H Wong
- Australian Centre for NanoMedicine (ACN), School of Chemical Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia
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