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Nonquaternary poly(diallylammonium) polymers with different amine structure and their biocidal effect on
Larisa M Timofeeva1, Natalia A Kleshcheva, Margarita O Shleeva
1A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky prosp. 29, Moscow, 119991, Russia, timofeeva@ips.ac.ru.
Abstract:
Mycobacteria, especially Mycobacterium tuberculosis, are one of the most dangerous types of microorganisms to cause diseases and mortality. Due to the known distinctive structure of their cell wall, mycobacteria are resistant to majority of antibiotics and common chemical disinfectants, including quaternized low molecular weight and polymer biocides. In this work, nonquaternary protonated polydiallylamines (PDAAs) based on protonated monomers of the diallylamine (DAA) series have been synthesized, secondary s-PDAA and tertiary t-Me-PDAA and t-Et-PDAA (with Me and Et N-substituents). The antimicrobial actions of PDAAs on M. tuberculosis and Mycobacterium smegmatis have been studied, namely, dependences of the activity on the amine structure, length of alkyl N-substituents, M w of polymers, treatment time, and cell concentration. All PDAAs examined at different conditions have been found to exhibit strong bactericidal effect on M. smegmatis and M. tuberculosis, including "nonculturable" dormant M. tuberculosis cells. The quaternary counterpart poly(diallyldimethylammonium chloride) (PDADMAC) and current antibiotics rifampicin and ciprofloxacin have been also tested and shown to be significantly less efficient or inactive at all (at the maximum tested concentration of 500 μg mL(-1)). s-PDAA appeared to be the most effective or exhibited similar activity to t-Me-PDAA, while t-Et-PDAA appeared to be less active, especially against M. tuberculosis. The results obtained indicate a key role of the nonquaternary ammonium groups in the mycobactericidal action of PDAAs. Examination under an optical microscope in the epifluorescence mode has evidenced damage of the inner membrane permeability of M. smegmatis cells under the impact of PDAAs after 20 min. Studies on electrophoretic mobility (zeta-potential) of M. smegmatis cells and some model liposomes in the presence of PDAAs have revealed a small negative charge of mycobacteria outer surface and recharge in the presence of PDAAs. A conclusion was made that bactericidal activity of PDAAs is related to the disturbance of the integrity of the mycobacterial cell wall followed by damage of the inner membrane permeability.
Insights
New nonquaternary protonated polydiallylamines (PDAAs) show potent bactericidal effects against Mycobacterium tuberculosis and Mycobacterium smegmatis, outperforming existing antibiotics and quaternary polymers. These PDAAs disrupt cell wall integrity and inner membrane permeability.
Area of Science:
- Microbiology
- Polymer Chemistry
- Antimicrobial Agents
Background:
- Mycobacteria, particularly Mycobacterium tuberculosis, pose significant global health threats due to their high mortality rates.
- The unique, resilient cell wall structure of mycobacteria confers resistance to conventional antibiotics and disinfectants.
- Existing treatments often struggle against dormant or nonculturable Mycobacterium tuberculosis strains.
Purpose of the Study:
- To synthesize and evaluate novel nonquaternary protonated polydiallylamines (PDAAs) for their antimycobacterial activity.
- To investigate the structure-activity relationship of PDAAs, including amine structure, N-substituents, and molecular weight.
- To compare the efficacy of PDAAs against conventional agents like quaternary polymers and antibiotics.
Main Methods:
- Synthesis of secondary (s-PDAA) and tertiary (t-Me-PDAA, t-Et-PDAA) nonquaternary protonated polydiallylamines.
- Antimicrobial testing against Mycobacterium tuberculosis and Mycobacterium smegmatis under various conditions.
- Microscopic examination (epifluorescence) and zeta-potential measurements to elucidate the mechanism of action.
Main Results:
- All synthesized PDAAs demonstrated significant bactericidal activity against both M. smegmatis and M. tuberculosis, including dormant cells.
- PDAAs were more effective than the quaternary polymer PDADMAC and antibiotics like rifampicin and ciprofloxacin.
- Nonquaternary ammonium groups were crucial for activity; s-PDAA and t-Me-PDAA showed higher efficacy than t-Et-PDAA.
- PDAAs induced damage to the inner membrane permeability of M. smegmatis and altered cell surface charge.
Conclusions:
- Nonquaternary protonated polydiallylamines represent a promising new class of antimycobacterial agents.
- The mechanism of action involves disruption of mycobacterial cell wall integrity and inner membrane function.
- PDAAs offer a potential alternative for combating infections caused by drug-resistant mycobacteria.
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