The present study provides antibacterial and thermal improvements of chitosan‐based systems through chemical modification with different quaternary ammonium salts using 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide (EDC) as mediator. Three different ammonium salts with a carboxylic acid end group are synthesized through a quaternization reaction between bromohexanoic acid and the respective tertiary amines (quinoline, N,N‐dimethylbenzylamine and pyridine). They are then chemically grafted along the chitosan backbone using EDC as a carboxyl activating agent for the coupling with the primary amine groups. This allows three different chitosan derivatives to be obtained: Quinolinium‐Chitosan (QA‐Cs), Benzalkonium‐Chitosan (BK‐Cs), and Pyridinium‐Chitosan (PA‐Cs), respectively. The chemical structures are characterized by 1H NMR analysis. The thermal stability is analyzed by thermogravimetric analysis. Antibacterial efficiencies of chitosan derivatives against Pseudomonas aeruginosa and Staphylococcus aureus strains are determined. All the chitosan derivatives show negligible antibacterial activity against Gram‐positive S. aureus strain. However, the antibacterial activity against Gram‐negative P. aeruginosa strain is significantly improved.
Three novel polyaspartate derivatives with antibacterial properties and low hemolytic effects are synthesized by the reaction of sodium polyaspartate (PAspNa) with different quaternary ammonium salts with a carboxylic end‐group, subsequently these are tested in vitro against different cancer and normal cell lines. 1‐(carboxypentyl) pyridinium bromide, 1‐(carboxypentyl) benzalkonium bromide, and 1‐(carboxypentyl) quinolinium bromide are synthesized from a quaternization reaction between 6‐bromohexanoic acid and the respective tertiary amines (pyridine, N,N‐dimethylbenzylamine, and quinoline). Then, these ammonium salts are chemically grafted along the sodium polyaspartate macromolecular chains through an acid–base reaction. Three different polyaspartate derivatives are obtained and their chemical structures analyzed and confirmed by FT‐IR and 1H NMR, the corresponding thermal stability is analyzed by thermogravimetric analysis. The antibacterial efficiency of these PAspNa derivatives against Escherichia coli is determined by measuring the minimum inhibitory concentration and the minimum bactericidal concentration. Hemolysis assays are performed on isolated human erythrocytes and finally the cell proliferation is studied by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) analysis. All the PAspNa derivatives show antibacterial activities, low hemolytic effects, and antiproliferative effect in some concentrations evaluated in murine fibroblast (3T3), and cancer cell lines of cervix (HeLa), breast (4T1), and liver (HepG2) cells lines.
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