title: The effect of substituent, degree of acetylation and positioning of the cationic charge on the antibacterial activity of quaternary chitosan derivatives.
abstract: A series of water-soluble cationic chitosan derivatives were prepared by chemoselective functionalization at the amino group of five different parent chitosans having varying degrees of acetylation and molecular weight. The quaternary moieties were introduced at different alkyl spacer lengths from the polymer backbone (C-0, C-2 and C-6) with the aid of 3,6-di-O-tert-butyldimethylsilyl protection of the chitosan backbone, thus allowing full (100%) substitution of the free amino groups. All of the derivatives were characterized using 1H-NMR, 1H-1H COSY and FT-IR spectroscopy, while molecular weight was determined by GPC. Antibacterial activity was investigated against Gram positive S. aureus and Gram negative E. coli. The relationship between structure and activity/toxicity was defined, considering the effect of the cationic group's structure and its distance from the polymer backbone, as well as the degree of acetylation within a molecular weight range of 7-23 kDa for the final compounds. The N,N,N-trimethyl chitosan with 100% quaternization showed the highest antibacterial activity with moderate cytotoxicity, while increasing the spacer length reduced the activity. Trimethylammoniumyl quaternary ammonium moieties contributed more to activity than 1-pyridiniumyl moieties. In general, no trend in the antibacterial activity of the compounds with increasing molecular weight or degree of acetylation up to 34% was observed.
authors.affiliation: Faculty of Pharmaceutical Sciences, School of Health Sciences, University of Iceland, Hofsvallagata 53, IS-107 Reykjavík, Iceland. prs1@hi.is.
authors.forename: Priyanka
authors.initials: P
authors.lastname: Sahariah
authors.affiliation: Faculty of Pharmaceutical Sciences, School of Health Sciences, University of Iceland, Hofsvallagata 53, IS-107 Reykjavík, Iceland. vsg3@hi.is.
authors.forename: Vivek S
authors.initials: VS
authors.lastname: Gaware
authors.affiliation: The REModeL Lab, The Blood Bank, Landspitali University Hospital, Snorrabraut 60, 105 Reykjavik, Iceland. ramona@landspitali.is.
authors.forename: Ramona
authors.initials: R
authors.lastname: Lieder
authors.affiliation: Department of Chemistry, Science Institute, University of Iceland, Dunhagi 3, IS-107 Reykjavik, Iceland. sigga@hi.is.
authors.forename: Sigríður
authors.initials: S
authors.lastname: Jónsdóttir
authors.affiliation: Department of _Biomedical Science, Faculty of_ Medicine, University of _Iceland, Stapi, Hringbraut 31, 101 Reykjavík, Iceland. hjalmars@hi.is.
authors.forename: Martha Á
authors.initials: MÁ
authors.lastname: Hjálmarsdóttir
authors.affiliation: The REModeL Lab, The Blood Bank, Landspitali University Hospital, Snorrabraut 60, 105 Reykjavik, Iceland. oes@landspitali.is.
authors.forename: Olafur E
authors.initials: OE
authors.lastname: Sigurjonsson
authors.affiliation: Faculty of Pharmaceutical Sciences, School of Health Sciences, University of Iceland, Hofsvallagata 53, IS-107 Reykjavík, Iceland. mmasson@hi.is.
authors.forename: Már
authors.initials: M
authors.lastname: Másson
mesh_terms: D000107:Acetylation; D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology*; D002412:Cations / Q000737:chemistry* / Q000494:pharmacology*; D048271:Chitosan / Q000737:chemistry* / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects; D008970:Molecular Weight; D011108:Polymers / Q000737:chemistry / Q000494:pharmacology; D013211:Staphylococcus aureus / Q000187:drug effects; D013329:Structure-Activity Relationship
chemical_list: D000900:Anti-Bacterial Agents; D002412:Cations; D011108:Polymers; D048271:Chitosan