An optimised Cu(0)-RDRP approach for the synthesis of lipidated oligomeric vinyl azlactone: toward a versatile antimicrobial materials screening platform

• Published in: Journal of materials chemistry. B, Materials for biology and medicine Materials for biology and medicine, 2019-11, Vol.7 (43), p.6796-689
• Main Authors: Grace, James L, Amado, Maite, Reid, Janet C, Elliott, Alysha G, Landersdorfer, Cornelia B, Truong, Nghia P, Kempe, Kristian, Cooper, Matthew A, Davis, Thomas P, Montembault, Véronique, Pascual, Sagrario, Fontaine, Laurent, Velkov, Tony, Quinn, John F, Whittaker, Michael R
• Format: Article
• Language: English
• Subjects: Amines; Antibacterial materials; Chemical Sciences; Copper bromide; Cryptococcus neoformans; Cytotoxicity; Deactivation; Degree of polymerization; Disruption; E coli; Erythrocytes; Ethylenediamine; Fluconazole; Fungi; Fungicides; Guanidine; Imidazole; Initiators; Lipids; Lysis; Minimum inhibitory concentration; NMR; Nuclear magnetic resonance; Oligomers; Organic chemistry; Oxazolone; Polymerization; Polymers; Ring opening polymerization; Selectivity; Synthesis; Toxicity
• ISSN: 2050-750X; 2050-7518
• DOI: 10.1039/c9tb01624d

This report details the synthesis of lipidated 2-vinyl-4,4-dimethyl-5-oxazolone (VDM) oligomers via an optimised Cu(0)-mediated reversible-deactivation radical polymerisation approach, and the use of these oligomers as a versatile functional platform for the rapid generation of antimicrobial materials. The relative amounts of CuBr 2 and Me 6 TREN were optimised to allow the fast and controlled polymerisation of VDM. These conditions were then used with the initiators ethyl 2-bromoisobutyrate, dodecyl 2-bromoisobutyrate, and ( R )-3-((2-bromo-2-methylpropanoyl)oxy)propane-1,2-diyl didodecanoate to synthesise a library of oligo(VDM) (degree of polymerisation = 10) with ethyl, dodecyl or diglyceride end-groups. Subsequently, ring-opening of the pendant oxazolone group with various amines ( i.e. , 2-(2-aminoethyl)-1,3-di-Boc-guanidine, 1-(3-aminopropyl)imidazole, N -Boc-ethylenediamine, or N , N -dimethylethylenediamine) expanded the library to give 12 functional oligomers incorporating different cationic and lipid elements. The antimicrobial activities of these oligomers were assessed against a palette of bacteria and fungi: i.e. Staphylococcus aureus , Escherichia coli , Candida albicans , and Cryptococcus neoformans . The oligomers generally exhibited the greatest activity against the fungus, C. neoformans , with a minimum inhibitory concentration of 1 μg mL −1 (comparable to the clinically approved antifungal fluconazole). To assess haemocompatibility, the oligomers were assayed against erythrocytes, with the primary amine or guanidine containing C 12 and 2C 12 oligomers exhibiting greater lysis against the red blood cells (HC 10 values between 7.1 and 43 μg mL −1 ) than their imidazole and tertiary amine counterparts (HC 10 of >217 μg mL −1 ). Oligomers showed the greatest selectivity for C. neoformans , with the C 12 - and 2C 12 -tertiary amine and C 12 -imidazole oligomers possessing the greatest selectivity of >54-109. These results demonstrate the utility of reactive oligomers for rapidly assessing structure-property relationships for antibacterial and antifungal materials. For the first time Cu(0)-RDRP conditions were optimised to allow for the fast and controlled polymerisation of vinyl azlactone with tuneable lipid elements: a versatile platform material for the high-throughput synthesis of antimicrobial materials.