Tobramycin-loaded complexes to prevent and disrupt Pseudomonas aeruginosa biofilms

Carbohydrate-based materials are increasingly investigated for a range of applications spanning from healthcare to advanced functional materials. Synthetic glycopolymers are particularly attractive as they possess low toxicity and immunogenicity and can be used as multivalent ligands to target sugar-binding proteins (lectins). Here, we utilised RAFT polymerisation to synthesize two families of novel diblock copolymers consisting of a glycopolymers block containing either mannopyranose or galactopyranose pendant units, which was elongated with sodium 2-acrylamido-2-methyl-1-propanesulfonate (AMPS) to generate a polyanionic block. The latter enabled complexation of cationic aminoglycoside antibiotic tobramycin through electrostatic interactions (loading efficiency in the 0.5-6.3 wt% range, depending on the copolymer). The resulting drug vectors were characterized by dynamic light scattering, zeta-potential, and transmission electron microscopy. Tobramycin-loaded complexes were tested for their ability to prevent clustering or disrupt biofilm of the Pseudomonas aeruginosa Gram-negative bacterium responsible for a large proportion of nosocomial infection, especially in immunocompromised patients. P. aeruginosa possesses two specific tetrameric carbohydrate-binding adhesins, LecA (PA-IL, galactose/N-acetyl-D-galactosamine-binding) and LecB (PA-IIL, fucose/mannose-binding), and the cell-associated and extracellular adhesin CdrA (Psl/mannose-binding) thus ideally suited for targeted drug delivery using sugar-decorated tobramycin-loaded complexes here developed. Both aliphatic and aromatic linkers were utilised to link the sugar pendant units to the polyacrylamide polymer backbone to assess the effect of the nature of such linkers on bactericidal/bacteriostatic properties of the complexes. Results showed that tobramycin-loaded complexes efficiently suppressed (40 to 60% of inhibition) in vitro biofilm formation in PAO1-L P. aeruginosa and that preferential targeting of PAO1-L biofilm can be achieved using mannosylated glycopolymer-b-AMPS_m.