Bismuth Phosphinates in Bi-Nanocellulose Composites and their Efficacy towards Multi-Drug Resistant Bacteria

A series of poorly soluble phenyl bis-phosphinato bismuth(III) complexes [BiPh(OP(=O)R¹R²)₂] (R¹=R²=Ph; R¹=R²=p-OMePh; R¹=R²=m-NO₂Ph; R¹=Ph, R²=H; R¹=R²=Me) have been synthesised and characterised, and shown to have effective antibacterial activity against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE). The bismuth complexes were incorporated into microfibrillated (nano-) cellulose generating a bismuth-cellulose composite as paper sheets. Antibacterial evaluation indicates that the Bi-cellulose materials have analogous or greater activity against Gram positive bacteria when compared with commercial silver based additives: silver sulfadiazine loaded at 0.43wt% into nanocellulose produces a 10mm zone of inhibition on the surface of agar plates containing S. aureus whereas [BiPh(OP(=O)Ph₂)₂] loaded at 0.34wt% produces an 18mm zone of inhibition. These phenyl bis-phosphinato bismuth(III) complexes show potential to be applied in materials in healthcare facilities, to inhibit the growth of bacteria capable of causing serious disease.