Uniform, length-tunable antibacterial 1D diblock copolymer nanofibers

Abstract

The rapid increase in antibiotic resistant strains of bacteria has led to an urgent need to develop new methods of treating bacterial infections. Antibacterial polymeric nanoparticles are of interest for their more general mechanism of action which involves targeting anionic bacterial membrane structures with cationic functional groups. In this work we utilized living crystallization-driven self-assembly (CDSA) to prepare low dispersity length-controlled block copolymer (BCP) nanofibers that consist of a poly(fluorenetrimethylenecarbonate) (PFTMC) core and a poly(dimethylaminoethyl methacrylate) (PDMAEMA) corona. These nanofibers were shown to function as effective antibacterial agents against Escherichia coli (E. coli) W3110. Three different lengths of PFTMC₁₆-b-PDMAEMA₁₃₁ nanofibers (L_n = 107 nm, 377 nm, 593 nm) with low length dispersities (Đ = 1.04–1.14) were investigated. In all three cases the nanofibers were found to have improved antibacterial activity over analogous nanospheres, as well as nanofibers containing a poly(ethyleneglycol) (PEG) corona. The longest nanofibers (L_n = 593 nm) had the highest activity, inhibiting bacterial growth at concentrations as low as 12.5 μg mL⁻¹ with a minimum inhibitory concentration (MIC) of 17 μg mL⁻¹. This MIC value falls within the range for antibiotics including erythromycin (32 μg mL⁻¹) and ampicillin (12.5 μg mL⁻¹) against the same strain of E. coli. In contrast to other antibacterial polymer systems which require prior quaternization of the PDMAEMA block, PFTMC₁₆-b-PDMAEMA₁₃₁ nanofibers are protonated in aqueous media and display high levels of antibacterial activity. Our findings indicate that the 1-dimensional (1D) nanofiber shape allows for improved antibacterial activity relative to nanospheres and highlight the role that nanoparticle shape, size, and coronal chemistry play in determining antibacterial activity.