Biofilm inhibition and bacterial eradication by C-dots derived from polyethyleneimine-citric acid

Protonable polyethyleneimine (PEI) and citric acid (CA) based C-dots were prepared via a hydrothermal process, yielding particles with a hydrodynamic diameter of ~100 and ~80 nm, and zeta potential of − 2.3 ± 0.1 and + 23.4 ± 0.2 mV for PEI-CA C-dots and their protonated form, respectively. Treating Staphylococcus aureus with these C-dots resulted in a statistically significant reduction in bacterial growth, specifically growth in the planktonic phase as well as in the development of bacterial biofilm when compared to untreated (p < 0.05). When 24 h matured S. aureus biofilms were treated with C-dots, a significant disruption and dispersion of bacteria from the existing biofilms was noted as compared to untreated (p < 0.05). Other Gram-positive microorganisms (B. cereus, S. epidermidis, S. pyogenes) and Gram-negative (P. mirabilis, E. coli, and P. aeruginosa) were also susceptible to the antimicrobial activity of the PEI-CA C-dots with significant inhibition of bacterial growth noted for all organisms after C-dot treatment. Only for B. cereus, S. epidermidis, and P. aeruginosa was this reduction in total growth reflected in decreased planktonic growth. However, biofilm formation by all organisms was reduced significantly upon treatment with the C-dots, including those for which planktonic growth was not impacted.