Enhanced bacterial uptake of I-131-labeled antimicrobial imidazolium bromide salts using fluorescent carbon nanodots

Imidazolium bromide salts have been shown as potent antibiotic molecules that show structure-based bioactivity related to their cation alkyl side chain length. To enhance the bioavailability of lipophilic alkyl side chains herein, a 1,8-naphthalimide group containing imidazolium bromide salts bearing different lengths of alkyl chains (NIM1, 2, and 3) are coupled with fluorescent carbon dots (C-NIMs) through electrostatic and pi-pi interactions. Further, obtained nanocarriers were radio-labeled with iodine-131 (I-131) to track the bacterial uptake of them by Staphylococcus aureus and Escherichia coli. Antibacterial activities were also investigated by the microdilution method. Comparison studies showed that both radiolabeling efficiency and lipophilicity increased when NIMs were integrated onto the CDots. More importantly, CDots resulted in 4-fold enhanced uptake of NIM1 by S. aureus bacterium as compared to pristine imidazolium bromide salts while at a higher number of alkyl chain lengths enhancement was 2-fold.