Fimbria targeting superparamagnetic iron oxide nanoparticles enhance the antimicrobial and antibiofilm activity of ciprofloxacin against quinolone‐resistant E. coli

High quinolone resistance of Escherichia coli limits the therapy options for urinary tract infection (UTI). In response to the urgent need for efficient treatment of multidrug‐resistant infections, we designed a fimbriae targeting superparamagnetic iron oxide nanoparticle (SPION) delivering ciprofloxacin to ciprofloxacin‐resistant E. coli. Bovine serum albumin (BSA) conjugated poly(acrylic acid) (PAA) coated SPIONs (BSA@PAA@SPION) were developed for encapsulation of ciprofloxacin and the nanoparticles were tagged with 4‐aminophenyl‐α‐D‐mannopyrannoside (mannoside, Man) to target E. coli fimbriae. Ciprofloxacin‐loaded mannoside tagged nanoparticles (Cip‐Man‐BSA@PAA@SPION) provided high antibacterial activity (97.1 and 97.5%, respectively) with a dose of 32 μg/mL ciprofloxacin against two ciprofloxacin‐resistant E. coli isolates. Furthermore, a strong biofilm inhibition (86.9% and 98.5%, respectively) was achieved in the isolates at a dose 16 and 8 times lower than the minimum biofilm eradication concentration (MBEC) of ciprofloxacin. Weaker growth inhibition was observed with untargeted nanoparticles, Cip‐BSA@PAA@SPIONs, confirming that targeting E. coli fimbria with mannoside‐tagged nanoparticles increases the ciprofloxacin efficiency to treat ciprofloxacin‐resistant E. coli. Enhanced killing activity against ciprofloxacin‐resistant E. coli planktonic cells and strong growth inhibition of their biofilms suggest that Cip‐Man‐BSA@PAA@SPION system might be an alternative and/or complementary therapeutic option for the treatment of quinolone‐resistant E. coli infections.