Escherichia coli biofilms are a
major causative agent of many intestinal infections, and there is
ongoing research aimed at E. coli biofilm
eradication. Gold nanoclusters (AuNCs) conjugated with various surface
ligands have been extensively investigated for antimicrobial properties
and provide a potential solution. There is little known about their in vivo safety because current standards of nanosafety research
involve incubation of AuNCs with cells in vitro to
confirm biocompatibility. In addition to systemic administration,
nanosafety research on AuNC-based antimicrobials designed to treat
gastrointestinal infections must also consider the potential for inducing
gastrointestinal disorders. We report the design and application of
two AuNCs coated with either hydroxyl (AuNC@PEG-OH)- or amine (AuNC@PEG-NH2)-functionalized poly(ethylene glycol), which enables the
eradication of E. coli biofilms. Gastrointestinal
safety of AuNC@PEG-OH and AuNC@PEG-NH2 was evaluated in
healthy mice up to 35 days after administration by oral gavage at
a dose of 10 mg/kg (or 1 mg/mL) daily for 14 days. No changes were
detected in the histopathology of major organs, serum chemistry, hematology,
and feces. Thus, oral administration of AuNCs is unlikely to be of
concern for systemic toxicity or in the induction of gastrointestinal
illnesses. Further studies on increasing time exposure and doses are
necessary to determine whether toxicity occurs at higher doses or
whether there is no adverse effect limit.