Microbial biosensing of ciprofloxacin residues in food by a portable lens-free CCD-based analyzer

We present a rapid and simple approach for sensitive detection of antibiotic residues in food samples based on luminescence induction by live bacterial sensor strains integrated into a CCD-based lens-free optical analyzer (LumiSense). Using ciprofloxacin as a model antibiotic, we demonstrate response times of between 20 and 80 min, and detection thresholds of 8 ng/mL for milk, egg white, and chicken essence, and 64 ng/mL for egg yolk. These values are below the minimal allowed values as defined by European Union regulations. Although not intended to replace traditional analytical equipment and regulation-approved methods, LumiSense and similar systems, sample preparation for which involves only simple mixing, dilution, and homogenization, may nevertheless provide a simple means for high-throughput food sample screening. [Figure not available: see fulltext.].