Langmuir-Blodgett based ordered deposition of functionalized iron oxide nanoparticles for ultrasensitive detection of Escherichia coli O157: H7

We report the synthesis and deposition of highly ordered poly(lactic-co-glycolic acid) coated iron oxide nano particles (Plg-IONPs) using the surface pressure-controlled Langmuir-Blodgett (LB) method. The deposition of different monolayers (2, 4, and 6 layers) has been attained by transferring the spread solution of Plg-IONPs at an optimized pressure (14 mN m(-1)) and temperature (25 degrees C). Surface morphological studies carried out using scanning electron microscopy clearly show the uniform deposition of Plg-IONPs@LB thin film on indium tin oxide (ITO) coated glass substrate. The Plg-IONPs@LB/ITO electrodes have been conjugated with monoclonal antibodies specific to Escherichia coli O157: H7 (E. coli). The fabricated biosensor has been utilized to detect E. coli in the concentration range 5.0 CFU mL(-1) to 10(6) CFU mL(-1) with a limit of detection of 3.0 CFU mL(-1). Further, the biosensor has shown specificity for detecting E. coli and has been able to discriminate other potential bacterial pathogens and non-pathogenic E. coli strain (DH5 alpha). As a proof of concept, the biosensor has been able to quantify E. coli O157: H7 in spiked food and water samples with high accuracy and reproducibility.