Quartz Crystal Microbalance In-Line Sensing of Escherichia Coli in a Bioreactor Using Molecularly Imprinted Polymers

Growing public concerns about biosafety make continuous monitoring of biospecies increasingly interesting. Escherichia coli (E. coli) is both an interesting analyte and a comparably non-pathogenic model organism for developing novel sensors suitable for that purpose. For such sensors, molecularly imprinted polymers (MIP) are a promising approach to create selective, sensitive and reversible recognition layers. This work presents a biosensor based on imprinted polyurethane and characterizes it in terms of selectivity and sensitivity towards b-strain E. coli. Atomic force microscopy (AFM) revealed successful imprinting and uptake of the bacteria into the polymer. On quartz crystal microbalance (QCM), such MIP yield linear sensor characteristics with a detection limit of 1.6*10⁸ cells/ml. The sensor shows a selectivity factor of five compared to smaller w-strain E. coli. To assess the capabilities of such sensors for on-line monitoring, we designed a small model bioreactor (50 ml) and followed growth processes as a proof of principle. The different phases of bacteria growth can be observed in real time via the frequency responses on the MIP. Sensor responses could be validated by cell counting.