Determination of sulphate-reducing bacteria based on vancomycin-functionalised magnetic nanoparticles using a modification-free quartz crystal microbalance

A fast, sensitive and reliable quartz crystal microbalance (QCM) biosensor is described for the selective detection of the marine pathogenic sulphate-reducing bacterium (SRB), D. desulfotomaculum. Based on the amplification of the response of vancomycin-functionalised magnetic nanoparticles (Van-mNPs), under an external magnetic field, the bacteria-mNPs conjugates attach to the surface of an Au electrode. The QCM biosensor gave a distinct response to the vancomycin-sensitive, D. desulfotomaculum, but had no obvious response to the vancomycin-resistant bacterium, Vibrio anguillarum. The effects of the optimization conditions such as the incubation time and pH on the detection were also investigated, respectively. Optimised assays showed that the biosensor could obtain the best response with a 30 min incubation of the bacteria with the Van-mNPs. A linear relationship between the QCM response and the logarithm of the bacterial concentration was observed in the range of 1.8 × 104 to 1.8 × 107 cfu/ml. The sensor system has a potential for further applications and provides a facile and sample method for detection of pathogenic bacteria.