with Salmonella spp. could be directly measured by electrochemical
impedance spectroscopy with a detection limit of
1 102 CFU/mL, with the linear relationship between change
in capacitance and logarithm of concentration being obtained
in the range of 1 102e1 105 CFU/mL. Using MNPs and optical
nanocrystal probes, Joo et al [29] developed a facile and
sensitive method for detection of Salmonella in milk. The
bacteria in milk were captured by antibody-conjugated MNPs,
followed by separating the bacteria-adsorbed probe using an
external magnetic field, exposing it again to antibodyimmobilized
TiO2 nanocrystals for absorption of UV light,
and then magnetically separating the MNPseSalmonellaeTiO2
complexes from solution for analysis of unbound TiO2 nanocrystals
with an UVevisible spectrometer. A detection limit of
100 CFU/mL was obtained for Salmonella in milk [29]. In an
attempt to improve the performance of electrochemical
biosensor by CNTs, Jain et al [30] immobilized CNTsfunctionalized
monoclonal antibodies onto a glassy carbon
electrode for S. typhimurium detection using electrochemical
impedance spectroscopy as a function of change in charge
transfer resistance and impedance. A detection limit of
1.6 104 CFU/mL was obtained with the linear response being
101 to 106 (serial dilution values of overnight bacterial culture)
[30].