Due to their all-electrical nature,
impedance biosensors have significant
potential for use as simple and portable sensors for environmental
studies and environmental monitoring. Detection of two endocrine-disrupting
chemicals (EDC), norfluoxetine and BDE-47, is reported here by impedance
biosensing, with a detection limit of 8.5 and 1.3 ng/mL for norfluoxetine
and BDE-47, respectively. Although impedance biosensors have been
widely studied in the academic literature, commercial applications
have been hindered by several technical limitations, including possible
limitations to small analytes, the complexity of impedance detection,
susceptibility to nonspecific adsorption, and stability of biomolecule
immobilization. Recent research into methods to overcome these obstacles
is briefly reviewed. New results demonstrating antibody regeneration
atop degenerate (highly doped) Si are also reported. Using 0.2 M KSCN
and 10 mM HF for antibody regeneration, peanut protein Ara h 1 is
detected daily during a 30 day trial.
An
antibody-based analytical method for the detection of a chemical
flame retardant using antibody fragments isolated from an alpaca has
been developed. One specific chemical flame retardant congener, 2,2′,4,4′-tetrabrominated
diphenyl ether (BDE-47), is often the major poly-BDE (PBDE) congener
present in human and environmental samples and that which is the most
frequently detected. An alpaca was immunized with a surrogate of BDE-47
covalently attached to a carrier protein. The resulting mRNA coding
for the variable domain of heavy-chain antibodies (VHH) were isolated,
transcribed to cDNA, and cloned into a phagemid vector for phage display
library construction. Selection of VHHs recognizing BDE-47 was achieved
by panning under carefully modified conditions. The assay sensitivity
for detecting BDE-47 was down to the part-per-billion (microgram per
liter) level. Cross-reactivity analyses confirmed that this method
was highly selective for BDE-47 and selected hydroxylated metabolites.
When exposed to elevated temperatures, the camelid VHH antibodies
retained more reactivity than a polyclonal antibody developed to the
same target analyte. The use of this VHH antibody reagent immobilized
onto a Au electrode for impedance biosensing demonstrates the increased
versatility of VHH antibodies.
Listeria monocytogenes is detected by electrochemical impedance spectroscopy using a mouse monoclonal antibody immobilized onto an Au electrode. This yields sensitivities of 0.825 kΩ cm2/(CFU/mL) and 1.129 kΩ cm2/(CFU/mL) and detection limits of 5 CFU/mL and 4 CFU/mL for ideal solutions and filtered tomato extract, respectively. Control experiments with an Au electrode onto which a mouse monoclonal antibody to GAPDH is immobilized demonstrate that non‐specific adsorption is insignificant for the system and methodology studied here. Control experiments with Salmonella enterica demonstrate no cross‐reactivity to this food pathogen. Potential technological hurdles to development of a multiplexed impedance biosensor for food pathogens are also discussed.
Food pathogens contaminate food products that allow their growth on the shelf and also under refrigerated conditions. Therefore, it is of utmost importance to lower the limit of detection (LOD) of the method used and to obtain the results within hours to few days. Biosensor methods exploit the available technologies to individuate and provide an approximate quantification of the bacteria present in a sample. The main bottleneck of these methods depends on the aspecific binding to the surfaces and on a change in sensitivity when bacteria are in a complex food matrix with respect to bacteria in a liquid food sample. In this review, we introduce surface plasmon resonance (SPR), new advancements in SPR techniques, and electrochemical impedance spectroscopy (EIS), as fluorescence-free biosensing technologies for detection of L. monocytogenes in foods. The application of the two methods has facilitated L. monocytogenes detection with LOD of 1 log CFU/mL. Further advancements are envisaged through the combination of biosensor methods with immunoseparation of bacteria from larger volumes, application of lab-on-chip technologies, and EIS sensing methods for multiplex pathogen detection. Validation efforts are being conducted to demonstrate the robustness of detection, reproducibility and variability in multi-site installations.
An impedance biosensor is reported that employs the bidentate thiol, 16- The antibody-coated electrodes retained activity towards Ara h1 for 10 and 20 days of regeneration of the monodentate-and BMPHA-coated Au electrodes, respectively, illustrating the superior stability of protein films atop the BMPHA bidentate thiol.3
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.