Biosensors Using Magnetics

Biosensors Using Magnetics, Fig. 1 Schematic of magnetically labeled biomolecule detection in a biosensor. Target bimnolecules bound with a magnetic particle interact with magnetraesistive sensor-bound counter biomolecules to be detected... 

Liu J, Bjornsson L, Mattiasson B (2000) Immobilised activated sludge based biosensor for biochemical oxygen demand measurement. Biosens Bioelectron 14 883-893 Sakai Y, Abe Y, Takahashi F (1995) BOD sensor using magnetic activated sludge. J Ferment Bioeng 80 300-303... 

Fig. 21.1. Schematic representation of the manipulation of DNA biosensors using different strategies. (A) DNA biosensors modified with DNA by (Al) dry-adsorption and (A2) wet-adsorption on GEC platform. (B) DNA biosensors based on the single-point immobilization of biotinylated DNA on Av-GEB universal affinity platform. (C) Immobilization of DNA on magnetic beads followed by (Cl) the capture of the modified beads on m-GEC electrode (more details in Pividori and Alegret [58]).

Salvaraju, T., Das, J., Han, S. W., Yang, H. (2008). Ultrasensitive electrochemical immunosensing using magnetic beads and gold nanocatalysts. Biosensors and Bioelectron. 23 932-938. 

The FABS, whose working principle was very similar to that of the AFM biosensor, was a cantilever-based immunosensor [7]. However, its configuration was much simpler than that of the AFM. Rather than using a piezoceramic translator to pull on intermolecular bonds, it used magnetic particles, which eliminated the need to manually position a tip and sample next to each other with picometer precision and stability. The cantilever-beam force transducer was the only element of the AFM retained by the FABS. 

The second group is composed of polymers that can interact with biomolecules or biostructures and are used in the construction of biosensors, the magnetic guidance of drug delivery systems, and in cell separation. 

The same authors used magnetic beads coated with a bio-recognition element for the specific separation and concentration of cells prior to impedance measurement. After separation and resuspension of bacterial cells in low conductivity 0.1 M mannitol solution, the concentrated sample was uniformly spread on the surface of IDpE. The impedance sensor detected a minimum of 7.4 x 10" and 8.0 x 10 cfu/ml of E. coli 0157 H7 in pure culture and ground beef samples, respectively. The concentration of bacterial cells attached to nanoparticle-antibody conjugates in the active layer of IDpE above the surface of electrodes was achieved with the help of a magnet placed underneath the electrode chip. This improved the sensitivity of the biosensor by 35% as compared to no use of the magnet. These experiments were performed on an open chip [54]. 

Moral-Vico, J., Barallat, J., Abad, L., OUve-MonUau, R., Munoz-Pascual, FJf., Galan Ortega, A., delCampo, F.J., Baldrich, E., 2015. Dual chronoamperometric detection of enzymatic biomarkers using magnetic beads and a low-cost llowcell. Biosensors and Bioelectronics 69, 328-336. 

Z. Zhang, X. Wang, X. Yang, A sensitive choline biosensor using Fe304 magnetic nanoparticles as peroxidase mimics. Analyst 136 (2011) 4960-4965. 

AHLs can be tentatively identified by comparison of the unknown with synthetic AHL standards after Thin Layer Chromatography (TLC) in which the plates are overlaid with agar containing one of the AHL biosensors described above [37,39,44,45]. However, for the unequivocal identification of AHLs the use of more powerful methods such as LC-mass spectrometry, nuclear magnetic resonance and infrared spectroscopy as described below are required. 

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