Magnetic-Based Biosensors

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... 

A biosensor is a device that combines a biological component a recognition layer) and a physico-chemical detector component (a transducer). The transduction unit can be electrochemical, optical, piezoelectric, magnetic, or calorimetric (1). Two groups of recognition molecules form the majority of biosensors affinity-based and catalytic-based biosensors. Affinity-based biosensors are used to bind molecular species of interest, irreversibly and noncatalytically. Examples include antibodies, nucleic acids, and... 

More details on inductance and other magnetically based sensors can be found in Chapter 3, Magnetic Biosensors. 

Electrochemical DNA-based biosensors and electrochemical sensing (assay) without use of the true biosensor are sometimes confused in the literature [8]. While in the electrochemical DNA biosensor the DNA layer has to be in an intimate contact with the electrode prior to and during the NA interaction with an anal)Ae, in electrochemical sensing the DNA itself or product of any DNA interaction, which was performed in solution or even at another solid surface (magnetic beads, etc.), is detected electrochemically, usually after preconcentration by an accumulation on the electrode surface. 

Miller MM, Prinz GA, Cheng SF, Bounnak S (2002) Detection of a micron-sized magnetic sphere using a ring-shaped anisotropic magnetoresistance-based sensor a model for a magnetoresistance-based biosensor. Appl Phys Lett 81 2211-2213... 

Disposable immunosensors for the determination of bacteria based on screen-printed platforms have been also reported in the literature. Afonso et al. (2013) fabricated a screen-printed carbon-based biosensor in combination with magnetic separation for the rapid detection of Salmonella in milk samples. Magnetic beads coated with anti-Salmonella antibodies (MBs-pSAb) and modified AuNPs coated with polyclonal anti-Salmonella antibody were used as the capture phase (preconcentrating step) and electrochemical labels, respectively. The modified magnetic beads were then captured onto the electrode surface by applying a magnetic field below the printed sensors and analysed electrochemically by DPV. 

Yu D, Renedo OD, Blankert B, Sima V, Sandulescu R, Arcos J, Kauffmann J-M (2006) A peroxidase-based biosensor supported by nanoporous magnetic silica microparticles for acetaminophen biotransformation and inhibition studies. Electroanalysis 18 1637-1642... 

BioMagnetICs program from the Defense Science Office oriented to the development of biosensors, magnetic base microanalysis devices, magnetically targeted therapeutics. A number of companies are also fabricating and... 

Particularly attractive for numerous bioanalytical applications are colloidal metal (e.g., gold) and semiconductor quantum dot nanoparticles. The conductivity and catalytic properties of such systems have been employed for developing electrochemical gas sensors, electrochemical sensors based on molecular- or polymer-functionalized nanoparticle sensing interfaces, and for the construction of different biosensors including enzyme-based electrodes, immunosensors, and DNA sensors. Advances in the application of molecular and biomolecular functionalized metal, semiconductor, and magnetic particles for electroanalytical and bio-electroanalytical applications have been reviewed by Katz et al. [142]. 

These two examples show how emulsion-based magnetic colloids can become the essential elements for two apparently very different issues. In fact, this section introduces the basics of using superparamagnetic emulsion-based colloids, and their spontaneous self-assembling ability under a field, as new biosensors. The... 

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]).

The idea behind a spintronic biochip or biosensor is to replace traditionally used fluorescent markers by magnetic labels. Instead of detecting biomolecular recognition using expensive optical or laser-based... 

---