Magnetic Microbeads

Rife J.C., Miller M.M., Sheehan P.E., Tamanaha C.R., Tondra M., Whitman L.J., Design and performance of GMR sensors for the detection of magnetic microbeads in biosensors, Sensor Actuat A-Phys. 2003 107 209-218. 

A new suspension array concept based on sedimentation and microscopic imaging was introduced by Moser et al. [98], Magnetic microbeads settle to the bottom of a microplate well by magnetic forces and form randomly ordered arrays, which are examined by fluorescence microscopy and automated imaging analysis. Each bead carries specific capture molecules and can be identified by a defined luminescent code. 

Mulvaney SP, Mattoussi HM, Whitman LJ (2004) Incorporating fluorescent dyes and quantum dots into magnetic microbeads for immunoassays. BioTechniques 36 602-609... 

Zhang, R., K. Hirakawa, D. Seto, et al. 2005. Sequential injection chemiluminescence immunoassay for anionic surfactants using magnetic microbeads immobilized with an antibody. Talanta 68 231-238. 

Zhang, R., H. Nakajima, N. Soh, et al. 2007. Sequential injection chemiluminescence immunoassay for nonionic surfactants by using magnetic microbeads. Anal. Chim. Acta 600 105-113. 

Other less common DNA sensors have been described, such as the use of magnetic microbeads on a solid substrate, to detect and characterize many individual biomolecular interaction events simultaneously using the concept of measuring changes in the intermolecular forces by arrays of microfabri-cated magnetoresistive DNA sensors, as developed by Baselt et al. [18]. 

Figure 3. Magnetic microbead transport in a cylindrical capillary over long-range distances using an array of simple planar cods (coil diameter = 3.5 mm). Transport of magnetic beads (1 pm diameter, Promega) is enabled by sequential actuation of the coils in a three-phase scheme (1,2, 3) (1 =+1 A) [16].

A. Rida, V. Fernandez, and M.A.M. Gijs Long-range transport of magnetic microbeads using simple planar coils placed in a uniform magnetostatic field Applied Physics Letters 83, 2396-2398 (2003). 

M.M. Miller, P.E. Sheehan, R.L. Edelstein, C.R. Tamanaha, L. Zhong, S. Bounnak, L.J. Whitman, and R.J. Colton A DNA array sensor utilizing magnetic microbeads and magnetoelectronic detection Journal of Magnetism and Magnetic Materials 225, 138-144 (2001). 

Tanyolac et al. [86] also prepared magnetic microbeads by applying the solvent evaporation method. They used chloroform as organic phase and polybutyral as polymeric material. The range of produced particle size was 125-250 pm. 

Fig. 8 Illustration of process involved in ECL immune assays based on magnetic microbeads as solid support. Reprinted with permission from Ref 19. Copyright (2008) Spinger.

P. Du, H. Li, and W. Cao, Construction of DNA sandwich electrochemical biosensor with nanoPbS and nanoAu tags on magnetic microbeads. Biosens. Bioelectron. 24, 3223-3228 (2009). 

Besse PA, Boero G, Demierre M, Pott V, Potovic R (2002) Detection of a single magnetic microbead using a miniaturized silicon Hall sensor. Appl Phys Lett 80 4199 201... 

Magnetic microbeads are spherical particles of a diameter in the micrometer range that have magnetic entities embedded in a latex shell. 

Aside from encapsulation of proteins, much work has been done on the surface functionalization of microparticles for cellular interaction and proliferative effects. Surface modification of PLGA microspheres with an amine-terminated dendrimer improved long-term proliferation of chondrocytes without observed changes in the cell phenotype, as compared to monolayer culture systems (Thissen et al. 2006). Additionally, surface functionalization ofpolystyrene magnetic microbeads with the DLL4 notch ligand used in coculture has been shown to efficiently generate T cells from mouse bone marrow hematopoietic stem cells (Taqvi et al. 2006). 

Liu et al., 2001). The magnetic microbeads coated with anti-Salmonella were used to separate Salmonella from sample solutions at room temperature for 30 min. A sandwich complex with alkaline phosphatase and the Salmonella immobilized on the magnetic beads was formed, separated fixam the solution by a magnetic filtration, and incubated with a p-nitrophenyl phosphate substrate at 37 °C for 30 min to produce p-nitrophenol by enzymatic hydrolysis. Salmonella was detected by measuring the absorbance of p-nitrophenol at 404 nm, with a hnear response of 2.2—104 and 2.2—106 CPU mL... 

The principle of magnetic separation of biomolecules, (a) Flow carrying magnetic microbeads, (b) immobilization of the magnetic microbeads. 

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