Examination of Cholesterol oxidase attachment to magnetic nanoparticles

Magnetic materials have been used with grain sizes down to the nanoscale for longer than any other type of material [1]. This is attributable to a number of factors including a large surface area to volume ratio and the possibility of immobilizing a biological entity of interest [2]. In the last decade increased investigations and development were observed in the field of nanosized magnetic particles [2]. Here the term nanoparticles is used to designate particulate systems that are less than 1μm, and effectively below 500 nm [2].Due to their magnetic character, magnetite (Fe3O4) nanoparticles can be attracted by a magnetic field and are easily separable in solution. Similarly, substances to which they have been attached can be separated from a reaction medium, or directed by an external magnetic field to site specific drug delivery targets [2]. Magnetic nanoparticles have been widely used in the immobilization of many bioactive substances such as proteins, peptides, enzymes [3-6], and antibodies [7]. Magnetite is one of the most commonly used magnetic materials because it has a strong magnetic property and low toxicity [4].The binding of magnetic particles to bioactive substances involves a number of interactions including the interactions between organic ligand, and the interactions between the amino acid side chains of proteins and the metals centers. Such bindings pave the way for the coupling of biomolecular entities of enhanced stability. Recently reported work in the area of enzyme immobilization has described the catalytic activity of yeast alcohol dehydrogenase [3] and lipase [4] directly bound to magnetite nanoparticles, via carbodimiide activation without the use of a ligand. This binding method offers tremendous scope because of its simplicity and high efficiency.Cholesterol oxidase is a flavin-enzyme (with a FAD prosphetic group) that produces hydrogen peroxide according to the reaction 1.Cholesterol + O2 → 4 - Cholesten - 3 - one + H2O2 (1)The structure