Application of Magnetic Nanoparticles in Pharmaceutical Sciences (2010)

Micro- and nano-sized magnetic support is a recently developed revolutionary technology for bioseparation, especially for ligand fishing, protein, enzyme, DNA, RNA and cell isolation or purification. Magnetic nanoparticles (MPs) are referred to by various synonyms, such as magnetic beads (MB) or micro- and nano-sized magnetic beads. They are also called ferrofluids or magnetic fluids, meaning colloidal suspensions of magnetic particles in a liquid carrier. Generally, these particles are part of nanotechnology, which can be defined as engineering of functional systems on a molecular scale. It has the potential to create many new materials and devices with a wide range of applications across the biomedical, chemical, electronic and mechanical fields.

Their superparamagnetic properties have opened promising new perspectives for their application in several areas. The pioneering “medical” application in the treatment of lymphatic nodes and metastases based on injecting “metallic particles” preheated in a magnetic field was first published by Gilchrist et al. in 1957 (1). Since then, magnetic particles have been modified by coating with antibodies, enzymes, proteins or specific ligands that enable them to bind to other biologically active compounds or receptors on the cell surface. In the last decade, magnetic particles have been increasingly used as a promising technique for a wide spectrum of biomedical applications. The number of publications presenting original studies on using magnetic beads is increasing year by year (Fig. 1). The growing interest in the magnetic carrier is focused on biochemistry, molecular biology and medical specialties. Because of the superparamagnetic properties and micro- and nano-dimensions, magnetic nanoparticles can be used to isolate any target and linked to various manual and automated applications (2–4). Innovative research has produced a new application for magnetic nanoparticles that carries an exciting biomedical and bioengineering potential, for instance, cell molecule and nucleic acid separation, immunoassays, pathogen detection, protein purification, gen mutation analysis and magnetic-force-based tissue engineering (5,6). Also, the interest in the potential application of the magnetic technique in pharmacy is significantly growing. It is currently being recognised that this magnetic nanotechnology could play an important role in this area. 



Fig. 1

The number of publications on the subject “Magnetic Beads” and “Biochemistry and Molecular Biology, Medicine or Pharmacology, Toxicology and Pharmaceutics” identified by Scopus (http://www.scopus.com/home.url).




DRUG DISCOVERY
The process of drug discovery in the modern scientific aspect is very complex. It integrates many disciplines, including biotechnology, medicine and pharmacology. For years, drug discovery has also focused on identification of unknown biomolecular interactions with known targets. A number of established methods are used in evaluating the binding of ligands/drugs to receptors and proteins, such as equilibrium dialysis, ultrafiltration, ultracentrifugation, bioaffinity chromatography and other spectroscopic methods. Also, the BIAcore system and surface plasmon resonance (SPR) are the two most popular recently technologies for real-time biomolecule interaction analysis. Because of the different modifications of multifunctional surface of the magnetic particles, these approaches are practically useful in this area.

The objective of the recent study was to adapt immobilized human serum albumin (HSA) onto the surface of magnetic beads for the purpose of “ligand fishing” (3). These beads correctly isolated a known binder from a mixture of known compounds, and the whole experiment was carried out manually using a magnet and automatically using the Magtration System. Furthermore, the magnetic separation technique was extended to the protein-ligand and protein–protein interaction using magnetic beads with immobilized heat-shock protein 90α (Hsp90α) (2). The advantage of this system is that the Hsp90α-coated magnetic beads can isolate interacting partners (ligand and proteins) from complex mixtures and cellular extracts (e.g. from KU-812 cells) in less than 15 min, unlike co-immunoprecipitation methods, which take several hours to recover the protein of interest. Presently, the extension of the magnetic beads method to multiple complex cellular extracts and complex plant extracts is being investigated. The most recent study demonstrates that ligand fishing based on biological functionalised MB is an effective and convenient way to identify and isolate bioactive small molecules from botanical extracts (Camptotheca acuminata and Dioscorea nipponica), and the process has a significant structure specifity (7,8).

Using a similar concept, protein-coated magnetic beads were used as a tool for a rapid drug-protein binding study (4). Knowledge of serum protein binding behaviour as a significant component of blood is very important for the rational use of drugs. An extensive understanding of the ligand/drug-protein interaction may be of special importance for the modelling of pharmacokinetics, including possible drug–drug interaction. In this context, magnetic beads with immobilized HSA have been successfully used to determine the affinity of known drugs for the protein (4). Moreover, the preliminary competition experiments suggest that protein-coated magnetic beads can be employed in drug–drug interaction studies. However, the validation of the proposed method is being investigated.