Magnetic particle

1. The introduction of magnetic particle

Magnetic particles are colloidal composites that can be uniformly dispersed in a certain base solution. It has some characteristics such as superparamagnetism, high specific surface area, can be modified by functional groups and other properties. Therefore, antigens / antibodies, enzymes, nucleic acids / oligonucleotides and small molecular drugs are used to immobilize on their surfaces.

2. The action principle of magnetic particle

Antitumor drugs which are chemically modified or embedded on magnetic particles include doxorubicin hydrochloride, mitomycin, actinomycin, fluorouracil, pingyangmycin, methotrexate and so on. These drugs have water solubility to some extent and do not chemically react with magnetic particles. The modified, adsorbed or coated drug concentrates on the lesion site under the action of an external magnetic field, and the drug is released slowly through diffusion and osmosis. When nano-sized magnetic drug-loaded microparticles are used, the microparticles and the drug will be extravagated at the same time (that is, leaving the blood vessel into the diseased tissue). So that on the one hand, it can be used for treatment. On the other hand, the drug-loaded magnetic particles that are exuded into the tissue can also serve as Magnetic resonance imaging (MRI) contrast agents. Hence, dynamic effects can be observed by MRI imaging in the course of treatment.

3. Therapeutical effect of magnetic particle

As a drug carrier, the system consists of three parts including magnetic particles, polymer materials and therapeutic drugs. The magnetic materials usually used are pure iron powder, carbonyl iron, magnetite, ferrate and so on. The diameter of magnetic particles is generally 10 ~ 100 nm. If the size of the magnetic particles is too large, it easily leads to microtubule embolization and is not easy to be removed from the body. At the same time, if the size is too small, it is easy to be intercepted. The superparamagnetic particles have the characteristics such as small particle size, low toxicity and good response in magnetic field. This property allows the drug-loaded magnetic particles not gather in the body and block the blood vessels, and can distribute evenly and spread to the target area to produce therapeutic effect. The polymer materials used include chitosan, dextran, starch, gelatin, protein and other organic macromolecules such as poly (lactic acid), polyvinyl alcohol (PVA) and polyethylene glycol (PEG). Carbon is also used in the preparation of magnetic complexes with iron due to its good adsorption on drugs. These carrier skeletons require not only certain mechanical strength and biodegradation rate, but also maximum biocompatibility and minimal immunogenicity. The skeleton of the carrier can be metabolized in vivo and can be safely discharged from the body within a certain period of time.

4. The application of magnetic particle

The application of magnetic nanoparticles in the field of biomedicine is mainly divided into two main categories. First, the applications in vitro including separation and purification, magnetic transfection, immune analysis, catalysis, magnnetoraxometrics, and solid-phase extraction and so on. Second, the application in vivo can be broadly divided into two categories: therapeutic and diagnostic. Meanwhile magnetic particles have many therapeutic applications such as thermotherapy and magnetic targeting drugs, as well as diagnostic applications such as nuclear magnetic resonance imaging (NMR).

5. Conclusion

Magnetic nanoparticles have a high specific surface area, and they are magnetic and have a permanent agglomeration. Therefore, the research and application of multifunctional magnetic nano-biomaterials have gradually become a hot spot in the biomedical field at home and abroad. Magnetic nanoparticles have shown great application prospects in biomedical fields such as bioseparation, hyperthermia, targeted drug delivery and tissue engineering, but they also face many challenges at the same time.

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