Nanotechnology has an important role in the medical field. Recently,magnetic nanoparticles (mNPs) have become essential tools in moleculardiagnosis, in vivo imaging and treatment of disease, and the major aim beingthe production of a more theranostic approach. Since they are small in size,the nanoparticles can cross most of the barriers like the blood brain barrier,the blood vessels, thus providing effortless access to most tissues. The nanoparticleuptake must be maximum to treat any disease. A new method like association ofmNPs with peptides which penetrate the cells to allow the excellenttranslocation of haul into the cell and by using an external magnetic field to facilitateits delivery is under study. There can be many inventions in the use ofmagnetic particles since their physical and magnetic properties, surfacecoatings can be changed as per one’s desires.
The uniqueness in their use isthat, for mechanotherapy, the particle diameters are of the same length as thebiological cells that need to be cross-examined. Most important is that, thereis not much loss of their magnetization even at the nanoscale. They can besynthesized with their diameter being only a few nanometers, but can stillachieve satisfactory uniformity in dimensions within a batch. At this size,each particle has only a single magnetic domain and super paramagneticproperties, as compared to the larger magnetic particles, which have multipleferromagnetic domains and permanent magnetic properties. The external magneticfield exerts a force which ranges from 10-12 to 10-9 newtons on the particle,which are the common levels experienced by the cells in the body. Formechanotherapeutic studies, particles made up from iron oxide have more oftenusage than other magnetic materials like cobalt or nickel since they are easierto synthesize from iron salts by the co-precipitation method.
Batches of pre-synthesizediron oxide micro- or nanoparticles are commercially available, from the manufacturerswith reactive functional groups on the surface as required for the purpose tobe used for. It is now possible to attach a ligand by using chemical methodsafter deciding the surface functional group, enabling it to bind to theappropriate receptor on the cell surface. But, a more uncomplicated method isby using the hydrophobic interactions to adsorb the matrix proteins from thesolution. Proteins like collagen or fibronectin have their originalconformation intact when adsorbed, and so cells bind through their receptors’ thatrecognize the protein’s ligand domains which are still intact. A major concern,is the biological compatibility of the materials used, so iron oxide is morefavorable to use than cobalt or nickel as iron homeostasis is controlled by thecell to flush excessive iron.
Many attractive possibilities have aroused in thebiomedical field. One can control their sizes ranging from a few nanometers upto tens of nanometers, due to which, their dimensions are smaller than orcomparable to those of a cell (10–100µm), a virus (20–450 nm), a protein (5–50nm) or a gene (2 nm).This shows their possibility of getting nearlyclose to a biological entity of one’s interest. Nevertheless, coating with asuitable biological molecule to help them bind to specific cell, therebyprovides a means of regulating it in the body. Since, the nanoparticles aremagnetic, they obey Coulomb’s law, and can be controlled by an externalmagnetic field. This ‘action from outside the body’, combined with theintrinsic penetration of magnetic nanoparticle into the human tissue, isopening up many new uses like the movability and/or immobilization of magneticnanoparticles.
Hence, they can be made to deliver an anticancer drug, or acluster of radionuclide atoms, to a targeted part of the body, for example, a tumor.The magnetic nanoparticles can be designed in a such a way that they show some responseto a time-varying magnetic field, with highly attractive results which can be relatedto the energy transfer from an already excited field to the nanoparticle. Forexample, when the particle is heated, it leads to their use as hyperthermiaagents, which can be used to deliver lethal amounts of thermal energy to tumorswhich can act as targeted regions; or as chemotherapeutic and radio therapeuticenhancement agents, where even a medium level of tissue warming is effective inmalignant cell destruction.
