Application of Iron Oxide Nanoparticles in Tumor Imaging and Treatment
Magnetic nanoparticles have received great attention in various fields due to their unique physicochemical properties and wide application potential.In the past decade, the synthesis and application of magnetic nanoparticles from the bottom up has been a hot topic in the field of chemistry, chemical engineering, materials science and biomedicine. High-quality magnetic nanoparticles can be synthesized by chemical methods such as coprecipitation, high temperature thermal decomposition, and sol-gel methods. Compared to the top-down synthesis method, the bottom-up synthesis method can synthesize nanoparticles with uniform particle size and can be widely used in various fields: data storage, catalysts, biological separation and biosensing.
A typical magnetic nanoparticle is synthesized by a bottom-up method comprising a magnetic core (Fe3O4) and an organic substance (polysaccharide, polymer, small molecule) or an inorganic shell (silica or other nanoparticle). The physical properties of nanoparticles are determined by the inorganic core of the particles, and the organic matter on the surface also plays an important role, especially when applied to living organisms. For example, grafting a hydrophilic material such as dextran or polyethylene glycol on the surface of magnetic nanoparticles can make the nanoparticles better used in living organisms, while increasing the colloidal stability of the particles. In addition, the application of multifunctional antibodies, peptides, small molecules, etc. on the surface enables the nanoparticles to specifically target tissues for multifunctional imaging and treatment.
Iron Oxide Nanoparticles As Contrast Agents for Tumor Targeted Imaging
Although the nanoparticles are in the blood circulation, due to the loopholes and irregularities of the blood vessels at the tumor site, the nanoparticles can reach the tumor site, resulting in passive targeting. However, some tumors have thicker blood vessel walls and even no vascularization around them, and the osmotic effect is weak, resulting in only a small number of nanoparticles reaching the tumor site. In order to efficiently aggregate the nanoparticles to the lesion site, a targeting ligand can be attached to the surface of the magnetic nanoparticles to enable the iron oxide nanoparticles to bind to overexpressed receptors on the surface of the cancer cell. When the iron oxide nanoparticles reach the vicinity of the lesion, the ligand on the surface of the magnetic nanoparticles can cause the iron oxide nanoparticles to adhere to the surface of the cancer cells or cause the cancer cells to take up the magnetic nanoparticles.
The rapid phase shift of the nucleus caused by the strong magnetic field of the iron oxide nanoparticles, and resulting in obvious signal attenuation, and then affecting the longitudinal and transverse relaxation processes (the process in which the nucleus returns from the excited state to the equilibrium state is called the relaxation process; it is required The time is called relaxation time; there are two kinds of relaxation time, T1 and T2, T1 is spin-lattice or longitudinal relaxation time, T2 is spin-spin or transverse relaxation time), but it affects the T2 relaxation time greater than the effect on T1 relaxation. When iron oxide nanoparticles are used as a contrast agent, the resulting image contrast is significant. Therefore, a clear image of the morphology of the tumor can be obtained by iron oxide nanoparticles that act as a contrast agent at the tumor site, which lays a foundation for further diagnosis and treatment.
Iron Oxide Nanoparticles As a Carrier for Drug Delivery
When the presence of a tumor is determined by diagnostic imaging, it is necessary to select a suitable and effective method for treatment. The most common method of cancer treatment is chemotherapy. Traditional chemotherapy methods, because the drug is not specific in the treatment, the drug also causes certain damage to normal tissues and cells while killing the cancer cells, so the chemotherapy has a large side effect.In order to solve this problem, we can functionalize the surface of the iron oxide nanoparticles and encapsulate the chemotherapeutic drug molecules into the iron oxide nanoparticles so that they can be directed to the tumor site under the leadership of the functionalized iron oxide nanoparticles. This method can not only reduce the side effects of chemotherapy drugs, but also enhance the therapeutic effect. For example, PEG-modified SPIONs (Superparamagnetic iron oxide nanoparticles) can circulate throughout the blood vessels for a long time, and promote the accumulation of SPIONs into tumor cells through the enhancement of vascular permeability of tumor tissues. Further, by using the magnetic responsiveness of the iron oxide nanoparticles, the iron oxide nanoparticles can be brought to the tumor site by the action of an external magnetic field.
In summary, PEG and PEI modified iron oxide nanoparticles synthesized by high temperature thermal decomposition have good biocompatibility and almost no toxicity. Therefore, it can be used as a contrast agent for MRI for bioimaging, and as a carrier for drugs, carrying chemotherapy drugs to reach tumor tissues. In this way, the purpose of treating the tumor can be achieved, and the effect after administration can be further observed, so that the doctor can better improve the treatment method and achieve a more therapeutic purpose.