Theranostics: Diagnosis and Care through Nanoparticles
The term nanosciences refers to disciplines that are dedicated to studying the properties of nanomaterials, i.e., any type of structure with dimensions of the order of magnitude of nanometers, 10-9m. Order structures nm obviously exists in nature. A single strand of DNA is wide about three nanometers. The wings of a Morpho butterfly contain nanostructures that they change the way the light waves interact with each other, giving the bright wings blue and green shades.
Their nanotechnology is the study that deals with both research and development of atomic, molecular, and macromolecular technologies, both of control and atomic material handling and development of the application of structures, devices, and systems characterized by new one's properties and functions due to their small size. Due to the reduced dimensions of these structures, it is, in fact, possible to study and exploit important material properties. The lengths on this scale are those that characterize the molecules and macromolecules and, since they are comparable with the de Broglie wavelength of the electrons, the effects quantum is no longer negligible—the spacing between the energy levels of the crystals.
Among the most important applications of nanoparticles in theranostics are target imaging and therapeutic delivery, which includes passive and active targeting. Passive targeting has been tested with nanoparticles of size between 10 and 500 nm through a mechanism known as EPR (enhance permeability and retention), in which the nanoparticles accumulate in the tumor after exiting from the vessels by means of a process called receptor-mediated endocytosis.
Inactive targeting, nanoparticles are joined to high-affinity binders for cancer cells. These specific target nanoparticles could accumulate in diseased tissues, thereby reducing unwanted absorption in the healthy tissue, thus limiting side effects to a minimum.
Composition of the nanoparticles
The nanoparticles used in theranostics, to a large extent, are characterized by four basic components:
1. A signal emitter
2. A therapeutic payload
3. A payload carrier
4. A binder
The emitter has optical, magnetic, or radioactive properties that characterize and can emit the signal spontaneously or following an excitement from an external source. This signal is identified by external detectors and is used for the construction of the image. The payload therapeutic may be a chemotherapy drug or a nucleic acid such as DNA or siRNA. The conveyor usually includes a polymeric matrix of materials with multiple functional groups, to which they can be combined signal emitters or the therapeutic load. The targeting ligand is chosen so that it binds and forms a complex with specification marker pathology, thus facilitating the transport of nanoparticles to the site of interest e allowing interactions with the cell or with diseased tissue.
The signal emitter and the therapeutic payload can be incorporated into the vector or conjugated on the surface of the core of the nanoparticle. While the targeting binder is always covalently joined to the surface of the support, which allows direct interaction with the target cell or tissue.
Nanoparticles can be engineered to develop structures relatively complex; a nanoparticle can also contain many signal emitters equipped with different signaling mechanisms, thus offering multimodal images that allow you to take advantage of the advantages of the individual imaging modalities and expand the applicability of the carrier. The signal emitter, as well as the therapeutic payload, can be encapsulated in a nanoparticle or can be conjugated to a carrier payload. Wide varieties of polymers, both synthetic and natural, are used as payload carriers. These polymers can be joined to the nanoparticles by covalent and non-covalent bonds during the synthesis of the nucleus of the nanoparticle or through surface modification following the synthesis of nuclei.
Nanoparticles as a contrast agent
There are several non-invasive imaging techniques that are used to view the real-time distribution of the nanoparticles. The most common are magnetic resonance tomography (MRI), computerized tomography X-ray (CT), positron emission tomography (PET), single-photon emission computed tomography (SPECT), and ultrasound tomography (US). Other imaging techniques, such as tomography by fluorescence (FMT) and photoacoustic tomography (PAT), are on the way of development. Each of them has advantages and disadvantages. For example, MRI is CT has a high spatial resolution and provide information detailed anatomical, but lack sensitivity. On the contrary, PET and SPECT are very sensitive but have a limited resolution and, therefore, not allow you to have precision in the image.
Controlled drug release is of great importance for applications therapeutic, such as cancer treatment. Nanoparticles magnetic can be used in the administration of drugs. The drug localization process is based on competition between the forces exerted on the carriers by the blood and the magnetic forces generated by an external magnet. When magnetic forces exceed those due to blood flow, the particle is retained and can be absorbed from the cells of the tissue or organ of interest.
Malignant tumors arising from the growth of mutated cells that survive they consume more energy than normal cells. The blood vessels are not able to supply sufficient nutrients and oxygen for them uncontrolled proliferation. Malignant tumors, therefore, stimulate the growth of other blood vessels (tumor angiogenesis process). These new pots they have chaotic structures compared to those of normal tissue. The unusual dimensions and circuits, given the irregularity of the structure of these vessels, often, large areas of the tumors are hypoxic. Also, since we are not able to dispose of harmful substances sufficiently through blood, cells hypoxic have a lower pH value. In these tumors are often observed also important variations of perfusion, since unstable blood vessels periodically collapse and take oxygen from the cells. It's a lot difficult to destroy cells with oxygen deficiency using irradiation ionizing (which produces oxygen radicals which in turn attack DNA), or chemotherapy (which requires blood flow to transport the cytostatics). Since hypoxic cancer cells tend to metastasize, it is. Therefore, it is an extremely high priority to destroy them for the treatment of the tumor. Hyperthermia destroys cancer cells by increasing the internal temperature tumor. So take advantage of the weaknesses described above of tumors Malignant. Since the body tries to cool the rising temperature for by means of perfusion, tumors with reduced or irregular perfusion do keep at a higher temperature.
Author: Vicki Lezama