Nanoparticles are a field of science that has provoked global interest due to their wide variability and applications. Novel interactions with the immune system show promise for suppression and triggering of this system. Their small size and variable nature can allow them to bypass the immune system as a whole, making them promising drug carrier candidates. Nanoparticles are defined as an aggregate of atoms, molecules, or ions with a diameter between 1 and a few 100 nanometers that have properties different from those atoms in bulk. Their unique size range allows for a broader range of properties, including variable surface charge, variable size, and variable shape. This is a direct effect of the surface to volume ratio increasing in nanoparticles compared to bulk materials. That ratio serves to allow nanoparticles to confine their electrons and have such a wide range of variability. This allows them to serve a wide range of functions, especially in the medical field.
Nanoparticles are often classified into two categories, hard and soft. Hard nanoparticles are those primarily synthesized from inorganic sources and are separated into a variety of subsections based on their sourcing. Soft nanoparticles are primarily organic and are divided into biological and synthetic categories. Biological nanoparticles include proteins, viruses, and DNA. The fundamental difference between these two categories is their rigidity. The foundational method of categorization was initially devised by Donald Tomalia and goes into extensive detail. These categories are used as the method of organizing research into this field. The wide variety of materials and properties made this research crucial in the forward movement of the field.
Cancer is a disease caused by genetic abnormalities leading to uncontrolled cell division. These cells lose inhibitory factors and are overrun by pro-divisionary factors, leading to uncontrolled and often harmful cell growth. This generally leads to the development of tumors, and once metastasis occurs, often leads to death. Methods of curing this disease are generally surgical removal and chemotherapy. Chemotherapy works to kill the cancerous cells, but is very harmful to the patient as that can lead to a weakened immune system. There are a variety of other treatment methods as well, all with their own setbacks. Nanoparticles show promise as a method of assisting this process, slipping past the immune system to deliver fatal drugs to the cancerous cells.
Image from Wikimedia Commons
Nanoparticles are often used to build “shells” around the drug that is being delivered, as seen above. One of the many issues with drugs made to combat cancer is their low water solubility, making it difficult for them to enter cells and perform their functions. The image above proposes a potential solution to this problem, by surrounding the hydrophobic drug in the nanoparticulate shell, allowing it to travel through the body undisturbed, and allowing antibodies, targeted ligands, and cell-penetrating functions to be attached. This attachment makes targeting more effective, allowing the body’s internal system to deliver the drugs to their intended target, all while keeping them safe within the shell created by nanoparticles.
Other forms of nanoparticle targeting systems include liposomes and dendrimers. Liposomes are phospholipid structures that essentially form an enclosure. These enclosures can contain drugs and operate to deliver those molecules into a cell. This is valuable due to the protection it provides to the drug against degradation, and the targeting it can perform. These structures have very low toxicity as they are biocompatible, and the bilayers they are formed of are what form the backbone of cell membranes. Dendrimers are structures that are branched at the ends and possess a unique 3-dimensional structure. This often in the form of an inner core with progressive shells or outward branches. Drugs can be contained inside these delivery systems to counter solubility issues while still retaining efficiency, and the branches contained in the structure allow for specific antigens to aid targeting systems.
These nanoparticulate systems allow for drugs to be contained and protected, as well as effectively delivered to cancerous cells. This is done either by harnessing the immune system’s recognition via specific receptor targeting ligands or antibodies or by editing surface qualities to avoid the immune response. Suppression of the immune system can also assist in drug delivery and pose as a solution to autoimmune responses. This modulation of the immune response can lead to more effective cancer therapy. Targeting factors and protective factors show promise for efficient and effective cancer treatments, especially methods that decrease the toxicity that many current methods exhibit. These new discoveries can provide the cavalry in the crusade against cancer.