Nanoparticles That Deliver Medicines Have Problems That May Be Solved

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Nanoparticles that can be used to deliver drugs to specifically targeted tissues have been shown to have problems, and researchers are working hard and fast to identify these problems so that solutions can be found and the technology can be moved forward. Two recently published studies reported problems with nanoparticle technology in how the nanoparticles can cause damage to bodily tissues. Nanoparticles are very small; that is, on the scale of nanometers, which are billionths of a meter. To offer a visual perspective, a sheet of paper is about 100,000 nanometers thick.

One of the studies, published in Nanotoxocology, reported a problem with toxicity when nanoparticles that were positively charged were intravenously injected to target the brain or were injected directly into the brain. The damage to the brain that was discovered included infiltration of phagocytic (immune cells), loss of neurons and apoptotic cell death. The results showed that negatively charged nanoparticles did not cause the same type of toxicity. The attractive and repulsive laws regarding charged particles may provide the explanation as to why positively charged versus negatively charged nanoparticles produced the adverse effect. The cells of the brain have a negative charge on their outer membrane and this would attract the positively charged nanoparticles, which would bring them inside the cell. This could disrupt the normal functions of the cell. The negatively charged nanoparticles, however, would not be brought inside the cell because of the repulsive force between to “like” charges. This is an important result that can lead scientists to chose negatively rather than positively charged nanoparticles in future studies.

In the second study, published by the journal Lab on a Chip, researchers employed a body-on-a-chip method that involved placing human tissues, in this case intestinal and liver tissues, on chips. These chips are considered to be miniaturized models of sections of the human body. The nanoparticles were then used to analyze toxicity. The results of the study showed that single nanoparticles and small aggregates were able to crossover from the intestinal cells to the liver cells in the system, which is an adverse effect. However, the larger nanoparticles were stopped from crossing over. This simulation study is an example of how future studies can be conducted to determine potential problems with nanotechnology in medical applications.

Nanoparticle technology is one of the exciting and fast moving, developing trends in medical technology. Nanoparticles can be filled with a drug and delivered to a specific part of the body to target a problem, like a tumor. The nanoparticles can either be injected into the body or can be taken in a pill form. In any case, the nanoparticles are meant to travel to a specific target to deliver the effect, which is different from conventional medicines that act systemically.

One of the most obvious and desired uses of nanotechnology in medicine is to design nanoparticles that can travel to cancerous tumors. These nanoparticles can transport chemotherapy drugs directly to the tumor and the rest of the body would be spared. This would be a highly desired effect and would reduce the severe side effects of systemic administration of chemotherapy drugs. An especially important potential benefit would be the preservation of the immune system with administration of chemotherapy drugs that only are applied to the cancerous tumor.

Another desired use of nanoparticle technology is to deliver drugs that can cross the blood-brain barrier. The blood-brain barrier is a natural part of the biology of the brain and it prevents most substances and many microbes that are in the blood stream to actually enter the brain and reach neurons. In order to treat some brain diseases, however, it would be desirable to be able to cross the blood-brain barrier and administer a drug directly to the neurons of the brain.

Nanoparticle technology is an exciting method for potentially treating many diseases and identifying the problems with nanoparticles in medical applications will illuminate potential solutions.

By Margaret Lutze

Chemistry World
Lab on a Chip
Scientific American