Course: SAT 170 Introductory Biotechnology

Unit 11 Learning Module

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Model Organisms and Nanomedicine

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Much of our understanding of human disease as well as how drugs can impact the human body relies on model organisms. A model organism is a non-human species which is used to study a particular biological process or phenomenon.

Some model organisms that are commonly used for medical studies include mice, rats, cats and even insects and fish. The reason that such seemingly unrelated organisms can be used to understand human disease is because of the similar genes that living things share. A gene that is found to be similar from one organism to another is referred to a homologue. To understand the role of this particular gene, it can be silenced in a model organism and the effect of that missing gene can then be observed. An organism that is engineered to have one or more gene inactivated in this way is referred to as a knockout organism, because it has had some of its genetic material silenced. For example, when researchers removed a gene in mice that codes for a protein known as leptin, they observed that the mice became obese. This discovery has led to a better understanding of certain weight problems facing many humans that are caused by deficient leptin production.

Figure 1 - The mouse on the left of this image illustrates the extra weight that is typical of a mouse that has had the gene for leptin inactivated. Such knockout mice are valuable in helping us to understand the role of particular genes in normal and disease development.

Another important use of model organisms is for evaluating the impacts of certain pharmaceutical drugs. To better understand the role of these model organisms, lets first review the process for getting a new pharmaceutical drug to market. Once a new drug has been developed it must first go through a set of preclinical trials. These preclinical trials are focused on identifying the safety of a particular treatment. Thus, having a model organism that has similar anatomy and physiology to humans (such as another mammal like a mouse or dog) can provide valuable insight to how the drug might impact humans. Only after a drug is considered to be safe for the organisms in these preclinical trials can it move to the next step of the drug approval process which includes humans as test subjects. This stage is referred to as the clinical trials.

A new and emerging part of the picture for these preclinical trials would be to use engineered tissues and organs, such as those described earlier to determine the impacts of new drug treatments on those tissues and organs. However, in order to get a better understanding of how a drug may impact an entire network of organs and organ systems, such as that which is found in the human body, tissue engineering has been taken to an entirely new level.

Nanomedicine is another emerging field in bionanotechnology. Nanomedicine is focused on generating nano-sized monitoring devices that can measure things like blood pressure and the presence of cancer cells while having minimal impacts on the patient. Another focus of nanomedicine is for the improvement of drug delivery systems. Nanoparticles are small (on the scale of 1-100 nanometers/nm) particles that can be made of a variety of materials from metals to plastics, and even organic materials. These particles can also be coated or filled with a particular drug treatment. Given their relatively small size, they can easily enter an individual’s cells. Nanoparticles used as a drug delivery system can be made of a variety of materials but they are often made with material similar to that of the cell membrane.  Generally, these particles are easily inhaled and can enter the bloodstream of the respiratory tract to be quickly delivered to the cells of the body where the drug can carry out its action. Some nanoparticles can even be designed to have markers on their surface which will allow them to bind to specific cell types. This is useful when you want to target a particular drug to a particular area of the body or cell type within the body. One example would be to create nanoparticles which contain chemotherapeutic agents and surface markers that will allow them to bind specifically to cancer cells. This will allow the particle to deliver the drug effectively to the cancer cells while reducing the impacts on the rest of the patient’s cells.

Figure 2 - This is an image of nanoparticles that are often used as drug delivery systems for nanomedicine. Notice the small size (see the 145 and 400 nm scale for reference) as well as the lipid coating that is similar to the content of an animal cell membrane.

These applications and many more are continually improving our ability to understand and treat disease. Diseases that were once thought to be incurable have been treated effectively with many of these techniques. In the future, there is hope that these methods can also help us to treat diseases and disorders that we are currently unable to treat including neurological diseases such as paralysis and Parkinson’s disease.