Team:UNILausanne/Implementation

Proposed Implementation

What our project could become

Since the conception of our project, we have had its implementation in mind. At its core, our system is an experimental therapy used to treat patients suffering from colorectal cancer (CRC). Our goal would be to further develop it, into a commercial cancer treatment and sell it as a complementary treatment for late stages of CRC (see Business Plan). Of course, our bacteria have only been taken as far as proof of concept, so in the future, our next big goal would be to complete animal trials, followed by pre-clinical trials. We would also need to think of an encapsulation design that would allow our bacteria to safely arrive at the affected colon area (see the text on Encapsulation below) after being orally ingested (as a normal pill).

Encapsulation

As our treatment consists of a drug secreted by a living organism, we would need to think how the storage for such a product will look like. Most definitely, it will be a pill that needs to be taken at the doctor's office, as it will need to be kept at really specific conditions for the bacteria to stay alive (chilled in a growth medium).

The encapsulation [1] consists of a coating or shell that would seal our bacteria, while being thin enough to be able to be swallowed and degraded, but strong enough to endure the harsh conditions in the body while keeping our cells alive. Because we are working with living microorganisms, it needs to be protected from the different degradation agents that exist from the mouth to the colon. If we want an orally administered treatment, this encapsulation device should be able to withstand degradation through the entire alimentary canal until its arrival to the targeted area where our probiotic would be released.

We spoke with Prof. Sandrine Gerber; whose area of expertise is the encapsulation of biomaterials such as cells for transplantation into the body. She helped us narrow down on possible encapsulation designs for our product. The first idea we pitched to her was to create a hydrogel sphere that would keep our bacteria inside. This hydrogel would be made out of alginate (it precipitates by crosslinking with divalent ions); however, this polymer is composed of ionic bonds that do not degrade in an acidic environment. There should be a monovalent ion present in big quantity in the environment (for example NaCl also known as "salting out"), which is not the case in the digestive tract where these ions are rare. These hydrogels would have to be kept in an aqueous solution similar to the bacterial medium. There is a paper showing microencapsulation in alginate microparticles coating with chitosan delivers viable bacterial cells to the colon, while maintaining their survival rate during refrigerated storage [2].

We then looked into the existing literature for other encapsulation options. Normally microorganisms, like for example yeast, are dehydrated to facilitate the storage. However, this would need to be tested with our probiotic, as normally bacteria have a low survival rate after drying. For example testing done in a paper by Anders Meyers Torp on the "Preparation and storage of bacteria used for a novel probiotic delivery system" found that spray drying E. coli Nissle resulted in the survival of less than 1% of the population [3]. Other polymers with interesting properties similar to alginate would be: xanthan, milk protein gel and starch.

All these designs would need to be tested to see if they are resilient enough to withstand the acidic environment of the gastrointestinal tract, as well as timing the release of bacteria correctly to be able to release it in the colon. Two additional aspects will need to be taken into consideration: the number of bacteria in each pill (depending on the size of E. coli) and the difficulties to keep them alive.

Safety Considerations/Challenges

Our system has a kill switch as a security mechanism in case the bacteria get deregulated, escape into other parts of the body or into the environment. However, if B.O.T. ever becomes a therapeutic system, we would need to design multiple layers of security to ensure that no adverse effects would come as a consequence of its ingestion. Secondly, as laws on medical GMOs vary in each country, we would need to adapt constantly [4] to be able to meet all of the legal requirements needed to put such a product in the market. We would need to prove with convincing evidence that the release of our bacteria would not be harmful to the environment to be allowed to go forward with our clinical trials.

Envisioned long-term applications

Our system uses E.Coli Nissle 1917 to secrete our anti-tumoral drug, as this bacteria has shown that it colonizes tumoral tissue quite easily [5]. This colonization property is not specific to one type of tumoral tissue, so in the future our system could be adapted for usage against other types of tumoral cancer. More specifically, azurin has shown to be effective against melanomas as well as breast cancer [6], so those two diseases would be the next applications for our system.

References (click to see)

A big thank you to our sponsors for their valuable support!