The concept ‘Nanomedicine’ does have somewhat of a futuristic nuance to it, but in fact, there already are several nanomedicines available on the market. Curious to know more about this intriguing area, we talked to Dr. Gustav Emilsson who is working as a Postdoc with nanomedicine development at the department of Advanced drug delivery in Pharmaceutical Science at AstraZeneca, a global, science-led biopharmaceutical company.
What is a nanomedicine?
A nanomedicine is a medicine where at least one dimension of the material used is in the nanoscale range, Dr. Emilsson explains. For example, it could be some sort of particle where one of its dimensions is between 1-100 nm. The other dimensions of the object could be larger than nm, they could even be in the um range. Typically, a nanomedicine consists of several different components. For example, it could be a nano-sized container used as a drug-delivery carrier.
Do traditional medicines, which have active molecules in the nm size range, qualify as nanomedicines?
In general, I would say that the design needs to be more complex than just the molecule itself, Dr. Emilsson says. It should be composed of more than one single component. Typically, you would combine a set of different components to achieve certain goals. For example, you could design a container, i.e., a drug carrier, which is then filled with the actual drug to be delivered to a target site in the body.
What makes nanomedicines so special?
When you make objects into the nm size range, you can gain new properties, Dr. Emilsson explains. This means you get access to new ways of working with medicines. For example, quite recently drugs have been approved where you have a container, in this case a liposome, which is filled with a combination of drugs. So, you do not just have one drug, but you have a cocktail of two drugs. The liposome, which is like a lipid-membrane encased volume of liquid, acts like a shell. This can then be filled with drug molecules.
Liposomes are quite prominent in nanomedicine, and there are a lot of liposomal drugs being investigated, and some that already have been approved, Dr. Emilsson says. An advantage with such a delivery system is that you can deliver multiple drugs at the same time and at a certain ratio. This means that you could gain new effects compared to if the different drugs were injected separately. In the example I just mentioned, it was shown that when the drugs were co-delivered, there was an increased effectiveness. This is beneficial because it means that you can use a lower dose compared to if the drugs were delivered separately.
How can you make sure that the nanomedicine is delivered at the target site?
I think that there is still a debate whether you can or not, but there will be a difference in distribution. This means that if you inject the drug by itself, it will distribute in a certain way, and if the drug is encapsulated it will be distributed in a different way, Dr. Emilsson explains.
In addition to encapsulating the drug to change the distribution, you can also modify the carrier with different targeting ligands, Dr. Emilsson says. I.e., you modify, for example, the outer layer of the liposome, with something that will bind to a certain receptor. You can then hopefully get the liposome to bind in an even higher degree to where to you want it and bind less to the other areas in the body.
What materials could be used as drug-delivery carriers to transport the drugs in the body?
There are quite a few possible materials that could be used, Dr. Emilsson says. In addition to liposomes, you could use polymeric carriers or shells. There is also something called dendrimers, which are quite small. In this case you are binding the drug to the carrier. You can also have protein bound particles.
In general, the carrier size range is quite wide. Even if we are in the nano size range, we could still have objects that are maybe five nanometers, or objects that are 100 nanometers. It is quite a big difference working with such different sizes. The goal, however, is of course the same. The definition of what is a carrier is also quite wide, but somehow you modify your material to enhance or change its properties. You also have, for example, drug nanocrystals, which I have been working with. The surface of these can e.g. be modified with proteins.
What are drug nanocrystals?
A drug nanocrystal is a drug that has been crystallized, Dr. Emilsson explains. The drug itself is then the nano-sized object, which means that drug nanocrystals are composed of purely the active compound that you want to deliver. Typically, you also change the properties of the crystal surface to stabilize it. This stabilizer is not as extensive as a container, it is more like a shell, Dr. Emilsson says.
What are the benefits of nano crystals?
Nanocrystals are a good option for poorly soluble drugs. If you have an active molecule that binds to the site where you want it, but it is very poorly soluble, it is not useable because if you give it to a person, it will dissolve too slowly. But if you make it into a smaller size, then the dissolution rate will increase. Other options are to dissolve the drug using solubilizing agents or oils. But these could be toxic, so perhaps you end up in a situation where the active substance is not the most toxic one, but the solubilizing component is, Dr. Emilsson says.
Another benefit with nanocrystals is that the system is very simple. Since your nano-object is made of pure drug, you have fewer components to characterize and verify prior to approval. Also, you have a high drug loading if you compare with for example a nano-carrier.
What parameters can you vary in the nano medicine design?
The nanomedicine design can be quite intricate. This is both an advantage and a challenge because there are a lot of parameters that can be varied and tuned, Dr. Emilsson says. You can for example vary the size and the surface chemistry.
Everything that will be injected as some sort of particle has an interface and this interface will be recognized by the body. When you make something into nano size you are increasing the area per volume. Comparing nano-sized objects to larger ones, such as micro-sized ones, the surface becomes more important, so, you can tailor the surface chemistry or the charge, what type of polymers are put on the surface or other surface properties. Then, once the objects go into the body, they will start accumulating proteins and they will get a biological profile. And then of course, the problem is much more complex, Dr. Emilsson says.
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Listen to the full interview with Dr. Emilsson to learn more about what nanomedicines are and how they work.