Microcapsules for drug delivery

Micrometre-sized capsules that are able to deliver drugs inside living cells to replace regular dosing are being developed by scientists at Queen Mary, University of London.


The technique inserts ‘micro shuttles’ that are loaded with a full course of prescription drugs under the skin. These are then opened remotely using biological triggers, such as a drop in blood sugar levels, or activated manually with a pulse of light.


Working on the project, Queen Mary PhD student Matthieu Bédard, said: ‘The main advantage of using such microcapsules is that they can be designed to be very stable inside the body, protecting their contents. This is particularly important for the many medications that are rapidly degraded or altered by the body. These capsules can be used to “store” drugs in the body for later use.’


The capsules, which are two micrometres in diameter, are built by wrapping strands of a metabolism-resistant material around spherical particles that are then dissolved in acid to leave behind an empty container.


These are then heated in a solution that contains a drug compound that causes them to shrink and traps part of the solution and compound inside. Once loaded, the capsules are inserted into live cells using electroporation (a small electrical shock) that makes the cell walls permeable for micrometre-sized particles.


The method has been shown to work in living tissue by delivering fluorescent test molecules in light-activated capsules. In the experiment, the capsules were exposed to an infrared laser beam, which had no affect on the cell but was picked up by nano-gold particles in the capsule walls. This changed its structure and released the micro shuttle contents.


Prof Gleb Sukhorukov at Queen Mary said: ‘This new technique could have many biological applications, including delivering DNA into cells for gene therapy. The capsules could also be filled in with magnetic particles that collect and extract miniscule samples from inside cells. Other applications could see patients needing internal medication after surgery being administered drugs without the need for further invasive procedures or hospital visits.


‘However, there are still questions about how to direct the capsules to the right cells as well as finding a way to make capsules that are safe for human use. It is possible that we will see useful applications for this technology being tested in the next five years.’


The work is in partnership with Dr Sebastian Springer at Jacobs University in Bremen and researchers at the Max Planck Institute of Colloids.