Drug delivery: drop stone sharpens
A new implantable drug delivery system is presented
Roman Ivanov, Computer
The time-stretched, controlled delivery of medicines exactly to their destination inside the body arouses genuine interest among both researchers engaged in experimental medicine and practitioners. And it only intensifies when it comes either to improving therapeutic means aimed at suppressing chronic pain, or preventive medicine designed to prevent the recurrence of cancer after surgery.
So, a team of researchers from Boston University (USA), led by Mark Greenstaff, has developed a unique material, and with it a drug delivery mechanism that gives life to implants capable of secreting medicine for months.
The system consists of a biocompatible, highly porous three-dimensional polymer material containing any targeted medicinal substance, and a certain amount of air that slows down the infiltration of the surrounding water. When water begins to be drawn into such a material, it slowly displaces the air, gradually washing out the medicine.
According to Mr. Grinshtaf, the idea was to create a three-dimensional material consisting entirely of polymer fibers with air contained inside. To prevent the instant filling of the implant with water and the rapid leaching of the drug, Mark Greenstaff and colleagues developed a mesh air-filled material that was so superhydrophobic that upon contact with its surface, water droplets instantly collected into small balls, reminiscent of how it happens when water hits a freshly waxed machine. The structure itself was obtained by electroforming, when micron-sized fibers are superimposed one on top of the other.
In order to control the rate of drug release, the researchers adjusted the chemical and physical properties of the material so that the air trapped by the material was held by it weaker or stronger. The stronger the air was retained, the more difficult it was for the water to displace it and the longer the release of the drug turned out to be.
Being filled with the anti-cancer drug SN-38, the system consisting of a polymer mesh and the air trapped by it proved to be a reliable and effective fighter against lung cancer cells in solution for 60 days in in vitro experiments. This proves the applicability and convenience of the technology for a long-term drug delivery procedure (however, this also suggests that after 60 days cancer cells continued to exist: the desired slowness of drug withdrawal is generously paid for by its uselessly low concentration at any given time). In the near future, Mr. Greenstaff's group plans to conduct a series of in vivo experiments to assess the potential clinical effectiveness of its development.
The results of the study are published in the January issue of the Journal of the American Chemical Society (Yohe et al., Superhydrophobic Materials for Tunable Drug Release: Using Displacement of Air To Control Delivery Rates).
Prepared based on the materials of Boston University:
The Power of Air. Novel Material Could Enable Long-Term, Controllable Drug Delivery.
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03.02.2012