The need to administer intermittent doses of medication that cannot be taken orally has seen the development of delivery techniques such as using an implanted heat source or relying on an implanted electronic chip or other stimuli as an “on-off” switch to release drugs into the body. Different methods have their own advantages and disadvantages, but now researchers have developed a drug delivery solution that combines magnetism with nanotechnology to produce a system that offers all the advantages of the various previous methods combined. The new method developed by researchers at the Children’s Hospital Boston is able to repeatedly turn dosing on and off, deliver consistent doses and adjust dosage according to the patient’s needs.
The system centers around a small implantable device, less than half an inch in diameter, that encapsulates the drug in a specially engineered membrane. The membrane is embedded with nanoparticles - 1/100,000 the width of a human hair - composed of magnetite, a mineral that, as its name suggests, has magnetic properties.
When a magnetic field is switched on outside the body, near the device, the nanoparticles heat up, causing the gels in the membrane to warm and temporarily collapse. Pores thus open up, allowing the drug to pass through into the body. Then, when the magnetic force is turned off, the membranes cool and the gels re-expand, closing the pores back up and halting drug delivery. No implanted electronics are required.
In animal experiments, the membranes remained functional over multiple cycles. The size of the dose was controllable by the duration of the "on" pulse, and the rate of release remained steady, even 45 days after implantation. Testing indicated that drug delivery could be turned on with only a 1 to 2 minute time lag before drug release, and turned off with a 5 to 10 minute time lag.
The membranes remained mechanically stable under tensile and compression testing, indicating their durability, showed no toxicity to cells, and were not rejected by the animals' immune systems. They are activated by temperatures higher than normal body temperatures, so would not be affected by the heat of a patient’s fever or inflammation.
According to Alison Cole, Ph.D., who oversees anesthesia grants at the National Institutes of Health's National Institute of General Medical Sciences (NIGMS), "while some distance away from use in humans, this technology has the potential to provide precise, repeated, long-term, on-demand delivery of drugs for a number of medical applications, including the management of pain."
The device, which Kohane’s team at the Children's Hospital Boston is continuing to develop for clinical use, is described in the journal Nano Letters.
