February 13th, 2008
A pharmacy in a nanotechnology-based thin film
MIT researchers have developed a new implantable device to improve our health. This nanoscale thin-film coating can deliver controlled drug doses to specific targets, acting as a ‘micro pharmacy’ inside our bodies. It could be used to deliver drugs for cancer, epilepsy, diabetes and other diseases. This film, which is about only 150 nanometers thick, can be remotely activated by a physician using radio signals by applying a small electric field to the device. The researchers even think that these implantable devices could ‘guess’ when they have to deliver a drug to a patient when it’s needed. But read more…
This research project has been led by Paula Hammond, professor of chemical engineering. As you can see on the left, Hammond also works on other projects. On this picture, she’s working with “a small-scale experimental fuel cell under tightly controlled conditions” (Credit: Len Rubenstein/MIT) For more details about this other project, you can read “Roll-Up Fuel Cells,” an article published in the Winter 2007 issue of MIT’s Spectrum quarterly magazine.
Let’s come back to this nanotechnology-based thin film project. Hammond worked with her colleagues in her research group which include Kris WoodT, now a postdoctoral associate at the Broad Institute of MIT and Harvard, Nicole Zacharia, now a postdoctoral associate at the University of Toronto, and Daniel Schmidt, a chemical engineering graduate student.
So how did these researchers make their films? “The films are made from alternating layers of two materials: a negatively charged pigment and a positively charged drug molecule, or a neutral drug wrapped in a positively charged molecule. The pigment, called Prussian Blue, sandwiches the drug molecules and holds them in place. (Part of the reason the researchers chose to work with Prussian Blue is that the FDA has already found it safe for use in humans.)”
And how does this work? “When an electrical potential is applied to the film, the Prussian Blue loses its negative charge, which causes the film to disintegrate, releasing the drugs. The amount of drug delivered and the timing of the dose can be precisely controlled by turning the voltage on and off. The electrical signal can be remotely administered (for example, by a physician) using radio signals or other techniques that have already been developed for other biomedical devices.”
The researchers even think that these implantable devices could ‘guess’ when they have to deliver a drug. “Eventually, devices could be designed that can automatically deliver drugs after sensing that they’re needed. For example, they could release chemotherapy agents if a tumor starts to regrow, or deliver insulin if a diabetic patient has high blood sugar. ‘You could eventually have a signaling system with biosensors coupled with the drug delivery component,’ said Daniel Schmidt.”
Like always, New Scientist is essential to decrypt this kind of news. Here is an excerpt of “Blue film delivers drugs at the flick of a switch.” “The researchers used nanoparticles of a pigment called Prussian blue — an inorganic iron hexacyanoferrate compound — to make the film and a chemical called dextran sulphate to represent the drug in their prototype. They took a glass substrate coated with indium tin oxide and dipped it in a solution containing dextran sulfate, which is positively charged. Next, they dipped the substrate into a solution containing negatively charged Prussian blue nanoparticles. By repeating the process they gradually built up alternating layers of pigment layers and ‘drug’ held together by electrostatic charge. Applying 1.25 volts to the substrate caused the layers to lose their charge and begin dissolving in a solution. When the voltage was removed, the layers stabilised and stopped dissolving.”
For more information about these future nanotechnology-based implants, this research work has been published online on February 12, 2008 in the Proceedings of the National Academy of Sciences under the name “Electroactive controlled release thin films.”
Here is a link to the abstract. “We present the fabrication of nanoscale electroactive thin films that can be engineered to undergo remotely controlled dissolution in the presence of a small applied voltage (+1.25 V) to release precise quantities of chemical agents. These films, which are assembled by using a nontoxic, FDA-approved, electroactive material known as Prussian Blue, are stable enough to release a fraction of their contents after the application of a voltage and then to restabilize upon its removal. As a result, it is possible to externally trigger agent release, exert control over the relative quantity of agents released from a film, and release multiple doses from one or more films in a single solution. These electroactive systems may be rapidly and conformally coated onto a wide range of substrates without regard to size, shape, or chemical composition, and as such they may find use in a host of new applications in drug delivery as well as the related fields of tissue engineering, medical diagnostics, and chemical detection.”
Sources: MIT News Office, February 11, 2008; Kurt Kleiner, New Scientist, February 11, 2008; and various websites
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