|Scanning electron microscopy images of image of (A) a hollow, open surfaced, biocontainer, and (B) a device loaded with glass microbeads. (C) Fluorescence microscopy images of a biocontainer loaded with cell-ECM-agarose with the cell viability stain, Calcein-AM. (D) Release of viable cells from the biocontainer.|
In a paper to be published later this month in the journal Biomedical Microdevices, Gracias and his team demonstrate a new tool for encapsulating and delivering drugs in a body, as well as for biosensors able to travel through the bloodstream. The new system uses a combination of biomimetics, nanomaterial production, computer chip manufacturing techniques, and old-fashioned chemistry. The result are microdevices that would be familiar to anyone who has ever made a box out of paper.
...Gracias and his colleagues begin with some of the same techniques used to make microelectronic circuits: thin film deposition, photolithography and electrodeposition. These methods produce a flat pattern of six squares, in a shape resembling a cross. Each square, made of copper or nickel, has small openings etched into it, so that it eventually will allow medicine or therapeutic cells to pass through.
What's more, they self-assemble:
The researchers use metallic solder to form hinges along the edges between adjoining squares. When the flat shapes are heated briefly in a lab solution, the metallic hinges melt. High surface tension in the liquified solder pulls each pair of adjoining squares together like a swinging door. When the process is completed, they form a perforated cube. When the solution is cooled, the solder hardens again, and the containers remain in their box-like shape.
What sets these microcontainers apart from other drug microencapsulation methods is that they're designed to be tracked and, eventually, controlled with magnetic imaging devices.
At the Johns Hopkins School of Medicine's In Vivo Cellular and Molecular Imaging Center, researcher Barjor Gimi and colleagues then used MRI technology to locate and track the metallic cubes as they moved through a sealed microscopic s-shaped fluid channel. This demonstrated that physicians will be able to use non-invasive technology to see where the therapeutic containers go within the body. Some of the cubes (those made mostly of nickel) are magnetic, and the researchers believe it should be possible to guide them directly to the site of an illness or injury.
For Dr. Gracias, this development is part of the "bioinspired" approach to chemical engineeering -- a combination of organic/biological and inorganic/mechanical characteristics.