Right up there in frequency with using nanotechnology for face powders has to be the myriad ways in which nanotech is, will, or can be used to deliver medicine. Why nanotech? For one thing, the nanoscale is small enough to be effective in attaching to or passing through cell membranes. Nanotech materials can be easier to target for specific cells such as those in cancerous tumors. For another, nanotech materials can be shaped into containers – miniscule pockets to contain drugs, especially those for cancer that are toxic to healthy tissues and need to be encapsulated until they reach the target. Both of these conditions are relevant to a new nanotechnology configuration developed by Eva Harth, professor of chemistry at Vanderbilt University (Tennessee, USA). The configuration is called a nanosponge, which is evocative, but not quite accurate as the shape isn’t really sponge-like (spongiform) but more like a network of molecules in three dimensions. The point is though that the nanosponge can use its shape to attach to cancer cells and to contain drugs.
The nanosponge is about the size of a virus with a ‘backbone’ (a scaffold structure) of naturally degradable polyester (not the stuff in suits). The long(ish) polyester strands are mixed with small molecules that have an affinity for certain portions of the polyester. They ‘cross link’ segments of the polyester to form a spherical shape that has many pockets (or cavities) where drugs can be stored. You might wonder about polyester; this particular version is predictably biodegradable, which means that when it breaks up in the body, the drug contained can be released on a known schedule. Better still; the nanosponge can be engineered to be of specific size and to release drugs over time – not just in the ‘burst’ mode common with other delivery methods. The engineering capacity of nanosponge is due to the relatively simple chemistry of its polyesters and linking material (peptides); compared to many other nanoscale drug delivery systems, nanosponge should be able to scale (e.g. ramp up to commercial production levels) without requiring unusual equipment or procedures.
Nanosponge is water soluble. This does not mean the molecules chemically break up in water, but it means that nanosponge particles can mix with water and use it as a transport fluid, for example to be injected. Most other forms of nanoparticle delivery systems must use various chemical transports (for example, adjuvant reagent), which may have side effects.
So…in theory nanosponge has several advantages over other delivery methods. It has been used in a successful single-injection test, delivering the drug paclitaxel (generic Taxol) to mice with glioma (a fast acting brain cancer) and cells with human breast cancer. The next tests will be a series of injections against whole tumors. In parallel to these tests, the approach must also be evaluated for toxicity. Like all nanomedical materials nanosponge will need lengthy phased trials, which means that commercial availability is still years away. It’s getting attention now because of its fundamental properties – particularly the engineering and production simplicity.
The other major advantage of Harth’s system is the simple chemistry required. The researchers have developed simple, high-yield “click chemistry” methods for making the nanosponge particles and for attaching the linkers, which are made from peptides, relatively small biological molecules built by linking amino acids.
“Many other drug delivery systems require complicated chemistry that will be difficult to scale up for commercial production, but we have continually kept this in mind,” Harth says.