As they say, there’s more than one way to skin a cat. Perhaps they should also say, there’s more than one way to make a cat skin. One of the key objectives of synthetic biology is to create materials that can imitate the functions of cells and tissues, like creating the building blocks of biological material that can eventually be used to engineer organs – like skin. This is a very active area of research with many approaches in development. You’ll see references to new materials that can encapsulate and deliver drugs or microparticles that are used to make biological ‘scaffolds’ for the construction of tissue. [SciTechStory: Making a start on a synthetic liver] A new approach, developed by researchers at MIT (Massachusetts Institute of Technology, USA) and published in the Journal of the American Chemical Society [18 July 2011, paywalled, Responsive Micromolds for Sequential Patterning of Hydrogel Microstructures] brings microparticles for drug delivery and synthetic organs together through the use of micromolds.
The most common way of making microparticles is to use a polymer gel, usually polyethylene glycol (PEG), which is hardened into shapes with ultraviolet light. The process is called photolithography and it has a proven track record, however, it has its limitations in the materials it can use and the complexity of shapes it can build. The new approach uses tiny (as in a few micrometers, millionths of a meter) molds – in a variety of shapes – that are filled with an appropriate liquid gel (usually a water-based substance called a hydrogel) and then cooled until the material sets. The MIT researchers have added a new wrinkle to this process by creating micromolds out of a material that shrinks as it gets warmer. This leaves the hardened gel in the mold with a space around it, allowing another layer to be added to the microparticle.
These two (or more) layered particles can be manufactured in a variety of shapes (cylindrical, cubed, striped) and can be used to create different kinds of tissues, for example, long stripe shaped particles can build the shape of a heart muscle or a neuron. For their study, the researchers used the striped particles to make a first layer of connective tissue (fibroblast), which form blood vessels. The microparticles, especially those with a double layer, can be loaded with drugs for delivery as part of a (temporary) synthetic tissue. The team is currently experimenting with particles that simulate collagen, a key component of structural tissue including cartilage.
This is a clever approach with very useful flexibility for synthetic biology. Like the other approaches it must go through the phase where its applications are explored and then enter the most difficult phase where it demonstrates its practicality. Can it be produced in sufficient quantity and quality? Can it compete with other similar approaches? Is it medically sound? Sometimes these questions are more difficult than making the original discovery.