Researchers devise biomaterial that could be used in the detection of toxins and pollutants

In research recently published in the leading international journal PNAS, Trinity researchers exploit the potential of a biomaterial to reveal the activity of important fat metabolising enzymes. The findings show that the biomaterial could possibly be used in the future detection of toxins, explosives, pollutants, and medicines.

Detection devices have superior sensitivity when the sensor itself can be packaged at high density.  Certain proteins that are found in the membranes of cells can act as sensors.  However, the density with which cellular membranes can be packed in a sensor of a defined volume can limit the application.  In this study, use was made of a particular form of matter, referred to as a liquid crystal or mesophase, that behaved as a densely packed mimic for cellular membranes.

Certain naturally occurring lipids or fats, when combined with water spontaneously form liquid crystals.  One of these lipids called monoolein is a product of fat digestion.  The liquid crystalline cubic phase that monoolein forms, when wet, has the lipid arranged as a bilayer just two molecules thick that is bathed on either side by water.  This hydrated bilayer resembles the membrane that surrounds the cells in living organisms. The cubic phase is particularly notable as a liquid crystal in the extraordinary density with which it packages the membrane and the enormous surface area that it has. Thus, for example, a mere thimbleful of the cubic phase has enough surface area to cover a football field.

The research conducted by Trinity’s Professor of Membrane Structural and Functional Biology, Martin Caffrey and Research Associate Dr  Dianfan Li in the School of Medicine and School of Biochemistry & Immunology used the cubic phase; but the cubic phase made from hydrated fat alone was useless.  It needed to have a membrane protein sensor incorporated into it and the protein needed to be active.  The test sensor used in the research was a membrane protein, referred to as DgkA.  DgkA is an enzyme that interconverts the fatty components of natural cellular membranes.  The enzyme was produced in E. coli bacteria, using recombinant DNA technology, as an inactive or dead ‘scrambled egg’ type of insoluble aggregate.   ‘Life’ was breathed back into the enzyme by dissolving the aggregated protein in a soapy solution and inserting it into the membrane of the cubic phase.  In this new and quite artificial environment the researchers showed that the protein had regained its original native enzyme activity and that it could behave as a model sensor.

The research sets the stage for the exploitation of this most extraordinary of biomaterials.  These include its use in high density, high sensitivity biosensors for the detection of biological molecules such as hormones, proteins, carbohydrates, and lipids, as well as toxins, explosives, pollutants, and drugs. 

Provided by Trinity College Dublin (news : web)

New biomaterial more closely mimics human tissue

 A new biomaterial designed for repairing damaged human tissue doesn’t wrinkle up when it is stretched. The invention from nanoengineers at the University of California, San Diego marks a significant breakthrough in tissue engineering because it more closely mimics the properties of native human tissue.

Shaochen Chen, professor in the Department of NanoEngineering at the UC San Diego Jacobs School of Engineering, hopes future tissue patches, which are used to repair damaged heart walls, blood vessels and skin, for example, will be more compatible with native human tissue than the patches available today. His findings were published in a recent issue of the journal Advanced Functional Materials.

The new biomaterial was created using a new biofabrication platform that Chen is developing under a four-year, $1.5 million grant from the National Institutes of Health. This biofabrication technique uses light, precisely controlled mirrors and a computer projection system -- shined on a solution of new cells and polymers -- to build three-dimensional scaffolds with well-defined patterns of any shape for tissue engineering.

“We are also exploring other opportunities,” said Chen. “It’s a new material. I think it’s just a matter of time before more people will pick up and find applications for it in defense, energy and communications, for instance.”

Although Chen’s team is focused on creating biological materials, he said the manufacturing technology could be used to engineer many other kinds of materials including metal parts used in ships and spacecraft, for example.

Shape turned out to be essential to the new material’s mechanical property. While most engineered tissue is layered in scaffolds that take the shape of circular or square holes, Chen’s team created two new shapes called “reentrant honeycomb” and “cut missing rib.” Both shapes exhibit the property of negative Poisson’s ratio (i.e. not wrinkling when stretched) and maintain this property whether the tissue patch has one or multiple layers. One layer is double the thickness of a human hair, and the number of layers used in a tissue patch depends on the thickness of the native tissue that doctors are trying to repair. A single layer would not be thick enough to repair a heart wall or skin tissue, for example.  The next phase of research will involve working with the Department of Bioengineering at the Jacobs School of Engineering to make tissue grafts to repair damaged blood vessels.

Provided by UC Davis (news : web)