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News Regenerative medicine


Gelatin bio-ink for printing tissues


Anthony King


German scientists have produced bio-inks that could be useful for ‘printing’ parts of the human body to make artificial skin and various organs. Working at the Fraunhofer Institute for Interfacial Engineering and Biotechnology in Stuttgart, they made the inks from modified liquid gelatin and printed them from a device like a desktop printer. They predict the technology could be used to print artificial tissue ‘within five years’ and claim it may even be used to make blood vessels. Currently, it is impossible to build artificial tissue thicker than microns because of a lack of blood vessels. The scientists have already used the ink to


create single layers of so-called chondrocyte cells from cartilage and now plan now to print endothelial cells from blood vessels. Up to now they have printed only simple structures such as spots and stripes. However, ‘we hope to print more complex structures by going to the third dimension,’ by building up the printed cells layer upon layer by using a matrix support, says lead scientist Kirsten Borchers. ‘We will use different cell types and different matrices, combining harder and softer ones.’ The key to producing the bio-inks is to


control viscosity, as the ink must remain liquid during printing, but transform to a gel after it is subsequently populated with tissue cells and


Corrigendum


Eagle-eyed readers of the leader column in the last issue (C&I, 2013, 10, 4) will have spotted an error in the ranking of the US ‘...


macroeconomic stability, which ranks 177 out of 148 economies....’ The correct figure should, of course, be 117 out of 148 economies.


cured with UV light. To control viscosity, the group modified the gelatin by methacrylation and acetylation of free amino groups (J. Mater. Chem. B, doi: 10.1039/c3tb20745e). UV light and other chemical modifications then allowed adjustment of the gel’s strength and swelling capabilities to simulate natural tissue properties – from solid cartilage to soft fatty tissue. In the next five years, Borchers says the technology may be used to produce vascularised skin, fatty tissue or bone substitutions, including tissues for toxicity testing. The technique will print several different types of cells in a matrix. ‘I expect that the cells will start to communicate, which is what they usually do in the body, and then hopefully they will self-assemble into a functional tissue,’ she says. However, ‘it is long way before we can say


that it will be reality to produce replacement organs using this technology. However, this is first step towards that goal,’ advises regenerative medicine expert Deepak Kalaskar of University College London, UK. ‘A simple organ like skin is feasible but we still need lot of work before this becomes a reality. [The] advantage of using gelatin is that it is medically approved and easy to get, even though it can be expensive. The disadvantage is that it can only be used for soft tissue printing such as skin but not for hard tissue such as bone, even though bone is mainly composed of collagen too.’


Ecology


Soil bacteria help invaders


Anthony King


Soil bacteria can ally with invasive plants and boost soil fertility, helping exotics oust native species. A study of invasive Sorghum from a prairie reserve in Texas, US, found that microbes offer support to the invaders by boosting the availability of nitrogen, phosphorus and iron (Amer. J.Botany, doi:10.3732/ajb.1200577). ‘The entire structure of the soil changed, so that it even looks and feels different,’ says author Marnie Rout at the University of Montana, who started studying the invasive plant and its prairie grass neighbours when she noticed a strong demarcation line between the two in a field. ‘It looked like a military invasion.’ The invasive grass Sorghum halepense has


encroached 0.5m/year into the tallgrass prairie, formerly dominated by the native little bluestem (Schizachyrium scoparium) for the past 25 years. Rout isolated five bacterial strains found inside the invader’s rhizomes - underground stems the plant uses for storage - and grew them in a lab. The studies showed that the microbes could fix nitrogen and mobilise phosphorus and iron, as well as a plant hormone that increases root growth – IAA (indole-3-acetic acid). When these bacteria were inhibited the plants in the experiment grew slower and were smaller, despite being given extra nitrogen. The changes in soil chemistry not only gave the invader an edge, but may also hold back the native prairie grass, though the mechanism is unclear. Rout says that she ‘would like invasion ecologists to start to recognise that plant invasions are not simply plant-plant interactions’ but also involve bacteria. ‘There is a huge potential that we could find a way to control the plant through the microbiome.’ She also suggests that the microbiome helpers from Sorghum could be tested to see if they could improve crop yields. Penny Hirsch, microbial ecologist at Rothamsted


Research in Hertfordshire, UK, praises the research but says she is unsure how it might help ‘with controlling invasive plants although it may help explain why they are invasive’. She also questions whether the research will have practical implications for crops: ‘The small amount of nitrogen provided by bacterial endophytes may give a weed a growth advantage but nowhere near the requirement of a grain crop such as wheat, maize or rice, which need extra nitrogen fertiliser.’


Chemistry&Industry • November 2013 11


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