{"id":70,"date":"2015-06-06T03:16:23","date_gmt":"2015-06-06T03:16:23","guid":{"rendered":"http:\/\/www.kurzweilai.net\/?p=253725"},"modified":"2015-06-08T07:40:31","modified_gmt":"2015-06-08T07:40:31","slug":"3-d-printing-tough-biogel-structures-for-tissue-engineering-or-soft-robots","status":"publish","type":"post","link":"https:\/\/hoo.central12.com\/fugic\/2015\/06\/06\/3-d-printing-tough-biogel-structures-for-tissue-engineering-or-soft-robots\/","title":{"rendered":"3-D printing tough biogel structures for tissue engineering or soft robots"},"content":{"rendered":"
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Lasagna? No, an open lattice of 3-D printed material, with materials having different characteristics of strength and flexibility indicated by different colors (credit: the researchers)<\/p><\/div>\n

Researchers at three universities have developed a new way of making tough — but soft and wet — biocompatible\u00a0hydrogel<\/a> materials into complex and intricately patterned shapes. The process might lead to scaffolds for repair or replacement of load-bearing tissues, such as cartilage. It could also allow for tough but flexible actuators for future robots, the researchers say.<\/p>\n

The new process is described in a paper in the journal\u00a0Advanced Materials<\/em>, co-authored by MIT<\/a> associate professor of mechanical engineering Xuanhe Zhao<\/a> and colleagues at MIT, Duke University<\/a>, and Columbia University<\/a>.<\/p>\n

Zhao says the process can produce complex hydrogel structures that are \u201cextremely tough and robust,\u201d but still allow for encapsulating cells in the structures. That could make it possible to 3D-print complex biostructures.<\/p>\n

Biocompatible structures<\/strong><\/p>\n

Hydrogels are defined by water molecules encased in rubbery polymer networks that provide shape and structure. They are similar to natural tissues such as cartilage, which is used by the body as a natural shock absorber.<\/p>\n

While synthetic hydrogels are commonly weak or brittle, a number of them that are tough and stretchable have been developed over the last decade. However, making tough hydrogels has usually involved \u201charsh chemical environments\u201d that would kill living cells encapsulated in them, Zhao says.<\/p>\n

The new hydrogel materials are generated by combining polyethylene glycol (PEG) and sodium alginate, which synergize to form a hydrogel tougher than natural cartilage. The materials are benign enough to synthesize together with living cells — such as stem cells — which could then allow high viability of the cells, says Zhao, who holds a joint appointment in MIT\u2019s Department of Civil and Environmental Engineering.<\/p>\n

3-D printing strong, flexible biomaterials<\/strong><\/p>\n

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3-D printed tough, biocompatible PEG\u2013alginate\u2013nanoclay hydrogels in ear and nose shapes (credit: Sungmin Hong et al.\/ Advanced Materials)<\/p><\/div>\n

Previous work was not able to produce complex 3-D structures with tough hydrogels, Zhao says. The new biocompatible tough hydrogel can be printed into diverse 3-D structures such as a hollow cube, hemisphere, pyramid, twisted bundle, multilayer mesh, or physiologically relevant shapes, such as a human nose or ear.<\/p>\n

The new method uses a commercially available 3D-printing mechanism, Zhao explains. \u201cThe innovation is really about the material — a new ink for 3-D printing of biocompatible tough hydrogel,\u201d he says, specifically, a composite of two different biopolymers.<\/p>\n

\u201cEach [material] individually is very weak and brittle, but once you put them together, it becomes very tough and strong. It\u2019s like steel-reinforced concrete.\u201d<\/p>\n

The PEG material provides elasticity to the printed material, while sodium alginate allows it to dissipate energy under deformation without breaking. A third ingredient, a biocompatible \u201cnanoclay,\u201d makes it possible to fine-tune the viscosity (how easily it flows) of the material, improving the ability to control its flow through the 3D-printing nozzle.<\/p>\n

The material can be made so flexible that a printed shape, such as a pyramid, can be compressed by 99 percent, and then spring back to its original shape, Sungmin Hong, a lead author of the paper and a former postdoc in Zhao\u2019s group, says; it can also be stretched to five times its original size. Such resilience is a key feature of natural bodily tissues that need to withstand a variety of forces and impacts.<\/p>\n

Such materials might eventually be used to custom-print shapes for the replacement of cartilaginous tissues in ears, noses, or load-bearing body joints, Zhao says. Lab tests have already shown that the material is even tougher than natural cartilage.<\/p>\n

Enhancing resolution<\/strong><\/p>\n

The next step in the research will be to improve the resolution of the printer, which is currently limited to details about 500 micrometers (0.5 millimeters) in size, and to test the printed hydrogel structures in animal models. \u201cWe are enhancing the resolution,\u201d Zhao says, \u201cto be able to print more accurate structures for applications.\u201d<\/p>\n

The technique could also be applied to printing a variety of soft but tough structural materials, he says, such as actuators for soft robotic systems.<\/p>\n

\u201cThis is really beautiful work that demonstrates major advances in the utilization of tough hydrogels,\u201d says David Mooney<\/a>, a professor of bioengineering at Harvard University<\/a> who was not involved in this work. \u201cThis builds off earlier work using other polymer systems, with some of this earlier work done by Dr. Zhao, but the demonstration that one can achieve similar mechanical performance with a common biomedical polymer is a substantial advance.<\/p>\n

\u201cIt is also quite exciting that these new tough gels can be used for 3-D printing, as this is new for these gels, to my knowledge.\u201d<\/p>\n

The work was supported by the National Institutes of Health, the Office of Naval Research, AOSpine Foundation, and the National Science Foundation.<\/p>\n

\n

Abstract of\u00a03D Printing of Highly Stretchable and Tough Hydrogels into Complex, Cellularized Structures<\/em><\/strong><\/p>\n

A 3D printable and highly stretchable tough hydrogel\u00a0is developed by combining poly(ethylene glycol) and sodium alginate, which synergize to form a hydrogel tougher than natural cartilage. Encapsulated cells maintain high viability over a 7 d culture period and are highly deformed together with the hydrogel. By adding biocompatible nanoclay, the tough hydrogel is 3D printed in various shapes without requiring support material.<\/p>\n","protected":false},"excerpt":{"rendered":"

Researchers at three universities have developed a new way of making tough — but soft and wet — biocompatible hydrogel materials into complex and intricately patterned shapes. The process might lead to scaffolds for repair or replacement of load-bearing tissues, such as cartilage. It could also allow for tough but flexible actuators for future robots, the […]<\/p>\n","protected":false},"author":13,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[45,43],"tags":[],"class_list":["post-70","post","type-post","status-publish","format-standard","hentry","category-biomedlongevity","category-news"],"_links":{"self":[{"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/posts\/70"}],"collection":[{"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/users\/13"}],"replies":[{"embeddable":true,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/comments?post=70"}],"version-history":[{"count":2,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/posts\/70\/revisions"}],"predecessor-version":[{"id":176,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/posts\/70\/revisions\/176"}],"wp:attachment":[{"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/media?parent=70"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/categories?post=70"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/tags?post=70"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}