Tag Archives: tissue engineering

Cartilage; the ‘official tissue’ of tissue engineering

What is this fascination with cartilage? For the second time this week (see yesterday’s [April 30, 2014] posting: Replacement cartilage grown on laboratory chip)  there’s a news item about a team, this time from Columbia University School of Engineering and Applied Sciences (aka Columbia Engineering), growing cartilage. From an April 30, 2014 news item on ScienceDaily,

Researchers at Columbia Engineering announced today that they have successfully grown fully functional human cartilage in vitro from human stem cells derived from bone marrow tissue. Their study, which demonstrates new ways to better mimic the enormous complexity of tissue development, regeneration, and disease, is published in the April 28 Early Online edition of Proceedings of the National Academy of Sciences (PNAS).

“We’ve been able — for the first time — to generate fully functional human cartilage from mesenchymal stem cells by mimicking in vitro the developmental process of mesenchymal condensation,” says Gordana Vunjak-Novakovic, who led the study and is the Mikati Foundation Professor of Biomedical Engineering at Columbia Engineering and professor of medical sciences. “This could have clinical impact, as this cartilage can be used to repair a cartilage defect, or in combination with bone in a composite graft grown in lab for more complex tissue reconstruction.”

An April 30, 2014 Columbia Engineering news release by Holly Evans, which originated the news item, provides some insight into the issues associated with tissue engineering and cartilage,

For more than 20 years, researchers have unofficially called cartilage the “official tissue of tissue engineering,” Vunjak-Novakovic observes. [emphasis mine] Many groups studied cartilage as an apparently simple tissue: one single cell type, no blood vessels or nerves, a tissue built for bearing loads while protecting bone ends in the joints. While there has been great success in engineering pieces of cartilage using young animal cells, no one has, until now, been able to reproduce these results using adult human stem cells from bone marrow or fat, the most practical stem cell source. Vunjak-Novakovic’s team succeeded in growing cartilage with physiologic architecture and strength by radically changing the tissue-engineering approach.

The general approach to cartilage tissue engineering has been to place cells into a hydrogel and culture them in the presence of nutrients and growth factors and sometimes also mechanical loading. But using this technique with adult human stem cells has invariably produced mechanically weak cartilage. So Vunjak-Novakovic and her team, who have had a longstanding interest in skeletal tissue engineering, wondered if a method resembling the normal development of the skeleton could lead to a higher quality of cartilage.

(I love the combination of “unofficially” with “official.”) Getting back to the cartilage research, the news release goes on to describe a new technique for engineering cartilage,

Sarindr Bhumiratana, postdoctoral fellow in Vunjak-Novakovic’s Laboratory for Stem Cells and Tissue Engineering, came up with a new approach: inducing the mesenchymal stem cells to undergo a condensation stage as they do in the body before starting to make cartilage. He discovered that this simple but major departure from how things were usually being done resulted in a quality of human cartilage not seen before.

Gerard Ateshian, Andrew Walz Professor of Mechanical Engineering, professor of biomedical engineering, and chair of the Department of Mechanical Engineering, and his PhD student, Sevan Oungoulian, helped perform measurements showing that the lubricative property and compressive strength—the two important functional properties—of the tissue-engineered cartilage approached those of native cartilage. The researchers then used their method to regenerate large pieces of anatomically shaped and mechanically strong cartilage over the bone, and to repair defects in cartilage.

“Our whole approach to tissue engineering is biomimetic in nature, which means that our engineering designs are defined by biological principles,” Vunjak-Novakovic notes. “This approach has been effective in improving the quality of many engineered tissues—from bone to heart. Still, we were really surprised to see that our cartilage, grown by mimicking some aspects of biological development, was as strong as ‘normal’ human cartilage.”

The team plans next to test whether the engineered cartilage tissue maintains its structure and long-term function when implanted into a defect.

Here’s a link to and a citation for the research paper,

Large, stratified, and mechanically functional human cartilage grown in vitro by mesenchymal condensation by Sarindr Bhumiratana, Ryan E. Eton, Sevan R. Oungoulian, Leo Q. Wan, Gerard A. Ateshian, and Gordana Vunjak-Novakovic. Proceedings of the National Academy of Sciences, 2014; DOI: 10.1073/pnas.1324050111

This paper is behind a paywall.

I have an observation about both this and the other cartilage story (Replacement cartilage grown on laboratory chip) featured here. It looks to me as if these two areas of research could be complementary. The ‘laboratory chip’ story is about a new way to use 3D printing to produce cartilage more quickly where this Columbia Engineering story is about better mimicking processes in the body to engineer stronger, more resilient cartilage. Taken separately or together cartilage tissue engineering has had an exciting week.

Replacement cartilage grown on laboratory chip

Most of us don’t think too much about cartilage (soft, flexible connective tissue found in the body) unless it’s damaged in which case it’s importance becomes immediately apparent. There is no substitute for cartilage although scientists are working on that problem and it seems that one team may have made a significant breakthrough according to an April 27, 2014 news item on ScienceDaily,

In a significant step toward reducing the heavy toll of osteoarthritis around the world, scientists have created the first example of living human cartilage grown on a laboratory chip. The researchers ultimately aim to use their innovative 3-D printing approach to create replacement cartilage for patients with osteoarthritis or soldiers with battlefield injuries.

“Osteoarthritis has a severe impact on quality of life, and there is an urgent need to understand the origin of the disease and develop effective treatments” said Rocky Tuan, Ph.D., director of the Center for Cellular and Molecular Engineering at the University of Pittsburgh School of Medicine, member of the American Association of Anatomists and the study’s senior investigator. “We hope that the methods we’re developing will really make a difference, both in the study of the disease and, ultimately, in treatments for people with cartilage degeneration or joint injuries.”

Osteoarthritis is marked by a gradual disintegration of cartilage, a flexible tissue that provides padding where bones come together in a joint. Causing severe pain and loss of mobility in joints such as knees and fingers, osteoarthritis is one of the leading causes of physical disability in the United States. It is estimated that up to 1 in 2 Americans will develop some form of the disease in their lifetime.

Although some treatments can help relieve arthritis symptoms, there is no cure. Many patients with severe arthritis ultimately require a joint replacement.

An April 27,2014 Experimental Biology (EB) 2014 news release provides more insight,

Tuan said artificial cartilage built using a patient’s own stem cells could offer enormous therapeutic potential. “Ideally we would like to be able to regenerate this tissue so people can avoid having to get a joint replacement, which is a pretty drastic procedure and is unfortunately something that some patients have to go through multiple times,” said Tuan.

In addition to offering relief for people with osteoarthritis, Tuan said replacement cartilage could also be a game-changer for people with debilitating joint injuries, such as soldiers with battlefield injuries. “We really want these technologies to help wounded warriors return to service or pursue a meaningful post-combat life,” said Tuan, who co-directs the Armed Forces Institute of Regenerative Medicine, a national consortium focused on developing regenerative therapies for injured soldiers. “We are on a mission.”

Creating artificial cartilage requires three main elements: stem cells, biological factors to make the cells grow into cartilage, and a scaffold to give the tissue its shape. Tuan’s 3-D printing approach achieves all three by extruding thin layers of stem cells embedded in a solution that retains its shape and provides growth factors. “We essentially speed up the development process by giving the cells everything they need, while creating a scaffold to give the tissue the exact shape and structure that we want,” said Tuan.

The ultimate vision is to give doctors a tool they can thread through a catheter to print new cartilage right where it’s needed in the patient’s body. Although other researchers have experimented with 3-D printing approaches for cartilage, Tuan’s method represents a significant step forward because it uses visible light, while others have required UV light, which can be harmful to living cells.

In another significant step, Tuan has successfully used the 3-D printing method to produce the first “tissue-on-a-chip” replica of the bone-cartilage interface. Housing 96 blocks of living human tissue 4 millimeters across by 8 millimeters deep, the chip could serve as a test-bed for researchers to learn about how osteoarthritis develops and develop new drugs. “With more testing, I think we’ll be able to use our platform to simulate osteoarthritis, which would be extremely useful since scientists really know very little about how the disease develops,” said Tuan.

As a next step, the team is working to combine their 3-D printing method with a nanofiber spinning technique they developed previously. They hope combining the two methods will provide a more robust scaffold and allow them to create artificial cartilage that even more closely resembles natural cartilage.

Rocky Tuan presented the research during the Experimental Biology 2014 meeting on Sunday, April 27 [2014].

I haven’t been able to find any papers published on this work but you can find Rocky Tuan’s faculty page (along with a list of publications) here and you may have more luck with the EB 2014 conference website than I did.

Mesenchymal condensation (a process embryos use to begin forming a variety of organs, including teeth, cartilage, bone, muscle, tendon, and kidney) for complex 3D tissue engineering

It seems that there are three strategies for creating complex 3D tissues and until now scientists have used only two of the three. From a March 5, 2014 news item on ScienceDaily,

A bit of pressure from a new shrinking, sponge-like gel is all it takes to turn transplanted unspecialized cells into cells that lay down minerals and begin to form teeth.

The bioinspired gel material could one day help repair or replace damaged organs, such as teeth and bone, and possibly other organs as well, scientists from the Wyss Institute for Biologically Inspired Engineering at Harvard University, Harvard School of Engineering and Applied Sciences (SEAS), and Boston Children’s Hospital report recently in Advanced Materials.

“Tissue engineers have long raised the idea of using synthetic materials to mimic the inductive power of the embryo,” said Don Ingber, M.D., Ph.D., Founding Director of the Wyss Institute, …, Professor of Bioengineering at SEAS, and senior author of the study. “We’re excited about this work because it shows that it really is possible.”

The March 5, 2014 Wyss Institute news release, which originated the news item, delves into the nature of the research,

Embryonic tissues have the power to drive cells and tissues to specialize and form organs. To do that, they employ biomolecules called growth factors to stimulate growth; gene-activating chemicals that cause the cells to specialize, and mechanical forces that modulate cell responses to these other factors.

But so far tissue engineers who want to build organs in the laboratory have employed only two of the three strategies — growth factors and gene-activating chemicals. Perhaps as a result, they have not yet succeeded in producing complex three-dimensional tissues.

A few years ago, Ingber and Tadanori Mammoto, M.D., Ph.D., Instructor in Surgery at Boston Children’s Hospital and Harvard Medical School, investigated a process called mesenchymal condensation that embryos use to begin forming a variety of organs, including teeth, cartilage, bone, muscle, tendon, and kidney.

In mesenchymal condensation, two adjacent tissue layers — loosely packed connective-tissue cells called mesenchyme and sheet-like tissue called an epithelium that covers it — exchange biochemical signals. This exchange causes the mesenchymal cells to squeeze themselves tightly into a small knot directly below where the new organ will form.

Here’s a video from the Wyss Institute illustrating the squeezing process,

When the temperature rises to just below body temperature, this biocompatible gel shrinks dramatically within minutes, bringing tooth-precursor cells (green) closer together. Credit: Basma Hashmi

Getting back to the research (from the news release),

By examining tissues isolated from the jaws of embryonic mice, Mammoto and Ingber showed that when the compressed mesenchymal cells turn on genes that stimulate them to generate whole teeth composed of mineralized tissues, including dentin and enamel.

Inspired by this embryonic induction mechanism, Ingber and Basma Hashmi, a Ph.D. candidate at SEAS who is the lead author of the current paper, set out to develop a way to engineer artificial teeth by creating a tissue-friendly material that accomplishes the same goal. Specifically, they wanted a porous sponge-like gel that could be impregnated with mesenchymal cells, then, when implanted into the body, induced to shrink in 3D to physically compact the cells inside it.

To develop such a material, Ingber and Hashmi teamed up with researchers led by Joanna Aizenberg, Ph.D., a Wyss Institute Core Faculty member who leads the Institute’s Adaptive Materials Technologies platform. Aizenberg is the Amy Smith Berylson Professor of Materials Science at SEAS and Professor of Chemistry and Chemical Biology at Harvard University.

They chemically modified a special gel-forming polymer called PNIPAAm that scientists have used to deliver drugs to the body’s tissues. PNIPAAm gels have an unusual property: they contract abruptly when they warm.

But they do this at a lukewarm temperature, whereas the researchers wanted them to shrink specifically at 37°C — body temperature — so that they’d squeeze their contents as soon as they were injected into the body. Hashmi worked with Lauren Zarzar, Ph.D., a former SEAS graduate student who’s now a postdoctoral associate at Massachusetts Institute of Technology, for more than a year, modifying PNIPAAm and testing the resulting materials. Ultimately, they developed a polymer that forms a tissue-friendly gel with two key properties: cells stick to it, and it compresses abruptly when warmed to body temperature.

As an initial test, Hashmi implanted mesenchymal cells in the gel and warmed it in the lab. Sure enough, when the temperature reached 37°C, the gel shrank within 15 minutes, causing the cells inside the gel to round up, shrink, and pack tightly together.

“The reason that’s cool is that the cells are alive,” Hashmi said. “Usually when this happens, cells are dead or dying.”

Not only were they alive — they activated three genes that drive tooth formation.

To see if the shrinking gel also worked its magic in the body, Hashmi worked with Mammoto to load mesenchymal cells into the gel, then implant the gel beneath the mouse kidney capsule — a tissue that is well supplied with blood and often used for transplantation experiments.

The implanted cells not only expressed tooth-development genes — they laid down calcium and minerals, just as mesenchymal cells do in the body as they begin to form teeth.

“They were in full-throttle tooth-development mode,” Hashmi said.

The researchers have future plans (from the news release),

In the embryo, mesenchymal cells can’t build teeth alone — they need to be combined with cells that form the epithelium. In the future, the scientists plan to test whether the shrinking gel can stimulate both tissues to generate an entire functional tooth.

Here’s a link to and a citation for the paper about the successful attempt to stimulate mesenchymal cells into the beginnings of tooth formation,

Developmentally-Inspired Shrink-Wrap Polymers for Mechanical Induction of Tissue Differentiation by Basma Hashmi, Lauren D. Zarzar, Tadanori Mammoto, Akiko Mammoto, Amanda Jiang, Joanna Aizenberg, and Donald E. Ingber. Advanced Materials Article first published online: 18 FEB 2014 DOI: 10.1002/adma.201304995

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Assembly-line 3-D tissue engineering

It looks as if the researchers at Singapore’s Institute of Bioengineering and Nanotechnology (IBN), have developed a template for producing complex tissues such as those in liver and in fat, from an Aug. 20, 2013 news item on ScienceDaily,

Researchers at the Institute of Bioengineering and Nanotechnology (IBN) have developed a simple method of organizing cells and their microenvironments in hydrogel fibers. Their unique technology provides a feasible template for assembling complex structures, such as liver and fat tissues, as described in their recent publication in Nature Communications.

According to IBN Executive Director Professor Jackie Y. Ying, “Our tissue engineering approach gives researchers great control and flexibility over the arrangement of individual cell types, making it possible to engineer prevascularized tissue constructs easily. This innovation brings us a step closer toward developing viable tissue or organ replacements.”

The Aug. 19, 2013 A*STAR’s (Singapore’s Agency for Science and Technology Research) IBN  press release, which originated the news item, offers a detailed explanation of how this discovery could make tissue and organ replacements much easier,

IBN Team Leader and Principal Research Scientist, Dr Andrew Wan, elaborated, “Critical to the success of an implant is its ability to rapidly integrate with the patient’s circulatory system. This is essential for the survival of cells within the implant, as it would ensure timely access to oxygen and essential nutrients, as well as the removal of metabolic waste products. Integration would also facilitate signaling between the cells and blood vessels, which is important for tissue development.”

Tissues designed with pre-formed vascular networks are known to promote rapid vascular integration with the host. Generally, prevascularization has been achieved by seeding or encapsulating endothelial cells, which line the interior surfaces of blood vessels, with other cell types. In many of these approaches, the eventual distribution of vessels within a thick structure is reliant on in vitro cellular infiltration and self-organization of the cell mixture. These are slow processes, often leading to a non-uniform network of vessels within the tissue. As vascular self-assembly requires a large concentration of endothelial cells, this method also severely restricts the number of other cells that may be co-cultured.

Alternatively, scientists have attempted to direct the distribution of newly formed vessels via three-dimensional (3D) co-patterning of endothelial cells with other cell types in a hydrogel. This approach allows large concentrations of endothelial cells to be positioned in specific regions within the tissue, leaving the rest of the construct available for other cell types. The hydrogel also acts as a reservoir of nutrients for the encapsulated cells. However, co-patterning multiple cell types within a hydrogel is not easy. Conventional techniques, such as micromolding and organ printing, are limited by slow cell assembly, large volumes of cell suspension, complicated multi-step processes and expensive instruments. These factors also make it difficult to scale up the production of implantable 3D cell-patterned constructs. To date, these approaches have been unsuccessful in achieving vascularization and mass transport through thick engineered tissues.

To overcome these limitations, IBN researchers have used interfacial polyelectrolyte complexation (IPC) fiber assembly, a unique cell patterning technology patented by IBN, to produce cell-laden hydrogel fibers under aqueous conditions at room temperature. Unlike other methods, IBN’s novel technique allows researchers to incorporate different cell types separately into different fibers, and these cell-laden fibers may then be assembled into more complex constructs with hierarchical tissue structures. In addition, IBN researchers are able to tailor the microenvironment for each cell type for optimal functionality by incorporating the appropriate factors, e.g. proteins, into the fibers. Using IPC fiber assembly, the researchers have engineered an endothelial vessel network, as well as cell-patterned fat and liver tissue constructs, which have successfully integrated with the host circulatory system in a mouse model and produced vascularized tissues.

Here’s a citation for and link to the published paper,

Patterned prevascularised tissue constructs by assembly of polyelectrolyte hydrogel fibres by Meng Fatt Leong,    Jerry K. C. Toh, Chan Du, Karthikeyan Narayanan, Hong Fang Lu, Tze Chiun Lim, Andrew C. A. Wan, & Jackie Y. Ying. Nature Communications 4, Article number: 2353 doi:10.1038/ncomms3353 Published 19 August 2013

This article is behind a paywall although you can preview it with ReadingCube access.

A ‘glass jaw’ might turn out to be a good thing

I don’t know if the phrase ‘glass jaw’ is used much any more but it was a term for someone who couldn’t ‘take’ a punch to the jaw (i.e., the person was instantly rendered unconscious or helplessly groggy). If scientists at Missouri University of Science and Technology (Missouri S&T)  have their way, the phrase ‘glass jaw’ will have a new meaning as per the July 26, 2012 news item on ScienceDaily,

Researchers at Missouri University of Science and Technology have developed a type of glass implant that could one day be used to repair injured bones in the arms, legs and other areas of the body that are most subject to the stresses of weight.

This marks the first time researchers have shown a glass implant strong enough to bear weight can also integrate with bone and promote bone growth, says lead researcher Dr. Mohamed N. Rahaman, professor of materials science and engineering at Missouri S&T.

The July 26, 2013 Missouri S&T news release by Andrew Careaga, which originated the news item, describes the work leading to this latest research,

In previous work, the Missouri S&T researchers developed a glass implant strong enough to handle the weight and pressure of repetitive movement, such as walking or lifting. In their most recent study, published in the journal Acta Biomaterialia, the research team reported that the glass implant, in the form of a porous scaffolding, also integrates with bone and promotes bone growth.

This combination of strength and bone growth opens new possibilities for bone repair, says Rahaman, who also directs Missouri S&T’s Center for Biomedical Science and Engineering, where the research was conducted.

The news release then goes on to describe one of the problems with using synthetic materials for bone repair and explains how this latest research addresses the issue,

Conventional approaches to structural bone repair involve either the use of a porous metal, which does not reliably heal bone, or a bone allograft from a cadaver. Both approaches are costly and carry risks, Rahaman says. He thinks the type of glass implant developed in his center could provide a more feasible approach for repairing injured bones. The glass is bioactive, which means that it reacts when implanted in living tissue and convert to a bone-like material.

In their latest research, Rahaman and his colleagues implanted bioactive glass scaffolds into sections of the calvarial bones (skullcaps) of laboratory rats, then examined how well the glass integrated with the surrounding bone and how quickly new bone grew into the scaffold. The scaffolds are manufactured in Rahaman’s lab through a process known as robocasting – a computer-controlled technique to manufacture materials from ceramic slurries, layer by layer – to ensure uniform structure for the porous material.

In previous studies by the Missouri S&T researchers, porous scaffolds of the silicate glass, known as 13-93, were found to have the same strength properties as cortical bone. Cortical bones are those outer bones of the body that bear the most weight and undergo the most repetitive stress. They include the long bones of the arms and legs.

But what Rahaman and his colleagues didn’t know was how well the silicate 13-93 bioactive glass scaffolds would integrate with bone or how quickly bone would grow into the scaffolding.

“You can have the strongest material in the world, but it also must encourage bone growth in a reasonable amount of time,” says Rahaman. He considers three to six months to be a reasonable time frame for completely regenerating an injured bone into one strong enough to bear weight.

In their studies, the S&T researchers found that the bioactive glass scaffolds bonded quickly to bone and promoted a significant amount of new bone growth within six weeks.

While the skullcap is not a load-bearing bone, it is primarily a cortical bone. The purpose of this research was to demonstrate how well this type of glass scaffolding – already shown to be strong – would interact with cortical bone.

Rahaman and his fellow researchers in the Center for Biomedical Science and Engineering are now experimenting with true load-bearing bones. They are now testing the silicate 13-93 implants in the femurs (leg bones) of laboratory rats.

In the future, Rahaman plans to experiment with modified glass scaffolds to see how well they enhance certain attributes within bone. For instance, doping the glass with copper should promote the growth of blood vessels or capillaries within the new bone, while doping the glass with silver will give it antibacterial properties.

It’s exciting work but they are years from human clinical trials. Still, for those who want to explore further, here’s a link to and a citation for the published paper,

Enhanced bone regeneration in rat calvarial defects implanted with surface-modified and BMP-loaded bioactive glass (13-93) scaffolds by Xin Liua, Mohamed N. Rahaman, Yongxing Liu, B. Sonny Bal, and Lynda F. Bonewald. Acta Biomaterialia, July 2013 issue (Volume 9, Issue 7)  http://dx.doi.org/10.1016/j.actbio.2013.03.039

This paper is behind a paywall.

Red River Valley clay turned into bones at North Dakota State University

A May 30, 2013 news item on Nanowerk highlights the Katti Group’s (at North Dakota State University [NDSU], US) research using clay from the Red River Valley as scaffolding for tissue engineering projects involving bone. From the news item (Note: A link has been removed),

Weak bones, broken bones, damaged bones, arthritic bones. Whether damaged by injury, disease or age, your body can’t create new bone, but maybe science can. Researchers at North Dakota State University, Fargo, are making strides in tissue engineering, designing scaffolds that may lead to ways to regenerate bone. Published in the Journal of Biomedical Materials Research Part A (“Nanoclays mediate stem cell differentiation and mineralized ECM formation on biopolymer scaffolds”), the research of Dr. Kalpana Katti, Dr. Dinesh Katti and graduate student Avinash Ambre includes a novel method that uses nanosized clays to make scaffolds to mineralize bone minerals such as hydroxyapatite.

The North Dakota State University May 30, 2013 news release, which originated the news item, explains (Note: A link has been removed),

The NDSU research team’s 3-D mesh scaffold is comprised of degradable materials that are compatible to human tissue. Over time, the cells generate bone and the scaffold deteriorates. As indicated in the NDSU team’s published scientific research from 2008 to 2013, the nanoclays enhance the mechanical properties of the scaffold by enabling scaffold to bear load while bone generates. An interesting finding by the Katti group shows that the nanoclays also impart useful biological properties to the scaffold.

“The biomineralized nanoclays also impart osteogenic or bone-forming abilities to the scaffold to enable birth of bone,” said Dr. Kalpana Katti, Distinguished Professor of civil engineering at NDSU. “Although it would have been exciting to say that this finding had a ‘Eureka moment,’ this discovery was a methodical exploration of simulations and modeling, indicating that amino acid modified nanoclays are viable new nanomaterials,” said Katti. The work was initially published in the Journal of Biomacromolecules in 2005. The current research findings in 2013 point toward the potential use of nanoclays for broader applications in medicine.

The NDSU’s group most recent study in the Journal of Biomedical Materials Research Part A reports that nanoclays mediate human cell differentiation into bone cells and grow bone. The Katti research group uses amino acids, the building blocks of life, to modify clay structures and the modified nanoclays coax new bone growth. “Our current research studies underway involve the use of bioreactors that mimic fluid/blood flow in the human body during bone tissue regeneration,” said Dr. Kalpana Katti.

Here’s a citation for and a link to the Katti Group’s latest published paper (from the press release),

Nanoclays mediate stem cell differentiation and mineralized ECM formation on biopolymer scaffolds
Journal of Biomedical Materials Research Part A
Avinash H. Ambre, Dinesh R. Katti and Kalpana S. Katti Article first published online : 15 FEB 2013, DOI: 10.1002/jbm.a.34561

This paper is behind a paywall.

More than human—a bionic ear that extends hearing beyond the usual frequencies

It’s now possible to print a bionic ear in 3D that can hear beyond the human range and all you need is off-the-shelf printing equipment—and technical expertise. A May 2, 2013 news item on Azonano provides more detail,

Scientists at Princeton University used off-the-shelf printing tools to create a functional ear that can “hear” radio frequencies far beyond the range of normal human capability.

“In general, there are mechanical and thermal challenges with interfacing electronic materials with biological materials,” said Michael McAlpine, an assistant professor of mechanical and aerospace engineering at Princeton and the lead researcher. “Previously, researchers have suggested some strategies to tailor the electronics so that this merger is less awkward. That typically happens between a 2D sheet of electronics and a surface of the tissue. However, our work suggests a new approach — to build and grow the biology up with the electronics synergistically and in a 3D interwoven format.”

McAlpine’s team has made several advances in recent years involving the use of small-scale medical sensors and antenna. Last year, a research effort led by McAlpine and Naveen Verma, an assistant professor of electrical engineering, and Fio Omenetto of Tufts University, resulted in the development of a “tattoo” made up of a biological sensor and antenna that can be affixed to the surface of a tooth.

The tooth tattoo is mentioned in my Nov. 9, 2012 posting; I focused more on Tufts University than Princeton in that piece. As for the ear (from the news item on Azonano),

The finished ear consists of a coiled antenna inside a cartilage structure. Two wires lead from the base of the ear and wind around a helical “cochlea” – the part of the ear that senses sound – which can connect to electrodes. Although McAlpine cautions that further work and extensive testing would need to be done before the technology could be used on a patient, he said the ear in principle could be used to restore or enhance human hearing. He said electrical signals produced by the ear could be connected to a patient’s nerve endings, similar to a hearing aid. The current system receives radio waves, but he said the research team plans to incorporate other materials, such as pressure-sensitive electronic sensors, to enable the ear to register acoustic sounds.

Here’s the technique the researchers used to create their bionic ear (from the news item),

Standard tissue engineering involves seeding types of cells, such as those that form ear cartilage, onto a scaffold of a polymer material called a hydrogel. However, the researchers said that this technique has problems replicating complicated three dimensional biological structures. Ear reconstruction “remains one of the most difficult problems in the field of plastic and reconstructive surgery,” they wrote.

To solve the problem, the team turned to a manufacturing approach called 3D printing. These printers use computer-assisted design to conceive of objects as arrays of thin slices. The printer then deposits layers of a variety of materials – ranging from plastic to cells – to build up a finished product. Proponents say additive manufacturing promises to revolutionize home industries by allowing small teams or individuals to create work that could previously only be done by factories.

Creating organs using 3D printers is a recent advance; several groups have reported using the technology for this purpose in the past few months. But this is the first time that researchers have demonstrated that 3D printing is a convenient strategy to interweave tissue with electronics.

The technique allowed the researchers to combine the antenna electronics with tissue within the highly complex topology of a human ear. The researchers used an ordinary 3D printer to combine a matrix of hydrogel and calf cells with silver nanoparticles that form an antenna. The calf cells later develop into cartilage.

Here’s an image of the ear,

Scientists used 3-D printing to merge tissue and an antenna capable of receiving radio signals. Credit: Photo by Frank Wojciechowski

Scientists used 3-D printing to merge tissue and an antenna capable of receiving radio signals. Credit: Photo by Frank Wojciechowski

For interested parties,a link to and a citation for the published research,

A 3D Printed Bionic Ear by Manu S Mannoor , Ziwen Jiang , Teena James , Yong Lin Kong , Karen A Malatesta , Winston Soboyejo , Naveen Verma , David H Gracias , and Michael C. McAlpine. Nano Lett., Just Accepted Manuscript DOI: 10.1021/nl4007744 Publication Date (Web): May 1, 2013

Copyright © 2013 American Chemical Society

This article is behind a paywall.

At this point, the ear is strictly for use in the laboratory they have not run any ‘in vivo’ experiments, which would be one of the next steps and a prerequisite before  human clinical trials are considered.

I have written about human enhancement before, notably in my Aug. 30, 2011 posting where I highlighted this excerpt from an article by Paul Hochman,

“I don’t think I would have said this if it had never happened,” says Bailey, referring to the accident that tore off his pinkie, ring, and middle fingers. “But I told Touch Bionics I’d cut the rest of my hand off if I could make all five of my fingers robotic.” [originally excerpted from Paul Hochman's Feb. 1, 2010 article, Bionic Legs, i-Limbs, and Other Super Human Prostheses You'll Envy for Fast Company]

The Bailey quote stimulated this question for me, what would you choose if you could get an ear that hears beyond the human range?

Squishy knees and tissue engineering at Johns Hopkins

Researchers at Johns Hopkins University School of Medicine’s Translational Tissue Engineering Center (TTEC) have developed a material (a kind of hydrogel) which they use with a new technique they’ve developed for growing new tissue and cartilage in knees. From the Jan. 15, 2013 news release on EurekAlert,

Proof-of-concept clinical trial in 18 patients shows improved tissue growth

In a small study, researchers reported increased healthy tissue growth after surgical repair of damaged cartilage if they put a “hydrogel” scaffolding into the wound to support and nourish the healing process. The squishy hydrogel material was implanted in 15 patients during standard microfracture surgery, in which tiny holes are punched in a bone near the injured cartilage. The holes stimulate patients’ own specialized stem cells to emerge from bone marrow and grow new cartilage atop the bone.

“Our pilot study indicates that the new implant works as well in patients as it does in the lab, so we hope it will become a routine part of care and improve healing,” says Jennifer Elisseeff, Ph.D., Jules Stein Professor of Ophthalmology and director of the Johns Hopkins University School of Medicine’s Translational Tissue Engineering Center (TTEC). Damage to cartilage, the tough-yet-flexible material that gives shape to ears and noses and lines the surface of joints so they can move easily, can be caused by injury, disease or faulty genes. Microfracture is a standard of care for cartilage repair, but for holes in cartilage caused by injury, it often either fails to stimulate new cartilage growth or grows cartilage that is less hardy than the original tissue.

Here are more details from the Johns Hopkins Jan. 15, 2013 news release,

Tissue engineering researchers, including Elisseeff, theorized that the specialized stem cells needed a nourishing scaffold on which to grow, but demonstrating the clinical value of hydrogels has “taken a lot of time,” Elisseeff says. By experimenting with various materials, her group eventually developed a promising hydrogel, and then an adhesive that could bind it to the bone.

After testing the combination for several years in the lab and in goats, with promising results, she says, the group and their surgeon collaborators conducted their first clinical study, in which 15 patients with holes in the cartilage of their knees received a hydrogel and adhesive implant along with microfracture. For comparative purposes, another three patients were treated with microfracture alone. After six months, the researchers reported that the implants had caused no major problems, and MRIs showed that patients with implants had new cartilage filling an average 86 percent of the defect in their knees, while patients with only microfracture had an average of 64 percent of the tissue replaced. Patients with the implant also reported a greater decrease in knee pain in the six months following surgery, according to the investigators.

The trial continues, has enrolled more patients and is now being managed by a company called Biomet. The trial is part of efforts to win European regulatory approval for the device.

In the meantime, Elisseeff says her team has begun developing a next-generation implant, one in which the hydrogel and adhesive will be combined in a single material. In addition, they are working on technologies to lubricate joints and reduce inflammation.

The study has been published in the AAAS’s (American Association for the Advancement of Science) Science Translational Medicine journal,

Human Cartilage Repair with a Photoreactive Adhesive-Hydrogel Composite

Surgical options for cartilage resurfacing may be significantly improved by advances and application of biomaterials that direct tissue repair. A poly(ethylene glycol) diacrylate (PEGDA) hydrogel was designed to support cartilage matrix production, with easy surgical application. A model in vitro system demonstrated deposition of cartilage-specific extracellular matrix in the hydrogel

Sci Transl Med 9 January 2013:
Vol. 5 no. 167 pp. 167ra6DOI:10.1126/scitranslmed.3004838

This article is behind a paywall and for some reason the authors are listed only in the news release,

Jennifer Elisseeff, Blanka Sharma, Sara Fermanian, Matthew Gibson, Shimon Unterman, Daniel A. Herzka, Jeannine Coburn and Alexander Y. Hui of the Johns Hopkins School of Medicine; Brett Cascio of Lake Charles Memorial Hospital; Norman Marcus, a private practice orthopedic surgeon; and Garry E. Gold of Stanford University

Autodesk in the tissue printing business

I came across the information about Autodesk’s venture into tissue printing in a Dec. 19, 2012 article by Kelsey Campbell-Dollaghan for Fast Company Co.Design.com (Note: Links have been removed),

Bioprinters–or 3-D printing hybrids that can print human tissue–have been around for a few years now. As the technology emerged, a single nagging question stuck out in the mind of this post-architecture school student: what’s the software of choice for a scientist modeling a human organ?

Today, an announcement from biomedical startup Organovo and software giant Autodesk goes a long way towards answering it. …

The Organovo Dec. 18, 2012 press release provides some detail about the deal,

Organovo Holdings, Inc. (OTCQX: ONVO) (“Organovo”), a creator and manufacturer of functional, three-dimensional human tissues for medical research and therapeutic applications, is working together with researchers at Autodesk, Inc., the leader in cloud-based design and engineering software, to create the first 3D design software for bioprinting.

The software, which will be used to control Organovo’s NovoGen MMX bioprinter, will represent a major step forward in usability and functionality for designing three-dimensional human tissues, and has the potential to open up bioprinting to a broader group of users.

This looks like it’s going to be a proprietary system, i.e., the software is designed for one type of hardware, Organovo’s hardware, reminiscent of the  late 1990s where printers in the graphic arts field were, in some cases, were trapped into proprietary computer-to-plate printing systems. There was an open source vs. proprietary systems competition which was eventually won by open source systems.

Organovo’s press release describes the technology they’ve developed,

Organovo’s 3D bioprinting technology is used to create living human tissues that are three-dimensional, architecturally correct, and made entirely of living human cells. The resulting structures can function like native human tissues, and represent an opportunity for advancement in medical research, drug discovery and development, and in the future, surgical therapies and transplantation.

The Dec. 17, 2012 article by Kim-Mai Cutler for TechCrunch adds more technical and business detail (Note: Link removed.),

Organovo, which went public earlier this year through a small cap offering and has a market cap of $98 million, manufactures a bioprinter that can create 1 millimeter-thick tissues. Based on research out of the University of Missouri, the company’s technology creates a bio-ink from cells and deposits new cells in a layer-by-layer matrix according to a computer design.

The Dec. 18, 2012 article by Joseph Flaherty for Wired magazine offers an analysis of the business advantages for both companies (Note: Links removed.),

Autodesk, the industry leader in CAD software, has announced it is partnering with biological printer manufacturer Organovo to create 3-D design software for designing and printing living tissue.

It’s an area of interest to Autodesk, whose software runs the industrial design and architecture worlds, allowing them to expand further into new fields by helping researchers interface with new tools.

“Autodesk is an excellent fit for developing new software for 3D bioprinters,” Organovo CEO Keith Murphy says in a press release. “This partnership will lead to advances in bioprinting, including both greater flexibility and throughput internally, and the potential long-term ability for customers to design their own 3D tissues for production by Organovo.”Jeff Kowalski, senior VP/CTO at Autodesk, echoes Murphy’s sentiment. “Bioprinting has the potential to change the world,” he says. “It’s a blend of engineering, biology and 3D printing, which makes it a natural for Autodesk. I think working with Organovo to explore and evolve this emerging field will yield some fascinating and radical advances in medical research.”

While this announcement is certainly big news, we’re multiple revisions away from 3-D printing replacement body parts. Even after the technical difficulties of printing organs or even tissue for live human use are worked through, any resulting process will need to be validated through complex clinical trials and a long review by the FDA and international authorities. Still, it will be exciting to see what medical researchers and DIY biohackers will do with these tools.

Oddly, as of today (Dec. 26, 2012) Autodesk has yet to post a press release about this deal on its own website.

Printing new knee cartilage

I was reminded of the 1992 Olympics in Barcelona while reading the Nov. 22, 2012 news item on Nanowerk about printing cartilage for knees. Some years ago I knew a Canadian wrestler who’d participated in those games and he had a story about knee cartilage that featured amputation.

Apparently, wrestlers in earlier generations had knee surgeries that involved removal of cartilage for therapeutic purposes. Unfortunately, decades later, these retired wrestlers found that whatever cartilage had remained was now worn through and bones were grinding on bones causing such pain that more than one wrestler agreed to amputation. I never did check out the story but it rang true largely because I’d come across a similar story from a physiotherapist regarding  a shoulder joint and the consequences of losing cartilage in there (very, very painful).

It seems that scientists are now working on a solution for those of us unlucky enough to have damaged or worn through cartilage in our joints, from the Nov. 22, 2012 IOP science news release, (Institute of Physics) which originated the news item,

The printing of 3D tissue has taken a major step forward with the creation of a novel hybrid printer that simplifies the process of creating implantable cartilage.


The printer is a combination of two low-cost fabrication techniques: a traditional ink jet printer and an electrospinning machine. Combining these systems allowed the scientists to build a structure made from natural and synthetic materials. …

In this study, the hybrid system produced cartilage constructs with increased mechanical stability compared to those created by an ink jet printer using gel material alone. The constructs were also shown to maintain their functional characteristics in the laboratory and a real-life system.

The key to this was the use of the electrospinning machine, which uses an electrical current to generate very fine fibres from a polymer solution. Electrospinning allows the composition of polymers to be easily controlled and therefore produces porous structures that encourage cells to integrate into surrounding tissue.

In this study, flexible mats of electrospun synthetic polymer were combined, layer-by-layer, with a solution of cartilage cells from a rabbit ear that were deposited using the traditional ink jet printer. The constructs were square with a 10cm diagonal and a 0.4mm thickness.

The researchers tested their strength by loading them with variable weights and, after one week, tested to see if the cartilage cells were still alive.

The constructs were also inserted into mice for two, four and eight weeks to see how they performed in a real life system. After eight weeks of implantation, the constructs appeared to have developed the structures and properties that are typical of elastic cartilage, demonstrating their potential for insertion into a patient.

The researchers state that in a future scenario, cartilage constructs could be clinically applied by using an MRI scan of a body part, such as the knee, as a blueprint for creating a matching construct. A careful selection of scaffold material for each patient’s construct would allow the implant to withstand mechanical forces while encouraging new cartilage to organise and fill the defect.

The researchers’ article in the IOP science jouBiofrarnal, Biofabrication, is freely available for 30 days after its date of publication, Nov. 21, 2012. You do need to register with IOP science to gain access. Here’s the citation and a link,

Hybrid printing of mechanically and biologically improved constructs for cartilage tissue engineering applications by Tao Xu, Kyle W Binder, Mohammad Z Albanna, Dennis Dice, Weixin Zhao, James J Yoo and Anthony Atala in 2013 Biofabrication 5 015001 doi:10.1088/1758-5082/5/1/015001

I believe all of the scientists involved in this bioprinting project are with the Wake Forest Institute for Regenerative Medicine.