Tag Archives: tissue scaffolding

Cooking up a lung one way or the other

I have two stories about lungs and they are entirely different with the older one being a bioengineering story from the US and the more recent one being an artificial tissue story from the University of Toronto and the University of Ottawa (both in Canada).

Lab grown lungs

The Canadian Broadcasting Corporation’s Quirks and Quarks radio programme posted a December 29, 2018 news item (with embedded radio files) about bioengineered lunjgs,

There are two major components to building an organ: the structure and the right cells on that structure. A team led by Dr. Joan Nichols, a Professor of Internal Medicine, Microbiology and Immunology at the University of Texas Medical Branch in Galveston, were able to tackle both parts of the problem

In their experiment they used a donor organ for the structure. They took a lung from an unrelated pig, and stripped it of its cells, leaving a scaffold of collagen, a tough, flexible protein.  This provided a pre-made appropriate structure, though in future they think it may be possible to use 3-D printing technology to get the same result.

They then added cultured cells from the animal who would be receiving the transplant – so the lung was made of the animal’s own cells. Cultured lung and blood vessel cells were placed on the scaffold and it was  placed in a tank for 30 days with a cocktail of nutrients to help the cells stick to the scaffold and proliferate. The result was a kind of baby lung.

They then transplanted the bio-engineered, though immature, lung into the recipient animal where they hoped it would continue to develop and mature – growing to become a healthy, functioning organ.

The recipients of the bio-engineered lungs were four pigs adult pigs, which appeared to tolerate the transplants well. In order to study the development of the bio-engineered lungs, they euthanized the animals at different times: 10 hours, two weeks, one month and two months after transplantation.

They found that as early as two weeks, the bio-engineered lung had integrated into the recipient animals’ body, building a strong network of blood vessels essential for the lung to survive. There was no evidence of pulmonary edema, the build of fluid in the lungs, which is usually a sign of the blood vessels not working efficiently.  There was no sign of rejection of the transplanted organs, and the pigs were healthy up to the point where they were euthanized.

One lingering concern is how well the bio-engineered lungs delivered oxygen. The four pigs who received the trasplant [sic] had one original functioning lung, so they didn’t depend on their new bio-engineered lung for breathing. The scientists were not sure that the bio-engineered lung was mature enough to handle the full load of oxygen on its own.

You can hear Bob McDonald’s (host of Quirks & Quarks, a Canadian Broadcasting Corporation science radio programme) interview lead scientist, Dr. Joan Nichols if you go to here. (Note: I find he overmodulates his voice but some may find he has a ‘friendly’ voice.)

This is an image of the lung scaffold produced by the team,

Lung scaffold in the bioreactor chamber on Day 1 of the experiment, before the cells from the study pig were added. (Credit: Joan Nichols) [downloaded from https://www.cbc.ca/radio/quirks/dec-29-2018-water-on-mars-lab-grown-lungs-and-more-the-biggest-science-stories-of-2018-1.4940811/lab-grown-lungs-are-transplanted-in-pigs-today-they-may-help-humans-tomorrow-1.4940822]

Here’s more technical detail in an August 1, 2018i University of Texas Medical Branch (UTMB) news release (also on EurekAlert), which originally announced the research,

A research team at the University of Texas Medical Branch at Galveston have bioengineered lungs and transplanted them into adult pigs with no medical complication.

In 2014, Joan Nichols and Joaquin Cortiella from The University of Texas Medical Branch at Galveston were the first research team to successfully bioengineer human lungs in a lab. In a paper now available in Science Translational Medicine, they provide details of how their work has progressed from 2014 to the point no complications have occurred in the pigs as part of standard preclinical testing.

“The number of people who have developed severe lung injuries has increased worldwide, while the number of available transplantable organs have decreased,” said Cortiella, professor of pediatric anesthesia. “Our ultimate goal is to eventually provide new options for the many people awaiting a transplant,” said Nichols, professor of internal medicine and associate director of the Galveston National Laboratory at UTMB.

To produce a bioengineered lung, a support scaffold is needed that meets the structural needs of a lung. A support scaffold was created using a lung from an unrelated animal that was treated using a special mixture of sugar and detergent to eliminate all cells and blood in the lung, leaving only the scaffolding proteins or skeleton of the lung behind. This is a lung-shaped scaffold made totally from lung proteins.

The cells used to produce each bioengineered lung came from a single lung removed from each of the study animals. This was the source of the cells used to produce a tissue-matched bioengineered lung for each animal in the study. The lung scaffold was placed into a tank filled with a carefully blended cocktail of nutrients and the animals’ own cells were added to the scaffold following a carefully designed protocol or recipe. The bioengineered lungs were grown in a bioreactor for 30 days prior to transplantation. Animal recipients were survived for 10 hours, two weeks, one month and two months after transplantation, allowing the research team to examine development of the lung tissue following transplantation and how the bioengineered lung would integrate with the body.

All of the pigs that received a bioengineered lung stayed healthy. As early as two weeks post-transplant, the bioengineered lung had established the strong network of blood vessels needed for the lung to survive.

“We saw no signs of pulmonary edema, which is usually a sign of the vasculature not being mature enough,” said Nichols and Cortiella. “The bioengineered lungs continued to develop post-transplant without any infusions of growth factors, the body provided all of the building blocks that the new lungs needed.”

Nichols said that the focus of the study was to learn how well the bioengineered lung adapted and continued to mature within a large, living body. They didn’t evaluate how much the bioengineered lung provided oxygenation to the animal.

“We do know that the animals had 100 percent oxygen saturation, as they had one normal functioning lung,” said Cortiella. “Even after two months, the bioengineered lung was not yet mature enough for us to stop the animal from breathing on the normal lung and switch to just the bioengineered lung.”

For this reason, future studies will look at long-term survival and maturation of the tissues as well as gas exchange capability.

The researchers said that with enough funding, they could grow lungs to transplant into people in compassionate use circumstances within five to 10 years.

“It has taken a lot of heart and 15 years of research to get us this far, our team has done something incredible with a ridiculously small budget and an amazingly dedicated group of people,” Nichols and Cortiella said.

Here’s a citation and another link for the paper,

Production and transplantation of bioengineered lung into a large-animal model by Joan E. Nichols, Saverio La Francesca, Jean A. Niles, Stephanie P. Vega, Lissenya B. Argueta, Luba Frank, David C. Christiani, Richard B. Pyles, Blanca E. Himes, Ruyang Zhang, Su Li, Jason Sakamoto, Jessica Rhudy, Greg Hendricks, Filippo Begarani, Xuewu Liu, Igor Patrikeev, Rahul Pal, Emiliya Usheva, Grace Vargas, Aaron Miller, Lee Woodson, Adam Wacher, Maria Grimaldo, Daniil Weaver, Ron Mlcak, and Joaquin Cortiella. Science Translational Medicine 01 Aug 2018: Vol. 10, Issue 452, eaao3926 DOI: 10.1126/scitranslmed.aao3926

This paper is behind a paywall.

Artificial lung cancer tissue

The research teams at the University of Toronto and the University of Ottawa worked on creating artificial lung tissue but other applications are possible too. First, there’s the announcement in a February 25, 2019 news item on phys.org,

A 3-D hydrogel created by researchers in U of T Engineering Professor Molly Shoichet’s lab is helping University of Ottawa researchers to quickly screen hundreds of potential drugs for their ability to fight highly invasive cancers.

Cell invasion is a critical hallmark of metastatic cancers, such as certain types of lung and brain cancer. Fighting these cancers requires therapies that can both kill cancer cells as well as prevent cell invasion of healthy tissue. Today, most cancer drugs are only screened for their ability to kill cancer cells.

“In highly invasive diseases, there is a crucial need to screen for both of these functions,” says Shoichet. “We now have a way to do this.”

A February 25, 2019 University of Toronto news release (also on EurekAlert), which originated the news item, offers more detail ,

In their latest research, the team used hydrogels to mimic the environment of lung cancer, selectively allowing cancer cells, and not healthy cells, to invade. In their latest research, the team used hydrogels to mimic the environment of lung cancer, selectively allowing cancer cells, and not healthy cells, to invade. This emulated environment enabled their collaborators in Professor Bill Stanford’s lab at University of Ottawa to screen for both cancer-cell growth and invasion. The study, led by Roger Y. Tam, a research associate in Shochet’s lab, was recently published in Advanced Materials.

“We can conduct this in a 384-well plate, which is no bigger than your hand. And with image-analysis software, we can automate this method to enable quick, targeted screenings for hundreds of potential cancer treatments,” says Shoichet.

One example is the researchers’ drug screening for lymphangioleiomyomatosis (LAM), a rare lung disease affecting women. Shoichet and her team were inspired by the work of Green Eggs and LAM, a Toronto-based organization raising awareness of the disease.

Using their hydrogels, they were able to automate and screen more than 800 drugs, thereby uncovering treatments that could target disease growth and invasion.

In the ongoing collaboration, the researchers plan to next screen multiple drugs at different doses to gain greater insight into new treatment methods for LAM. The strategies and insights they gain could also help identify new drugs for other invasive cancers.

Shoichet, who was recently named a Distinguished Woman in Chemistry or Chemical Engineering, also plans to patent the hydrogel technology.

“This has, and continues to be, a great collaboration that is advancing knowledge at the intersection of engineering and biology,” says Shoichet.

I note that Shoichet (pronounced ShoyKet) is getting ready to patent this work. I do have a question about this and it’s not up to Shoichet to answer as she didn’t create the system. Will the taxpayers who funded her work receive any financial benefits should the hydrogel prove to be successful or will we be paying double, both supporting her research and paying for the hydrogel through our healthcare costs?

Getting back to the research, here’s a link to and a citation for the paper,

Rationally Designed 3D Hydrogels Model Invasive Lung Diseases Enabling High‐Content Drug Screening by Roger Y. Tam, Julien Yockell‐Lelièvre, Laura J. Smith, Lisa M. Julian, Alexander E. G. Baker, Chandarong Choey, Mohamed S. Hasim, Jim Dimitroulakos, William L. Stanford, Molly S. Shoichet. Advanced Materials Volume 31, Issue 7 February 15, 2019 1806214 First published online: 27 December 2018 DOI: https://doi.org/10.1002/adma.201806214

This paper is behind a paywall.

Making 3D patches for the brain

They’re not ready to start patching any brains yet but the research seems promising. From an April 1, 2015 news item on ScienceDaily,

Damage to neural tissue is typically permanent and causes lasting disability in patients, but a new approach has recently been discovered that holds incredible potential to reconstruct neural tissue at high resolution in three dimensions. Research recently published in the Journal of Neural Engineering demonstrated a method for embedding scaffolding of patterned nanofibers within three-dimensional (3D) hydrogel structures, and it was shown that neurite outgrowth from neurons in the hydrogel followed the nanofiber scaffolding by tracking directly along the nanofibers, particularly when the nanofibers were coated with a type of cell adhesion molecule called laminin. It was also shown that the coated nanofibers significantly enhanced the length of growing neurites, and that the type of hydrogel could significantly affect the extent to which the neurites tracked the nanofibers.

A March 31, 2015 Institute of Neural Regeneration & Tissue Engineering press release on EurekAlert, which originated the news item, describes the thinking underlying this research and future research plans,

“Neural stem cells hold incredible potential for restoring damaged cells in the nervous system, and 3D reconstruction of neural tissue is essential for replicating the complex anatomical structure and function of the brain and spinal cord,” said Dr. McMurtrey, author of the study and director of the research institute that led this work. “So it was thought that the combination of induced neuronal cells with micropatterned biomaterials might enable unique advantages in 3D cultures, and this research showed that not only can neuronal cells be cultured in 3D conformations, but the direction and pattern of neurite outgrowth can be guided and controlled using relatively simple combinations of structural cues and biochemical signaling factors.”

The next step will be replicating more complex structures using a patient’s own induced stem cells to reconstruct damaged or diseased sites in the nervous system. These 3D reconstructions can then be used to implant into the damaged areas of neural tissue to help reconstruct specific neuroanatomical structures and integrate with the proper neural circuitry in order to restore function. Successful restoration of function would require training of the new neural circuitry over time, but by selecting the proper neurons and forming them into native architecture, implanted neural stem cells would have a much higher chance of providing successful outcomes. The scaffolding and hydrogel materials are biocompatible and biodegradable, and the hydrogels can also help to maintain the microstructure of implanted cells and prevent them from washing away in the cerebrospinal fluid that surrounds the brain and spinal cord.

McMurtrey also noted that by making these site-specific reconstructions of neural tissue, not only can neural architecture be rebuilt, but researchers can also make models for studying disease mechanisms and developmental processes just by using skin cells that are induced into pluripotent stem cells and into neurons from patients with a variety of diseases and conditions. “The 3D constructs enable a realistic replication of the innate cellular environment and also enable study of diseased human neurons without needing to biopsy neurons from affected patients and without needing to make animal models that can fail to replicate the full array of features seen in humans,” said McMurtrey.

The ability to engineer neural tissue from stem cells and biomaterials holds great potential for regenerative medicine. The combination of stem cells, functionalized hydrogel architecture, and patterned and functionalized nanofiber scaffolding enables the formation of unique 3D tissue constructs, and these engineered constructs offer important applications in brain and spinal cord tissue that has been damaged by trauma, stroke, or degeneration. In particular, this work may one day help in the restoration of functional neuroanatomical pathways and structures at sites of spinal cord injury, traumatic brain injury, tumor resection, stroke, or neurodegenerative diseases of Parkinson’s, Huntington’s, Alzheimer’s, or amyotrophic lateral sclerosis.

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

Patterned and functionalized nanofiber scaffolds in three-dimensional hydrogel constructs enhance neurite outgrowth and directional control by Richard McMurtrey (Journal of Neural Engineering Volume 11 Number 6) 2014 J. J. Neural Eng. 11 066009 doi:10.1088/1741-2560/11/6/066009

This paper is open access.

A little unusually for me, here’s the abstract for the paper,

Objective. Neural tissue engineering holds incredible potential to restore functional capabilities to damaged neural tissue. It was hypothesized that patterned and functionalized nanofiber scaffolds could control neurite direction and enhance neurite outgrowth. Approach. A method of creating aligned electrospun nanofibers was implemented and fiber characteristics were analyzed using environmental scanning electron microscopy. Nanofibers were composed of polycaprolactone (PCL) polymer, PCL mixed with gelatin, or PCL with a laminin coating. Three-dimensional hydrogels were then integrated with embedded aligned nanofibers to support neuronal cell cultures. Microscopic images were captured at high-resolution in single and multi-focal planes with eGFP-expressing neuronal SH-SY5Y cells in a fluorescent channel and nanofiber scaffolding in another channel. Neuronal morphology and neurite tracking of nanofibers were then analyzed in detail. Main results. Aligned nanofibers were shown to enable significant control over the direction of neurite outgrowth in both two-dimensional (2D) and three-dimensional (3D) neuronal cultures. Laminin-functionalized nanofibers in 3D hyaluronic acid (HA) hydrogels enabled significant alignment of neurites with nanofibers, enabled significant neurite tracking of nanofibers, and significantly increased the distance over which neurites could extend. Specifically, the average length of neurites per cell in 3D HA constructs with laminin-functionalized nanofibers increased by 66% compared to the same laminin fibers on 2D laminin surfaces, increased by 59% compared to 2D laminin-coated surface without fibers, and increased by 1052% compared to HA constructs without fibers. Laminin functionalization of fibers also doubled average neurite length over plain PCL fibers in the same 3D HA constructs. In addition, neurites also demonstrated tracking directly along the fibers, with 66% of neurite lengths directly tracking laminin-coated fibers in 3D HA constructs, which was a 65% relative increase in neurite tracking compared to plain PCL fibers in the same 3D HA constructs and a 213% relative increase over laminin-coated fibers on 2D laminin-coated surfaces. Significance. This work demonstrates the ability to create unique 3D neural tissue constructs using a combined system of hydrogel and nanofiber scaffolding. Importantly, patterned and biofunctionalized nanofiber scaffolds that can control direction and increase length of neurite outgrowth in three-dimensions hold much potential for neural tissue engineering. This approach offers advancements in the development of implantable neural tissue constructs that enable control of neural development and reproduction of neuroanatomical pathways, with the ultimate goal being the achievement of functional neural regeneration.

I have a few comments, this work was performed in vitro and I imagine it will be several years before it is attempted in human clinical trials. As well, the ethics issues raised by this work are interesting. While the doctors are talking about repairs to injured tissues, it’s only a matter of time until someone tries to improve on the brain or human enhancement. After all, modern plastic surgery was developed as a form of repair for soldiers and others who were disfigured. These days, much of the practice is concerned with preserving youth or enhancing someone’s looks. Not altogether coincidentally, I wrote about the second volume of a report from the US Presidential Bioethics Commission in my April 2, 2015 post titled: Gray Matters volume 2: Integrative Approaches for Neuroscience, Ethics, and Society issued March 2015 by US Presidential Bioethics Commission.

Finally, you can find out more about the Institute of Neural Regeneration & Tissue Engineering here.

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

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.

The body as an electronic device—adding electronics to biological tissue

What makes this particular combination of electronic s  and living tissue special is t that it was achieved in 3-D rather than 2-D.  From the Boston Children’s Hospital Aug. 26, 2012 news release on EurekAlert,

A multi-institutional research team has developed a method for embedding networks of biocompatible nanoscale wires within engineered tissues. These networks—which mark the first time that electronics and tissue have been truly merged in 3D—allow direct tissue sensing and potentially stimulation, a potential boon for development of engineered tissues that incorporate capabilities for monitoring and stimulation, and of devices for screening new drugs.

The Aug. 27, 2012 news item on Nanowerk provides more detail about integration of the cells and electronics,

Until now, the only cellular platforms that incorporated electronic sensors consisted of flat layers of cells grown on planar metal electrodes or transistors. Those two-dimensional systems do not accurately replicate natural tissue, so the research team set out to design a 3-D scaffold that could monitor electrical activity, allowing them to see how cells inside the structure would respond to specific drugs.

The researchers built their new scaffold out of epoxy, a nontoxic material that can take on a porous, 3-D structure. Silicon nanowires embedded in the scaffold carry electrical signals to and from cells grown within the structure.

“The scaffold is not just a mechanical support for cells, it contains multiple sensors. We seed cells into the scaffold and eventually it becomes a 3-D engineered tissue,” Tian says [Bozhi Tian, a former postdoc at MIT {Massachusetts Institute of Technology} and Children’s Hospital and a lead author of the paper ].

The team chose silicon nanowires for electronic sensors because they are small, stable, can be safely implanted into living tissue and are more electrically sensitive than metal electrodes. The nanowires, which range in diameter from 30 to 80 nanometers (about 1,000 times smaller than a human hair), can detect voltages less than one-thousandth of a watt, which is the level of electricity that might be seen in a cell.

Here’s more about why the researchers want to integrate living tissue and electronics, from the Harvard University Aug. 26, 2012 news release on EurekAlert,

“The current methods we have for monitoring or interacting with living systems are limited,” said Lieber [Charles M. Lieber, the Mark Hyman, Jr. Professor of Chemistry at Harvard and one of the study’s team leaders]. “We can use electrodes to measure activity in cells or tissue, but that damages them. With this technology, for the first time, we can work at the same scale as the unit of biological system without interrupting it. Ultimately, this is about merging tissue with electronics in a way that it becomes difficult to determine where the tissue ends and the electronics begin.”

The research addresses a concern that has long been associated with work on bioengineered tissue – how to create systems capable of sensing chemical or electrical changes in the tissue after it has been grown and implanted. The system might also represent a solution to researchers’ struggles in developing methods to directly stimulate engineered tissues and measure cellular reactions.

“In the body, the autonomic nervous system keeps track of pH, chemistry, oxygen and other factors, and triggers responses as needed,” Kohane [Daniel Kohane, a Harvard Medical School professor in the Department of Anesthesia at Children’s Hospital Boston and a team leader] explained. “We need to be able to mimic the kind of intrinsic feedback loops the body has evolved in order to maintain fine control at the cellular and tissue level.”

Here’s a citation and a link to the paper (which is behind a paywall),

Macroporous nanowire nanoelectronic scaffolds for synthetic tissues by Bozhi Tian, Jia Lin, Tal Dvir, Lihua Jin, Jonathan H. Tsui, Quan  Qing, Zhigang Suo, Robert Langer, Daniel S. Kohane, and Charles M. Lieber in Nature Materials (2012) doi:10.1038/nmat3404 Published onlin26 August 2012.

This is the image MIT included with its Aug 27, 2012 news release (which originated the news item on Nanowerk),

A 3-D reconstructed confocal fluorescence micrograph of a tissue scaffold.
Image: Charles M. Lieber and Daniel S. Kohane.

At this point they’re discussing therapeutic possibilities but I expect that ‘enhancement’ is also being considered although not mentioned for public consumption.

New type of scaffolding for tissue engineering

Since the international July 2011 coverage of Andemariam Teklesenbet Beyene’s synthetic trachea transplant (mentioned in my Aug. 2, 2011 posting), I’ve been quite interested in tissue engineering. Scientists at Northwestern University (US) have developed a new type of scaffolding for tissue engineering.

There’s a description in the Feb. 12, 2012 news release on EurekAlert of  tissue engineering and scaffolding and some of the disadvantages with the current technology,

Through tissue engineering, researchers seek to regenerate human tissue, such as bone and cartilage, that has been damaged by injury or disease. Scaffolds — artificial, lattice-like structures capable of supporting tissue formation — are necessary in this process to provide a template to support the growing cells. Over time, the scaffold resorbs into the body, leaving behind the natural tissue.

Scaffolds are typically engineered with pores that allow the cells to migrate throughout the material. The pores are often created with the use of salt, sugar, or carbon dioxide gas, but these additives have various drawbacks; They create an imperfect pore structures and, in the case of salt, require a lengthy process to remove the salt after the pores are created, said Guillermo Ameer, professor of biomedical engineering at the McCormick School of Engineering and professor of surgery at the Feinberg School of Medicine.

The new scaffolds are more flexible and can be tailored to ‘resorb’ at different times,

The new scaffolds, created from a combination of ceramic nanoparticles and elastic polymers, were formed in a vacuum through a process termed “low-pressure foaming” that requires high heat, Ameer said. The result was a series of pores that were highly interconnected and not dependent on the use of salt.

The new process creates scaffolds that are highly flexible and can be tailored to degrade at varying speeds depending on the recovery time expected for the patient. The scaffolds can also incorporate nano-sized fibers, providing a new range of mechanical and biological properties, Ameer said. [emphasis mine]

I wonder what “new range of mechanical and biological properties” will be enabled; I was not able to find any speculation.

In the meantime, here’s an image of the scaffolding from the McCormick School (at Northwestern University) http://www.mccormick.northwestern.edu/news/articles/article_1043.html,

For anyone who’s interested in an update on Andemariam Teklesenbet Beyene, according to this Dec. 9, 2011 posting on StemSave, he’s doing well.

ETA Feb. 14, 2012: Michael Berger at Nanowerk has written an article titled, Tissue engineering of 3D tubular structures, which provides some insight into another aspect of creating scaffolding, the tubular nature of many of our organs.

Making nanotechnology-enabled body parts

In my Aug. 2, 2011 posting, Body parts nano style, I mentioned a scaffolding, developed by Dr. Alex Seifalian, made of a biocomposite. Today’s (Aug. 16, 2011) news item on Nanowerk offers more information about the biocomposite,

The composite made from POSS® and PCU (Polyhedral Oligomeric Silsesquioxane & Poly (carbonateurea) Urethane) had been developed by Dr. Alex Seifalian of the University College London Medical School. The effort has been so effective that Dr. Seifalian says he now has six more tracheas on order. … Moreover the composite scaffold can be transformed into a human artery, vein, heart valve, tear duct or trachea. It might in the future be used to make larynxes, noses, breasts, ears or other parts of the human body.

Hybrid has developed a platform technology called POSS® (Polyhedral Oligomeric Silsesquioxane). It is a revolutionary new Nanotechnology based on silicon-derived building blocks that provide nanometerscale control to dramatically improve the properties of traditional polymers. They release no VOCs and, thereby, produce no odor or air pollution. They are biocompatible and recyclable. POSS® nanoscopic chemical technology provides unique opportunities to create revolutionary material combinations through a melding of the desirable properties of ceramics and polymers at the 1 nm length scale. These new combinations enable the circumvention of classic material performance trade-offs by exploiting the synergy and properties that only occur between materials at the nanoscale.

Yes, it’s a bit puffy with hype but that’s to be expected when the news item is released by the company, Hybrid Plastics, that produces at least part of the biocomposite (POSS®) used to create the scaffolding.

Walking on eggshells? and sunshine too?

Tissue scaffolding, egg shells, and nanostructures all come together in work being done by Ryerson University (Toronto, Ontario, Canada) researchers Bo Tan and Krishnan Venkatakrishnan. From the Feb. 28, 2011 news item on physorg.com,

… Venkatakrishnan and Tan first began studying nanostructures within micro-electronics. More recently, though, the researchers have started developing nanostructures using a variety of materials.

One example: the pair’s research on eggshell-based nanostructures – co-authored with Ryerson PhD candidate Amirhossein Tavangar – was published last month in the Journal of Nanobiotechnology. But eggshells aren’t the only materials that can support nanostructures; bones and other natural bio-materials are also being studied in Venkatakrishnan and Tan’s lab.

Typically, fragile ceramics or rigid polymers are used in surgery to fix broken, old or cancer-damaged bones. Nanostructures embedded within actual bones, however, offer a better solution and can help “glue” deteriorated or fragmented bones back together. Through a biomedical process called tissue scaffolding, a porous, artificially created material is used to simulate real tissue and stimulate new bone growth in the body – something that other grafting materials are limited in their capacity to do.

This couple (partners in research and in life) are also working on solar energy panels and water quality monitoring as part of their investigations into nanostructures. I recommend reading this article for a good general introduction about how multidisciplinary research on nanostructures can be applied to many fields.

After writing my headline about “walking on eggshells” I was reminded of a song, “Walking on Sunshine” by Katrina and the Waves. Enjoy a happy weekend,