Tag Archives: tissue scaffolding

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,