Martin King helped create an implantable artificial heart.
The reason most students have never even heard of such a thing bordering on the miraculous is because the technology is not accepted yet, according to King, a biotextiles and textiles technology professor and director of undergraduate programs in the College of Textiles.
The Prince Rainer of Monaco sponsored the research because his family has a history of heart disease, King said.
The biggest problems were related to the lack of an acceptable power source. The patients with artificial hearts had to carry around a large battery pack — it wasn’t the dream solution of a new heart installed in a patient with no further problems.
“It doesn’t necessarily improve your quality of life,” King said. King states that it takes a lot of engineering to get to that point and current technologies are not even at step one.
“In fact,” King said, “a patient who had such a heart implanted died within three to four months of the operation.”
A paradigm shift has occurred among researchers in the area and they are not trying to create completely artificial organs, anymore.
Apparently any implant (tooth fillings, metal plates to fix broken legs) lasts for only so long before it begins to wear out.
“So, why not harness the biological metabolism and physiological processes of the body to regenerate tissue to replace the injured part or organ?” King asked. Researchers learn how cells replicate and how they build different types of tissue. They then build scaffolds which are open structures that allow cells to grow on and into them. Cells are grown on these scaffolds, in an engineered predictable fashion, so that they end up with new tissue.
“The scaffold itself is normally resorbable material, which, once inside the body, breaks down into innocuous products like carbon dioxide and water,” King said. “These may be excreted without toxic effects.”
Textiles are suited for these applications, as most of what is present in a spun fabric is just air. This basically provides the porosity which allows cells to grow in a controlled environment.
There are two approaches to regenerate cells to replace damaged organs. The first is to put the scaffolds into the part of the body that requires regeneration and make the cells grow on it.
The second, and more popular, technique is to create some cells on the scaffold before it is implanted. Some cells are placed on the scaffold and then put into a “bioreactor,” which is filled with nutrients to allow the cells to grow.
Once grown, the cells may be implanted into the body, thus meeting with greater success.
This particular technique finds applications in a wide variety of areas, one of which is the replacement of cardio-myocites — cells that are injured when one suffers a heart attack.
“We get the heart muscles to regenerate and replace the injured part of the heart to get the heart pumping again,” King said. Ajit Moghe, a doctoral student in fiber and polymer science, works on the development of nanofibrous tissue engineering scaffolds.
“I am working on using a technique known as ‘electrospinning’ to prepare nanofiber webs, which can be used to grow cells and generate desired tissues,” he said.
King is also working with researchers from UNC to generate liver tissue by growing hepatocytes (liver tissue) so that liver patients do not require transplants. Jessica Gluck is a masters student whose research topic involves the use electrospinning,
“We use the resulting nanofibrous webs in a cell structure to create liver tissue,” she said. King also collaborates with researchers from the biomedical engineering department to regenerate ligament, tendon and bone tissue.
“Creation of bone tissue is challenging, as it requires other processes, such as mineralization of cells,” he said. Their focus is to engineer cartilage and bone tissues using scaffolds, according to Moghe.
King elaborates that there are various ways to get cells to do what you want to them to do.
“Some are chemical cues by exposing them to certain growth factors,” he said. “Another approach is by exposing the scaffold to electrical and mechanical pulses, so that cells feel the strain. They respond to the pulses and line up in the direction of the strain.”
There exist potential hurdles to be crossed while using such techniques to grow tissues. The biggest problem is that the human body is conditioned to attack and reject any foreign material that is inserted, especially if the cells originate from another species or even another person.
“A device or organ that can be created, packaged and shelved to be put to future use is not there yet,” King said. To overcome this hurdle stem cells from a patient’s body are harvested and differentiated into new cells to help regenerate body parts.
“Come back in ten years, and we will have the technology where we’ll have removed all the proteins that uniquely identify the cells; hence they will not elicit an immune response,” King said. Researchers start from stem cells, as they are younger cells and are more likely to succeed, according to King. This is more productive especially if you know the signals that are required to differentiate the stem cells into new cells.Although it may seem fantasy, one company makes artificial skin grown using a tissue regeneration technique, King said. Also, colleagues of King’s from the Université Laval in Canada are working on creating skin for burn victims using these techniques. They grow new skin in two to three weeks, and the only real issue is being able to stabilize patients for that period of time.
“So if you were really forward thinking,” said King, “you might want to store some cells in a cell bank, like people store embryos and sperm these days, in case you need a skin graft in the future.” One other important area of research which King follows, is that of barbed sutures.
“The question arises,” said King, ” as to why you would want to put ‘barbs’ on surgical sutures. The main reason is to avoid tying a knot. The knot is the weakest link where sutures typically break, because pressure exists at these points and the fabric gets twisted. Just creation of knots puts defects in the material.”
This problem is particularly noticeable in heart surgeries such as the installation of heart valves in patients. To make sure the valve stays in place, surgeons typically use at least five throws in the heart. To compare, one typically use two throws while tying his or her shoelaces. Hence, a huge lump is created in the heart, which doesn’t aid in the healing process. It also leads to scar formation. Barbed sutures may be pulled through the tissue and will stay in place because of the barbs, hence, completely avoiding the need for knots. These barbed sutures are in use today in cosmetic surgery.
Also, barbed sutures placed beneath the skin dissolve in six to eight weeks with hardly any scarring, which is a huge plus for cosmetic surgeries.
“Material scientists are working on modeling these barbed sutures to try and understand the characteristics of the barbs – from the size, shape and frequency of the barbs to its interactions with various types of tissues,” said King.
King has also worked on creating ventricular devices and arterial stents. N.C. State is also pioneering a curriculum in the study of “medical textiles.” “Medical textiles is a broad term which represents all applications of textiles in the medical field, such as surgical implants, medical devices, tissue engineering scaffolds, etc.,” Moghe said. King points out that this is the first ever such curriculum and is a three to four year undergraduate program. It covers a wide variety of topics germane to the field, such as biopolymers, supply-chain for marketing and regulatory affairs.
“The classes offered in textiles do a great job in introducing the basics of medical textiles from materials science as well as manufacturing standpoints. One class even teaches students about testing and characterizing biomaterials and medical devices and talks about the entire FDA approval process which is essential for anyone who wants to work in the medical device industry,” Moghe said. “I find this field very exciting and, although quite new, is emerging very fast with great potential.”
