Sore knees may get 3-D printed relief
PITTSBURGH, Pa. — When it comes to building replacement body parts, 3-D printed plastics have proven their worth. Doctors have printed prosthetic fingers and hands, for instance, to replace ones that their patients had lost in accidents. Veterinarians have printed replacement legs and feet for injured pets. But the latest wave in 3-D printing for medicine goes beyond a reliance on long-lived plastic. Two award-winning examples got their national debut here, two weeks ago, at a major science competition.
This year's Intel International Science & Engineering Fair brought together almost 1,800 finalists from 81 nations, regions and territories. The students competed for about $5 million in prizes and scholarships. Two of them worked on the cutting edge of medicine to design new 3-D printed implants.
Anna Feldbush, 19, built a tissue-like replacement for damaged cartilage in knees and other joints. A 12th grader, she attends West Shore Junior/Senior High School in Melbourne, Fla. Bhargav Ramesh, 16, developed a new way to support damaged tissues as they heal. He is an 11th grader at duPont Manual High School in Louisville, Ky.
About one in every three finalists took home some award. Anna’s project earned a second-place in materials science. That’s a field of research that analyzes the properties of materials or designs new materials with specific traits. Intel Foundation provided the award, worth $1,500. Bhargav snagged a second-place award, worth $500, from the Samvid Educational Foundation.
Tweaking a printer
Knees are joints that really take a beating. Fortunately, cartilage cushions bones that come together at joints. It keeps bones from rubbing together painfully. But wear and tear can damage that cartilage. This tissue is slow to heal, Anna notes, largely because it doesn’t have its own blood supply. So athletes and many others can end up losing that beneficial joint-cushioning tissue. The result can be intense pain — and sometimes a need for surgery to replace the joint.
Anna wanted to 3-D print some replacement cartilage.
Most 3-D printers, she notes, melt some type of plastic. They slowly dispense this so-called “ink” through tiny nozzles. A computer controls the back-and-forth movement of those nozzles. As the plastic cools, it hardens into some computer-designed solid. But Anna wasn’t interested in printing plastic. She wanted her printer to squeeze out a material that was more like natural cartilage.
The recipe for her ink included a gelatin. It’s a protein that readily dissolves in water. She added a chemical called sodium alginate (AL-jih-nayt) and then mixed both into a solution that also included calcium chloride. That last chemical, over time, helps the gelatin chemically bond to the sodium alginate. This bonding, Anna explains, helps create a firm solid.
Anna had to develop a new printer design to handle her novel ink. She started with an off-the-shelf 3-D printer. Then, she swapped out some parts. These included the system that pumped her solution through the printer. She also replaced the printer’s nozzles with tiny needles. Doctors often use similar-size needles to take blood samples or to give injections.
Anna tested a lot of recipes for her ink. She wanted the end product to be as similar to real cartilage as possible. And as a materials scientist, she tested six properties of each mock-cartilage, including how slick and squishy it was. Anna now estimates that her best ink recipe should cost less than a penny to print enough cartilage to repair a damaged knee. And because the printer works so quickly, she says a new joint cushion could be printed right in an operating room during joint-replacement surgery.
This artificial cartilage might last about 10 years, Anna says. That’s about how long the parts used in a total knee replacement typically last. What’s more, she suspects that her approach to knee repair might well be easier and less painful.
Sometimes doctors aren’t looking to make materials to permanently replace a body’s tissues. Instead, they’re looking to create something that aids healing, then dissolves when it’s no longer needed. That’s what Bhargav investigated.
He wanted to print what doctors call a scaffold. Such structures support tissues as they heal or regrow. Scaffolds tend to be porous. That allows cells to move into them, latch on and then grow, the teen explains. Some scaffolds are permanent. He wanted to create one that was temporary and would dissolve, leaving behind only living tissue.
Bhargav’s recipe included just two ingredients. One was polyethylene glycol (Pah-lee-ETH-uh-leen GLY-kol), or PEG. It’s a polymer that biodegrades. That means it will break down in the body over time. The other component was polylactic acid, or PLA. It, too, is a polymer that naturally degrades. These materials firm up to provide a strong material to which cells can attach. But over time they will down and will be flushed from the body.
Like Anna, Bhargav tested different recipes to see which worked best.
A 50:50 blend of PEG and PLA hardened into a brittle — and easily breakable — solid. But both a 3:1 and 9:1 mix of PLA to PEG worked well for scaffolding. In Bhargav’s tests, two types of cells quickly latched onto and then grew upon his fibrous polymer scaffolds. Those tests also showed that the polymers would have dissolved after spending somewhere between 5 and 8 weeks in the body. That’s more than enough time for most tissues to heal, the teen explains.
Each polymer that Bhargav used costs about $80 per kilogram (or about $36 per pound). That might sound like a lot. But porous scaffoldings have so much empty space inside them that they can be made using very little material. Plus, many of them are small to begin with. Together, this means that some types of scaffolding might be 3-D-printed for just a few dollars each.
These materials could serve as more than scaffolding, adds Bhargav. They might deliver drugs. As a material dissolves away, any medicine embedded in it would be gradually released into the body. So, the teen tested this, too. And he showed that the embedded drug he used was released in amounts big enough to be effective.
Society for Science & the Public created ISEF and has been running the competition since 1950. (The Society also runs Science News for Students and this blog.) Intel sponsored this year’s event.
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3-D Short for three-dimensional. This term is an adjective for something that has features that can be described in three dimensions — height, width and length.
3-D printing A means of producing physical items — including toys, foods and even body parts — using a machine that takes instructions from a computer program. That program tells the machine how and where to lay down successive layers of some raw material (the “ink”) to create a three-dimensional object.
calcium chloride A compound made of calcium and chlorine. It has a strong affinity for water and chemists use it to dry out liquid solutions. It can also be used to help de-ice slippery roads in the winter.
cartilage (adj. cartilaginous) A type of strong connective tissue often found in joints, the nose and ear. In certain primitive fishes, such as sharks and rays, cartilage provides an internal structure — or skeleton — for their bodies.
cell The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.
chemical A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.
component Something that is part of something else (such as pieces that go on an electronic circuit board or ingredients that go into a cookie recipe).
concentration (in chemistry) A measurement of how much of one substance has been dissolved into another.
dissolve To turn a solid into a liquid and disperse it into that starting liquid. (For instance, sugar or salt crystals, which are solids, will dissolve into water. Now the crystals are gone and the solution is a fully dispersed mix of the liquid form of the sugar or salt in water.)
fiber Something whose shape resembles a thread or filament. (in nutrition) Components of many fibrous plant-based foods. These so-called non-digestible fibers tend to come from cellulose, lignin, and pectin — all plant constituents that resist breakdown by the body’s digestive enzymes.
field An area of study, as in: Her field of research was biology. Also a term to describe a real-world environment in which some research is conducted, such as at sea, in a forest, on a mountaintop or on a city street. It is the opposite of an artificial setting, such as a research laboratory.
gelatin A substance made from animal collagen, usually bones and cow or pig hides. It starts out as a pale colored, tasteless powder. It contains proteins and amino acids. It can make jiggly desserts (like those known as Jell-O). But this substance also is used in yogurt, soups, candies and more. It can even be used as the basis of the clear capsules used to hold single-serving amounts of dry medicines.
high school A designation for grades nine through 12 in the U.S. system of compulsory public education. High-school graduates may apply to colleges for further, advanced education.
implant A device manufactured to replace a missing biological structure, to support a damaged biological structure, or to enhance an existing biological structure. Examples include artificial hips, knees and teeth; pacemakers; and the insulin pumps used to treat diabetes. Or some device installed surgically into an animal’s body to collect information on the individual (such as its temperature, blood pressure or activity cycle).
infection A disease that can spread from one organism to another. It’s usually caused by some type of germ.
materials science The study of how the atomic and molecular structure of a material is related to its overall properties. Materials scientists can design new materials or analyze existing ones. Their analyses of a material’s overall properties (such as density, strength and melting point) can help engineers and other researchers select materials that are best suited to a new application. A scientist who works in this field is known as a materials scientist.
nozzle A round spout or slot at the end of a pipe, hose or tube. Nozzles are typically used to control the flow of a jet of some high-pressure liquid or gas.
petri dish A shallow, circular dish used to grow bacteria or other microorganisms.
plastic Any of a series of materials that are easily deformable; or synthetic materials that have been made from polymers (long strings of some building-block molecule) that tend to be lightweight, inexpensive and resistant to degradation.
polylactic acid (abbreviated PLA) A plastic made by chemically linking long chains of lactic-acid molecules. Lactic acid is a substance present naturally in cow’s milk.
polymer A substance made from long chains of repeating groups of atoms. Manufactured polymers include nylon, polyvinyl chloride (better known as PVC) and many types of plastics. Natural polymers include rubber, silk and cellulose (found in plants and used to make paper, for example).
porous The description of a substance that contains tiny holes, called pores , through which a liquid or gas can pass. (in biology) The minute openings in the skin or in the outer layer of plants.
prosthetic Adjective that refers to a prosthesis.
protein A compound made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They form the basis of living cells, muscle and tissues; they also do the work inside of cells. Among the better-known, stand-alone proteins are the hemoglobin (in blood) and the antibodies (also in blood) that attempt to fight infections. Medicines frequently work by latching onto proteins.
scaffold A framework erected to temporarily supports something, such as people putting siding onto the exterior of a building. (in medicine) A structure implanted into the body to support tissues as they heal or grow.
sodium A soft, silvery metallic element that will interact explosively when added to water. It is also a basic building block of table salt (a molecule of which consists of one atom of sodium and one atom of chlorine: NaCl). It is also found in sea salt.
tissue Made of cells, it is any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.
veterinarian A doctor who studies or treats animals (not humans).