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Nanomedicine could improve surgical implants

Nanomedicine technology offers promise of helping lower the risk of infections from surgical implants

Tom Webster, a chemical engineer at Northeastern, examined bone cancer cells at a school research center.

Jessica Rinaldi/Globe Staff

Tom Webster, a chemical engineer at Northeastern, examined bone cancer cells at a school research center.

When New England Patriots tight end Rob Gronkowski missed the first six games of last season because of a forearm injury, what kept him off the field was not the broken bone he suffered months earlier but rather a persistent infection where he received a metal plate to help repair his arm.

Tom Webster, a chemical engineer at Northeastern University, believes Gronkowski might have avoided infection and returned to action faster if the plate had been made of a new kind of material in development at his nanomedicine laboratory.

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Nanomaterials, as they are called, have been shown in tests to repel bacteria and help surrounding tissue heal faster than normal because their structures more closely resemble those of real bone and muscle.

In reality, the materials are not new. They are just smaller. The chief principle of nanomedicine is that the properties of materials used for medical parts — titanium, for instance, or silicon nitride, a ceramic used in joint replacements — can be altered simply by shrinking their fundamental building blocks.

Conventional replacement materials are built in blocks of about 1,000 nanometers — 80 times smaller than the width of a human hair, but still much larger than the building blocks of the tissues they are implanted in.

Webster and his team can reduce the size of a substance’s building blocks more than 10 times, to under 100 nanometers or roughly the scale of natural human tissue, helping replacement parts fit into the body more easily.

“The fundamental question we ask ourselves is, ‘Can we create materials that are similar to natural materials?’ ” Webster said. “Can we trick cells into behaving very naturally and increasing tissue growth while keeping bacteria from infecting our tissues?”

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Lab tests suggest the answer could be yes, though Webster estimates he is five years from gaining FDA approval for replacement hips and knees. His team has found that nanomaterials implanted in lab rats help surrounding tissue heal faster and virtually eliminate the possibility of infection.

A scientist used a 96 well plate to test different concentrations of nanoparticle treatment for antibiotic resistant bacteria at Northeastern University. The stronger the glow, the stronger the bacteria are.

Jessica Rinaldi/Globe staff

A scientist used a 96 well plate to test different concentrations of nanoparticle treatment for antibiotic resistant bacteria at Northeastern University. The stronger the glow, the stronger the bacteria are.

One reason is the smaller building blocks create surfaces that appear spiky under a high-powered microscope, unlike the smoother surfaces found on conventional materials.

It is the difference between a piece of sheet metal and a bed of nails, Webster explained: Just as you would be able to lie down on the sheet metal but would leap, howling, off the nails as quickly as possible, bacterial cells that can bond to the smooth surfaces of conventional materials bounce off the tiny spikes on the surfaces of nanomaterials.

Webster’s work is part of the growing field of nanotechnology, a broad term that refers to the study and application of extremely small things. Since the invention of the scanning tunneling microscope in 1981 made it possible to see individual atoms, scientists have discovered some universal benefits of materials constructed at what is known as the nanoscale — in building blocks of one to 100 nanometers.

Advantages include increased strength and better electrical conductivity.

Wide-ranging uses for nanomaterials include bulletproof vests, beer bottles that extend shelf life, and T-shirts that change color in the sun.

In medicine, Webster believes the fastest way to get nanomaterials into the operating room is to start with coatings for existing products, like joint replacements. Today’s ceramic hip, for example, could instead be coated with a nano version of the same ceramic to provide fast-healing, infection-fighting qualities.

Webster is planning to launch a nano-coating company in the near future.

Down the line, he aims to use nanotechnology to create synthetic cartilage and ligaments, and injectable liquids that could be blended with stem cells to help regrow tissue.

Because nanomaterials mimic the scale of natural bone and muscle structures, they adhere to tissue in a way that resembles the bonding of Velcro, which occurs when tiny hooks on the scratchy strip snare miniature loops on the soft strip. Webster believes this “stickiness,” as he calls it, could allow a synthetic anterior cruciate ligament, for instance, to be attached to a patient’s knee bones without the screws used today.

There is another potential fix for Gronkowski: His latest injury is a torn ACL.

Callum Borchers can be reached at callum.borchers@globe.com. Follow him on Twitter @callumborchers.

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