“I want to put glass inside your body.”
That’s the way William Lepry (PhD ‘17) sometimes likes to start a conversation about his work. Lepry, a doctoral student in the Department of Mining and Materials Engineering, slides into a conference room swivel chair somewhere in the labyrinthine Wong Building to explain his research on bioactive glass.
“When people think of biomaterials, glass is usually pretty low on their list,” he says. “The cool thing about glass is that it’s a material that’s been around for thousands of years, and only recently we’re discovering its positive effects on the body.”
Bioactive glasses are biomaterials that, when implanted in the body, help to regrow bone tissue. Lepry’s spent the last four years of his life exploring its potential in a form of borate-focused chemistry.
PERSONAL QUEST
His interest in using these materials for medical application was forged after several knee surgeries stemming from a skiing accident as a 17-year-old. To potentially fill screw holes in his tibia left behind from previous surgeries, the surgeon suggested he might need to perform two surgeries, one to fill the bone graft and one to repair the ligament. When asked why it couldn’t be done in one operation, the surgeon replied that the graft material needed at least six weeks to fill the bone graft.
“It got me thinking,” Lepry says, “if there was not a faster way.” That initial curiosity led him to pursue his doctoral studies. He chose McGill’s Faculty of Engineering mostly for the three-year funding he was offered via the Vadasz Doctoral Fellowships. Thus began his research into bioactive borate glass for bone tissue repair.
BORATE DREAMS
When placed in simulated body fluid, the calcium and phosphorous in bioactive glass react to form hydroxylcarbonated apatite (HCA), the inorganic component of bone. HCA bonds to bone and soft connective tissues, gradually replacing the biomaterial, and acting as a scaffold on which healthy tissue forms.
What’s more, the calcium and phosphorus ions that are released during the dissolution process promote healing by stimulating the body’s natural healing ability. Traditional commercialized silica bioglasses or synthetic hydroxy-apatite ceramics, similar to the screws used for Lepry’s knee surgeries, are typically slow to resorb and can leave behind the original implant material, which some studies have shown to be problematic.
Bioactive borate glasses, on the other hand, have a low chemical durability, allowing the body to remodel the biomaterial into tissue at a much higher rate, leaving no evidence that an implant was there.
“What makes our approach with bioactive borate glasses unique is the novel production method, the sol-gel process, which increases the glass surface and porosity, allowing for increased reabsorption rates of the biomaterial,” explains Lepry.
In his experiments, carried out under the supervision of Professor Showan Nazhat, Associate Professor in the Department of Mining and Materials Engineering, this porosity increased over two orders of magnitude compared to traditional glasses, resulting in the onset of mineralization and conversion to bone-like material at a 25-fold increase in bioactivity rate relative to melt-derived borate-based glasses.
“Right now there’s not too many drawbacks,” says Lepry. “But further testing is needed to see how these materials will react in a living environment.”
After submitting a patent for the process in 2014, Lepry and Nazhat are now moving towards animal testing of their invention.
“I’ve been fortunate to have knee surgeries and recover well from them, but there are better ways to improve bone healing,” says Lepry, leaning forward in his chair. “My dream is to have a product that can improve the lives of hundreds of thousands of people.”