Scientists from the University of British Columbia (UBC) and McMaster University say they have developed what could be new bone implant material: a foamlike substance that can be injected into the body and provide scaffolding for the growth of new bone.
“Chemically cross-linked cellulose nanocrystal (CNC) aerogels possess many properties beneficial for bone tissue scaffolding applications. CNCs were extracted using sulfuric acid or phosphoric acid, to produce CNCs with sulfate and phosphate half-ester surface groups, respectively. Hydrazone cross-linked aerogels fabricated from the two types of CNCs were investigated using scanning electron microscopy, x-ray micro-computed tomography, x-ray photoelectron spectroscopy, nitrogen sorption isotherms, and compression testing. CNC aerogels were evaluated in vitro with osteoblast-like Saos-2 cells and showed an increase in cell metabolism up to 7 days while alkaline phosphate assays revealed that cells maintained their phenotype. All aerogels demonstrated hydroxyapatite growth over 14 days while submerged in simulated body fluid solution with a 0.1 M CaCl2 pre-treatment,” wrote the investigators.
“Sulfated CNC aerogels slightly outperformed phosphated CNC aerogels in terms of compressive strength and long-term stability in liquid environments, and were implanted into the calvarian bone of adult male Long Evans rats. Compared to controls at 3- and 12-week time points, sulfated CNC aerogels showed increased bone volume fraction of 33% and 50%, respectively, compared to controls, and evidence of osteoconductivity. These results demonstrate that cross-linked CNC aerogels are flexible, porous and effectively facilitate bone growth after they are implanted in bone defects.”
“These findings show, for the first time in a lab setting, that a cellulose nanocrystal aerogel can support new bone growth,” said study co-author Emily Cranston, PhD, a professor of wood science and chemical and biological engineering who holds the President’s Excellence Chair in Forest Bio-products at UBC. She added that the implant should break down into nontoxic components in the body as the bone starts to heal.
The innovation can potentially fill a niche in the $2-billion bone graft market in North America, said study co-author Kathryn Grandfield, PhD, a professor of materials science and engineering, and biomedical engineering at McMaster who supervised the work.
“We can see this aerogel being used for a number of applications including dental implants and spinal and joint replacement surgeries,” said Grandfield. “And it will be economical because the raw material, the nanocellulose, is already being produced in commercial quantities.”
The researchers say it will be some time before the aerogel makes it out of the lab and into the operating room.
“This summer, we will study the mechanisms between the bone and implant that lead to bone growth,” said Grandfield. “We’ll also look at how the implant degrades using advanced microscopes. After that, more biological testing will be required before it is ready for clinical trials.”