The tradeoff in fiberglass insulation products has always been between strength and safety: making glass fibers stronger for the harshest applications by adding aluminum oxide to them also increases the risk that they will cause lung cancer when inhaled.
But at a recent meeting of the American Chemical Society, biomaterials and biophotonics researchers at the University at Buffalo reported on the surprising chemical mechanism behind one type of fiberglass fortified with aluminum oxide that does not persist in the lungs.
The UB researchers have found that once this glass fiber, known as RIF (HT), is inhaled, its long strong, glass fibers are broken down into smaller pieces outside of cells, apparently through the same mechanism that the body uses to break down old bone. The smaller pieces, they found, then are safely ingested and digested by cells.
"These findings violate everything that is known about the laboratory chemistry of these glass fibers," said Robert Baier, Ph.D., UB professor of oral diagnostic sciences, director of the UB Industry-University Cooperative Research Center on Biosurfaces (IUCB) and principal investigator on the study.
The finding goes a long way toward solving a puzzle that has perplexed chemists and regulators for a decade, since a Danish company, Rockwool Corp., developed RIF (HT), which is very strong, but does not persist in the lungs.
"That discovery threw the regulatory world into a tizzy," said Baier.
A number of scientific groups began to investigate the phenomenon. Members of TC26, the international industry committee that oversees research and development into glass fibers, requested that Baier and his colleagues embark on animal studies to try to understand the chemical mechanism.
"They told us, 'You know how foreign materials interact with the body, we want you to study this "inadvertent implant" and help us understand what's going on here,'" Baier said. The IUCB's expertise lies in surface interactions, particularly those that occur at the surfaces of implantable devices.
On October 16, members of TC26 will visit UB to review and discuss the UB team's results.
For decades, Baier explained, it has been accepted that cells can digest fibers only up to 20 microns in length, but the alumina-enriched fibers are typically longer than 20 microns.
"Good, durable glasses immediately get you into potential trouble in the lung," said Baier.
An advanced imaging technique created by scientists at UB's Institute for Lasers, Photonics and Biophotonics that pairs a confocal microscope with a spectrophotometer allowed Baier's group an unprecedented opportunity to look at fibers in and around rat lung cells in great detail.
"The combination confocal microscope and spectrophotometer at the institute allowed us to virtually 'walk through' cross-sections of clusters of cells and detect chemical changes occurring right around the fibers down to a single micrometer," said Baier.
"The instrument allows us to determine spectroscopic details, that is, how much visible and non-visible light is being absorbed or emitted by the cells," Baier explained, "which reveals whether the local environment is acid or alkaline."
Using this technique, Baier and his colleagues tracked chemical changes in lung cells of rats that had inhaled these glass fibers.
"At first, the cells in the vicinity responded with a quick burst of acid, detecting the fiber as a foreign object," Baier said, "but as the fibers began to break into small parts outside of the cells, the environment around them became more and more alkaline."
That finding surprised the researchers.
"This is the first time that it's ever been shown that fibers this long can break down outside of cells," said Baier.
As the researchers continued their analysis, Baier said, they began to suspect the involvement of osteoclasts, cells that aid in the natural breakdown and resorption of bone in the body.
"We therefore wondered if this fiberglass contained any calcium and we discovered that it does," he said.
"This glass fiber seems to trick the body into thinking it's a piece of bone," he continued, "so cells that come into contact with these fibers differentiate into osteoclasts, which then go to work on it, breaking it down. We think we've found that by adjusting the chemical composition of a material, we can actually dictate the fate of cells that come into contact with it."
The finding not only points the way toward the development of stronger yet safer building materials, but also suggests that glass fibers may have promising biomedical applications, such as in tissue engineering, Baier said.
"This research demonstrates that we may be able to go from using glass fibers as an external building material to using them as a kind of internal building material as well, if you will, where we could rebuild body parts on fiberglass scaffolding, which then would simply dissolve away," he added.
"We may have tripped across a way to foster a revolution in tissue engineering."
The research was funded by industry members of the National Science Foundation-sponsored IUCB.
Co-authors on the paper with Baier are Peter A. Nickerson, Ph.D., UB professor of pathology and anatomical sciences; Maria H. Kozak, research technician; and Anne E. Meyer, Ph.D., principal research scientist and director of the IUCB and, at the Institute for Lasers, Photonics and Biophotonics, Haridas Pudavar, Ph.D., postdoctoral research associate; Earl J. Bergey, Ph.D., deputy director of biophotonics, and Paras N. Prasad, Ph.D., SUNY Distinguished Professor in the Department of Chemistry in the UB College of Arts and Sciences and director of the institute. Walter Eastes, Ph.D., and Russell Potter, Ph.D., both of the Owens-Corning Science & Technology Center, and Domenic Tessari, Ph.D., of the CertainTeed Corp., also are co-authors.
Materials provided by University At Buffalo. Note: Content may be edited for style and length.
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