| NEWS & IDEAS |
July 1998
CHEMICAL ENGINEERING:
Cellulose Dressing Heals Wounds
NANOPHASE COMPOSITES:
Tiny Particles Have Big Potential
MATERIAL SCIENCE:
Ozone Disinfectants Cause Corrosion
CHEMICAL ENGINEERING:
Cellulose Dressing Heals Wounds
An inexpensive new cellulose wound care dressing has demonstrated remarkable ability to promote healing in difficult-to-treat leg ulcers and bed sores, even those that have resisted other treatments for months.
In a clinical study of 31 patients, 13 out of the 13 with serious leg ulcers responded positively, with 54 percent of the wounds completely healed and 46 percent showing marked progress during an eight-week period. Results in patients with pressure ulcers (bed sores) were almost as good.
The dressing received Federal Drug Administration approval in June for care of all types of wounds as well as first- and second-degree burns. It is made from a high-quality microbial cellulose produced by a process patented by Rensselaer Polytechnic Institute and licensed to Xylos, a new company located in the Rensselaer business incubator and partially owned by the university.
Although the cellulose has potential for a broad range of applications, Xylos is concentrating first on the rapidly growing field of moist wound care. The market for these products totaled $278 million in 1995 and is expected to reach more than $350 million by 2000. Xylos has negotiated licensing agreements and a "right of first offer" with Johnson & Johnson on the wound-care products it develops.
No one is quite sure why the Xylos dressings work so well, according to John Brennan, Xylos president. The answer may be in the physical characteristics of the microbial cellulose, which has extraordinary absorbency. It also has tremendous strength, shape memory, and durability, and it is completely non-toxic and biodegradable, he said.
Most cellulose now used by industry comes from plants, but a tiny microbe, Acetobacter xylinum, produces the world's best cellulose, according to Gonzalo (Al) Serafica, Xylos vice president. In 1993 and 1994, he supervised a commercial operation in the Philippines that produced this cellulose for use as a popular sweet treat - Nata de coco. At Rensselaer, Serafica earned his doctorate in chemical engineering, developing an efficient, controlled process for growing the cellulose.
Johnson & Johnson had patented the idea of using microbial cellulose in wound-care dressings but was not able to produce the cellulose economically. In license agreements signed with Xylos, Johnson & Johnson gave the new firm exclusive worldwide rights to the patents and received the "right of first offer" on any wound-care products Xylos develops.
Traditionally, batches of the cellulose have been grown on the surface of plastic trays of a nutrient-rich liquid. Serafina developed an improved process that produces a high-quality cellulose at greatly reduced cost.
After successful animal studies, Xylos contracted with Etris Associates of Philadelphia to see how the cellulose would perform on human wounds. In addition to the 13 patients with leg ulcers, others had bed sores of varying severity and other types of wounds. Etris tried the dressing on 31 patients averaging 68 years of age, with a range from 28 to 96. Participants had had their wounds for an average of 7.8 months, with a range of one month to more than 24 months. A variety of other treatments had already been tried in almost all cases.
The results, reported this spring at the Symposium on Advanced Wound Care in Miami, were extremely promising, with wounds of 29 of the 31 patients completely healed or improved.
Contacts: John Brennan (215) 504-8080 xylos1@aol.com, Gonzalo Serafica (518) 276-2238
NANOPHASE COMPOSITES:
Tiny Particles Have Big Potential
A whole new class of "nanophase" composites has the potential to create superior protective coatings, mechanical parts, electrical insulation, and even human bone replacements, according to Richard W. Siegel.
In one area alone, superior protective coatings, their economic impact could be staggering, he said. U.S. industry loses $80 billion a year because of corrosion of metal in products such as automobiles, aircraft, bridges, and industrial machinery.
Siegel, the Robert W. Hunt Professor and head of materials science and engineering at Rensselaer, chaired a panel June 19 on the future of nanomaterials during the closing session of the fourth International Conference on Nanostructured Materials in Stockholm, Sweden.
Siegel heads a committee for the World Technology Evaluation Center that has just completed a two-year study of nanostructure science and technology around the world, funded by the National Science Foundation and other federal agencies. He reported some of the results during the panel discussion.
Nanostructure science and technology is a new scientific field that is in an early stage of development, similar to the position of computer and information technology in the 1950s, he said.
Nanophase materials, made of particles much smaller than those found in ordinary substances, have different properties from normal metals and ceramics. At Rensselaer, Siegel and his colleagues have established a research program to create and study polymer composites made with nanophase materials. The work is funded by NSF.
The researchers believe these materials can be engineered to resist scratching, stand up to twisting and stretching, survive high temperatures, and insulate electrical current far better than materials now in use.
Although nanoparticles occur naturally in such materials as bone, teeth, and seashells, humans have begun manufacturing them only in recent decades, Siegel explains. The chemical composition of the nanophase materials is the same as their ordinary counterparts, but the particles or crystals that serve as basic building blocks of the material are far smaller.
This alters their mechanical, optical, chemical, electrical, and magnetic properties, creating, for example, copper that is five times harder than normal and ceramics that bend instead of breaking. Only since the 1990s have the gas condensation methods used in the manufacture of nanophase metals and ceramics been well enough understood to scale up the process for commercial production, Siegel said.
In one of the first efforts to create and understand composites using these materials, Rensselaer has been making and studying nanocomposites made from polymer epoxy filled with nanophase titanium dioxide. These nanophase particles measure about 32 nanometers across, about 3,000 times smaller than the diameter of a human hair. This is more than 10 times smaller than ordinary titanium dioxide crystals, and the nanoparticles interreact in different ways with the chains that make up the polymers.
The results, reported during the Stockholm conference, indicate that the nanophase composite has better scratch resistance and strength than a material made with ordinary titanium dioxide.
Another Rensselaer presentation described efforts to understand how biological systems react with nanophase materials that might be used for bone replacement, implants, grafts, or prostheses. Early results show that bone cells adhere significantly better to nanophase alumina, a ceramic form of aluminum, than to alumina with normal grain sizes, indicating new hope for improved orthopedic implants.
Contact: Richard W. Siegel (518) 276-6373, rwsiegel@rpi.edu
MATERIAL SCIENCE:
Ozone Disinfectants Cause Corrosion
Ozone, increasingly seen as a safer way to disinfect water than chlorine, could create extensive corrosion problems for ships if not used with great care, according to David J. Duquette.
Duquette, professor of materials science and engineering at Rensselaer Polytechnic Institute, recently completed corrosion studies for the U.S. Navy. He and his colleagues tested a variety of stainless steel, copper, and nickel alloys in both ozonated and chlorinated seawater.
In almost all cases, corrosion was greater in the ozonated water, especially in "crevice" areas such as those created when bolts and washers come in contact with the alloy.
Ozone was first used to disinfect municipal drinking water in Nice, France in the early 1900s. Since then ozonation has been favored over chlorination in Europe because of improved taste, odor control, and disinfection. Today, due to the environmental hazards of chlorination byproducts, ozone is increasingly replacing chlorine in the United States in sterilization of drinking water, treatment of sewage and waste water, algae control in swimming pools, and fouling control in water towers.
Some states are passing legislation to eliminate chlorinated compounds as a biocide, Duquette says. The Navy, which currently uses chlorine to prevent fouling on ships, is being pushed by many to switch to ozone. Because of concern about increased corrosion, the Navy asked Duquette to take make an in-depth study.
There would be a lot of advantages over chlorine, including the ability to generate ozone on site, Duquette said. "But a great deal of care would be needed."
"Stainless steel may prove to be a problem if used in an ozonated seawater solution," Duquette said.
In addition, Teflon, now used for many gaskets, would create particular difficulties, Duquette said. The material is not inert in ozone. Instead, it releases fluorine, creating hydrofluoric acid, which corrodes virtually all alloys.
Contact: David Duquette (518) 276-6448, duqued@rpi.edu
