Texas A&M Chemist Conducting Research on Polymer-Coated Nanoparticles and Nanocages for Diverse Applications

Texas A&M University chemist Karen L. Wooley and her team of researchers are seeing big solutions in small packages -- specifically, synthetic nanoparticles custom-designed to deliver a world of diverse opportunities ranging from materials to medicine.

"The field of materials has always been something that I've been interested in," Wooley said. "As a chemist, I had an interest in making matter that no one had ever made before. But at the same time, I wanted that matter to do something and to serve a purpose, to benefit society in some way. Polymer materials allow for that to happen."

Wooley, a distinguished professor of chemistry and holder of the W.T. Doherty-Welch Chair in Chemistry since 2009, is widely respected as a top international chemist in the burgeoning field of materials and polymer chemistry, as evidenced by her recent selection as the first woman to receive the American Chemical Society Award in Polymer Chemistry. The prestigious accolade recognizes outstanding fundamental contributions and achievements toward addressing global needs for advanced polymer systems and materials.

Her 30-member research group spans seven distinct project areas and has an annual budget of more than $1.5 million. The name of its world-changing game? Organic nanomaterials-based chemistry focused on creating polymer-coated nanoparticles and nanocages 100 times thinner than a single human hair which can absorb, adhere to or encapsulate a variety of substances and materials to address specific needs and problems.

"Plastics are the most commonly recognized form of polymer material," Wooley said. "Garbage bags are made out of polymers; the plastic top of a coffee cup is made out of polymers. In my laboratory, we work to develop complex polymer materials to incorporate function in them beyond what we would consider as a typical kind of polymer material that might serve as containment unit. We incorporate functionalities that allow them to be utilized in various kinds of applications, from anti-biofouling coatings for the marine environment to nanoparticles to deliver drugs to treat cancer, lung infections and reoccurring urinary tract infections."

On any given day, graduate students and postdocs as well as undergraduates are working at various stages of research and development for several different types of target materials, both nanoscopic and macroscopic, hoping to find the next viable "nano-solution" for any number of situations and purposes. What starts as small molecules progresses to increasingly complex nanostructures with widespread applications, including infectious disease treatment and cancer therapy, magnetic oil recovery and clean-up systems, anti-biofouling and anti-icing coatings, natural product-based engineering materials and degradable polymers, and advanced photoresist technologies for the construction of microelectronics devices.

"The objects are larger than typical molecules but smaller than macroscopic or microscopic objects," Wooley said. "So, they're much smaller than a cell -- more on the size scale of a protein, for instance. Being able to produce synthetic materials that are on the size scale of, say, proteins or viruses, means we can incorporate into those objects functions that can operate on biological systems in a similar way, leading to all kinds of possibilities."

At the moment, tiny, reusable, oil-absorbing nanoparticles being refined in Wooley's laboratory are making a big splash in their potential effectiveness in cleaning up oil spills, including the 2010 Deepwater Horizon disaster in the Gulf of Mexico -- one of 20,000 spills reported annually in the United States. The magnetic particles, detailed in a recent paper published in the journal ACS Nano, feature an iron oxide core surrounded by a polymer mesh shell -- a mixture of Styrofoam and the absorbent material found in baby diapers. Each magnetic-polymer nanoparticle can absorb more than 10 times its own weight in crude oil, which still lingers beneath the Gulf's surface, both in the water and mixed in the sand at its floor. The polymer coating mixes with the water to take the "nano-sponges" below the surface, where they soak up oil and change color from light tan to black. Buoyed by the Styrofoam and captured oil, they eventually float to the surface, where they are collected with a magnet and washed with ethanol to remove the oil and ready them for reuse.

While Wooley notes they are improbable as a sole solution, given that soaking up a barrel of crude oil (roughly 300 pounds) would require about 30 pounds of nanoparticles, she says they certainly could be effective in a clean-up role after employing more traditional methods to mop up the majority of the spill. (Read more about the process here.)

"My laboratory has always had a balance of fundamental basic science investigations that have allowed us to create materials that have never been created before and then to study their properties," Wooley said. "The process we use is going from an idea to a hypothesis to a design of a material that logically would meet that hypothesis. Once we understand how the materials behave and how their composition and structure relates to their properties, then we can define potential applications for those materials."

Sometimes such materials and applications are the result of accident -- the happy kind. For instance, while working to synthesize polymers with protein-like properties, Wooley's group unexpectedly found that they form gels. Through further investigation, they learned these gels are based upon various amino acids and polypeptides -- the basic components of proteins and natural materials that, when synthetically linked together in unique sequences, can produce gel-like materials with fine-tuned, targeted properties, such as novel tissue engineering scaffolds capable of growing customized artificial tissue, depending on the repair or purpose needed.

"Most of our nanoparticles are based on degradable polymers, and we wanted to shift from what were polyesters to polyamides to make protein-like synthetic particles," Wooley said. "As we were synthesizing those polymers, they gelled, which was completely surprising to us. We are looking into using these gels -- some of which are very stiff and some that are very flexible -- for tissue engineering scaffolds to grow artificial tissues that might then allow for implantation and treatment of various kinds of diseases, from artificial liver for transplant to skin-graft applications."

Since 2005, Wooley has served as both a principal and co-principal investigator in a to-date $23 million National Heart Lung and Blood Institute-supported Program of Excellence in Nanotechnology (PEN) involving five collaborating institutions that has produced promising results using targeted nanoparticles to deliver anti-microbial agents to improve treatment for lung infections.

"We've found that when anti-microbial agents are loaded to our nanoparticles, they have a greater than ten-fold increase in the efficacy of lung-infection treatment, in comparison to the small drug alone and without the particle," Wooley said. "Moreover, by combining our gelatinous polypeptide materials with some of our nanoparticle anti-microbials, one can imagine additional possibilities in the design of specialized tissue scaffolds, for instance, for burn victims to prevent bacterial infection that would occur as the skin grows into the gelatinous material and replaces it."

Another broad, news-making area under further investigation in the Wooley lab stems from the group's ongoing emphasis on sustainable polymers and the use of natural products-based materials as a potential replacement for the controversial chemical BPA, short for bisphenol-A, found in many plastics, canned food linings and even cash-register receipts and shown to have weak, hormone-like effects linked to possible fertility and cancer issues in both women and men.

"The additional surprising feature, beyond the expected mechanical properties, was a high fluorescence emission activity," Wooley said. "Obviously, these materials are exciting for their environmental reasons but also for their added built-in optical properties, which could prove helpful in environmental sensing and other respects down the road."

It's precisely that unexpected and unexplored potential which never fails to excite and inspire Wooley, who says it's highly rewarding, not only to work with students, but also to observe and to assist in the overall discovery process -- a critical phenomenon that relies on multidisciplinary approaches at the crossroads of basic and applied efforts underpinned by external funding and support, from federal agencies to industry sources.

"I think it's really important to have some efforts that are basic, because those advance knowledge in general and they allow for evolution of new kinds of products that one wouldn't really be able to predict what the characteristics would be," Wooley said. "The National Science Foundation and The Welch Foundation are critical in their support of our basic chemistry studies. Then, in the other sense is the applied area, where we can take that knowledge that's generated and apply it to a system that ultimately can benefit society. We receive significant amounts of funding from the Office of Naval Research and the National Institutes of Health to perform our research, and there should be some payback to that and some creation of intellectual property and products that could ultimately transfer to the marketplace and be used in everyday life.

"Because polymer materials are so important in products that people encounter every day, there's a huge connection with industry. We are uniquely familiar with industry's current needs, what they can and can't offer in terms of materials, and where there might be opportunities for us to design some materials that could meet their needs, including some they maybe can't imagine themselves. In turn, they give us ideas for materials we can develop in the laboratory but aren't able to translate to products without their help. These connections provide us with opportunity to design new systems and also then, ultimately, to have a potential outlet for producing a tangible product."

To learn more about Wooley and her research, visit http://www.chem.tamu.edu/faculty/wooley.

Source: http://www.science.tamu.edu