‘Nightmare bacteria:’ Michigan Engineers discuss how to combat antibiotic resistance Drug-resistant bugs are on the rise and new approaches are needed.

Health officials at the U.S. Centers for Disease Control and Prevention earlier this month said they are seeing rising cases of “nightmare bacteria” that show strong resistance to antibiotics. More than 200 cases were reported in the last year alone, and across every state in the U.S.

“Unusual resistance germs—which are resistant to all or most antibiotics tested and are uncommon or carry special resistance genes—are constantly developing and spreading,” the CDC said.

A particular concern is the number of cases that crop up in hospitals and nursing homes where IVs, catheters and medical implants—all particularly susceptible to infection—are common.

“Antibiotic resistance is one of the most important public health problems of the 21st century,” said Angela Violi, professor of mechanical engineering and chemical engineering at U-M.

Violi is one of many researchers at Michigan Engineering who are are tackling this issue from a variety of angles. Some are exploring new ways to combine antibiotics to stay one step ahead of the bugs. Others are looking beyond antibiotics—to nanoparticles.

Nicholas Kotov, the Joseph B. and Florence V. Celka professor of chemical engineering, is part of a team researching the use of nanoparticles as a new form of antibiotics. Nanoparticles can be shaped specifically to get past a bacterium’s defenses and shut down processes essential to its survival. Nanoparticles can also be used to coat medical implants in order to prevent infection from drug resistant bacteria.

“New methods of suppressing or otherwise diminishing the health impact of antibiotic resistant bacteria are needed,” Kotov said. “Molecular and nanoscale engineering of inorganic nanoparticles offers this opportunity by utilizing the latest experimental and computational tools targeting the bacteria where it does not expect.”

Violi helps identify the best pathways for utilizing nanoparticles to attack antibiotic resistant bacteria.

“Potentially, all it takes is a single mutated bacterium to render an antibiotic useless for that infection,” she said. “When that mutant cell replicates, it will pass on its resistant phenotype to its daughter cells, and so on.

“At that point part of the replicating bacteria will be drug resistant: the drug will kill only those cells that do not have the newly evolved drug-resistance capacity. Eventually, the entire bacterial population will become resistant to the prescribed antibiotic.

“It is only when antibiotics are used that drug-resistant phenotypes have a selective advantage and survive.

“Nano and chemical engineering approaches provide unparalleled flexibility to control the composition, size, shape, surface chemistry, and functionality of nanostructures that can be used to develop a new generation of modified materials or to coat existing solid surfaces to fight bacteria.”

Professor working on a computer in the lab
Sriram Chandrasekaran, an assistant professor of biomedical engineering, uses computer simulations to develop strategies for using current antibiotics in combination as well as roadmaps for creating new classes of antibiotics. Photo by Joseph Xu

Sriram Chandrasekaran, an assistant professor of biomedical engineering, approaches drug resistant bacteria from a different angle. He and his team study proteins and analyze their behaviors via computer simulations to develop strategies for using current antibiotics in combination as well as roadmaps for creating new classes of antibiotics.

“In addition to better stewardship of antibiotics, we also need to come up with smarter treatment strategies that can reduce the rise of resistance,” Chandrasekaran said.

“For example, our lab and others are designing combinations of antibiotics that are more effective in retarding the evolution of drug resistance compared to using drugs individually. Such combinations of FDA approved drugs can also reach the clinic faster than developing new drugs from scratch.

“We are also developing computer algorithms that can identify the most optimal combination of drugs for a specific strain of pathogen. Overall, what we can learn from this crisis is that we cannot take antibiotics for granted. We have to keep investing on new treatments as bacteria will always eventually evolve resistance to whatever new drug we throw at it.”


High-tech labels to fight counterfeiting

By Kate McAlpine
Michigan Engineering

An outline of Marilyn Monroe's iconic face appeared on the clear, plastic film when a researcher fogs it with her breath.

Terry Shyu, a doctoral student in chemical engineering at the University of Michigan, was demonstrating a new high-tech label for fighting drug counterfeiting. While the researchers don't envision movie stars on medicine bottles, they used Monroe's image to prove their concept.

The iconic face of Marilyn Monroe is revealed in the fog of breath from doctoral student Terry Shyu.

The iconic face of Marilyn Monroe is revealed in the fog of breath from doctoral student Terry Shyu. Photo: Joseph Xu

Counterfeit drugs, which at best contain wrong doses and at worst are toxic, are thought to kill more than 700,000 people per year. While less than 1 percent of the U.S. pharmaceuticals market is believed to be counterfeit, it is a huge problem in the developing world where as much as a third of the available medicine is fake.

To fight back against these and other forms of counterfeiting, researchers at U-M and in South Korea have developed a way to make labels that change when you breathe on them, revealing a hidden image.

"One challenge in fighting counterfeiting is the need to stay ahead of the counterfeiters," said Nicholas Kotov, the Joseph B. and Florence V. Cejka Professor of Chemical Engineering who led the Michigan effort.

The method requires access to sophisticated equipment that can create very tiny features, roughly 500 times smaller than the width of a human hair. But once the template is made, labels can be printed in large rolls at a cost of roughly one dollar per square inch. That's cheap enough for companies to use in protecting the reputation of their products—and potentially the safety of their consumers.

"We use a molding process," Shyu said, noting that this inexpensive manufacturing technique is also used to make plastic cups.

The labels work because an array of tiny pillars on the top of a surface effectively hides images written on the material beneath. Shyu compares the texture of the pillars to a submicroscopic toothbrush. The hidden images appear when the pillars trap moisture.

"You can verify that you have the real product with just a breath of air," Kotov said. The simple phenomenon could make it easy for buyers to avoid being fooled by fake packaging.

Previously, it was impossible to make nanopillars through cheap molding processes because the pillars were made from materials that preferred adhering to the mold rather than whatever surface they were supposed to cover. To overcome this challenge, the team developed a special blend of polyurethane and an adhesive.

The liquid polymer filled the mold, but as it cured, the material shrunk slightly. This allowed the pillars to release easily. They are also strong enough to withstand rubbing, ensuring that the label would survive some wear, such as would occur during shipping. The usual material for making nanopillars is too brittle to survive handling well.

The team demonstrated the nanopillars could stick to plastics, fabric, paper and metal, and they anticipate that the arrays will also transfer easily to glass and leather.

"You can verify that you have the real product with just a breath of air." Nicholas Kotov

Following seed funding from the National Science Foundation's Innovation Corps program and DARPA's Small Business Technology Transfer program, the university is pursuing patent protection for the intellectual property and is seeking commercialization partners to help bring the technology to market.

This work is reported in Advanced Materials in a paper titled, "Shear-Resistant Scalable Nanopillar Arrays with LBL-Patterned Overt and Covert Images."

It was funded by the Defense Advanced Research Projects Agency; the National Science Foundation; the Korea Ministry of Science, Information and Communications Technology and Future Planning; the Ministry of Knowledge Economy; and the Korea Evaluation Institute of Industry Technology.

Spiky “hedgehog particles” for safer paints, fewer VOC emissions

By Gabe Cherry
Michigan Engineering

A new process that can sprout microscopic spikes on nearly any type of particle may lead to more environmentally friendly paints and a variety of other innovations.

Made by a team of University of Michigan engineers, the “hedgehog particles” are named for their bushy appearance under the microscope. Their development is detailed in a paper published in the Jan. 29 issue of Nature.

The new process modifies oily, or “hydrophobic” particles, enabling them to disperse easily in water. It can also modify water-soluble, or “hydrophilic” particles, enabling them to dissolve in oil or other oily chemicals.

A hedgehog particle magnified by an electron microscope. Photo by: Joong Hwan Bahng

A hedgehog particle magnified by an electron microscope. Photo by: Joong Hwan Bahng

two people

A hedgehog particle magnified by an electron microscope. Photo by: Joong Hwan Bahng


The unusual behavior of the hedgehog particles came as something of a surprise to the research team, said Nicholas Kotov, the Joseph B. and Florence V. Cejka Professor of Engineering.

“We thought we’d made a mistake,” Kotov said. “We saw these particles that are supposed to ‘hate’ water dispersing in it and we thought maybe the particles weren’t hydrophobic, or maybe there was a chemical layer that was enabling them to disperse. But we double-checked everything and found that, in fact, these particles defy the conventional chemical wisdom that we all learned in high school.”

The team found that the tiny spikes made the particles repel each other more and attract each other less. The spikes also dramatically reduce the particles’ surface area, helping them to diffuse more easily.

One of the first applications for the particles is likely to be in paints and coatings, where toxic volatile organic compounds (VOCs) like toluene are now used to dissolve pigment. Pigments made from hedgehog particles could potentially be dissolved in non-toxic carriers like water, the researchers say.

This would result in fewer VOC emissions from paints and coatings, which the EPA estimates at over eight million tons per year in the United States alone. VOCs can cause a variety of respiratory and other ailments and also contribute to smog and climate change. Reducing their use has become a priority for the Environmental Protection Agency and other regulatory bodies worldwide.

Spikes grown on the surface of nano-scale particles enable a host of innovative possibilities.

“VOC solvents are toxic, they’re flammable, they’re expensive to handle and dispose of safely,” Kotov said. “So if you can avoid using them, there’s a significant cost savings in addition to environmental benefits.”

While some low- and no-VOC coatings are already available, Kotov said hedgehog particles could provide a simpler, more versatile and less expensive way to manufacture them.

For the study, the team created hedgehog particles by growing zinc oxide spikes on polystyrene microbeads. The researchers say that a key advantage of the process is its flexibility; it can be performed on virtually any type of particle, and makers can vary the number and size of the spikes by adjusting the amount of time the particles sit in various solutions while the protrusions are growing. They can also make the spikes out of materials other than zinc oxide.

A hedgehog particle magnified by an electron microscope. Photo by: Joong Hwan Bahng

U-M chemical engineering student Joong Hwan Bahng shows a vial of hydrophobic hedgehog particles dispersed in water. Photo by: Joseph Xu

two people

U-M chemical engineering student Joong Hwan Bahng shows a vial of hydrophobic hedgehog particles dispersed in water. Photo by: Joseph Xu


“I think one thing that’s really exciting about this is that we’re able to make such a wide variety of hedgehog particles,” said Joong Hwan Bahng, a chemical engineering doctoral student. “It’s very controllable and very versatile.”

The researchers say the process is also easily scalable, enabling hedgehog particles to be created “by the bucketful,” according to Kotov. Further down the road, Kotov envisions a variety of other applications, including better oil dispersants that could aid in the cleanup of oil spills and better ways to deliver non-water-soluble prescription medications.

“Anytime you need to dissolve an oily particle in water, there’s a potential application for hedgehog particles,” he said. “It’s really just a matter of finding the right commercial partners. We’re only just beginning to explore the uses for these particles, and I think we’re going to see a lot of applications in the future.”

Kotov is also a professor of chemical engineering, biomedical engineering, materials science and engineering and macromolecular science and engineering. The paper is titled “Anomalous Dispersions of Hedgehog Particles” and based upon work partially supported by the Center for Solar and Thermal Energy Conversion, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Support has also been provided by the NSF and the US Department of Defense.

Traces of DNA exposed by twisted light

By Kate McAlpine
Michigan Engineering

Structures that put a spin on light reveal tiny amounts of DNA with 50 times better sensitivity than the best current methods, a collaboration between the University of Michigan and Jiangnan University in China has shown. Highly sensitive detection of DNA can help with diagnosing patients, solving crimes and identifying the origins of biological contaminants such as a pathogen in a water supply.

“It really does not matter where the target DNA is from,” said Nicholas Kotov, the Joseph B. and Florence V. Cejka Professor of Chemical Engineering at U-M. “In order to detect a specific DNA, we just need to know a small portion of its sequence.”

Current DNA analysis methods rely on copying segments of a strand of DNA. The process unzips the double helix and then short, lab-made ‘primer’ DNA strands attach to each half of the original DNA. These primers kick-start the copying process, using the unzipped DNA as a template. Targeted segments of DNA can be replicated in this way, doubling every cycle. If enough DNA is produced before copying errors become a major problem, then further analysis can show whether the sample matches a suspect, for example.
DNA detection
Yoonseob Kim, a chemical engineering graduate student in the Kotov lab, works with a solution of gold nanoparticles. From the solution's red color, he knows that the nanoparticles are not bound together.But if the primers were very selective for the suspected DNA sequence, then a match could be determined by simply detecting whether the DNA had copied or not. Studies revealed that small amounts of DNA could be observed when spherical gold nanoparticles were attached to the primers. If the DNA matched suspicions, strings of particles bound together with DNA would form in the replication process. The nanoparticle solution would change color from red to blue, due to the way the strings of particles interact with light.

“Impressive detection limits were attained for short DNAs with nanoparticles, however, not for long DNA,” Kotov said.

The problem, he explained, is that if the particles are further apart than a few nanometers, or millionths of a millimeter, “they do not interact strongly and the blue color does not happen.” Longer strands are needed to differentiate between species and individuals with greater accuracy.

“If the strands are too short, you could mix up the DNA of a killer with that of the friend’s dog—or a signature of malignant stomach cancer with the piece of a chicken burrito,” Kotov said.

He and his partner Chuanlai Xu, a professor of food science and technology at Jiangnan University in China, led an effort to see whether a more subtle optical change would hold up to longer distances.
Twisted ladders
Rather than using spherical nanoparticles, the team started with nanorods, shaped like tiny Mike and Ike candies, about 62 nanometers long and 22 nanometers in diameter. They attached the primer DNA to the sides of these.

When nanorods line up, they tend to misalign by about 10 degrees. After a few rounds of copying, the gold and DNA structures resembled twisted rope ladders. Light passing through the spiral of golden spokes reacted by rotating.

“The light can be rotated even when the nanorods are far away from each other,” Kotov said. “This gives our methods a tremendous advantage in sensitivity for long DNA strands.”

The rotation happens because light is composed of electric and magnetic waves moving in tandem, and electric and magnetic fields exert forces on charged particles that have freedom to move, such as electrons in metals. The electrons in gold respond very well to the frequency of visible light waves, so they begin to move back and forth in the gold, synced with the light. This effect is a two-way street: the moving electrons in the gold can also affect the light waves.

Kotov compares the light to a rope with ripples running through it. “Now imagine that the air around the rope can move more easily along certain directions,” Kotov said.

For light passing through the gold nanorods, it’s easiest if the electric wave moves up and down the length of the nanorods, so the light rotates as it moves from nanorod to nanorod and continues twisting after it leaves the structure. And depending on whether the light starts out rotating clockwise or counterclockwise, it feels the twist from the nanorods most at different wavelengths.

“For analytical purposes, this is a gift,” Kotov said. The two peaks in the amount of twisting for clockwise and counterclockwise light can be added together, which makes for a stronger signal and allows the method to identify a match with smaller amounts of DNA.

“The strength of the rotation reaches maximum when the gap between nanorods is 20 nanometers, which is exactly what we need for the detection of long, selective and species-specific DNA strands,” Kotov said. “The calculations presented show that we can potentially increase the sensitivity even more in the future and to even longer DNAs.”

The paper, “Attomolar DNA detection with Chiral Nanorod Assemblies,” was published in Nature Communications on Oct. 28. Kotov is a professor of chemical engineering, biomedical engineering, materials science and engineering, and macromolecular science and engineering.

This work was funded by the U.S. Department of Energy and National Science Foundation, National Natural Science Foundation of China, China Ministry of Science and Technology, and grants from the Ministries of Finance and Education in Jiangsu Province, China.

Meningitis: Steps to prevent future contamination

U-M researchers discuss how a recent outbreak of fungal meningitis distributed through spinal steroid injections has once again brought to light the difficulty of compounding pharmaceutical companies to maintain quality control over their products. Professors Kotov and Wang explain how a combination of better oversight and easier testing methods could ultimately help prevent issues like this in the future.

ABOUT THE PROFESSOR: Henry Wang is a professor of Chemical Engineering and Biomedical Engineering at the University of Michigan. His research interests include the global healthcare sector, comprised of pharmaceutical, biotechnology, medical device companies, regulatory agencies such as FDA, healthcare providers, insurers and consumers.

Nicholas A. Kotov is the Joseph B. and Florence C. Cejka Professor of Engineering. He is committed to engaging in the “most creative, forward looking, and unorthodox scientific and engineering discoveries.” He runs The Kotov Lab at the University of Michigan.

Stretchable conductors

Polyurethane studded with gold nanoparticles can conduct electricity even when stretched, Michigan engineers have discovered. This feat could pave the way for flexible electronics and gentler medical devices. The nanoparticles start out randomly arranged, but they drift into wire-like formations as the material is stretched.

About the Professor: Nicholas Kotov is the Joseph B. and Florence V. Cejka Professor of Engineering and a professor of chemical engineering, biomedical engineering, materials science and engineering and macromolecular science and engineering at the University of Michigan College of Engineering. His research interests include the 3D self-organization of nanoparticles and cells, and in using these principles to improve technologies and health care.