Now, researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a single-material, single-stimuli microstructure that can outmaneuver even living cilia. These programmable, micron-scale structures could be used for a range of applications, including soft robotics, biocompatible medical devices, and even dynamic information encryption.

The research is published in Nature.

“Innovations in adaptive self-regulated materials that are capable of a diverse set of programmed motions represent a very active field, which is being tackled by interdisciplinary teams of scientists and engineers,” said Joanna Aizenberg, the Amy Smith Berylson Professor of Materials Science and Professor of Chemistry & Chemical Biology at SEAS and senior author of the paper. “Advances achieved in this field may significantly impact the ways we design materials and devices for a variety of applications, including robotics, medicine and information technologies.”

Unlike previous research, which relied mostly on complex multi-component materials to achieve programmable movement of reconfigurable structural elements, Aizenberg and her team designed a microstructure pillar made of a single material — a photoresponsive liquid crystal elastomer. Because of the way the fundamental building blocks of the liquid crystal elastomer are aligned, when light hits the microstructure, those building blocks realign and the structure changes shape.

As this shape change occurs, two things happen. First, the spot where the light hits becomes transparent, allowing the light to penetrate further into the material, causing additional deformations. Second, as the material deforms and the shape moves, a new spot on the pillar is exposed to light, causing that area to also change shape.

This feedback loop propels the microstructure into a stroke-like cycle of motion.

“This internal and external feedback loop gives us a self-regulating material. Once you turn the light on, it does all its own work,” said Shucong Li, a graduate student in the Department of Chemistry and Chemical Biology at Harvard and co-first author of the paper.

When the light turns off, the material snaps back to its original shape.

The material’s specific twists and motions change with its shape, making these simple structures endlessly reconfigurable and tunable. Using a model and experiments, the researchers demonstrated the movements of round, square, L- and T-shaped, and palm-tree-shaped structures and laid out all the other ways the material can be tuned.

“We showed that we can program the choreography of this dynamic dance by tailoring a range of parameters, including illumination angle, light intensity, molecular alignment, microstructure geometry, temperature, and irradiation intervals and duration,” said Michael M. Lerch, a postdoctoral fellow in the Aizenberg Lab and co-first author of the paper.

To add another layer of complexity and functionality, the research team also demonstrated how these pillars interact with each other as part of an array.

“When these pillars are grouped together, they interact in very complex ways because each deforming pillar casts a shadow on its neighbor, which changes throughout the deformation process,” said Li. “Programming how these shadow-mediated self-exposures change and interact dynamically with each other could be useful for such applications as dynamic information encryption.”

“The vast design space for individual and collective motions is potentially transformative for soft robotics, micro-walkers, sensors, and robust information encryption systems,” said Aizenberg.

The paper was co-authored by James T. Waters, Bolei Deng, Reese S. Martens, Yuxing Yao, Do Yoon Kim, Katia Bertoldi, Alison Grinthal and Anna C. Balazs. It was supported in part by the U.S. Army Research Office, under grant number W911NF-17-1-0351 and the National Science Foundation through the Harvard University Materials Research Science and Engineering Center under award DMR-2011754.

The study, published in the Ecological Society of America’s journal, Ecology, said these declines are expected not only because of climate-related stressors, but also because of the expanding influence of new invasive predators whose impacts are occurring much farther up the estuary.

“Our study found that climate change and biological invasions can interact in coastal estuaries in unpredictable ways,” said lead author Benjamin Rubinoff, a Ph.D. student in the UC Davis Department of Environmental Science and Policy when the research was conducted. “This increased risk of predation makes it difficult for native species that are already dealing with increasingly stressful environmental conditions.”

The researchers tested the influence of environmental stress and predation on sessile invertebrates in Tomales Bay, California during the summer of 2019. Sessile invertebrates are animals without backbones that attach to reefs or seagrasses and barely move, such as bryozoans and ascidians. Their predators include sea stars, crabs, and snails, among other species.

Estuaries a unique environment

In estuaries, changes in salinity and water temperature strongly influence the distribution of many invertebrate species, from mussels to crabs to sea squirts. These gradients can be especially steep in the estuaries of California, which are highly vulnerable to climate change and invasive species.

In most estuaries, stressful conditions for marine organisms such as low salinity and high temperature increase as you move inland from the ocean. With increased stress, native predators typically consume fewer prey.

But the study found that biological invasions are changing this equation, since many non-native predators tolerate stress better than native ones. So highly stressed native prey species are subjected to large numbers of stress-tolerant invaders that compete with them for resources, if not consume them.

Stressful situation

“The stress gradients typical of West Coast estuaries are being rapidly altered by climate change,” said co-leading author Edwin “Ted” Grosholz, a UC Davis professor with the Department of Environmental Science and Policy and the Bodega Marine Laboratory. “These changing gradients are scrambling the historical predator-prey landscape, creating novel matchups and putting native prey at much higher risk from invaders.”

Grosholz adds that such changes are hard to predict, and only experimental studies like this can disentangle the interacting effects of climate change and invasions on struggling native species.

For the study, the researchers deployed square plates made of PVC with different caging treatments at three locations across Tomales Bay from June to October 2019. Some plates were protected from predators while others allowed predator access. At the end of the period, the researchers brought the plates back into the lab and identified organisms using a microscope and determined percent cover.

The study was funded by grants from UC Davis and Point Reyes National Seashore Association.

Story Source:

Materials provided by University of California – Davis. Original written by Kat Kerlin. Note: Content may be edited for style and length.

A new study suggests that women who get recurrent UTIs may be caught in a vicious cycle in which antibiotics given to eradicate one infection predispose them to develop another. The study, by researchers at Washington University School of Medicine in St. Louis and the Broad Institute of MIT and Harvard, showed that a round of antibiotics eliminates disease-causing bacteria from the bladder but not from the intestines. Surviving bacteria in the gut can multiply and spread to the bladder again, causing another UTI.

At the same time, repeated cycles of antibiotics wreak havoc on the community of helpful bacteria that normally live in the intestines, the so-called gut microbiome. Similar to other disorders in which gut microbes and the immune system are linked, women with recurrent UTIs in the study had less diverse microbiomes that were deficient in an important group of bacteria that helps regulate inflammation, and a distinct immunological signature in their blood indicative of inflammation.

The study is published May 2 in Nature Microbiology.

“It’s frustrating for women who are coming in to the doctor with recurrence after recurrence after recurrence, and the doctor, who’s typically male, gives them advice about hygiene,” said co-senior author Scott J. Hultgren, PhD, the Helen L. Stoever Professor of Molecular Microbiology at Washington University. “That’s not necessarily what the problem is. It’s not necessarily poor hygiene that’s causing this. The problem lies in the disease itself, in this connection between the gut and the bladder and levels of inflammation. Basically, physicians don’t know what to do with recurrent UTI. All they have is antibiotics, so they throw more antibiotics at the problem, which probably just makes things worse.”

Most UTIs are caused by Escherichia coli (E. coli) bacteria from the intestines that get into the urinary tract. To understand why some women get infection after infection and others get one or none, Hultgren teamed up with Broad Institute scientists Ashlee Earl, PhD, the senior group leader for the Bacterial Genomics Group at Broad and the paper’s co-senior author, and Colin Worby, PhD, a computational biologist and the paper’s lead author.

The researchers studied 15 women with histories of recurrent UTIs and 16 women without. All participants provided urine and blood samples at the start of the study and monthly stool samples. The team analyzed the bacterial composition in the stool samples, tested the urine for the presence of bacteria, and measured gene expression in blood samples.

Over the course of a year, 24 UTIs occurred, all in participants with histories of repeated UTIs. When participants were diagnosed with a UTI, the team took additional urine, blood and stool samples.

The difference between the women who got repeated UTIs and those who didn’t, surprisingly, didn’t come down to the kind of E. coli in their intestines or even the presence of E. coli in their bladders. Both groups carried E. coli strains in their guts capable of causing UTIs, and such strains occasionally spread to their bladders.

The real difference was in the makeup of their gut microbiomes. Patients with repeat infections showed decreased diversity of healthy gut microbial species, which could provide more opportunities for disease-causing species to gain a foothold and multiply. Notably, the microbiomes of women with recurrent UTIs were particularly scarce in bacteria that produce butyrate, a short-chain fatty acid with anti-inflammatory effects.

“We think that women in the control group were able to clear the bacteria from their bladders before they caused disease, and women with recurrent UTI were not, because of a distinct immune response to bacterial invasion of the bladder potentially mediated by the gut microbiome,” Worby said.

The findings highlight the importance of finding alternatives to antibiotics for treating UTIs.

“Our study clearly demonstrates that antibiotics do not prevent future infections or clear UTI-causing strains from the gut, and they may even make recurrence more likely by keeping the microbiome in a disrupted state,” Worby said

Hultgren has long worked on finding innovative therapies to eradicate disease-causing strains of E. coli from the body while sparing the rest of the bacterial community. His research forms the basis of an experimental drug based on the sugar mannosideand an investigational vaccine, both of which are being tested in people. Another strategy would be to rebalance the microbiome through fecal transplants, probiotic foods or other means.

“This is one of the most common infections in the United States, if not the world,” Hultgren said. “A good percentage of these UTI patients go on to get these chronic recurrences, and it results in decreased quality of life. There is a real need to develop better therapeutics that break this vicious cycle.”