(Press-News.org) CAMBRIDGE, Mass. — The flexible properties of hydrogels — highly absorbent, gelatinous polymers that shrink and expand depending on environmental conditions such as humidity, pH and temperature — have made them ideal for applications from contact lenses to baby diapers and adhesives.
In recent years, researchers have investigated hydrogels' potential in drug delivery, engineering them into drug-carrying vehicles that rupture when exposed to certain environmental stimuli. Such vesicles may slowly release their contents in a controlled fashion; they may even contain more than one type of drug, released at different times or under various conditions.
However, it's difficult to predict just how hydrogels will rupture, and up until now it's been difficult to control the shape into which a hydrogel morphs. Nick Fang, an associate professor of mechanical engineering at MIT, says predicting how hydrogels transform could help in the design of more complex and effective drug-delivery systems.
"What kind of shape is more efficient for flowing through the bloodstream and attaching to a cell membrane?" Fang says. "With proper knowledge of how gels swell, we can start to generate patterns at our wish."
Fang and postdoc Howon Lee, along with colleagues at Arizona State University, are studying the mechanics of shape-shifting hydrogels: looking for relationships between a hydrogel structure's initial shape, and the medium in which it transforms, in order to predict its final shape. In a paper to appear in Physical Review Letters, the researchers report that they can now create and predict complex shapes — including star-shaped wrinkles and waves — from hydrogels.
The findings may provide an analytical foundation for designing intricate shapes and patterns from hydrogels.
From PowerPoint to 3-D
To create various hydrogel structures, Fang and his collaborators used an experimental setup that Fang helped invent in 2000. In this setup, researchers project PowerPoint slides depicting various shapes onto a beaker of photosensitive hydrogel, causing it to assume the shapes depicted in the slides. Once a hydrogel layer forms, the researchers repeat the process, creating another hydrogel layer atop the first and eventually building up a three-dimensional structure in a process akin to 3-D printing.
Using this technique, the team created cylindrical shapes of various dimensions, suspending the structures in liquid to observe how they transformed. All cylinders morphed into wavy, star-shaped structures, but with characteristic differences: Short, wide cylinders evolved into structures with more wrinkles, whereas tall, slender cylinders transformed into less wrinkly shapes.
Fang concluded that as a hydrogel expands in liquid, various forces act to determine its final shape.
"This kind of tubular structure has two ways of deforming," Fang says. "One is that it can bend, and the other is that it can buckle, or squeeze. So these two modes actually compete with each other, and the height tells how stiff it is to bending, while the diameter tells how easy it is to stretch."
From their observations, the team drew up an analytical model representing the relationship between a structure's initial height, diameter and thickness and its ultimate shape. Fang says the model may help scientists design specific shapes for more efficient drug-delivery systems.
Wrinkling naturally
Fang says the group's results may also help explain how complex patterns are created in nature. He points to peppers — whose cross-sections can vary widely in shape — as a case in point: Small, spicy peppers tend to be triangular in cross-section, whereas larger bell peppers are more star-shaped and wavy. Fang speculates that what determines a pepper's shape, and its number of waves or wrinkles, is its height and diameter.
Fang says the same principle may explain other intricate shapes in nature — from the creases in the brain's cortex to wrinkles in fingerprints and other biological tissues that "leverage mechanical instability to create a wealth of complex patterns."
The team plans to study and predict more hydrogel shapes in the future to help scientists design drug vesicles that transform predictably.
INFORMATION:
The research was supported by the National Science Foundation and Lawrence Livermore National Laboratory. Collaborators from Arizona State University include Jiaping Zhang and Hanqing Jiang.
Written by: Jennifer Chu, MIT News Office
END
Astronomers from Queen's University Belfast have gathered the most direct evidence yet of a supermassive black hole shredding a star that wandered too close. The Queen's astronomers are part of the Pan-STARRS international team, whose discovery has been published in the journal Nature today (Wed, 2 May).
Supermassive black holes, weighing millions to billions times more than the Sun, lurk in the centers of most galaxies. These hefty monsters lie quietly until an unsuspecting 'victim', such as a star, wanders close enough to get ripped apart by their powerful gravitational ...
When it comes to the food used to raise fish in aquaculture "farms," it seems that you may get what you pay for. In a new study,* researchers from the National Institute of Standards and Technology (NIST) and the South Carolina Department of Natural Resources (SCDNR) looked at the health effects of raising farmed fish on a diet incorporating less than the usual amount of fishmeal—a key but expensive component of current commercial fish food products. They learned that reduced fishmeal diets may be cheaper, but the fish were less healthy.
Commercial aquaculture is one ...
It began in the eighties, in the days of taffeta prom dresses and big hair rock bands. During this decade, use of hand held video cameras became commonplace for most families. Now digital devices from cameras to iPhones have video capabilities. With improvements in technology almost everyone has a video recording device within reach at all times.
Occasionally, a recording of an infant's delivery may catch a misdiagnosis or delay in intervention -- sometimes these medical mistakes have resulted in a tragic, yet preventable birth injury.
The use of these video recordings ...
As of May 1, 2012, the military has two new drugs in its testing repertoire. Henceforth, service members may be tested for hydrocodone and benzodiazepines, two of the most commonly abused prescription drugs on the market.
Servicemen and servicewomen are randomly tested for drugs at least once a year. A positive test result could mean serious legal complications, putting a servicemember anywhere in the chain of command in need of military drug offense lawyers.
Hydrocodone and Benzodiazepine Part of Expanded Testing Regiment
Hydrocodone is a component in a number ...
ATLANTA – April 19, 2012 – A new study finds differences in screening account for more than 40 percent of the disparity in colorectal cancer incidence and nearly 20 percent of colorectal cancer mortality between blacks and whites. Differences in stage-specific survival, which likely reflect differences in treatment account for additional 35% of the black-white disparity in colorectal cancer mortality rates. The study, appearing early online in Cancer Epidemiology Biomarkers and Prevention, concludes that equal access to care could substantially reduce the racial disparities ...
Changing the conditions that zebrafish are kept in could have an impact on their behaviour in animal studies and the reliability of results, according to scientists from Queen Mary, University of London.
Zebrafish, like rats and mice, are often used by neuroscientists to explore mechanisms controlling behaviour and in the search for new compounds to treat behavioural disease such as addiction, attention deficit disorders or autism.
It is known that housing and handling affects the results of behavioural studies done in rats and mice, but until now there have been few ...
Birth injuries, sometimes known as birth traumas, are physical injuries the baby receives while being born. Such injuries can be caused by the process of labor and delivery itself, but they can also be the result of medical malpractice.
Causes of Birth Injuries
Birth injuries are more likely to occur if the birth is a difficult one. A difficult birth is generally caused by the size or position of the baby during labor and delivery. Difficult births usually involve one or more of the following:
- Premature babies (born earlier than 37 weeks)
- Prolonged labor, ...
Recent raids of religious compounds in Texas and British Columbia make clear that polygamy is, to say the least, frowned upon by western governments. But legal questions aside, can polygamy ever be morally permissible?
An article in the latest issue of the journal Ethics makes the case that traditional forms of polygamy are inherently unequal and therefore morally objectionable.
"In traditional polygamy, only one person may marry multiple spouses. This central spouse divides him or herself among multiple spouses, but each peripheral spouse remains exclusively devoted ...
UCSF scientists have identified patterns of brain activity in the rat brain that play a role in the formation and recall of memories and decision-making. The discovery, which builds on the team's previous findings, offers a path for studying learning, decision-making and post-traumatic stress syndrome.
The researchers previously identified patterns of brain activity in the rat hippocampus, a brain region critical for memory storage. The patterns sometimes represented where an animal was in space, and, at other times, represented fast-motion replays of places the animal ...
Following are highlights of presentations that will be given by researchers from NewYork-Presbyterian Hospital/Columbia University Medical Center at the upcoming American Psychiatric Association (APA) annual meeting in Philadelphia (May 5-9, 2012).
Jeffrey Lieberman, MD, the Lawrence C. Kolb Professor and chairman of the Department of Psychiatry at Columbia University Medical Center and NewYork-Presbyterian Hospital/Columbia and director of the New York State Psychiatric Institute, will be officially installed as APA president-elect at the meeting.
To speak with Dr. ...
