(Press-News.org) A colloid is a substance spread out evenly inside another substance. Everyday examples include milk, styrofoam, hair sprays, paints, shaving foam, gels and even dust, mud and fog. One of the most interesting properties of colloids is their ability to self-assemble – to aggregate spontaneously into well-defined structures, driven by nothing but local interactions between the colloid's particles. Self-assembly has been of major interest in industry, since controlling it would open up a whole host of new technologies, such as smart drug-delivery patches or novel paints that change with light. In a recent Nature Communications publication, scientists from EPFL and the University of Cambridge have discovered a technique to control and direct the self-assembly of two different colloids.
Contrary to solutions that are made up of discrete molecules, colloidal solutions are made up of large particles, dispersed in a liquid solvent. This unusual structure gives colloids unique properties such as Brownian motion (the random zig-zag movement of particles as they collide with the molecules of the dispersion medium), electrophoresis (the unidirectional movement of particles under and electric current) and optical properties such as the Tyndall effect (light entering a colloid scatters and exits as a different color). It is because of such properties that colloids are so commonplace in everyday life; but one particular property holds special interest: self-assembly.
Self-assembly refers to the ability of a colloid's particles to spontaneously form a kind of stable structural arrangement as a result of the shape and direction of the colloid's particles as they interact with the dispersal medium. Although no external force is required, self-assembly generally takes place as a response to a change in an environmental factor such as temperature, light, etc. In biological colloids like DNA, proteins and other macromolecules, self-assembly is usually the first step to self-organization, which underlies many cellular structures. But in terms of technology, self-assembling colloids could have a wide range of applications, fuelling much research in the field.
But what about self-assembly of two – or more – species of different colloids? This is the question addressed by Giuseppe Foffi's group at EPFL, working in collaboration with Erika Eiser's group at the University of Cambridge. The scientists showed that when the interactions between the particles of two different colloids are carefully designed, they result in the formation of new structures. Specifically, they have discovered a ways to obtain self-assembled structures that depend strongly on temperature changes. Giuseppe Foffi says: "In a sense, the new structures have a 'memory' of their preparation history."
Using DNA-coated colloids, the group of Erika Eiser was able to control the self-assembling progress between two different colloidal species. Fluorescent polystyrene spheres were coated with different DNA strands (giving them a 'hairy' appearance) that acted as means of particle interaction and can be used to characterize the different species. The advantage of using DNA strands was that the interactions between the particles could be programed using the compatibility of the DNA sequences. Another very interesting property is their responsiveness to sharp changes in temperature, offering a high degree in specificity and programmability. The two species of colloids were mixed together in a 'binary mixture' where one could aggregate faster, therefore creating a structural 'scaffold' for the other to assemble upon.
By exploiting the selectivity of DNA base-pairing, supported by simulation studies by the EPFL group, the scientists found that they could achieve an unprecedented control of the morphology of the interacting colloids. By gathering data about the system's morphology and the dynamics of particle interactions, the authors concluded that this approach is not restricted to nano-scale objects like other methods, but can be applied to the entire range of colloidal sizes. In addition, they foresee that this method can have a number of applications, for example light-reacting paints or smart patches that respond to changes in the body's temperature or pH by releasing particles filled with a drug like an antibiotic or antipyretic.
INFORMATION:
DNA brings materials to life
2013-06-13
ELSE PRESS RELEASES FROM THIS DATE:
DNA sequencing uncovers secrets of white cliffs of Dover
2013-06-13
The University of Exeter recently contributed to a major international project to sequence the genome of Emiliania huxleyi, the microscopic plankton species whose chalky skeletons form the iconic white cliffs of Dover. The results of the project are published this week in the journal Nature.
Emiliania huxleyi is one of the most abundant marine phytoplankton species and is a key player in the process of CO2 exchange between the atmosphere and the ocean. In some marine systems 20% of the total carbon is fixed by E. huxleyi. This microscopic alga has influenced the global ...
UF study finds brain-imaging technique can help diagnose movement disorders
2013-06-13
GAINESVILLE, Fla. — A new University of Florida study suggests a promising brain-imaging technique has the potential to improve diagnoses for the millions of people with movement disorders such as Parkinson's disease.
Utilizing the diffusion tensor imaging technique, as it is known, could allow clinicians to assess people earlier, leading to improved treatment interventions and therapies for patients.
The three-year study looked at 72 patients, each with a clinically defined movement disorder diagnosis. Using a technique called diffusion tensor imaging, the researchers ...
Gene offers an athlete's heart without the exercise
2013-06-13
Researchers at Case Western Reserve University have found that a single gene poses a double threat to disease: Not only does it inhibit the growth and spread of breast tumors, but it also makes hearts healthier.
In 2012, medical school researchers discovered the suppressive effects of the gene HEXIM1 on breast cancer in mouse models. Now they have demonstrated that it also enhances the number and density of blood vessels in the heart – a sure sign of cardiac fitness.
Scientists re-expressed the HEXIM1 gene in the adult mouse heart and found that the hearts grew heavier ...
Study points to role of nervous system in arthritis
2013-06-13
Arthritis is a debilitating disorder affecting one in 10 Canadians, with pain caused by inflammation and damage to joints.
Yet the condition is poorly managed in most patients, since adequate treatments are lacking – and the therapies that do exist to ease arthritis pain often cause serious side effects, particularly when used long-term. Any hope for developing more-effective treatments for arthritis relies on understanding the processes driving this condition.
A new study in the Journal of Neuroscience by researchers at McGill University adds to a growing body of ...
A peptide to protect brain function
2013-06-13
A structure called "the microtubule network" is a crucial part of our nervous system. It acts as a transportation system within nerve cells, carrying essential proteins and enabling cell-to-cell communications. But in neurodegenerative diseases like Alzheimer's, ALS, and Parkinson's, this network breaks down, hindering motor abilities and cognitive function.
Now Prof. Illana Gozes of Tel Aviv University's Sackler Faculty of Medicine has developed a new peptide in her lab, called NAP or Davunetide, that has the capacity to both protect and restore microtubule function. ...
Helping to restore balance after inner ear disorder
2013-06-13
Many disorders of the inner hear which affect both hearing and balance can be hugely debilitating and are currently largely incurable. Cochlear implants have been used for many years to replace lost hearing resulting from inner ear damage. However, to date, there has not been an analogous treatment for balance disorders resulting from inner ear disease. One potential new treatment is an implantable vestibular prosthesis which would directly activate the vestibular nerve by electrical stimulation. This prosthetic treatment is tested in a new study by Christopher Phillips ...
US forest management policy must evolve to meet bioenergy targets
2013-06-13
CHAMPAIGN, Ill. — In order to keep pace with the burgeoning demand for renewable energy, forest management policy in the U.S. must change to address environmental sustainability issues, according to an article by a University of Illinois expert in bioenergy law.
Unless the forestry sector can tailor sustainable forest management policies specifically to forest-to-energy feedstocks, its role in helping the country broaden its energy portfolio – and by extension, meeting ambitious bioenergy targets – may be limited in large part because of uncertainty about whether existing ...
No good substitute for race in college admissions: Research
2013-06-13
COLLEGE PARK, Md. – As the U.S. Supreme Court decides in a case involving racial preferences in higher education admissions (Fisher v. Texas), new University of Maryland-led research finds that socioeconomic diversity is no replacement for a direct consideration of race, as some have suggested. Still the research finds that a mix of students from differing socio-economic backgrounds has benefits.
The peer-reviewed study appears in the June issue of the "American Educational Research Journal." It evaluates the use of "socio-economic status" as a racially blind way to build ...
Yale researchers unravel genetics of dyslexia and language impairment
2013-06-13
A new study of the genetic origins of dyslexia and other learning disabilities could allow for earlier diagnoses and more successful interventions, according to researchers at Yale School of Medicine. Many students now are not diagnosed until high school, at which point treatments are less effective.
The study is published online and in the July print issue of the American Journal of Human Genetics. Senior author Jeffrey R. Gruen, M.D., professor of pediatrics, genetics, and investigative medicine at Yale, and colleagues analyzed data from more than 10,000 children born ...
Men with restless legs syndrome may be at higher risk of early death
2013-06-13
MINNEAPOLIS – Men who experience restless legs syndrome (RLS) may have a higher risk of dying earlier, according to research that appears in the June 12, 2013, online issue of Neurology®, the medical journal of the American Academy of Neurology. The disorder is characterized by an irresistible urge to move the legs and often causes leg sensations of burning, creeping, and tugging, which are usually worse at night.
"RLS affects five to 10 percent of adults across the country," said study author Xiang Gao, MD, PhD, with Harvard School of Public Health, Harvard Medical School ...