DNA brings materials to life

June 13, 2013
This shows two colloids interacting over time in relation to temperature. Credit: Giuseppe Foffi, EPFL

DNA-coated colloids have been used to create novel self-assembling materials in a breakthrough experiment by EPFL and University of Cambridge scientists.

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 is their ability to self-assemble – to aggregate spontaneously into well-defined structures, driven by nothing but local interactions between the colloid's particles. has been of major interest in industry, since controlling it would open up a whole host of new technologies, such as -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 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 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 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.

Explore further: Particles magnetically 'click' to form superstructures

Related Stories

Particles magnetically 'click' to form superstructures

April 10, 2012

(Phys.org) -- Geomag, the popular children's toy, contains small metal spheres that can be magnetically connected with a click to build a variety of towers, bridges, and sculptures. In a new study, scientists have done something ...

New gel material can modify properties at will

November 6, 2012

Controlling and modifying at will the transparency, electrical properties, and stiffness of a gel - such are the promises of a new discovery by researchers supported by the Swiss National Science Foundation (SNSF). This marks ...

Physicists shine a light on particle assembly (w/ video)

January 31, 2013

New York University physicists have developed a method for moving microscopic particles with the flick of a light switch. Their work, reported in the journal Science, relies on a blue light to prompt colloids to move and ...

Fighting bacteria with a new genre of antibodies

April 24, 2013

In an advance toward coping with bacteria that shrug off existing antibiotics and sterilization methods, scientists are reporting development of a new family of selective antimicrobial agents that do not rely on traditional ...

Weird science: Crystals melt when they're cooled

May 23, 2013

(Phys.org) —Growing thin films out of nanoparticles in ordered, crystalline sheets, to make anything from microelectronic components to solar cells, would be a boon for materials researchers, but the physics is tricky because ...

Recommended for you

Making polymers from a greenhouse gas

July 28, 2015

A future where power plants feed their carbon dioxide directly into an adjacent production facility instead of spewing it up a chimney and into the atmosphere is definitely possible, because CO2 isn't just an undesirable ...

New material opens possibilities for super-long-acting pills

July 28, 2015

Medical devices designed to reside in the stomach have a variety of applications, including prolonged drug delivery, electronic monitoring, and weight-loss intervention. However, these devices, often created with nondegradable ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

Protoplasmix
not rated yet Jun 13, 2013
It should be possible to use that for encoding a self-extracting hardware/firmware platform that assembles and maintains a neural net and I/O and - muuhaaaaa

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.