Geometry affects drift and diffusion across entropic barriers

June 16, 2010

College Park, MD (June 16, 2010) -- An understanding of particle diffusion in the presence of constrictions is essential in fields as diverse as drug delivery, cellular biology, nanotechnology, materials engineering, and spread of pollutants in the soil. When a driving force is applied, displacement of particles occurs as well as diffusion. A paper in the Journal of Chemical Physics, which is published by the American Institute of Physics (AIP), quantifies the effects of periodic constrictions on drift and diffusion in systems experiencing a driving force.

In a uniform cylinder, both the mobility and the diffusion coefficient of the particle are independent of the driving force. This is not true, however, when the cylinder diameter varies. Constrictions provide periodic entropic barriers, which slow down drift and diffusion when the driving force is weak. This research examined two types of cylinders. In the first, a tube consisted of sequential spherical compartments connected by small circular openings. The driving force suppressed the slowdown due to the constrictions. The particle subjected to a strong driving force showed no change in effective diffusion coefficient or mobility as a result of the periodic restrictions. In a tube of cylindrical chambers, however, the results were dramatically different. Under a strong driving force, mobility decreased while the diffusion coefficient became extremely large due to intermittency that occurred in the particle transitions between openings connecting neighboring compartments.

While author Alexander Berezhkovskii of the National Institutes of Health acknowledges that the original idea for the project was inspired by devices that deliver drugs locally in small amounts, he looks at the research as a quest for a broader understanding. "Nature is very complicated because of geometry, but we are looking for something simple that underlies the complexity," he says.
-end-
The article, "Drift and diffusion in a tube of periodically varying diameter. Driving force induced intermittency" by Alexander Berezhkovskii et al will appear in the Journal of Chemical Physics. See: http://jcp.aip.org/

Journalists may request a free PDF of this article by contacting jbardi@aip.org.

ABOUT THE Journal of Chemical Physics

The Journal of Chemical Physics publishes concise and definitive reports of significant research in methods and applications of chemical physics. Innovative research in traditional areas of chemical physics such as spectroscopy, kinetics, statistical mechanics, and quantum mechanics continue to be areas of interest to readers of JCP. In addition, newer areas such as polymers, materials, surfaces/interfaces, information theory, and systems of biological relevance are of increasing importance. Routine applications of chemical physics techniques may not be appropriate for JCP. Content is published online daily, collected into four monthly online and printed issues (48 issues per year); the journal is published by the American Institute of Physics. See: http://jcp.aip.org/

ABOUT AIP

The American Institute of Physics is a federation of 10 physical science societies representing more than 135,000 scientists, engineers, and educators and is one of the world's largest publishers of scientific information in the physical sciences. Offering partnership solutions for scientific societies and for similar organizations in science and engineering, AIP is a leader in the field of electronic publishing of scholarly journals. AIP publishes 12 journals (some of which are the most highly cited in their respective fields), two magazines, including its flagship publication Physics Today; and the AIP Conference Proceedings series. Its online publishing platform Scitation hosts nearly two million articles from more than 185 scholarly journals and other publications of 28 learned society publishers.

American Institute of Physics

Related Drug Delivery Articles from Brightsurf:

Modelling microswimmers for drug delivery
An international group of theoretical physicists led by Abdallah Daddi-Moussa-Ider from Düsseldorf, Germany, has modelled the motion of microscopic, motile bodies - either powered micro-machines or living cells - in viscous liquid drops, using the Navier-Stokes equations.

Millimetre-precision drug delivery to the brain
Focused ultrasound waves help ETH researchers to deliver drugs to the brain with pinpoint accuracy, in other words only to where their effect is desired.

New smart drug delivery system may help treatment for neurological disorders
A Rutgers-led team has created a smart drug delivery system that reduces inflammation in damaged nervous tissues and may help treat spinal cord injuries and other neurological disorders.

Novel drug delivery particles use neurotransmitters as a 'passport' into the brain
Drug-carrying lipid nanoparticles were created that incorporate neurotranmitters to help them cross the blood-brain barrier in mice.

Advances in nanoparticles as anticancer drug delivery vector: Need of this century
This review article provides a summary of current advances in the use of nanoparticles (NPs) as anticancer drug-delivery vectors.

Microcapsules for targeted drug delivery to cancer cells
A team of scientists from Peter the Great St. Petersburg Polytechnic University together with their colleagues developed a method of targeted drug delivery to cancer cells.

Improving drug delivery for brain tumor treatment
Despite improvements in drug delivery mechanisms, treating brain tumors has remained challenging.

Nanoparticle orientation offers a way to enhance drug delivery
MIT engineers have shown that they can enhance the performance of drug-delivery nanoparticles by controlling an inherent trait of chemical structures, known as chirality -- the 'handedness' of the structure.

News about drug delivery
Nanocontainer for drugs can have their pitfalls: If they are too heavily loaded, they will only dissolve poorly.

Deflating beach balls and drug delivery
Gwennou Coupier and his colleagues at Grenoble Alps University, Grenoble, France have shown that macroscopic-level models of the properties of microscopic hollow spheres agree very well with theoretical predictions.

Read More: Drug Delivery News and Drug Delivery Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.