Exclusion-Zone Dynamics Explored with Microfluidics and Optical Tweezers

Entropy

István N. Huszár¹  Zsolt Mártonfalvi¹  András József Laki²  Krist༿ Iván² 

[1] Department of Biophysics and Radiation Biology, Semmelweis University, Tűzoltó utca 37-47, Budapest H1094, Hungary; E-Mails:;Faculty of Information Technology and Bionics, Pázmány Péter University, Práter utca 50/A, Budapest H1083, Hungary; E-Mails:

关键词: exclusion zone;    microfluidic device;    optical trapping;    atomic force microscopy;    non-equilibrium process;    chemical gradient;    diffusion;    coupled transport;   

DOI  :  10.3390/e16084322

来源: mdpi

【 摘 要 】

The exclusion zone (EZ) is a boundary region devoid of macromolecules and microscopic particles formed spontaneously in the vicinity of hydrophilic surfaces. The exact mechanisms behind this remarkable phenomenon are still not fully understood and are debated. We measured the short- and long-time-scale kinetics of EZ formation around a Nafion gel embedded in specially designed microfluidic devices. The time-dependent kinetics of EZ formation follow a power law with an exponent of 0.6 that is strikingly close to the value of 0.5 expected for a diffusion-driven process. By using optical tweezers we show that exclusion forces, which are estimated to fall in the sub-pN regime, persist within the fully-developed EZ, suggesting that EZ formation is not a quasi-static but rather an irreversible process. Accordingly, the EZ-forming capacity of the Nafion gel could be exhausted with time, on a scale of hours in the presence of 1 mM Na₂HPO₄. EZ formation may thus be a non-equilibrium thermodynamic cross-effect coupled to a diffusion-driven transport process. Such phenomena might be particularly important in the living cell by providing mechanical cues within the complex cytoplasmic environment.

PACS Codes: 05; 47; 64; 68; 82; 83; 97

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland