Author/Editor		Vrhovec, Saša; Mally, Mojca; Kavčič, Blaž; Derganc, Jure
Title		A microfluidic diffusion chamber for reversible environmental changes around flaccid lipid vesicles
Type		članek
Source		Lab Chip
Vol. and No.		Letnik 11, št. 24
Publication year		2011
Volume		str. 4200-6
Language		eng
Abstract		The reversible environmental changes around flaccid lipid vesicles represent a considerable experimental challenge, particularly because of remarkable softness of flaccid membranes, which can warp irreversibly under the slightest hydrodynamic flow. As a result, we have developed a microfluidic device for the controlled analysis of individual flaccid, giant lipid vesicles in a changing chemical environment. The 10 setup combines the advantages of a flow-free microfluidic diffusion chamber and optical tweezers, which are used to load the sample vesicles into the chamber. After a vesicle is loaded into the diffusion chamber, its chemical environment is controllably and reversibly changed solely by means of diffusion. The chamber is designed as a 250-micrometers-long and 100-micrometers-wide dead-end microchannel, which extends from a T-junction of the main microchannels. Measurements of the flow-velocity profile in 15 the chamber show that the flow rate decreases exponentially and scales linearly with the flow rate in the main channel. The characteristic length of the exponential decrease is 15 ± 2 micrometers, meaning that a large part of the diffusion chamber is effectively flow-free. The diffusion properties are assessed by monitoring the diffusion of a dye into the chamber. It was found that a simple 1D diffusion model fits well to the experimental data. The time needed for the exchange of solutes in the chamber is of the order 20 of minutes, depending on the solute's molecular weight. Here, we demonstrate how the diffusion chamber can be used for reversible environmental changes around flaccid, giant lipid vesicles and membrane tethers (nanotubes).
Descriptors		BIOPHYSICS MEMBRANES, ARTIFICIAL LIPIDS MEMBRANE FLUIDITY DIFFUSION RHEOLOGY OSMOLAR CONCENTRATION