Posted by
Dan Focht on
URL: http://confocal-microscopy-list.275.s1.nabble.com/perfusion-system-tp5674677p5679659.html
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Hana
Perfusing a closed system chamber is not trivial.
When a fluid is enclosed in an optical cavity where one surface is a coverslip having an unsupported aperture you can easily notice any variation in flow as it translates to a Z axis shift in the specimen plane.
There are advantages and disadvantages to three basic methods of perfusion.
Gravity - inexpensive and you can get it anywhere! It is hard to regulate in very slow flow rates but it sure is cheap!
Positive displacement pumps , such as a syringe pump - have limited capacity and as you increase its capacity by using a larger syringe you also increase the ratio of hydraulic flow in the tubing. As frictional forces build and release themselves as the piston is pressed forward you will find that the larger piston can cause instantaneous high velocity advancement of the fluid flow that causes the coverslip to flex out of focus. Therefore, you have to make sure the syringe size is both adequate for the duration of the experiment and not too large to cause the afore mentioned problem. Also always make sure that the drive motor of a any pump used for microscopy applications is NOT a stepper motor. The last thing you need is steps in your fluid flow!
Peristaltic pumps - Bioptechs has sampled every pump we have come in contact with to determine the best means of perfusion for microscopy. We have what we call a microperfusion pump that is driven by a tachometer regulated DC motor with a multiple stage gear reduction. This means that the motor is in continuous motion (without steps) and the output spindle can rotate extremely slow and smooth. This pump has its own internal speed control and can also be controlled by an external reference voltage supplied by a USB interface and control program. Flow rates are available from 0.02ml/hr to 180 ml/hr. Note; this is not a perfect solution but it is the best means of controlled perfusion we know.
The only problem we have experienced with this pump is a small glitch that occurs when the captured flow in the pump head is allow to combine with the downstream flow that has exited the pump-head. At the instant that the two fluid bodies combine, if there is a difference in preload and post load pressure, a "glitch" can be seen in the outflow. other than that no problem.
Additional information available at:
http://www.bioptechs.com/Products/MPP/mpp.htmland for precise control of two perfusion supplies with the ability to control the effect of dead-volume and diffusion gradient:
http://www.bioptechs.com/Products/MPP/perftempctrl.htmlIf you have any further questions please call during U.S. eastern time 9:00 AM to 5:00 PM
Phones answered by live human beings. We do not use answering machines during business hours.
There are other "tricks" to having a smooth flow through a closed system chamber on our web site. See bottom of page:
http://www.bioptechs.com/Instructions/Co2_Renderings/co2_setup.htmlDan
On Oct 26, 2010, at 9:42 AM, Hana Uhlirova wrote:
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Dear list,
Has anyone experiences with perfusion system for live cell imaging?
Particularly I need to rinse with two liquids of precise concentration. We
have a home-made closed system and have problems with air bubbles and mixing
of those liquids by loss of the concentration accuracy. Any tips how to
figure this out?
Thank you all.
Hana
Hana Uhlirova PhD
Laboratory of Optical Microscopy
Institute of Physical Engineering
Faculty of Mechanical Engineering
Brno University of Technology
Czech Republic
Dan Focht
Bioptechs, Inc.
3560 Beck Rd.
Butler, PA 16002
www.bioptechs.com
P: (724)282-7145
F: (724)282-0745
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