The University of Alabama at Birmingham

Application
Gas Mixing for Biomedical Research

Product
Sierra’s SmartTrak® Model 100 Digital Thermal Mass Flow Controller

Mass Flow Solution
Dr. Kraus installed two Model 100s in a manifold system to duplicate the environment of the body by bubbling a mixture of 5 slpm N2 and air into a vessel bath chamber, containing suspended rat aorta to test if H2S causes vessels to constrict or dilate.

Research Impact
Sierra's Mass Flow Technology

Early in his experiments, Dr. Kraus used a make-shift system to deliver N2 and air to his experiments.  He rigged up different gas cylinders, each with a specific gas content.  “Switching cylinders and maintaining exact oxygen concentrations was difficult and required excess time,” remembers Kraus.

In 2005, Dr. Kraus decided to make a much needed change.  Rakesh Patel, an experienced vascular biologist, advised Dr. Kraus to give Sierra’s SmartTrak® a try.  Kraus contacted David Burks, our Sierra representative from Engineered Products, LLC out of Birmingham, Alabama, and explained his need for an instrument that was accurate, could easily change ranges, and handle the fluctuating conditions of his laboratory. 

According to Burks, Kraus’ application "fit exactly into the Dial-A-Gas® concept and was very well received—small size, easy configuration and interface, temperature and pressure changes had no effect on calibrations, and accuracy were nice selling features.” 

The Model 100 Duplicates the Conditions Found in the Body 
Dr. Kraus decided to give SmartTrak® a try.  He installed his 2 Model 100s into a manifold system that simultaneously controlled 8 organ baths.   Through a series of pipes, the Model 100s precisely controlled the N2 and air levels delivered to each of the plasma rich organ baths which contained ¼ inch thick rat aorta.  Each Model 100 bubbled “a mixture of N2 and air, each containing 5% CO2, to maintain a specific O2 concentration from 30-50 micro-moles (Kraus, “Hydrogen Sulfide Mediates the Vasoactivity of Garlic”)."

Amazingly, when small amounts of H2S were injected into these vessel baths, Dr. Kraus observed the rat aorta relaxing—not constricting.  Dr. Kraus and his team proved that H2S, a compound found in garlic, does indeed help relax the smooth muscles in our bodies.  These results further prove that by eating garlic, we can decrease the risk of cardiovascular disease, diabetes, and stroke. 

After installing his Model 100s, David Burks reported that Dr. Kraus “was hooked on performance”.  He has recommended the SmartTrak® to Dr. Xinjin and Dr. Claudiu Lung, his colleagues at the University of Alabama. 

Dr. Kraus Eliminates Variance in His Experiments                              
For Dr. Kraus, accuracy of the Model 100 is essential for the success of his experiments.  The Model 100 precisely  “duplicates the conditions of the body”, says Dr. Kraus, exposing his test tissue to the same O2 pressure and temperature that the body experiences.   To achieve publishable results, Dr. Kraus must isolate the effects of H2S on his test tissues by eliminating the experimental variables.  He must be certain that he is observing the effects of H2S on the body, not the effects of an external variable.  So far, Dr. Kraus has been very pleased that the SmartTrak® has helped “eliminate variance” in his experiments.  He excitedly remarks that he has observed “vasorelaxation in the range of the body”--vessels relaxing under the exact conditions experienced by the body. 

To achieve this type of stability, the Model 100 sensor goes through unprecedented testing measures before it even qualifies for installation.  Mark McMahon, Sierra’s Scientific Product Manager explains that “many of our sensors don’t even make it through our quality control process, ensuring that the sensors in your SmartTrak® are of the highest quality, holding factory calibration with minimal drift over time.” 

In November of 2007, Dr. Kraus and his team did indeed publish their findings in the Proceedings of the National Academy of Science Journal in the article, “Hydrogen Sulfide Mediates the Vasoactivity of Garlic”.  Dr. Kraus even referenced Sierra in this article.

Dr. Kraus Uses the Pilot Module to Facilitate Multiple Experiments on Same Set of Tissues
Like many scientists, Dr. Kraus loves the ease-of-use of the SmartTrak®’s Pilot Module.  He is able to "punch in different parameters on the fly", changing the gas composition within minutes to test the next desired condition on a unique set of tissues.  With this ability to instantaneously change mass flow rate, Kraus “facilitated multiple experiments” and quickly defined exactly how much H2S was required to achieve vasorelaxation over an oxygen concentration range found in the body.

When innovating the Model 100, Mark McMahon, the mastermind of the SmartTrak® , was having a drink with Michael Gallagher, Sierra’s representative out of Boston and asked him:  What do scientists need most?  And the answer was the ability to change flow rates instantaneously and remotely.  Thus the Pilot Module was born.

Garlic lovers rejoice.  Now, we have proof that the folklore about garlic is true. 

“Experience Our Passion For Flow!™”