Week 2
For those of you who would like to see in depth the scope of this project, I have uploaded my proposal.
A vital step before beginning experimentation is to develop a theory behind the concepts that you wish to experiment on. This is crucial because it narrows the huge number of variables to a select few that will impact the outcome the most. For this project, the most crucial factors are assessing the vacuum needed for proper sample transfer, the shelf life and permeability of gas, or the leaking rate. These were modeled mathematically with certain assumptions. So far we have developed a theoretical analysis for determining the vacuum threshold for which there will be proper sample transfer of blood from finger to the VacuStor tube.Theoretical Analysis
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| Figure 1 |
Figure 1 depicts the evacuated VacuStor tube with the reagent inside the tube. There is 200 microliters of reagent prior to blood collection. After blood collection, 20 microliters of blood are added to the 200 microliters of reagent in the tube. We have to factor in the occupied space by the reagent and the reagent and blood when determining the vacuum required for sample transfer. Hence, we used different models to develop an equality to determine the critical pressure to ensure sample transfer. This equation is:
where Pa,c is the critical pressure, above which the sample will not transfer. Vr, Vs, and Vt are the volume of reagent, sample, and the tube itself respectively. Pout is the outside pressure, Pc is the capillary pressure to be overcome for blood draw, and Pw is the water vapor pressure.
Table 1 tabulates these values for a glass tube and a plastic tube and shows the critical pressures at 10,000 ft and at sea level.
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| Table 1 |
Once again, these are just models to narrow our experimental focus. We need to confirm these theories through our experiments which we hope to start soon. We hope to develop a model for the permeability of gas as well, which can affect the shelf life of the tube. In addition, we are going to start testing the rise time, or the time it takes for the vacuum within the tube to equilibrate with the outside pressure.
Hey Siva!
ReplyDeleteCould you describe how you plan on testing the final Vacustor?
The Vacustor tube is simply the tube which stores the blood after it has been collected from the finger. To test the tube, we probably will use blood samples and simply test that it is indeed collecting the amount of blood we want it to and that it mixes well with the reagents so that it can be stored. However, the device itself integrates this tube and other parts to make it easy to use and self-administrable. To test the device, we probably will have patients test the use of the device, which will test how well the lancet works and that the blood can be collected once the finger has been pricked.
DeleteI hope this helps!
Hello Siva Kailas,
ReplyDeleteI have a few questions. Given this theoretical data, once experiments begin, what elements of the experiment will you tweak to get the "ideal" result? Additionally, what is this ideal result? Is it a device that is commercially viable and safe for public use? Who will be the main consumers of this device?
Thanks!!!
I am unsure of what you are asking. We use the theoretical model to narrow where to start for experimentation. For example, Table 1 provides the theoretical critical pressure for sample transfer. We do not know for sure if this is true, so we have to experimentally determine where the threshold pressure is. But, the model allows us to start near our calculated value, rather than starting from a random pressure and aimlessly searching for this critical pressure value. We only tweak the experiment if the theoretical value does not reflect what we expected from the experiment. In the case of determining the critical pressure, we would try different pressures from that point on. Hence, depending on the experiment, the variable may have to be tweaked to obtain the result we desire.
DeleteAnd yes, the goal of the project is to develop a device that is commercially viable and safe for public use, as well as easy to use. Since the development of this device is solely for the case of triage, it will probably be bought by hospitals or emergency response units, which heavily rely on triage throughput to be high and efficient.
Let me know if you have any questions or if I did not quite answer your question.
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ReplyDeleteHey Siva! I was wondering if you could explain a little bit about how the assay works and how you would determine the amount of reagent that goes into each container? How is the ratio of the reagent and the blood determined? Creating a working device which could be used by the general populace seems really interesting and looking forward to seeing what you find!
ReplyDeleteThe reagents in the tube are pre-processing reagents which expedite the assay procedure. We determine which reagent and how much of that reagent goes into the tube based on what assay will the blood be used for. The assay for which the blood will be used for also determines the ratio of reagent to blood. For example, if the blood will be used for a biodosimetry assay, which determines the radiation exposure of the patient's blood, will have a cell culture reagent that needs to have a blood:reagent ratio of 1:10. Thus, our tube will have 200 micoliters of reagent and collect 20 microliters of blood. However, depending on the assay, the reagent, amount of reagent, and ratio can change.
DeleteThanks!