INTERVIEWS WITH N. SPOONER & J. RUDGE


volume pipetting. The idea behind it is that you’ve got a small, absorptive hydrophilic polymer on the end of what looks like a pipette tip; when you apply the tip at a positive angle at a blood pool, whether that’s a finger prick or taken from an animal’s tail, and then very rapidly the blood (in this case) is absorbed onto the tip, allowed to dry. It’s quantitative so it usually takes up 10 or 20 microlitres which solves one of the fundamental issues of DBS. Then in very much the same way as dried blood spotting (DBS), the blood on the tips are dried and they can be sent via regular mail to a laboratory, so it allows for remote sampling and analysis at a laboratory many thousands of miles away. Within the laboratory this is where the pipette tip comes into play – having the pipette tip means you have the option to automate a product onto standard lab liquid handling systems.


Q Q What are the uses of the technology?


JR: the uses of the technology are quite wide, from drug clinical trials in which the blood of individuals needs monitoring through to research in low-resourced regions, through to analyzing even larger molecules such as proteins and peptides – even RNA and DNA!


What are the limitations of the technology?


JR: The limitations of the technology are based upon what it is the lab really wants to measure and how it’s going to measure it. If one takes, for example, an immunosuppressive like (Tacrolimus), it’s a perfect candidate for volumetric absorbative microsampling because that molecule will partition mainly into the hematocrit, and in actual fact, in the lab it is analyzed from blood and not a portion of blood such as plasma or serum. On the flip side, if one wanted to measure potassium then it wouldn’t be a good candidate and the reason for that is because plasma-potassium is tested quite a bit in terms of measuring electrolytes. The body will selectively pump potassium into cells so when you collect blood and you let that blood dry onto a surface like a DBS card then the drying action causes a release of cellular potassium into the plasma massively biasing the results and making them interpretable. If you’ve got compounds which only exist in the plasma fraction such as vitamin D then you can measure vitamin D levels using VAMs but then one has to be aware that the plasma concentration. This is because for the same volume is always going to be higher for the blood concentration because the blood cells take up some of that volume so one has to think about different reference ranges or adjusting the data to match the plasma data. So it really depends on what it is you want to do.


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