WHERE ARE WE NOW?
MICROSAMPLING: WHERE ARE WE NOW? BY TIM SANGSTER (CHARLES RIVER LABORATORIES, UK)
Microsampling has been an interest of mine since the 1990s and to reflect where we are in the field today I would like to review how we got here by taking a personal look at microsampling over the last couple of decades.
I began working in this industry in 1995 and instrumentation and chromatographic advances rapidly changed over my first couple of years as a bioanalytical chemist. The first instrument I had the pleasure of using was an API300, which rapidly advanced to API365 and then API3000. While the mass spectrometers increased in sensitivity through the generations, we also improved, or more correctly, changed the chromatography to give enhanced sensitivity. The increase in sensitivity in the early years was used to reduce the complexity of the sample preparation performed. A lot of the methodology being developed moved away from the selective techniques that were commonly used, such as liquid–liquid extraction or solid-phase extraction, to use protein precipitation.
So while sensitivity increased in our assays, the volume of plasma or blood being collected
from the animals was not reduced. I looked at the available techniques in the late 1990s and the only thing that appeared to be commercially available and appropriate to separate low volumes of blood to plasma was the microvettes from Sarstedt (Numbrecht, Germany). I had some success separating 150 ml of blood to create plasma in the laboratory, but, when I tried to get support to utilize the reduced volumes to change our toxicology study designs, I was unable to find support to move this forward.
In the early years of the millennium, microsampling was not a major focus for me and there was not a lot of visible activity in the industry. We routinely reduced samples to generate our bioanalytical data and the impetus to change sampling on either toxicological or clinical studies was relatively minimal. The advantage of the sensitivity was used to really drive down the amount of sample being extracted and to reduce the impact of matrix on analysis. The bioanalytical community became highly aware of the impact of matrix effects when using electrospray ionization, and one of the easiest ways to deal with this was to reduce the amount of matrix included in the final extract. So, we utilized the enhanced sensitivity we had gained to reduce the limit of quantification in our assays, while also using significantly less matrix.
During the 1990s there were some real advances in microsampling. The team at GSK (UK) had started to use dried blood spots (DBS) for samples in both preclinical and clinical studies. While we are acutely aware of the problems that have since come to light related to DBS, I firmly believe that the microsampling cause was significantly accelerated by the work that GSK undertook.
At a similar period of time, the team at AstraZeneca (Södertälje, Sweden) was also investigating
microsampling and they came up with an approach that was initially targeted at blood microsampling, but adapted to generate extremely small volumes of plasma. The teams I worked in then were very keen on both of these new techniques. Since then we have done significant amounts of research and studies with both approaches supporting preclinical development.
9
www.bioanalysis-zone.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48
