Recent advances in the bioanalytical field, specifically the increasing sensitivity of modern state-of-the-art mass spectrometry equipment, has made it possible to obtain better information from smaller volumes of samples. Microsampling is a technique that allows quantitative drawing of small (5-50 uL) volumes of blood. Although small, these sample volumes are enough to quantify many drugs (small molecules) and proteins (large molecules) via LC-MS/MS techniques. Microsampling techniques have been successfully implemented at Nucro-Technics through the collective efforts of the Bioanalytical and Toxicology departments.
The small volume in microsampling allows serial samples to be drawn from the same animal, rather than collecting a series of terminal bleeds from several animals. This feature is quite favorable for building pharmacokinetic and toxicokinetic (PK/TK) profiles, as it eliminates organism-to-organism variability making the PK/TK data more precise. In addition, microsampling reduces the total number of animals required for PK/TK studies. Such reduction is beneficial both from humane and financial considerations as it improves research animal welfare.
Dry Blood Spot Testing
Dry Blood Spot (DBS) testing is another microsampling technique that is gaining popularity in the bioanalytical industry. Recent improvements in the sensitivity of mass spectrometry instrumentation have overcome the major limitation of this technique – small sample size. The technique was first introduced in clinics over 40 years ago and has been successfully used for neonatal screening of phenylketonuria.
Sampling is done by blotting several droplets of blood onto specially manufactured adsorbent filter paper. The blood is allowed to saturate the paper. It is then air dried and stored in a sealed plastic bag with desiccant added to reduce humidity. Since the majority of small molecules, protein and DNA are stable when stored dry, these dry blood specimens can be stored long-term at ambient temperatures. When a specimen arrives at an analytical laboratory, a small disc of saturated filter is separated from the collection sheet using a hole punch. Next, an analyte of interest is extracted from the disc using a relevant extraction technique. The benefit of this type of testing is in the simplicity of shipping, storing, and sampling. In addition, this sampling technique is safer to the staff that handle the samples because the possibility of a spill or leakage is eliminated.