Bioanalytics – Chemical
Blood microsampling continues to gain increasing interest in drug discovery and development due to the simplification of sample collection, transport, storage and processing, and additionally complies with the objectives of the three Rs of animal welfare. Further, some microsampling techniques enable remote-site collection and patient self-sampling. Recent improvements in LC-MS/MS sensitivity and selectivity have also allowed the introduction of microsampling techniques which support exceptionally low sample volumes (2.5 – 5.0 µL); these include membrane devices which remove blood HCT with “plasma” filtrate collected and dried on a volumetric disc (Dried Plasma Spot, or DPS), precise volume microfluidic-delivered dried-blood spot (MF-DBS) and capillary microsampling (CMS) using devices which support the entire process from sampling to fractionation of a pre-determined volume of plasma. Another recent and promising microsampling approach is Volumetric Absorptive Microsampling (VAMS), a technique wherein a fixed and accurate volume of blood is absorbed by capillary action onto a hydrophilic polymeric tip. Unlike classical DBS wherein the area of the dried-blood spot varies with blood HCT, resulting in sampling volume biases when using a sub-punch approach, the blood volume collected using VAMS is independent of HCT and the entirety of the sampled tip is displaced from an anchoring handle for sample analysis. However, whilst the HCT-induced sampling volume bias is largely eliminated, reduced analyte recovery from the VAMS substrate is observed with increasing blood HCT, the extent of which is compound dependent and extraction related. In this presentation, Impact-Assisted Extraction is introduced as a universal and novel sample preparation workflow for overcoming the recovery bias due to blood HCT in VAMS assays, the efficacy of which is illustrated in case studies for both small and large molecule applications. Further, the challenges associated with implementation of VAMS technology in a regulated environment are considered from a sample collection, bioanalytical methodology and validation point of view, and contrasted with other current microsampling approaches such as DPS, MF-DBS and CMS.