Blood microsampling for untargeted lipidomics

Lipidomics has become a good bioanalytical tool for biomarker identification in a wide range of diseases. To this aim, whole blood could be promisingly exploited to obtain as much information as possible, despite the well-known intrinsic problems of this biological matrix, mainly related to sampling invasiveness, pre-analytical manipulation and processing, when compared to plasma and serum. To overcome the disadvantages of classic whole blood analysis, two microsampling approaches are proposed: Dried Blood Spot (DBS) and Volumetric Absorptive Microsampling (VAMS). Both techniques allow the collection of small amounts of matrix (20 µL) in a minimally invasive way, directly by fingerprick followed by drying and storage at room temperature. After the loss of water, often responsible for degradation reactions, dried microsamples ensure analyte stability. In addition, VAMS device can absorb a fixed and highly reproducible whole blood volume by means of a hydrophilic polymer tip, regardless of haematocrit value. Fast and feasible original pretreatment procedures have been developed and optimised by testing different pure and mixture solvents and extraction means. To evaluate the best performances for each lipid class and sampling mode, 15 benchmark lipids have been chosen, being representative for the most abundant lipid categories. Quali-quantitative results by means of an originally developed high-resolution UHPLC-MS/MS method were processed and compared by using a multivariate data analysis approach. This allowed to define the best extraction protocol for DBS and VAMS and, after comparison with fluid blood, to suggest VAMS strategy as a promising alternative procedure for blood sampling for untargeted lipidomics.