Lipid extraction from dried blood spots and dried milk spots for high throughput lipidomics

Dried blood spots (DBS) and dried milk spots (DMS) represent convenient matrices for collecting and storing human samples. However, the use of these sample types for researching lipid metabolism remains relatively poorly explored, and especially the efficiency of lipid extraction is unclear. A visual inspection of punched DBSs after standard extraction suggests that the samples remain largely intact. DMSs comprise a dense aggregate of milk fat globules on one side of the card, suggesting that the lipid fraction may be physically inaccessible. This led us to the hypotheses that decoagulating may facilitate lipid extraction from both DBSs and DMSs. We tested decoagulation using a mixture of strong chaeotropes (guanidine and thiourea) in both DBS and DMS in the context of high throughput lipidomics (96/384w plate). Extraction of lipids from DMSs was tested with established extractions and one novel solvent mixture in a high throughput format. We found that exposure of DBSs to chaeotropes facilitated collection of the lipid fraction but was ineffective for DMSs. The lipid fraction of DMSs was best isolated without water, using a mixture of xylene/methanol/isopropanol (1:2:4). We conclude that decoagulation is essential for efficient extraction of lipids from DBSs and that a non-aqueous procedure using a spectrum of solvents is the best procedure for extracting lipids from DMSs. These methods represent convenient steps that are compatible with the sample structure and type, and with high throughput lipidomics. HighlightsO_LIThe efficiency of lipid extractions on dried milk and dried blood spots was tested C_LIO_LIThe number of lipid variables and the total signal strength were used as objective measures C_LIO_LIDecoagulation of dried blood spots improved extraction efficiency C_LIO_LIA mixture of xylene, methanol and isopropanol isolates the lipid fraction best from DMSs C_LIO_LIAn aqueous extraction using dichloromethane was the most efficient method for isolating lipids from DBSs C_LI