Hold a bottle of normal serum up to the light and it's faintly cloudy. That haze is lipid, chylomicrons and lipoproteins that scatter light, coat plastic and bind hydrophobic molecules. In a spectrophotometric assay it reads as absorbance. In a cell culture it's an uncontrolled variable. Delipidized serum is the same serum with the lipid taken out.
How it's done
Lipid is removed by adsorption onto a solid phase such as fumed silica, or by extraction with an organic solvent, followed by clarification. Done gently, the process leaves proteins, hormones and small molecules where they were and gives a clear serum with much lower triglyceride and cholesterol. Because the delipidized product can be sterile filtered without clogging the filter, it's usually sold sterile.
Where it helps
In optical assays, turbidity adds absorbance at every wavelength and light scatter in fluorescence and nephelometric readings. Delipidized serum as a diluent, calibrator matrix or blank removes that offset. It matters most for low-analyte measurements and for assays read near 340 nm, where lipid interference is worst.
In immunoassays, lipoproteins bind non-specifically to antibodies and to plate surfaces, which raises background and now and then produces a false positive. A delipidized matrix gives cleaner standard curves and tighter replicates in ELISA and lateral-flow development.
In cell culture, serum lipid feeds cells but also varies from lot to lot and species to species. A delipidized base lets you add back defined lipids, or none at all, so experiments on lipid metabolism, lipoprotein uptake or drug binding start from a known baseline.
In mass spectrometry and chromatography, removing the lipid reduces ion suppression and column fouling when serum is the sample matrix.
What it doesn't do
Delipidization removes lipid, not protein, so albumin, immunoglobulins, complement and hormones all stay, so delipidized serum isn't a substitute for a depleted or protein-free product. Some lipid-soluble vitamins and steroid hormones travel with the lipid fraction and come down with it. If those are your analyte, measure the delipidized lot before you use it as a blank.
Handling
Store it frozen, thaw it once and aliquot it. Delipidized serum is less likely than whole serum to throw a precipitate on thawing, but mix it gently and look at it before use anyway.
We offer sterile, non-hemolyzed delipidized serum from goat, bovine and donor-herd horse, the species most often used as immunoassay diluents and culture supplements. If your assay needs another species delipidized, or a heat-inactivated delipidized lot, ask us about a custom preparation.