Characterisation and quantification of liposome-type nanoparticles in a beverage matrix using hydrodynamic chromatography and MALDI-TOF mass spectrometry

This paper describes the characterisation of liposome-type nanoparticles (NPs) dispersed in a beverage matrix. Characterisation is based on a two-step procedure: first, liposomes are separated on the basis of size in the nanometre range by use of hydrodynamic chromatography (HDC); second, chemical characterisation is performed by use of MALDI-TOF mass spectrometry (MS). Characterisation of three types of Coatsome liposome, a commercially available type of empty liposome, was investigated. All three liposome types, Coatsome A = anionic, N = neutral, and C = cationic, gave single peaks in HDC, reflecting diameters of 153, 187, and 205 nm, respectively. Subsequent MALDI-TOF MS in positive mode furnished major signals at m/z = 734.5 ([M + H](+) adduct) and m/z = 756.6 ([M + Na](+) adduct) of l-(alpha)-dipalmitoylphosphatidylcholine (DPPC) monomer and dimeric adducts at m/z = 1468.1 and m/z = 1490.1, respectively. MALDI-TOF MS in negative mode gave a signal at m/z = 721.3 ([M -aEuro parts per thousand H](-) adduct) of l-(alpha)-dipalmitoylphosphatidylglycerol (DPPG), except for Coatsome C which lacks this phospholipid. After HDC separation of Coatsome A NPs the major DPPC and DPPG signals can be detected in the expected fractions by use of MALDI-TOF MS in positive and negative modes, respectively. Validation of the analytical strategy revealed linearity (R (2) > 0.99), repeatability (relative standard deviation < 10 %), and reproducibility (relative standard deviation between days < 10 %) were good, recovery was 61 +/- 5 %, and the limit of quantification was 1 mg mL(-1) in this matrix. With 4 mg Coatsome A mL(-1) 20 out of 20 samples furnished the 734.5 and 756.6 signals typical of DPPC in MALDI-TOF MS characterisation.