Quantitation of amyloid beta peptides Aβ1–38, Aβ1–40, and Aβ1–42 in human cerebrospinal fluid by ultra-performance liquid chromatography–tandem mass spectrometry

Quantitative detection of amyloid-β peptides by mass spectrometry: state of the art and clinical applications

“…After thawing CSF, in order to recover monomeric Aβ peptides that otherwise spontaneously auto-aggregate, aggregate to other proteins or get adsorbed to the walls of tubes, the most common approach is to denature samples with guanidine hydrochloride (Gnd HCl 5M). This can also help minimizing enzymatic activities and thus improving intermediate precision of measurements by reducing sample degradation [40]. After denaturation, the samples can be analyzed by various MS techniques as described below and Table 1.…”

“…IP was progressively replaced by solid phase extraction (SPE) which resulted in a very efficient detection of Aβ peptides [40,42] (Figure 2C). The first SPEs of Aβ peptides used hydrophilic-lipophilic balanced (HLB) [59] and SepPak C18 [60] stationary phases.…”

“…The first SPEs of Aβ peptides used hydrophilic-lipophilic balanced (HLB) [59] and SepPak C18 [60] stationary phases. Recent advances on mixed-mode of SPE with Mild Cation eXchange (MCX), improved the selectivity and recovery of Aβ peptides [40,42]. Of note, regardless of the prefractionation approach, CSF is generally dried in a lyophilizer or a vacuum centrifuge concentrator (speedvac) in order to concentrate, freeze-dry and store them before analysis.…”

“…To overcome this hurdle, standards are often pretreated with hexafluoroisopropanol (HFIP) [71] in order to denature beta sheets and favor α-helix conformations. Aβ standards need eventually to be re-suspended in solvents compatible with MS analysis, i.e., acetonitrile/ammonium hydroxide (20%:1%, v/v) [42,66] or dimethylsulfoxide (DMSO) [40].…”

“…For Aβ peptides, it is also important to verify that the model matrix does not induce any aggregation or non-specific adsorption. For quantification of Aβ peptides, several model matrices have been used, including human CSF depleted of Aβ peptides, rat CSF, artificial CSF (Na 150; K 3.0; Ca 1.4; Mg 0.8; P 1.0; Cl 155 in mM, Tocris Bioscience), artificial CSF supplement with 5% of rat plasma or with 4 mg/mL of bovine serum albumin [40,56,66,72].…”