An LC-MS/MS-based platform for the quantification of multiple amyloid beta peptides in surrogate cerebrospinal fluid.

ABSTRACT

Introduction: The accurate quantification of amyloid beta (Aß) peptides in cerebrospinal fluid (CSF) is crucial for Alzheimer's disease (AD) research, particularly in terms of preclinical and biomarker studies. Traditional methods, such as the enzyme-linked immunosorbent assay (ELISA), have limitations. These include high costs, labor intensity, lengthy processes, and the possibility of cross-reactivity. Objectives: The primary objectives of this research were twofold to comprehensively characterize Aß peptides and to develop a reliable and accurate method for the simultaneous quantification of Aß 1-40 and Aß 1-42 peptides in surrogate CSF that is traceable to the International System of Units (SI). Methods: We developed a novel method that combined solid phase extraction (SPE) with isotope dilution liquid chromatography/tandem mass spectrometry (ID-LC/MSMS). SPE was employed to efficiently eliminate matrix interferences, while [15N] Aß1-40 and [15N] Aß1-42 served as internal standards to improve accuracy. In addition, we introduced Peptide Impurity Corrected Amino Acid Analysis (PICAA) to ensure traceability to the SI and reliable quantification of Aß peptides. Results: The developed platform demonstrated a linear calibration range of 300-20000 pg/ml for both Aß1-42 and Aß1-40 peptides, accompanied by strong correlation coefficients greater than 0.995. Quality Control (QC) samples demonstrated an accuracy of at least 90.0 %. Conclusion: The enhanced specificity and flexibility of the developed platform potentially have implications for Alzheimer's disease diagnosis and future investigations of novel Aß peptide biomarkers.