Quantification of thymosin β4 in human cerebrospinal fluid using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI–TOF–MS) has been applied to the analysis of a wide range of biomolecules. To date, there are two specific areas of application where MALDI–TOF–MS is viewed as impractical: analysis of low-mass analytes and relative quantitative applications. However, these limitations can be overcome and quantification can be routine. Increased levels of thymosin β4 (TB4) have been recently found in cerebrospinal fluid (CSF) from Creutzfeldt–Jakob disease (CJD) patients. Our objective was to apply a label-free quantitative application of MALDI–TOF–MS to measure TB4 levels in human CSF by adding the oxidized form of TB4 as an internal standard. The relative peak area or peak height ratios of the native TB4 to the added oxidized form were evaluated. Considering the relative peak area ratios, healthy individuals showed a mean value of 40.8 ± 21.27 ng/ml, whereas CJD patients showed high values with a mean of 154 ± 59.07 ng/ml, in agreement with the previous observation found in CJD patients. Similar results were obtained considering peak height ratios. The proposed method may provide a simple and rapid screening method for quantification on CSF of TB4 levels suitable for diagnostic purposes.