Potential of MALDI TOF mass spectrometry for detection and quantification of corticosterone in the blood of loggerhead sea turtles

Abstract

The endangered loggerhead sea turtles (Caretta caretta) are a relatively abundant sea turtle species in Madeiran waters, where they encounter various environmental stressors: from natural to anthropogenic. The physiological stress response is increased corticosterone (CS) level in the blood, achieving 2 ng/mL. Although there are various analytical methods for determining the CS concentration in turtle blood, most of them require tedious procedures for the preparation. In this work, we have tested the possibility of using matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI TOF MS) for fast screening and detection of CS in blood from a turtle captured at the coast of Madeira Island. MALDI does not require sample derivatization and is suitable for low sample volume. The linearity, precision, and limit of detection and quantification with three organic MALDI matrices were investigated in this study. The signal-to-noise ratio of the CS-derived signal was used as a parameter for quantification. Isotopically labelled corticosterone was added as a correction factor at fixed concentration to achieve better linearity and precision. Our results demonstrate that this method has the potential for quantification of CS in turtle blood. However, the lowest concentration of CS extracted from plasma that was still detectable by MALDI TOF MS was about 0.04 mg/mL, which is about ten times higher than the expected CS concentration in blood.