Solvent-resistant microfluidic paper-based analytical device/spray mass spectrometry for quantitative analysis of C18-ceramide biomarker

We developed a highly efficient and low-cost organic solvents-resistant microfluidic paper-based analytical device (mu PAD) coupled with paper spray mass spectrometry (PS-MS) for quantitative determination of C-18-ceramide as a prognostic biomarker for several diseases. Several models of mu PAD patterns have been examined to select the most resistant and efficient microchannel barriers, which can provide continuous spray at ionization zone and prevent "coffee ring" effect. Moreover, the developed mu PAD has enabled the analysis of low concentration of C-18-ceramide because of the maximum supply of deposited analyte through microchannel. The MS results confirmed the formation of doubly and singly charged metal ion complexes between ceramide and different metal ions. Notably, the complexation that occurs between lithium ions and C-18-ceramide showed a high relative abundance compared with other formed complexes. Taking into account the relative abundance of complex [Cer + Li](+)at 572.8 m/z, it can be considered as a stable ion and therefore be used for the analysis of C-18-ceramide at low concentrations. Complexation of C-18-ceramide and lithium confirmed with quantum chemical calculations. The proposed method represents good linearity with a regression coefficient of 0.9956 for the analysis of C-18-ceramide and reaches a limit of detection to 0.84 nM. It has been adapted successfully for practical application in human serum samples with high recovery values in range of 92%-105%. The developed mu PAD-MS technique provides clear advantages by reducing the experimental steps and simplifying the operation process and enables to identify subnanomolar concentration of C-18-ceramide in human serum samples.