Covalent organic framework film-based laser desorption/ionization mass spectrometry for rapid and sensitive quantification of homocysteine in human serum.

Abstract

Homocysteine (hcy) is a metabolite in the human body and an important determinant of cardiovascular health. To assist in the assessment of human cardiovascular safety, a rapid and accurate quantitative analysis method must be developed. Laser desorption/ionization mass spectrometry (LDI-MS) has been widely used in biological, chemical and medical analysis due to its excellent characteristics of high throughput, low sample consumption and high speed. Herein, a LDI-MS method based on covalent organic framework (COF) film was developed for rapid and sensitive determination of hcy in human serum using an isotope-labeled internal standard. We tried to cultivate COFs on indium-tin oxide (ITO) substrate at room temperature to form thin film, which was used in LDI-MS. Compared with the traditional organic matrices, the COF film showed clean background and high signal response for the detection of hcy. In addition, using COF film as the substrate that can analyze a series of small molecules such as amino acids, bisphenols (Bps), estrogens, drugs, etc., with high signal intensity and clean background. We evaluated the limit of detection (LOD) and the reproducibility of this method. Finally, the calibration curve was made for the quantification of serum hcy using isotope labeled internal standard, and was applied to the rapid determination of hcy in clinical human serum. COF film-assisted LDI-MS had higher response signal and cleaner background compared to four conventional organic matrices. The LOD of the method for hcy was 0.5 μmol/L, equivalent to 500 fmol. This method exhibited excellent performance for small molecule compounds including amino acids, Bps, drugs, and estrogens. The reproducibilities of this method for shot-to-shot and dot-to-dot were proved to be good. This method was applied to the rapid analysis of hcy in clinical human serum, showing good correlation with those obtained by hospital testing. The COF film-based LDI-MS method showed simple sample preparation, short analysis time, clean background and good reproducibility for hcy analysis. As an important indicator of human health, the detection of serum hcy is of great significance to human health.