Development Of Novel MALDI Matrices Based On Carbon Dots For The Analysis Of Small Molecules

Recently,MALDI-TOF MS has emerged as a popular analytical tool with the advantages of easy sample preparation,good salt tolerance,as well as fast and high throughput data acquisition ability.However,for the existing matrices,it was limited in detecting low-molecular-weight analytes due to the matrix-related peaks and low reproducibility.Therefore,the development of new matrices is highly desirable.Here,a new matrix N,S-CDs,for the first time,was synthesized and used for small molecule analysis.Comprehensive assessments of N,S-CDs were conducted including structural characterization,comparisons with conventional CHCA and 9-AA matrices in detecting amino acids,peptides and nucleosides in different ion modes.The results showed that N,S-CDs could be a sensational matrix which enhanced the signal intensity of the analytes without matrix-related interference,especially in negative ion mode.What's more,N,S-CDs matrix displayed good salt tolerance and signal reproducibility.In addition,the N,S-CDs matrix was further applied for serum detection and the classification of different subtypes of breast cancer cell lines.The detection of various endogenous metabolites in serum analysis and significant distinguish between two cell lines indicated the ability of our new matrix to be applied in complex biological sample.Furthermore,we investigate the ionization mechanism of the N,S-CDs as matrix.This work creates a new application branch for N,S-CDs and provides an improved MALDI matrix for small molecule analysis.Glycosylation is one of the most important protein post-translational modification process.It not only affects the behavior of protein folding,transport and localization in the cell,but also regulates the activation of the receptor through the specific mechanism of sugar-protein interaction.Sialic acid is often located at the end of the protein sugar chain structure and is an important part of the glycosylated protein.Because of its unique position characteristics and its structural characteristics,it can regulate a large number of physiological and pathological processes,and thus the occurrence and development of many diseases have an important relationship with it.In the protein digestion products,only about 2%-5%of them are glycopeptide.The one containing sialic acid end is very limit,so to achieve the determination of sialylated sugar,enrichment method is critical.In this paper,we synthesized a new material Fe ₃O₄@CDs@5-HT which can be specific with the sialic acid in a certain acid-base conditions.It can be effectively enriched through the magnet and can be directly used as a MALDI matrix.We derivatized the analyst to prevent the fracture improving the signal.The results showed that Fe₃O₄@CDs@5-HT had good specificity for sialic acid and had higher detection sensitivity.It has great potential in the development of metabolomics,biomarker discovery,screening,immune system research and the development of virology and other disciplines.