Liu Huwei / Baiyu research group of Peking University has made important progress in ultra-high sensitivity detection and imaging of disease biomarkers by mass spectrometry

As a common clinical biomarker and drug target, biomolecules such as membrane protein and glycan participate in many life processes, and their abnormal expression is closely related to the occurrence and development of diseases Therefore, it has important scientific significance and practical value for the accurate and rapid detection of membrane protein and glycan expression levels in body fluids, cells and tissues, as well as visual imaging analysis Although the commonly used enzyme-linked immunosorbent assay and fluorescence or electrochemical methods can meet the requirements of detection sensitivity, there are some defects, such as overlapping bands, serious background interference, limited number of labeled probes, and it is difficult to achieve multi-target simultaneous detection Mass spectrometry (MS) has the advantage of high-quality resolution, which can meet the needs of single point and multi-target simultaneous detection However, the direct detection of protein and glycan based on MS has the problems of low ionization efficiency and limited detection sensitivity By designing a specific probe to identify and mark the target to be tested, the pyrolytic probe technology can transform the detection of a series of target to the detection of MS report group on the probe, and greatly improve the detection sensitivity through this signal amplification process Based on this, Liu Huwei / Baiyu group of School of chemistry and molecular engineering of Peking University designed and synthesized a new rhodamine type MS tag, and based on this, developed a new method of ultra-high sensitivity, high throughput, multi-objective and easy to operate atmospheric open mass spectrometry (AMS) immunoassay for membrane protein biomarkers This method can be used to detect disease protein markers in micro upgraded body fluids or on the surface of dozens of cells in situ The detection sensitivity is up to the level of zeptomol (zmol) Relevant achievements were published in J am Chem SOC (DOI: 10.1021 / JACS 8b10853) under the title of "ultrasensitive ambient mass spectrum immunologies: multiplex detection of proteins in serum and on cell surfaces"; in addition, the research group designed a dual function laser lysable gold nanomass spectrometer probe (lcmp) for glycan detection It can be used not only as a probe for the recognition and detection of glycan, but also as a matrix for laser desorption to directly realize the subsequent MS detection and imaging The probe has been successfully used in MS imaging of tumor tissue surface glycans, which is expected to provide a powerful tool for disease diagnosis and MS based visualization imaging Relevant achievements were published in Chem SCI (DOI: 10.1039 / c8sc04642e) under the title of "bifunctional clear probe for in situ multiple glycation and imaging using mass spectrometry" The schematic diagram and detection flow of AMS immunoassay method are shown in Figure 1 Using the platform, the detection limit (LOD) of thrombin spiked samples was 10.9 zmol (PBS) and 35.1 zmol (serum), respectively This method can detect CA125 and other biomarkers in serum samples, which is expected to be used in the early diagnosis of ovarian cancer and breast cancer At the same time, the platform can also detect the three important biomarkers (CA125, CEA and EpCAM) on the surface of OVCAR-3 and MCF-7 cells at the level of 25 cells at the same time and in situ, which shows the ultra-high sensitivity and multi-target simultaneous detection ability, and has universality and expansibility Fig 1 Open mass spectrometry (AMS) immunoassay method and flow chart (source: J am Chem SOC.) for in-situ detection and MS imaging analysis of glycans, our team designed a dual energy lcmp probe based on lectin recognition and three kinds of PEG small molecule MS signal molecules labeled separately (Fig 2) The probe can transform the detection of glycan into the detection of a large number of modified PEG MS reporter groups, so as to overcome the problems of low efficiency of glycan ionization, low sensitivity of detection, and difficulty in spectral analysis The designed recognition unit is suitable for lectin, antibody and aptamer systems Using these probes, the team carried out in-situ analysis of monosaccharide (mannose, terminal sialic acid and N-acetylglucosamine) on the cell surface and MS imaging of the surface glycan of tumor tissue The imaging results can directly reflect the changes of glycan content in cancer tissue and adjacent tissue, different pathological changes in the same tissue and different microstructure areas It is not only helpful to reveal the changes of glycan content in the process of tumor development, but also is expected to be used in clinical diagnosis and tumor marker screening Fig 2 synthesis of bifunctional laser pyrolysis mass spectrometer probe and its application in glycan detection and MS imaging (source: Chem Sci.) Liu Huwei/ Baiyu research group has been committed to the separation and detection of complex biological samples for a long time It aims to develop efficient sample processing methods based on new nano separation media, new analytical methods based on mass spectrometry with high sensitivity, high throughput and high selectivity, and clinical histological research The corresponding author of the above paper is Associate Professor Bai Yu The first author is Xu Shuting (J am Chem SOC., DOI: 10.1021 / JACS 8b10853), a doctoral student of grade 15, and Ma Wen (chem SCI., DOI: 10.1039 / c8sc04642e), a doctoral student of grade 14 The research work was supported by the national key R & D program of NSFC and the Ministry of science and technology.