Laser Cleavable Probes-Based Cell Surface Engineering for in Situ Sialoglycoconjugates Profiling by Laser Desorption/Ionization Mass Spectrometry

Cell-surface sialoglycoconjugates (sialoglycoproteins and sialoglycolipids) play important roles in cell–cell interactions and related tumor metastasis process. Although there have been some analytical methods to evaluate the sialoglycoconjugates, an effective method providing both qualitative and quantitative information is still deficient. Here we establish an extraction-free, sensitive, and high-throughput platform to realize in situ detection of the cell-surface sialoglycoconjugates on various cell lines, e.g., cancer and normal cells by laser desorption/ionization mass spectrometry (LDI MS). In this proposal, azide groups were introduced into the ends of cell-surface sialoglycoconjugates by the biorthogonal method, and then the sialoglycoconjugates were armed with a laser-cleavable probe (Tphsene) through click chemistry. We can easily get the probes signal under laser irradiation, which reflected the presence of cell-surface sialoglycoconjugates. Different cell lines were discriminated simultaneously, and the LDI relative quantification agreed with fluorescent results. Besides, a linear quantitation relationship in the range of 100 fmol to 100 pmol was obtained with a designed and synthesized internal standard (phTsane) added. A detection limit of 5 fmol was obtained with good reproducibility. Based on the quantitative and high-throughput ability, we conducted pharmacodynamics study of drug (tunicamycin) on cancer cells. In addition, we found the tag was safe from sweet-spot effect of matrix adding. The simultaneous detection of sialoglycoconjugates and metabolites was therefore achieved. We believe that this laser cleavable probes-based cell-surface engineering for sialoglycoconjugates platform means great significance to diagnosis, prognosis, and therapeutic purposes. Besides, this strategy can be applied to other glycoconjugates which is hard to detect and the related disease processes when more corresponding chemically modified sugar substrates and exact biorthogonal reactions are developed.