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Sialyl-Tn (STn or sialyl-Thomsen-nouveau) is a carbohydrate antigen expressed by more than 80% of human carcinomas. We here report a strategy for ratiometric STn detection and dual-color cancer cell labeling, particularly, by molecularly imprinted polymers (MIPs). Imprinting was based on spectroscopic studies of a urea-containing green-fluorescent monomer 1 and STn-Thr-Na (sodium salt of Neu5Acα2-6GalNAcα-O-Thr). A few-nanometer-thin green-fluorescent polymer shell, in which STn-Thr-Na was imprinted with 1, other comonomers, and a cross-linker, was synthesized from the surface of red-emissive carbon nanodot (R-CND)-doped silica nanoparticles, resulting in dual fluorescent STn-MIPs. Dual-color labeling of cancer cells was achieved since both red and green emissions were detected in two separate channels of the microscope and an improved accuracy was obtained in comparison with single-signal MIPs. The flow cytometric cell analysis showed that the binding of STn-MIPs was significantly higher (p < 0.001) than that of non-imprinted polymer (NIP) control particles within the same cell line, allowing to distinguish populations. Based on the modularity of the luminescent core–fluorescent MIP shell architecture, the concept can be transferred in a straightforward manner to other target analytes.
Dual-fluorescent molecularly imprinted nanoparticles with a red-emissive carbon nanodot-doped silica core and a chlorogenic acid-imprinted fluorescent polymer layer are prepared and their use in ratiometric fluorometric analysis is described. Nanoparticle probes consisting of a shielded and stably emitting core and a shell with embedded binding sites that indicates the presence of an analyte with a change in emission allow for internally referenced measurements potentially accounting for detrimental influences from instrument drifts, light source fluctuations or sensor materials-related inhomogeneities.
Glycosylation is heavily altered in tumor cells compared with healthy cells, because of the different levels of expression of glycosyltransferases, glycosidases and monosaccharide transporters within a cancerous microenvironment. 1 Tumor-associated glycans, especially sialic acid (SA) conjugates, which are good candidates of tumor markers, can be used for Cancer early diagnosis. 2 However, studies on SA-binding lectins demonstrate that the type of SAlinkage and the glycosylation position of carbohydrate can greatly influence the affinity. 3 Therefore, there is a need for diagnostic tools owning high specificity and strong affinity to analyze and determine SA glycosylation motifs. 4 Herein, we report the development of fluorescent core/shell/shell nanoparticles where the outermost layer is a thin molecularly imprinted polymer (MIP) film binding to tumor cells in vitro by targeting cell surface SA. The core is made of N-doped red carbon nanodots (R-CNDs) which were prepared by hydrothermal synthesis, emitting intense red fluorescence under fluorescence microscopy imaging conditions. Silica coating of R-CNDs was achieved by a microemulsion method, resulting in ca. 40 nm large silica-coated CNDs (named R-CSNs).
Finally, a thin MIP-shell was accomplished by using a combination of non-fluorescent
monomer (3), functional monomers (1, 2) and cross-linker (EGDMA) for polymerization
(Figure 1). Transmission electron microscopy (TEM) is used for structural characterization of
the formation of MIP layer, and the results of cell-based binding tests show a promising binding
affinity of MIPs to tumor cells, allowing a relatively robust, specific and rapid analytical
method for cancer biopsies.