Galectin-3 (Gal-3), a member of the β-galactoside-binding lectin family, is a tumor biomarker and involved in tumor angiogenesis and metastasis. Gal-3 is therefore considered as a promising target for early cancer diagnosis and anticancer therapy. We here present the synthesis of a library of tailored multivalent neo-glycoproteins and evaluate their Gal-3 binding properties. By the combinatorial use of glycosyltransferases and chemo-enzymatic reactions, we first synthesized a set of N-acetyllactosamine (Galβ1,4GlcNAc; LacNAc type 2)-based oligosaccharides featuring five different terminating glycosylation epitopes, respectively. Neo-glycosylation of bovine serum albumin (BSA) was accomplished by dialkyl squarate coupling to lysine residues resulting in a library of defined multivalent neo-glycoproteins. Solid-phase binding assays with immobilized neo-glycoproteins revealed distinct affinity and specificity of the multivalent glycan epitopes for Gal-3 binding. In particular, neo-glycoproteins decorated with N′,N″-diacetyllactosamine (GalNAcβ1,4GlcNAc; LacdiNAc) epitopes showed high selectivity and were demonstrated to capture Gal-3 from human serum with high affinity. Furthermore, neo-glycoproteins with terminal biotinylated LacNAc glycan motif could be utilized as Gal-3 detection agents in a sandwich enzyme-linked immunosorbent assay format. We conclude that, in contrast to antibody-based capture steps, the presented neo-glycoproteins are highly useful to detect functionally intact Gal-3 with high selectivity and avidity. We further gain novel insights into the binding affinity of Gal-3 using tailored multivalent neo-glycoproteins, which have the potential for an application in the context of cancer-related biomedical research.

中文翻译：

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量身定制的多价新糖蛋白：结合Galectin-3的聚糖配体的文库的合成，评估和应用

Galectin-3（Gal-3）是β-半乳糖苷结合凝集素家族的成员，是一种肿瘤生物标志物，参与肿瘤血管生成和转移。因此，Gal-3被认为是早期癌症诊断和抗癌治疗的有希望的靶标。我们在这里提出了定制的多价新糖蛋白文库的合成，并评估了它们的Gal-3结合特性。通过结合使用糖基转移酶和化学酶促反应，我们首先合成了一组N-乙酰基乳糖胺（Galβ1,4GlcNAc； LacNAc 2型）为基础的寡糖，分别具有五个不同的终止糖基化表位。牛血清白蛋白（BSA）的新糖基化是通过将二烷基方酸与赖氨酸残基偶联而完成的，从而形成一个确定的多价新糖蛋白文库。固定化的新糖蛋白的固相结合测定显示了多价聚糖表位对Gal-3结合的独特亲和力和特异性。特别是，用N '，N修饰的新糖蛋白″-二乙酰基乳糖胺（GalNAcβ1,4GlcNAc; LacdiNAc）表位显示出高选择性，并被证明可以高亲和力从人血清中捕获Gal-3。此外，具有末端生物素化的LacNAc聚糖基序的新糖蛋白可以用作三明治酶联免疫吸附测定形式的Gal-3检测剂。我们得出的结论是，与基于抗体的捕获步骤相比，提出的新糖蛋白对检测功能完整的Gal-3具有高度的选择性和亲和力非常有用。我们进一步获得使用定制的多价新糖蛋白对Gal-3的结合亲和力的新颖见解，这些蛋白在癌症相关生物医学研究中具有潜在的应用前景。