Sialic‐acid‐binding, immunoglobulin‐type lectin‐7 (Siglec‐7) is present on the surface of natural killer cells. Siglec‐7 shows preference for disialylated glycans, including α(2,8)‐α(2,3)‐disialic acids or internally branched α(2,6)‐NeuAc, such as disialosylglobopentaose (DSGb5). Herein, DSGb5 was synthesized by a one‐pot multiple enzyme method from Gb5 by α2,3‐sialylation (with PmST1) followed by α2,6‐sialylation (with Psp2,6ST) in 23 % overall yield. DSGb5 was also chemoenzymatically synthesized. The protection of the nonreducing‐end galactose of Gb5 as 3,4‐O‐acetonide, 3,4‐O‐benzylidene, and 4,6‐O‐benzylidene derivatives provided DSGb5 in overall yields of 26 %, 12 %, and 19 %, respectively. Gb3, Gb4, and Gb5 were enzymatically sialylated to afford a range of globo‐glycans. Surprisingly, DSGb5 shows a low affinity for Siglec‐7 in a glycan microarray binding affinity assay. Among the synthesized globo‐series glycans, α6α3DSGb4 shows the highest binding affinity for Siglec‐7.

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Heterogeneous copper nanoparticles (CuNPs) have emerged as a promising alternative to complete the Cu(I)-catalyzed azide−alkyne cycloaddition (CuAAC) owing to better stability and biocompatibility and provide opportunities for surface functionalization of biomolecules. Herein, we fabricated Ag-coated cuprous oxide (Cu 2 O) NP slides to promote dual functions: the metal-enhanced fluorescence effect and external copper ionfree CuAAC reaction. The Cu 2 O NPs were in situ generated on a Ag-coated glass slide, thus accelerating the catalytic process of the surface cycloaddition reaction. Considering the catalytic activity of the Ag-coated Cu 2 O NP surface, the azide−alkyne cycloaddition was studied employing an azido-linked ganglioside GD3 glycan and a caged biotin; the latter surface enabled the detection of fluoride with a sensitivity of 0.82 μM that cannot be used on bare glass slides due to erosion by fluorine. Moreover, the immobilization of antibodies (Ab's) using the BA-tosyl-oriented pathway was further introduced to this newly developed slide surfaces and showed better sensitivity compared to the random Ab immobilization method. The Ag-coated Cu 2 O NP surfaces developed herein represent a practical and alternative sensing platform for biological or diagnostic applications.

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Antibodies have exquisite specificities for molecular recognition, which have led to their incorporation into array sensors that are crucial for research, diagnostic, and therapeutic applications. Many of these platforms rely heavily on surface-bound reactive groups to covalently tether antibodies to solid substrates; however, this strategy is hindered by a lack of orientation control over antibody immobilization. Here, we report a mild electrophilic phenylsulfonate (tosylate) ester-containing boronic acid affinity ligand for attaching antibodies to glass slides. A high level of antibody coupling located near the Fc region of the boronated antibody complex could be achieved by the proximal nucleophilic amino acid driven substitution reaction at the phenylsulfonate center. This enabled the full-length antibodies to be permanently tethered onto surfaces in an oriented manner. The advantages of this strategy were demonstrated through the individual and multiplex detection of protein and serum biomarkers. This strategy not only confers stability to the immobilized antibodies but also presents a different direction for the irreversible attachment of antibodies to solid supports in an orientation-controlled way.