Beijing National Laboratory for Molecular Sciences; Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China.
School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
Anal Chem. 2021 May 18;93(19):7317-7322. doi: 10.1021/acs.analchem.1c00880. Epub 2021 May 5.
Sialic acid (SA) is an important monosaccharide that is involved in incurable cancer immunotherapy. However, it is difficult to detect SA in situ using the existing strategy based on the SA-terminated glycopeptide extraction from the cell lysate. The countermeasures of the bottleneck caused by cell disruption and peptide extraction should be designed based on a "cell-surface attachment and controlled enzymolysis" protocol. Herein, a poly(styrene--maleic anhydride-acrylic acid-concanavalin A) (PSM-PAA-ConA) was synthesized and developed as a pH-regulated enzyme nanoreactor after being loaded with sialidase and myoglobin. The nanoreactor showed controllable biocatalysis induced by a cascade enzyme reaction and applied for the in situ detection of SA on a living cell surface. The addition of an acidic solution resulted in a decrease in the size of the nanoreactor and enhancement of its permeability, triggering an "on" state of the SA catalysis. Subsequent pH increase led to increased hydrophilicity of the nanoreactor, increasing its size and resulting in the catalytic "off" state. ConA assisted the cell-surface attachment of the enzyme reactor. Furthermore, SA on the surface of living cancer cells was successfully monitored by the pH-regulated enzyme nanoreactor, demonstrating the feasibility of high specificity in situ analysis for SA. This pH-induced catalytic efficiency control by the enzyme nanoreactor provides a potential platform for functional stimuli-responsive catalytic systems as well as a strategy for in situ analysis of biomolecules on the cell surface.
唾液酸（SA）是一种重要的单糖，参与了无法治愈的癌症免疫疗法。然而，基于从细胞裂解物中提取 SA 末端糖肽的现有策略，很难在原位检测 SA。应该基于“细胞表面附着和控制酶解”方案来设计克服细胞破碎和肽提取瓶颈的对策。在此，合成了聚（苯乙烯-马来酸酐-丙烯酸-伴刀豆球蛋白 A）（PSM-PAA-ConA），并在负载了唾液酸酶和肌红蛋白后，将其开发为 pH 调控的酶纳米反应器。该纳米反应器通过级联酶反应显示出可控的生物催化作用，并应用于活细胞表面 SA 的原位检测。添加酸性溶液会导致纳米反应器的尺寸减小，渗透性增强，触发 SA 催化的“开启”状态。随后 pH 值的增加会增加纳米反应器的亲水性，从而增加其尺寸，并导致催化“关闭”状态。ConA 辅助酶反应器在细胞表面的附着。此外，通过 pH 调控的酶纳米反应器成功监测了活癌细胞表面的 SA，证明了针对 SA 的高特异性原位分析的可行性。这种由酶纳米反应器诱导的 pH 依赖性催化效率控制为功能刺激响应催化系统提供了一个潜在的平台，并为细胞表面生物分子的原位分析提供了一种策略。
