A universal strategy of glyconanoparticle preparation using a bifunctional linker for lectin sensing and cell imaging

Glyconanoparticles (G-NPs), biofunctional nanomaterials that can fully combine the unique properties of nanoparticles (NPs) with the bioactivities of carbohydrates, have become an appealing nanoplatform in analytical chemistry and biomedical research. However, there is currently a lack of an efficient and universal method for facile immobilization of reducing carbohydrates on NPs while maintaining their structure integrity, greatly limiting the preparation and application of G-NPs. Herein, a new and universal strategy for preparing carbohydrate-functionalized gold nanoclusters (Au NCs) was developed by using S-(3-(methoxyamino)propyl) thioacetate (MPTA) as a new bifunctional linker. MPTA with an N-methoxyamine group (-NHOMe) and a thioacetyl group (-SAc) was synthesized by a two-step strategy and then grafted onto Au NCs by an efficient click reaction. Subsequently, reducing carbohydrates could be readily immobilized onto MPTA-functionalized Au NCs (MPTA-Au NCs) by a reducing end ring-closure reaction under mild conditions. The obtained G-NPs showed average size of 1.9 ± 0.42 nm and strong fluorescence at 610 nm. Carbohydrates grafted on G-NPs still retained their structure integrity and specific recognition ability toward their receptor proteins. Notably, the affinity between G-NPs and proteins was increased by 1300 times compared with free carbohydrates with an association constant of (1.47 ± 0.356) × 10⁶ M^-1. The prepared fluorescent G-NPs were also successfully applied to lectin sensing and targeted breast cancer cell imaging with good performance. These results indicated that the intact immobilization of reducing carbohydrates (whether naturally or chemically accessed) on NPs could be easily achieved using MPTA, providing a simple, efficient, and universal strategy for G-NP preparation.