Achieving highly water-soluble and luminescent gold nanoclusters modified by β–cyclodextrin as multifunctional nanoprobe for biological applications

We designed and synthesized a highly water-soluble biological nanoprobe (Au-GS@β-CD) through the covalent bonding of β–cyclodextrin (β-CD) onto the surface of gold nanoclusters (NCs) (Au-GS). The morphology, composition and photophysical properties of as-prepared Au-GS and Au-GS@β-CD NCs were fully characterized. The maximum emission intensity at about 600 nm of Au-GS@β-CD NCs increased significantly as compared to Au-GS NCs, which is consistent with its effective absorption enhancement. The water solubility and biocompatibility of resultant Au-GS@β-CD NCs were also notably enhanced, which allow it to be selectively uptaken by gastric cancer cells (MGC-803) and exhibit red luminescence in the cells. Thus, the as-prepared Au-GS@β-CD NCs could be used as promising biological nanoprobes for diagnosis of gastric cancer cells. The successful loading of doxorubicin (DOX) also allows it to hold attractive ability of drug delivery. Moreover, both Au-GS and Au-GS@β-CD NCs are thermally responsive. Furthermore, the metal ions detection experiments indicate that both Au-GS NCs and Au-GS@β-CD NCs can selectively recognize Pb ²⁺ , Al ³⁺ , Cu ²⁺ , Fe ³⁺ and Ag ⁺ ions through luminescence change. The detection limits of Pb ²⁺ and Fe ³⁺ are improved for Au-GS@β-CD NCs due to the synergistic effect of β-CD and Au NCs.