Spiropyran-Functionalized Gold Nanoclusters with Photochromic Ability for Light-Controlled Fluorescence Bioimaging

Abstract

Fluorescent gold nanoclusters with unique luminescence properties have drawn great attention in bioimaging. The gold nanoclusters with controlled multicolor fluorescence may benefit accurate fluorescence imaging. In this work, gold-nanoclusterengineered spiropyran ligands (AuNC-SP) were reported to achieve controlled dual-color imaging under single excitation. Through switching the Forster resonance energy transfer from the gold nanocluster segment to the open-ring state merocyanine by UV−vis irradiation, AuNC-SP possesses reversibly dual-color fluorescence. After AuNC-SP combined with chitosan to form AuNC-SP@CS nanoparticles, the steric protection of chitosan largely improved the oxidative stability of AuNC-SP upon UV irradiation. Moreover, the AuNC-SP@ CS could be internalized within cancer cells and released AuNC-SP that further underwent transportation into the nucleus. Thus, the AuNC-SP@CS exhibits excellent and reversible dual-color fluorescence to label not only the cytoplasm but also the nucleus. We envisage the AuNC-SP@CS as an ideal probe for fine subcellular assays in the cell interior.

Advances of gold nanoclusters for bioimaging

“…Using suitable biomolecules and ligands with different activities, the FL emission wavelength of AuNCs can be modified, and the imaging categories of AuNCs in cells or animals can be identified. Cong et al. (2021) created AuNCs-SP@CS (SP: spiropyran, CS: chitosan) by combining the photoisomerization of SP with the spatially protective ability of CS.…”

Conjugated Polymer-Functionalized Stretchable Supramolecular Hydrogels to Monitor and Control Cellular Behavior

“…In a typical Förster resonance energy transfer (FRET) process, an excited fluorescent donor transfers energy to a fluorescent acceptor in a space. − In most cases, the shorter the donor–acceptor distance, the higher the FRET efficiency . Organic fluorescent molecules, inorganic metal nanoclusters, or quantum dots with a high emission efficiency can act as energy donors. − Among them, conjugated molecules possess π-conjugated backbones that allow large absorption coefficients. , Relying on an effective energy transfer from conjugated molecules, amplified signals of the acceptor can be gained for detection . More importantly, the side chains of conjugated molecules are readily customized with functional groups, − which promotes them to form photofunctional supramolecular hydrogels via molecular interactions.…”

Controlling the Interaction between Fluorescent Gold Nanoclusters and Biointerfaces for Rapid Discrimination of Fungal Pathogens

“…Fluorescent signal tracking has been a powerful and efficient method to gain temporal and spatial information on dynamic events in complex biosystems. − Fluorescent materials, such as organic dyes, quantum dots, metal nanoclusters, and fluorescent composites, have been developed for biodetection. − Among them, fluorescent gold nanoclusters have emerged from ordered aggregates of gold atoms and gold­(I)–thiolate motifs. − The special Au 0 @Au I –ligand core–shell structure endows the gold nanoclusters structural stability and reconfigurable surfaces. − Through facile modification of the surface ligands, functional groups are induced to the gold nanoclusters . Then the biointerface interaction between gold nanoclusters and the biosystem can be constructed to gain corresponding fluorescence signals .…”