Dopamine-Modified AuCu Bimetallic Nanoclusters as Charge Transfer-Based Biosensors for Highly Sensitive Glycine Detection

Abstract

Glycine is the simplest amino acid in living organisms and plays important roles in biology and medicine. However, few biosensors for glycine sensing have been reported. Herein, we present a facile strategy to construct dopaminemodified AuCu bimetallic nanoclusters (denoted as AuCu NC− DA) as charge transfer-based biosensors for highly sensitive glycine sensing. The AuCu NCs stabilized by bovine serum albumin (BSA) exhibited a fluorescence maximum at 400 nm. Because of the high affinity of BSA for dopamine (DA), the surface of the AuCu NCs was modified with DA without any complicated chemical reactions, resulting in fluorescence quenching through a charge transfer process. Among 20 amino acids, AuCu NC−DA exhibited an off/on fluorescence switching response specifically toward glycine through the formation of hydrogen bonds with oxidized DA, which inhibited the charge transfer process, leading to the emergence of a new emission peak at 475 nm. Spectroscopic and thermodynamic results combined with molecular docking analyses provided comprehensive understanding of the sensing mechanism. Furthermore, we showed that AuCu NC−DA was able to sense glycine in cells by imaging. Finally, the practicability of AuCu NC−DA for glycine detection was validated in milk drink samples. This study presents a promising type of a charge transfer-based sensor.

Support, composition, and ligand effects in partial oxidation of benzyl alcohol using gold–copper clusters

“…AuCu nanoparticles are known to exhibit fluorescence and are used for this reason in sensing applications. 69,70 In addition to UV-vis spectral changes, shifts in the photoluminescence spectra give additional insights that correlate to differences in the alloyed AuCu cluster–TPP ligand interaction as compared to the monometallic Au cluster–ligand interaction. Fig.…”

Origin of luminescence properties and synthetic methods for gold- and bimetallic gold-based nanomaterials

“…[147][148][149][150][151] Compared to metal NCs comprised of a single metal, BMNCs comprised of heterometals in their system possess better cooperative electronic, optical, sensing and biological properties. 102,138,[152][153][154][155] This section discusses the synthetic procedures available to synthesize metal-based luminescent nanomaterials.…”

Controllable Synthesis of Bimetallic Nanostructures Using Biogenic Reagents: A Green Perspective

“…In addition to Au–Ag, other examples of bimetallic systems that have been prepared via BSA-mediated synthesis are Au–Cu, Au–Ni, Au–Pt, and Pt–Bi. − Meanwhile, lysozyme is another protein aside from BSA that has been found useful in the protein-directed synthesis of Au–Ag nanoclusters . Other related studies involve peptides with much shorter amino acid chains than proteins. , As an example, Wang et al made use of glutathione (GSH), a peptide comprised of only three amino acids, to synthesize composition-tunable Au–Ag nanoclusters via the galvanic replacement route …”

“…135 Chen et al demonstrated that through surface modification with dopamine, BSA-capped Au−Cu nanoclusters can be used as a fluorescent biosensor for glycine detection based on an off/on fluorescence switching behavior. 99 The fluorescence of the presynthesized BSA-capped nanoclusters was switched off after modification with dopamine as a result of a charge transfer process. In the presence of glycine, this charge transfer process was inhibited due to hydrogen bonding interactions, thereby turning on the fluorescence.…”