Polypeptide-Templated Au Nanoclusters with Red and Blue Fluorescence Emissions for Multimodal Imaging of Cell Nuclei

Abstract

Noble metal nanoclusters (<2 nm) prepared using special molecules such as proteins and peptides as templates have been attracting increasing attention in biomedical applications and cell imaging because of their excellent biocompatibility, size-dependent fluorescence properties, and relatively simple synthesis. Although cell imaging using metal clusters has developed rapidly in recent years, multimodal imaging of the cell nucleus remains challenging. Herein, we report the successful synthesis of two different types of gold nanoclusters, one with blue fluorescence emission (λex 320 nm, λem 405 nm) and the other with red fluorescence emission (λex 560 nm, λem 657 nm), using the same polypeptide SV (sequence: NH2–CCYGGPKKKRKVG-COOH) as a template. The synthesis of these two optically distinct Au nanoclusters (Au NCs) was achieved through the optimization of synthesis conditions, including light, pH, the Au: polypeptide ratio, reaction time, and temperature. The multimodal imaging ability of the Au NCs were subsequently explored, with particular emphasis on the enzyme-like catalysis of the NCs and their use in the optical imaging of cell nuclei. Results show that the Au NCs possessed similar biological activities as the parent peptide used in their synthesis as well as demonstrating peroxidase-like activity due to the Au nanocluster core. Further, the Au NCs targeted the cell nucleus, with their strong fluorescence allowing cell imaging (cells containing Au clusters could be distinguished by eye, eliminating the need for additional labels). Finally, the Au NCs exhibited excellent multimodal cell imaging abilities. The results suggest that the Au NCs introduced here are promising candidates for the labeling and analysis of pathological samples.

Qualitative and Quantitative Analysis of Tumor Cell Invasion Using Au Clusters

“…The fluorescent properties of Au clusters could make them used as fluorescent inks ( Figure 1 C). As depicted in Figure 1 D, the absorption peak position of peptide is located at 275 nm, while the position of the absorption peak of Au clusters is located at 243 and 292 nm, which was the characteristic absorption peaks of peptide-Au clusters [ 42 , 43 ]. As shown in Figure S1 , the peaks of C, Au, S, O, and N were obviously detected by X-ray photoelectron spectroscopy (XPS) spectrum.…”

Photoluminescent nanocluster-based probes for bioimaging applications

“…Optimizing synthetic conditions (e.g., light, pH, Au/peptide ratio, reaction time and temperature), Liu et al were able to fine-tune the emission properties of SV-capped gold nanoclusters, obtaining two distinct Au NC families, characterized by blue (λ ex = 320 nm, λ em = 405 nm) and red fluorescence emission (λ ex = 560 nm, λ em = 657 nm), respectively. Such SV-Au NCs exhibited an excellent multimodal imaging ability, enabling dual-color imaging even by naked eye, and moreover, they showed effective peroxidase-like activity in the oxidation of tetramethylbenzidine [64]. The association between CCY domains with self-assembling peptide motifs afforded supramolecular structures of Au NCs with improved luminescence.…”

State of the Art and Perspectives on the Biofunctionalization of Fluorescent Metal Nanoclusters and Carbon Quantum Dots for Targeted Imaging and Drug Delivery

“…In addition, the targeted imaging of subcellular organelles including mitochondria, nuclei, and nucleoli staining using AuNCs is crucial to modulating the cellular fate and organelle-related diseases. , Fang et al developed mitochondria-targeting peptide (CCYKFR)-templated AuNCs for anticancer treatment with an improved radiosensitization effect . Red and blue fluorescent AuNCs were synthesized using the same polypeptide SV (sequence NH 2 -CCY­GGP­KKK­RKVG-COOH) as a template which possessed the multimodal imaging capability of cell nuclei . Wang et al reported novel AuNCs where the stabilizing ligands were positively charged tripeptides (Lys-Cys-Lys).…”

“…80 Red and blue fluorescent AuNCs were synthesized using the same polypeptide SV (sequence NH 2 -CCYGGPKKKRKVG-COOH) as a template which possessed the multimodal imaging capability of cell nuclei. 82 Wang et al reported novel AuNCs where the stabilizing ligands were positively charged tripeptides (Lys-Cys-Lys). These AuNCs selectively stained nucleoli and enabled the monitoring of nucleolar dynamics during the process of reverse transformation in malignant cells (Figure 7B).…”