Synthesis of Exosome-Based Fluorescent Gold Nanoclusters for Cellular Imaging Applications

Abstract

In recent years, fluorescent metal nanoclusters have been used to develop bioimaging and sensing technology. Notably, protein-templated fluorescent gold nanoclusters (AuNCs) are attracting interest due to their excellent fluorescence properties and biocompatibility. Herein, we used an exosome template to synthesize AuNCs in an eco-friendly manner that required neither harsh conditions nor toxic chemicals. Specifically, we used a neutral (pH 7) and alkaline (pH 11.5) pH to synthesize two different exosome-based AuNCs (exo-AuNCs) with independent blue and red emission. Using field-emission scanning electron microscopy, energy dispersive X-ray microanalysis, nanoparticle tracking analysis, and X-ray photoelectron spectroscopy, we demonstrated that AuNCs were successfully formed in the exosomes. Red-emitting exo-AuNCs were found to have a larger Stokes shift and a stronger fluorescence intensity than the blue-emitting exo-AuNCs. Both exo-AuNCs were compatible with MCF-7 (human breast cancer), HeLa (human cervical cancer), and HT29 (human colon cancer) cells, although blue-emitting exo-AuNCs were cytotoxic at high concentrations (≥5 mg/mL). Red-emitting exo-AuNCs successfully stained the nucleus and were compatible with membrane-staining dyes. This is the first study to use exosomes to synthesize fluorescent nanomaterials for cellular imaging applications. As exosomes are naturally produced via secretion from almost all types of cell, the proposed method could serve as a strategy for low-cost production of versatile nanomaterials.

Glutathione Disulfide as a Reducing, Capping, and Mass-Separating Agent for the Synthesis and Enrichment of Gold Nanoclusters

“…Gold nanoclusters (AuNCs) are a family of molecular-like photoluminescent nanostructures typically composed of a few to approximately 100 Au atoms, which are less than 2 nm in size [ 1 , 2 ]. Unlike other nanomaterials that are synthesized with relatively strong reductants [ 3 , 4 ], water-soluble gold nanoclusters (AuNCs) are synthesized using weak reducing reagents, including phosphoniums, folic acid, amino acids, peptides, Good’s buffers, proteins, exosomes, and thiolates [ 5 , 6 , 7 , 8 , 9 , 10 ]. Among them, glutathione-protected AuNCs (GSH–AuNCs) have attracted extensive research interest.…”

Advances in Exosomes as Diagnostic and Therapeutic Biomarkers for Gynaecological Malignancies

“…The fluorescent gold nanoclusters with protein templates have highly fluorescent properties and biocompatibility. Combining them with exosomes successfully obtained nuclear staining of CC cells and was compatible with membrane-staining dyes, which proposes that the use of exosome synthesis for cellular imaging applications is also feasible [81].…”

Nanomaterials modulate tumor-associated macrophages for the treatment of digestive system tumors

“…Moreover, exosomes exhibit remarkable permeability and retention capabilities, making them highly suitable for targeted drug delivery [ 342 ]. Given their ability to be secreted naturally by various cells, exosomes offer a cost-effective approach to produce multifunctional nanomaterials [ 343 ]. Macrophage-derived exosomes regulate GC development [ 344 , 345 ] ( Fig.…”