Rose Bengal-Derived Ultrabright Sulfur-Doped Carbon Dots for Fast Discrimination between Live and Dead Cells

Abstract

The discrimination between dead and live cells is crucial for cell viability evaluation. Carbon dots (CDs), with advantages like simple and costeffective synthesis, excellent biocompatibility, and high photostability, have shown potential for realizing selective live/dead cell staining. However, most of the developed CDs with the live/dead cell discrimination capacity usually have low photoluminescence quantum yields (PLQYs) and excitation wavelengthdependent fluorescence emission (which can cause fluorescence overlap with other fluorescent probes and make dual-color live/dead staining impossible), and hence, developing ultrabright CDs with excitation wavelength-independent fluorescence emission property for live/dead cell discrimination becomes an important task. Here, using a one-pot hydrothermal method, we prepared ultrasmall (∼1.6 nm), ultrabright (PLQY: ∼78%), and excitation wavelengthindependent sulfur-doped carbon dots (termed S-CDs) using rose bengal and 1,4-dimercaptobenzene as raw materials and demonstrated that the S-CDs could rapidly (∼5 min) and accurately distinguish dead cells from live ones for almost all the cell types including bacterial, fungal, and animal cells in a wash-free manner. We confirmed that the S-CDs could rapidly pass through the dead cell surfaces to enter the interior of the dead cells, thus visualizing these dead cells. In contrast, the S-CDs could not enter the interior of live cells and thus could not stain these live cells. We further verified that the S-CDs presented better biocompatibility and higher photostability than the commercial live/dead staining dye propidium iodide, ensuring its bright application prospect in cell imaging and cell viability assessment. Overall, this work develops a type of CDs capable of realizing the live/dead cell discrimination of almost all the cell types (bacterial, fungal, and animal cells), which has seldom been achieved by other fluorescent nanoprobes.

An Emerging Fluorescent Carbon Nanobead Label Probe for Lateral Flow Assays and Highly Sensitive Screening of Foodborne Toxins and Pathogenic Bacteria

“…More importantly, the absolute fluorescence quantum yield (QY) of the FCNBs was determined to be 90.1%, which was a very competitive value among most CDs. Such a high QY was mainly attributed to the dehalogenation and cross-link-enhanced emission mechanism. , A distinctive pH-dominant fluorescence character of FCNBs was observed in Figure S3a, which was similar with that of the resulting fluorescein phosphors in the process of dehalogenation of RB . In addition, FCNBs showed quite stable fluorescence emission under continuous ultraviolet irradiation, excellent tolerance to high ionic strength, and long-term storage stability under ambient conditions (Figure S3b–d).…”

“…RB is a halogenated derivative of fluorescein and shows extremely low fluorescence emission. But in the presence of amino compounds, i.e., b-PEI, the halogen of RB could be replaced via a nucleophile substitution reaction, and thus, highly emissive fluorescein phosphors were generated. , Besides, b-PEI could provide heterogeneous N-doping and abundant amino groups, which were beneficial for improving the fluorescence quantum yield as well as facile surface modification. ,, More importantly, the unique branch and polymer structure of b-PEI caused serious self-cross-linking of small nanophosphors by extensive hydrogen bonds and thereby promoted the formation of large-particle-sized FCNBs …”

Recent Advances in Synthesis, Modification, Characterization, and Applications of Carbon Dots

“…Most CDs that can discriminate between live and dead cells exhibit excitation-wavelength-dependent fluorescence and low photoluminescence quantum yields [ 168 ]. It may cause problems such as possible fluorescence overlap with the other fluorescent probe.…”

“…Excitation-wavelength-independent sulfur-doped CDs (S-CDs) were used to demonstrate that the S-CDs could distinguish dead cells from live cells for fungal, bacterial, and animal cells. Yu et al [ 168 ] found that S-CDs could reach the interior of the dead cells, allowing the visualization of these cells. On the other hand, live cells cannot be stained by S-CDs because S-CDs cannot enter the live cells.…”

Smart contact lens containing hyaluronate–rose bengal conjugate for biophotonic myopia vision correction

“…In particular, RB is an attractive material, which was also used in the fabrication of carbon dots for various biomedical applications. 9–11 Although RB has several advantages such as effective corneal crosslinking with high mechanical strength, simple green light irradiation for cornea fibrils and lower cytotoxicity than riboflavin, 12,13 it faces a critical challenge for further medical applications due to its low penetration depth into the cornea. 14–18…”