Fluorescent Carbon Dots for Sensitive and Rapid Monitoring of Intracellular Ferrous Ion

Advancing glioblastoma imaging: Exploring the potential of organic fluorophore-based red emissive carbon dots

Over time, the interest in developing stable photosensitizers (PS) which both absorb and emit light in the red region (650 and 950 nm) has gained noticeable interest. Recently, carbon dots (CDs) have become the material of focus to act as a PS due to their high extinction coefficient, low cytotoxicity, and both high photo and thermal stability. In this work, a Federal and Drug Association (FDA) approved Near Infra-Red (NIR) organic fluorophore used for photo-imaging, indocyanine green (ICG), has been explored as a precursor to develop water-soluble red emissive CDs which possess red emission at 697 nm. Furthermore, our material was found to yield favorable red-imaging capabilities of glioblastoma stem-like cells (GSCs) meanwhile boasting low toxicity. Additionally with post modifications, our CDs have been found to have selectivity towards tumors over healthy tissue as well as crossing the blood-brain barrier (BBB) in zebrafish models.

Multiple heteroatom dopant carbon dots as a novel photoluminescent probe for the sensitive detection of Cu2+ and Fe3+ ions in living cells and environmental sample analysis

Heavy metal ion pollution harms human health and the environment and continues to worsen. Here, we report the synthesis of boron (B), phosphorous (P), nitrogen (N), and sulfur (S) co-doped carbon dots (BP/NS-CDs) by a one-step facile hydrothermal process. The optimum synthetic parameters are of 180 °C temperature, 12 h reaction time and 15% of PBA mass. The as-synthesized BP/NS-CDs exhibits excellent water solubility, strong green photoluminescence (PL) at 510 nm, and a high quantum yield of 22.4%. Moreover, BP/NS-CDs presented high monodispersity (7.2 ± 0.45 nm), excitation-dependent emission, PL stability over large pH, and high ionic strength. FTIR, XRD, and XPS are used to confirm the successful B and P doping of BP/NS-CDs. BP/NS-CD photoluminescent probes are selectively quenched by Cu²⁺ and Fe³⁺ ions but showed no response to the presence of other metal cations. The PL emission of BP/NS-CDs exhibited a good linear correlation with Cu²⁺ and Fe³⁺ concentrations with detection limits of 0.18 μM and 0.27 μM for Cu²⁺ and Fe³⁺, respectively. Furthermore, the HCT116 survival cells kept at 99.4 ± 1.3% and cell imaging capability, when the BP/NS-CDs concentration is up to 300 μg/mL by MTT assay. The proposed sensor is potential applications for the detection of Cu²⁺ and Fe³⁺ ions in environmental water samples.

N, S-Doped Carbon Dots Prepared by Peanut Protein Isolates and Cysteamine as Highly Sensitive Fluorescent Sensors for Fe2+, Fe3+ and Lactoferrin

Lactoferrin (LF) is an iron-binding glycoprotein with various biological activities that has been extensively used in food and medical applications. Several methods for detecting LF have been reported, but they still face challenges in terms of sensitivity and simplicity of detection. To achieve an accurate and efficient detection of LF, we developed a method for the determination of LF in lactoferrin supplements using carbon dots (CDs) fluorescent probes. The N, S-doped PPI carbon dots (N, S-PPI-CDs) were prepared using a protein (peanut protein isolate) and cysteamine as precursors. The prepared N, S-PPI-CDs exhibited intense blue fluorescence and good biocompatibility, while the fluorescence intensity of the N, S-PPI-CDs showed a good linear relationship with Fe²⁺/Fe³⁺ concentration (0-2 μM). The N, S-PPI-CDs exhibited a high potential ability to rapidly detect Fe²⁺/Fe³⁺ within 30 s, with a limit of detection (LoD) of 0.21 μM/0.17 μM. Due to the reversible binding of LF to Fe, the N, S-PPI-CDs showed a high sensitivity and selectivity for LF, with a limit of detection (LoD) of 1.92 μg/mL. In addition, LF was quantified in real sample LF supplements and showed a fluctuation in recovery of less than 2.48%, further demonstrating the effectiveness of the fluorescent N, S-PPI-CDs sensor.

Collagen-based hydrogels cross-linked via laccase - mediated system incorporated with Fe3+ for wound dressing

Pure fish skin collagen hydrogels as a wound dressing have lower thermodynamic stability than mammalian collagen and usually suffer from poor mechanical properties, weak degradation resistance and insufficient functionalities such as antioxidant and anti-inflammatory properties to meet clinical needs that limit its further application. Here, a silver carp skin collagen hydrogel is successfully constructed via the cross-linking of the laccase-protocatechuic aldehyde (LAC-PAL) and the structure of the hydrogel is further consolidated and strengthened by the interaction of PAL and Fe3+. In this collagen hydrogel system, Fe3+, acting as a second cross-linker, consolidates and enhances the stability of the hydrogel after LAC-PAL cross-linking. This cross-linking method improves the resistance to degradation with a reduction in its degradation rate from 89.45% to 38.66% and endows the hydrogel with antioxidant activity. The in vitro data show that the hydrogel promotes cell proliferation and adhesion exhibiting good biocompatibility. Animal experiments show that the hydrogel contributes to angiogenesis and improves inflammatory response in the early stages of wound healing, resulting in promoting wound healing. Altogether, this newly developed collagen hydrogel is expected to be applied in wound repair as a wound dressing.

Solid-Phase Synthesis of Red Fluorescent Carbon Dots for the Dual-Mode Detection of Hexavalent Chromium and Cell Imaging

The excellent optical properties and biocompatibility of red fluorescence carbon dots (R-CDs) provide a new approach for the effective analysis of hexavalent chromium Cr(VI) in environmental and biological samples. However, the application of R-CDs is still limited by low yield and unfriendly synthesis route. In this study, we developed a new type of R-CDs based on a simple and green solid-phase preparation strategy. The synthesized R-CDs can emit bright red fluorescence with an emission wavelength of 625 nm and also have an obvious visible light absorption capacity. Furthermore, the absorption and fluorescence signals of the R-CDs aqueous solution are sensitive to Cr(VI), which is reflected in color change and fluorescence quenching. Based on that, a scanometric and fluorescent dual-mode analysis system for the rapid and accurate detection of Cr(VI) was established well within the limit of detection at 80 nM and 9.1 nM, respectively. The proposed methods also possess high specificity and were applied for the detection of Cr(VI) in real water samples. More importantly, the synthesized R-CDs with good biocompatibility were further successfully applied for visualizing intracellular Cr(VI) in Hela cells.

Facile Synthesis of Green Fluorescent Carbon Dots and Their Application to Fe3+ Detection in Aqueous Solutions

Carbon dots (CDs), a class of fluorescent nanomaterials, have attracted widespread attention from researchers. Because of their unique chemical properties, these high-quality fluorescent probes are widely used for ion and molecule detection. Excess intake of many ions or molecules can cause harm to the human body. Although iron (in the form of Fe³⁺ ions) is essential for the human body, excess iron in the human body can cause many diseases, such as iron poisoning. In this study, we have synthesized fluorine and nitrogen co-doped carbon dots (FNCDs) by a hydrothermal method. These FNCDs exhibited good stability, selectivity, and anti-interference ability for Fe³⁺. Fe³⁺ could be detected in the range of 0.2–300 μM, and their detection limit is up to 0.08 μM. In addition, the recovery and relative standard deviation measured by the standard addition recovery method were not higher than 107.5% and 1.1%, respectively, indicating that FNCDs have good recovery and accuracy for Fe³⁺ detection.