Fluorescent Carbon Dots for Selective Labeling of Subcellular Organelles

The develop of persistent luminescence nanoparticles with excellent performances in cancer targeted bioimaging and killing: a review

The use of fluorescent nanomaterials in tumor imaging and treatment effectively avoids the original limitations of traditional tumor clinical diagnostic methods. The PLNPs emitted persistent luminescence after the end of excitation light. Owing to their superior optical properties, such as a reduced laser irradiation dose, spontaneous fluorescence interference elimination, and near-infrared imaging, PLNPs show great promise in tumor imaging. Moreover, they also achieve excellent anti-tumor therapeutic effects through surface modification and drug delivery. However, their relatively large size and limited surface modification capacity limit their ability to kill tumors effectively enough for clinical applications. Thus, this article reviews the synthesis and modification of PLNPs and the research progress in targeted tumor imaging and tumor killing. We also discuss the challenges and prospects of their future applications in these fields. This review has value for accelerating the design of PLNPs based platform for cancer diagnosis and treatment.

Synthesis of carbon dots from spent coffee grounds: transforming waste into potential biomedical tools

Carbon dots (CDs) are small-sized, spherical nanoparticles presenting amorphous carbon cores with nanocrystalline regions of a graphitic structure. They show unique properties such as high aqueous solubility, robust chemical inertness, and non-toxicity and can be manufactured at a relatively low cost. They are also well known for outstanding fluorescence tunability and resistance to photobleaching. Together, these properties boost their potential to act as drug delivery systems (DDSs). This work presents a low-cost synthesis of CDs by upcycling spent coffee grounds (SCGs) and transforming them into value-added products. This synthetic route eliminates the use of highly toxic heavy metals, high energy-consuming reactions and long reaction times, which can improve biocompatibility while benefiting the environment. A series of physico-chemical characterisation techniques demonstrated that these SCG-derived CDs are small-sized nanoparticles with tunable fluorescence. In vitro studies with 120 h of incubation of SCG-derived CDs demonstrated their specific antiproliferative effect on the breast cancer CAL-51 cell line, accompanied by increased reactive oxygen species (ROS) production. Importantly, no impact was observed on healthy breast, kidney, and liver cells. Confocal laser scanning microscopy confirmed the intracellular accumulation of SCG-derived CDs. Furthermore, the drug efflux pumps P-glycoprotein (P-gp) and the breast cancer resistance protein (BCRP) did not impact CD accumulation in the cancer cells.

Applications of Green Carbon Dots in Personalized Diagnostics for Precision Medicine

Green carbon dots (GCDs) have emerged as a revolutionary tool in precision medicine, offering transformative capabilities for personalized diagnostics and therapeutic strategies. Their unique optical and biocompatible properties make them ideal for non-invasive imaging, real-time monitoring, and integration with genomics, proteomics, and bioinformatics, enabling accurate diagnosis and tailored treatments based on patients' genetic and molecular profiles. This study explores the potential of GCDs in advancing individualized patient care by examining their applications in precision medicine. It evaluates their utility in non-invasive diagnostic imaging, targeted therapy delivery, and the formulation of personalized treatment plans, emphasizing their interaction with advanced genomic, proteomic, and bioinformatics platforms. GCDs demonstrated exceptional versatility in enabling precise diagnostics and delivering targeted therapies. Their integration with cutting-edge technologies showed significant promise in crafting personalized treatment strategies, enhancing their functionality and effectiveness in real-time monitoring and patient-specific applications. The findings underscore the pivotal role of GCDs in reshaping healthcare by advancing precision medicine and improving patient outcomes. The ongoing development and integration of GCDs with emerging technologies promise to further enhance their capabilities, paving the way for more effective, individualized medical care.

Fluorescence tunable carbon dots for in vitro nuclear dynamics and gastrointestinal imaging in live zebrafish and their in vivo toxicity evaluation by cardio-craniofacial disfunction assessment

Sub-cellular organelle anomalies are frequently observed in diseases such as cancer. Early and precise diagnosis of these alterations can be crucial for patient outcomes. However, current diagnostic tools using conventional organic dyes or metal quantum dots face limitations, including poor biocompatibility, stringent storage conditions, limited solubility in aqueous media, and slow staining speeds. These challenges underscore the need for safer, more effective diagnostic and therapeutic solutions. In these aspects, we have developed highly photostable, biocompatible, water-dispersible carbon dots (TNCDs) with an average size of 5.5 nm using tartaric acid and ethylenediamine via a hydrothermal route. The synthesized TNCDs have shown bright blue fluorescence under the irradiation of UV-light at an excitation wavelength of 365 nm. They exhibit a quantum yield (QY) of 25.1% with maximum emission at 390 nm. A nice tri-exponential fitting of the decay curve with characteristic lifetimes of 1.52 ns, 3.05 ns and 6.11 ns for TNCDs was obtained. In vitro studies demonstrated that TNCDs have high biocompatibility (20 μg ml-1) with almost 100% cell viability and excellent nucleus targeting and staining capabilities with low background interference (with 10-12 times enhancement in fluorescence intensity). Additionally, if tagged with photosensitizers or radionuclides, TNCDs can serve as therapeutic agents in photodynamic therapy against cancer cells. Importantly, TNCDs exhibited negligible toxicity in developing zebrafish even at high concentrations (up to 400 mg L-1) as investigated by cardio and craniofacial disfunction assessment. Live organism imaging revealed that TNCDs produced aggregation-induced strong and specific green fluorescence in the gut of zebrafish larvae even at low concentrations, indicating their potential for nucleus staining and gut-specific optical imaging (at 50 mg L-1). Thus, our TNCDs represent a robust nanoplatform for cellular and whole-organism fluorescence imaging, offering both diagnostic and therapeutic potential.

Progress on Carbon Dots with Intrinsic Bioactivities for Multimodal Theranostics

Carbon dots (CDs) with intrinsic bioactivities are candidates for bioimaging and disease therapy due to their diverse bioactivities, high biocompatibility, and multiple functionalities in multimodal theranostics. It is a multidisciplinary research hotspot that includes biology, physics, materials science, and chemistry. This progress report discusses the CDs with intrinsic bioactivities and their applications in multimodal theranostics. The relationship between the synthesis and structure of CDs is summarized and analyzed from a material and chemical perspective. The bioactivities of CDs including anti-tumor, antibacterial, anti-inflammatory etc. are discussed from biological points of view. Subsequently, the optical and electronic properties of CDs that can be applied in the biomedical field are summarized from a physical perspective. Based on the functional review of CDs, their applications in the biomedical field are reviewed, including optical diagnosis and treatment, biological activity, etc. Unlike previous reviews, this review combines multiple disciplines to gain a more comprehensive understanding of the mechanisms, functions, and applications of CDs with intrinsic bioactivities.

Synthesis of Eucommia ulmoides-derived carbon dots for anti-inflammatory and accelerated wound healing

Inflammation affects the pathology of wound healing and is strongly associated with many chronic wounds that do not heal. Natural herbs with anti-inflammatory effects have received much attention in clinical treatment because they are inexpensive, readily available, safe, and effective. In this study, EUO-NAC-CDs were prepared using a hydrothermal method in which Eucommia ulmoides (EUO) and n-acetylcysteine (NAC) were used as carbon sources. EUO-NAC-CDs have a small particle size distribution with an average particle size of 2.84 nm, emit stable blue-green fluorescence, and are biocompatible. EUO-NAC-CDs have been used for in vitro bioimaging, where high anti-inflammatory activity and accelerated wound healing have been demonstrated in vivo and in vitro. Additionally, EUO-NAC-CDs significantly decreased the expression of TNF-α, IL-6, and IL-1β and increased the expression of IL-10, suggesting that EUO-NAC-CDs had good anti-inflammatory effects. In a rat model of skin defects, EUO-NAC-CDs promoted wound healing, stimulated the formation of blood vessels and tissue regeneration near the wound, increased the expression of CD31, VEGF, and CD206, and decreased the expression of INOS, further demonstrating the therapeutic function of CDs. Therefore, fluorescent EUO-NAC-CDs can be effective in clinical wound treatment as imaging tools and functional wound dressings.

Fluorescent carbon dots for labeling of bacteria: mechanism and prospects-a review

The search for bacteria-labeling agents that are more efficient and less toxic compared to existing staining dyes is ongoing. Fluorescent quantum dots and carbon dots (CDs) have been extensively researched for various bioimaging applications. Priority is given to CDs due to several advantages, including lower toxicity, versatility in tuning their properties, and better photostability compared to metal-based quantum dots. Although significant progress is still needed to replace existing dyes with CDs for bacteria labeling, they offer promising potential for further improvement in efficiency. Surface charges and functional groups have been reported as decisive factors for bacterial discrimination and live/dead assays; however, a complete guideline for preparing CDs with optimum properties for efficient staining and predicting their labeling performance is lacking. In this review, we discuss the application of fluorescent CDs for bacterial labeling and the underlying mechanisms and principles. We primarily focus on the application and mechanism of CDs for Gram differentiation, live imaging, live/dead bacteria differentiation, bacterial viability testing, biofilm imaging, and the challenges associated with application of CDs. Based on proposed mechanisms of bacterial labeling and ambiguous results reported, we provide our view and guidelines for the researchers in this field to overcome the challenges associated with bacteria labeling using fluorescent CDs.

Mild synthesis of ultra-bright carbon dots with solvatochromism for rapid lipid droplet monitoring in varied physiological processes

Lipid droplets (LDs) participating in various cellular activities and are increasingly being emphasized. Fluorescence imaging provides powerful tool for dynamic tracking of LDs, however, most current LDs probes remain inconsistent performance such as low Photoluminescence Quantum Yield (PLQY), poor photostability and tedious washing procedures. Herein, a novel yellow-emissive carbon dot (OT-CD) has been synthesized conveniently with high PLQY up to 90%. Besides, OT-CD exhibits remarkable amphiphilicity and solvatochromic property with lipid-water partition coefficient higher than 2, which is much higher than most LDs probes. These characters enable OT-CD high brightness, stable and wash-free LDs probing, and feasible for in vivo imaging. Then, detailed observation of LDs morphological and polarity variation dynamically in different cellular states were recorded, including ferroptosis and other diseases processes. Furthermore, fast whole imaging of zebrafish and identified LD enrichment in injured liver indicate its further feasibility for in vivo application. In contrast to the reported studies to date, this approach provides a versatile conventional synthesis system for high-performance LDs targeting probes, combing the advantages of easy and high-yield production, as well as robust brightness and stability for long-term imaging, facilitating investigations into organelle interactions and LD-associated diseases.

Functionalized Phytochemicals-Embedded Carbon Dots Derived from Medicinal Plant for Bioimaging Application

Precise visualization of biological processes necessitates reliable coloring technologies, and fluorescence imaging has emerged as a powerful method for capturing dynamic cellular events. Low emission intensity and solubility of intrinsic fluorescence are still challenging, hindering their application in the biomedical field. The nanostructurization and functionalization of the insoluble phytochemicals, such as chlorophyll and curcumin, into carbon dots (CDs) were conducted to address these challenges. Due to their unique fluorescence characteristics and biocompatibility, CDs derived from medicinal plants hold promise as bioimaging agents. Further, the nitrogen in situ functionalization of the as-synthesized CDs offered tunable optical properties and enhanced solubility. The surface modification aims to achieve a more positive zeta potential, facilitating penetration through biological membranes. This work provides valuable insights into utilizing functionalized phytochemical-embedded carbon dots for bioimaging applications. The doping of nitrogen by adding urea showed an alteration of surface charge, which is more positive based on zeta potential measurement. The more positive CD particles showed that Andrographis paniculata-urea-based CDs were the best particles to penetrate cells than others related to the alteration of the surface charge and the functional group of the CDs, with the optimum dose of 12.5 μg/mL for 3 h of treatment for bioimaging assay.

Polyphenolic Carbon Quantum Dots with Intrinsic Reactive Oxygen Species Amplification for Two-Photon Bioimaging and In Vivo Tumor Therapy

Recent studies indicate that mitochondrial dysfunctions and DNA damage have a critical influence on cell survival, which is considered one of the therapeutic targets for cancer therapy. In this study, we demonstrated a comparative study of the effect of polyphenolic carbon quantum dots (CQDs) on in vitro and in vivo antitumor efficacy. Dual emissive (green and yellow) shape specific polyphenolic CQDs (G-CQDs and Y-CQDs) were synthesized from easily available nontoxic precursors (phloroglucinol), and the antitumor property of the as-synthesized probe was investigated as compared to round-shaped blue emissive CQDs (B-CQDs) derived from well-reported precursor citric acid and urea. The B-CQDs had a nuclei-targeting property, and G-CQDs and Y-CQDs had mitochondria-targeting properties. We have found that the polyphenol containing CQDs (at a dose of 100 μg mL-1) specifically attack mitochondria by excess accumulation, altering the metabolism, inhibiting branching pattern, imbalanced Bax/Bcl-2 homeostasis, and ultimately generating oxidative stress levels, leading to oxidative stress-induced cell death in cancer cells in vitro. We show that G-CQDs are the main cause of oxidative stress in cancer cells because of their ability to produce sufficient •OH- and 1O2 radicals, evidenced by electron paramagnetic resonance spectroscopy and a terephthalic acid test. Moreover, the near-infrared absorption properties of the CQDs were exhibited in two-photon (TP) emission, which was utilized for TP cellular imaging of cancer cells without photobleaching. The in vivo antitumor test further discloses that intratumoral injection of G-CQDs can significantly augment the treatment efficacy of subcutaneous tumors without any adverse effects on BalB/c nude mice. We believe that shape-specific polyphenolic CQD-based nanotheranostic agents have a potential role in tumor therapy, thus proving an insight on treatment of malignant cancers.

Synthesis, properties and potential applications of photoluminescent carbon nanoparticles: A review

Photoluminescent-carbon nanoparticles (PL-CNPs) are a new class of materials that received immense interest among researchers due to their distinct characteristics, including photoluminescence, high surface-to-volume ratio, low cost, ease of synthesis, high quantum yield, and biocompatibility. By exploiting these outstanding properties, many studies have been reported on its utility as sensors, photocatalysts, probes for bio-imaging, and optoelectronics applications. From clinical applications to point-of-care test devices, drug loading to tracking of drug delivery, and other research innovations demonstrated PL-CNPs as an emerging material that could substitute conventional approaches. However, some of the PL-CNPs have poor PL properties and selectivity due to the presence of impurities (e.g., molecular fluorophores) and unfavourable surface charges by the passivation molecules, which impede their applications in many fields. To address these issues, many researchers have been paying great attention to developing new PL-CNPs with different composite combinations to achieve high PL properties and selectivity. Herein, we thoroughly discussed the recent development of various synthetic strategies employed to prepare PL-CNPs, doping effects, photostability, biocompatibility, and applications in sensing, bioimaging, and drug delivery fields. Moreover, the review discussed the limitations, future direction, and perspectives of PL-CNPs in possible potential applications.

Design of carbon dots for bioimaging and behavior regulation of stem cells

Carbon dots (CDs) have been widely used in bioimaging, biosensing and biotherapy because of their good biocompatibility, optical properties and stability. In this review, we comprehensively summarize the research on CDs in terms of synthesis methods, optical properties and biotoxicity. We describe and envisage the directions for CDs application in stem cell imaging and differentiation, with the aim of stimulating the design of future related CDs. We used 'carbon dots', 'stem cells', 'cell imaging', 'cell differentiation' and 'fate control' as keywords to search for important articles. The Web of Science database was used to extract vital information from a total of 357 papers, 126 review articles and 231 article proceedings within 12 years (2011-2022).

Carbon dots labeled Lactiplantibacillus plantarum: a fluorescent multifunctional biocarrier for anticancer drug delivery

A carbon dots (CDs)-biolabeled heat-inactivated Lactiplantibacillus plantarum (HILP) hybrid was investigated as a multifunctional probiotic drug carrier with bioimaging properties using prodigiosin (PG) as anticancer agent. HILP, CDs and PG were prepared and characterized using standard methods. CDs-labeled HILP (CDs/HILP) and PG loaded CDs/HILP were characterized by transmission electron microscopy (TEM), laser scanning confocal microscopy (LSCM) and for entrapment efficiency (EE%) of CDs and PG, respectively. PG-CDs/HILP was examined for stability and PG release. the anticancer activity of PG-CDs/HILP was assessed using different methods. CDs imparted green fluorescence to HILP cells and induced their aggregation. HILP internalized CDs via membrane proteins, forming a biostructure with retained fluorescence in PBS for 3 months at 4°C. Loading PG into CDs/HILP generated a stable green/red bicolor fluorescent combination permitting tracking of both drug carrier and cargo. Cytotoxicity assay using Caco-2 and A549 cells revealed enhanced PG activity by CDs/HILP. LCSM imaging of PG-CDs/HILP-treated Caco-2 cells demonstrated improved cytoplasmic and nuclear distribution of PG and nuclear delivery of CDs. CDs/HILP promoted PG-induced late apoptosis of Caco-2 cells and reduced their migratory ability as affirmed by flow cytometry and scratch assay, respectively. Molecular docking indicated PG interaction with mitogenic molecules involved in cell proliferation and growth regulation. Thus, CDs/HILP offers great promise as an innovative multifunctional nanobiotechnological biocarrier for anticancer drug delivery. This hybrid delivery vehicle merges the physiological activity, cytocompatibility, biotargetability and sustainability of probiotics and the bioimaging and therapeutic potential of CDs.

Carbon dots with tissue engineering and regenerative medicine applications

Carbon dots (CDs) with unique physicochemical features such as exceptional biocompatibility, low cost, eco-friendliness, abundant functional groups (e.g., amino, hydroxyl, and carboxyl), high stability, and electron mobility have been broadly investigated in nano- and biomedicine. In addition, the controlled architecture, tunable fluorescence emission/excitation, light-emitting potential, high photostability, high water solubility, low cytotoxicity, and biodegradability make these carbon-based nanomaterials suitable for tissue engineering and regenerative medicine (TE-RM) purposes. However, there are still limited pre- and clinical assessments, because of some important challenges such as the scaffold inconsistency and non-biodegradability in addition to the lack of non-invasive methods to monitor tissue regeneration after implantation. In addition, the eco-friendly synthesis of CDs exhibited some important advantages such as environmentally friendly properties, low cost, and simplicity compared to the conventional synthesis techniques. Several CD-based nanosystems have been designed with stable photoluminescence, high-resolution imaging of live cells, excellent biocompatibility, fluorescence properties, and low cytotoxicity, which make them promising candidates for TE-RM purposes. Combining attractive fluorescence properties, CDs have shown great potential for cell culture and other biomedical applications. Herein, recent advancements and new discoveries of CDs in TE-RM are considered, focusing on challenges and future perspectives.

Cancer cells inhibition by cationic carbon dots targeting the cellular nucleus

Nucleus targeting is tremendously important in cancer therapy. Cationic carbon dots (CCDs) are potential nanoparticles which might enter cells and penetrate nuclear membranes. Although some CCDs have been investigated in nucleus targeting and applied in nuclear imaging, the CCDs derived from drugs, that are able to target the nucleus, bind with DNA and inhibit the growth of cancer cells have not been reported. In this project, 1, 2, 4, 5-benzenetetramine (Y15, a focal adhesion kinase inhibitor) derived cationic carbon dots (Y15-CDs) were prepared via a hydrothermal approach utilizing Y15, folic acid and 1,2-ethylenediamine as precursors. Based on the structural, optical, and morphologic characterizations, Y15-CDs possess rich amine groups and nitrogen in structure, an excitation-dependent photoluminescence emission, and a small particle size of 2 to 4 nm. The DNA binding experiments conducted through agarose gel electrophoresis, UV-vis absorption, fluorescence emission, and circular dichroism spectroscopies, prove that Y15-CDs might bind with DNA via electrostatic interactions and partially intercalative binding modes. In addition, the cell imaging and cytotoxicity studies in human foreskin fibroblasts (HFF), prostate cancer (PC3) and osteosarcoma cells (U2OS) indicate the nucleus targeting and anticancer abilities of Y15-CDs. Most interestingly, Y15-CDs exhibit a higher cytotoxicity to cancer cells (PC3 and U2OS) than to normal cells (HFF), inferring that Y15-CDs might be potentially applied in cancer therapy.

Fluorescent carbon dots tailored iron oxide nano hybrid system forin vivooptical imaging of liver fibrosis

Hybrid nanoparticles are innovative invention of last decade designed to overcome limitations of single-component nanoparticles by introducing multiple functionalities through combining two or more different nanoparticles. In this study, we are reporting development of magneto-fluorescent hybrid nanoparticles by combining iron oxide and carbon nanoparticles to enablein vivofluorescence imaging which also has all the required characteristic properties to use as Magnetic Resonance Imaging (MRI) contrast agent. In order to achieve dual-functional imaging, alginate and pullulan coated super paramagnetic iron oxide nanoparticles (ASPION and PSPION) and Carbon dots (Cdts) were synthesised separately. ASPIONs and PSPIONs were further chemically conjugated with Cdts and developed dual-functional nanohybrid particles ASPION-Cdts and PSPION-Cdts. Subsequently, evaluation of the materials for its size, functionalisation efficiency, fluorescence and magnetic properties, biocompatibility and cellular uptake efficiency has been carried out. Fluorescence imaging of liver fibrosis was performedin vivoin rodent model of liver fibrosis using the two nanohybrids, which is further confirmed by high fluorescence signal from the harvested liver.

Scavenging neurotoxic aldehydes using lysine carbon dots

Reactive aldehydes generated in cells and tissues are associated with adverse physiological effects. Dihydroxyphenylacetaldehyde (DOPAL), the biogenic aldehyde enzymatically produced from dopamine, is cytotoxic, generates reactive oxygen species, and triggers aggregation of proteins such as α-synuclein implicated in Parkinson's disease. Here, we demonstrate that carbon dots (C-dots) prepared from lysine as the carbonaceous precursor bind DOPAL molecules through interactions between the aldehyde units and amine residues on the C-dot surface. A set of biophysical and in vitro experiments attests to attenuation of the adverse biological activity of DOPAL. In particular, we show that the lysine-C-dots inhibit DOPAL-induced α-synuclein oligomerization and cytotoxicity. This work underlines the potential of lysine-C-dots as an effective therapeutic vehicle for aldehyde scavenging.

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.

In Vivo and In Vitro Biodistribution of Inulin-Tethered Boron-Doped Amine-Functionalized Carbon Dots

Carbon dots (CDs) are considered a potential substance for use in biomarker applications due to their exceptional light stability. However, there are several unsolved uncertainties about CD toxicity in vitro and in vivo. In this study, a redesigned derivative of the natural polysaccharide inulin is connected with boron-doped amine-functionalized carbon dots (In@BN-CDs) through carbodiimide coupling to improve the biocompatibility of the nanoformulation. The toxicity and biodistribution of ln@BN-CDs in vivo and in vitro were explored in detail. The In@BN-CDs were tested after a single inhalation dosage of 10, 7, 5, 3, and 1 mg/kg. We explored a dose- and time-dependent technique of collecting blood samples and then centrifuged the blood samples and obtained serum samples, which were then analyzed for fluorescence inspection; findings showed that the fluorescence intensity decreased with time. Similarly, In@BN-CDs were effectively used as in vitro toxicity and fluorescent probes for cellular imaging in living cells due to their biocompatibility and cell membrane accessibility. The biocompatibility and efficacy of In@BN-CDs as fluorescent imaging agents have been demonstrated. The data suggest that the usage of In@BN-CDs in vitro and in vivo should be examined.

Nitrogen, sulfur, and phosphorus Co-doped carbon dots-based ratiometric chemosensor for highly selective sequential detection of Al3+ and Fe3+ ions in logic gate, cell imaging, and real sample analysis

Heteroatom-doped photoluminescent (PL) carbon dots (CDs) have recently gained attention as optical sensors due to their excellent tunable properties. In this work, we propose a one-pot hydrothermal synthesis of PL nitrogen (N), sulfur (S), and phosphorus (P) co-doped carbon dots (NSP-CDs) using glutathione and phosphoric acid (H₃PO₄) as precursors. The synthesized NSP-CDs were characterized using different spectroscopic and microscopic techniques, including ultraviolet-visible (UV-Vis) spectroscopy, fluorescence spectroscopy, Fourier-transform infrared (FTIR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analysis. The NSP-CDs exhibited excellent PL properties with green emission at 492 nm upon excitation at 417 nm, a high quantum yield of 26.7%, and dependent emission behavior. The as-prepared NSP-CDs were spherical with a well-monodispersed average particle size of 5.2 nm. Moreover, NSP-CDs demonstrate high PL stability toward a wider pH, high salt ionic strength, and various solvents. Furthermore, the NSP-CDs showed a three-state "off-on-off" PL response upon the sequential addition of Al³⁺ and Fe³⁺ ions, with a low limit of detection (LOD) of 10.8 nM for Al³⁺ and 50.7 nM for Fe³⁺. The NSP-CD sensor can construct an INHIBIT logic gate with Al³⁺ and Fe³⁺ ions as the chemical inputs and emissions as the output mode. Owing to an excellent tunable PL property and biocompatibility, the NSP-CDs were applied for sensing Al³⁺ and Fe³⁺ ions as well as live cell imaging. Furthermore, NSP-CDs were designed as PL sensors for detecting Al³⁺ and Fe³⁺ ions in real water show their potential application.

Carbon nanomaterials for phototherapy

Phototherapy attracts increasing interest for broad bio-applications due to its noninvasive and highly selective nature. Owing to their good biocompatibility, unique optoelectronic properties and size/surface effects, carbon nanomaterials show great promise for phototherapy. Various carbon nanomaterials have been demonstrated as efficient phototherapy agents for a large variety of phototherapeutic applications, including cancer treatment, anti-bacteria, and Alzheimer's disease. This review summarizes the recent progress of carbon nanomaterials for phototherapy. Current challenges and future perspectives are also discussed.

Subcellular Localization Prediction of Human Proteins Using Multifeature Selection Methods

Subcellular localization attempts to assign proteins to one of the cell compartments that performs specific biological functions. Finding the link between proteins, biological functions, and subcellular localization is an effective way to investigate the general organization of living cells in a systematic manner. However, determining the subcellular localization of proteins by traditional experimental approaches is difficult. Here, protein–protein interaction networks, functional enrichment on gene ontology and pathway, and a set of proteins having confirmed subcellular localization were applied to build prediction models for human protein subcellular localizations. To build an effective predictive model, we employed a variety of robust machine learning algorithms, including Boruta feature selection, minimum redundancy maximum relevance, Monte Carlo feature selection, and LightGBM. Then, the incremental feature selection method with random forest and support vector machine was used to discover the essential features. Furthermore, 38 key features were determined by integrating results of different feature selection methods, which may provide critical insights into the subcellular location of proteins. Their biological functions of subcellular localizations were discussed according to recent publications. In summary, our computational framework can help advance the understanding of subcellular localization prediction techniques and provide a new perspective to investigate the patterns of protein subcellular localization and their biological importance.

Resveratrol Carbon Dots Disrupt Mitochondrial Function in Cancer Cells

Resveratrol, a natural polyphenol, exhibits beneficial health properties and has been touted as a potential anti-tumor agent. Here, we demonstrate potent anti-cancer effects of carbon dots (C-dots) synthesized from resveratrol. The mild synthesis conditions retained resveratrol functional moieties upon the carbon dots' (C-dots) surface, an important requisite for achieving specificity toward cancer cells and biological activities. Indeed, the disruptive effects of the resveratrol-C-dot were more pronounced in several cancer cell types compared to normal cells, underscoring targeting capabilities of the C-dots, a pertinent issue for the development of cancer therapeutics. In particular, we observed impairment of mitochondrial functionalities, including intracellular calcium release, inhibition of cytochrome-C oxidase enzyme activity, and mitochondrial membrane perturbation. Furthermore, the resveratrol C-dots were more potent than either resveratrol molecules alone, known anti-cancer polyphenolic agents such as curcumin and triphenylphosphonium, or C-dots prepared from different carbonaceous precursors. This study suggests that resveratrol-synthesized C-dots may have promising therapeutic potential as anti-cancer agents.

Carbon dots for multicolor cell imaging and ultra-sensitive detection of multiple ions in living cells: One Stone for multiple Birds

Given the significant impact of ions on environment pollution and human health, it is urgently needed to establish effective and convenient ion detection approaches, particularly in living cells. In this paper, we constructed multicolor N-doped-carbon dots (mPD-CDs) by facile one-step hydrothermal carbonization of m-phenylenediamine (mPD). mPD-CDs were successfully deployed for multicolor cellular imaging for animal cells, fungi, and bacteria in a wash-free way with high photostability and satisfactory biocompability. Moreover, mPD-CDs can be used as a fluorescent sensing probe for ultrasensitive detection of both iodide ion (I^-) and typical heavy metals such as cadmium (Cd²⁺), copper (Cu²⁺), mercury (Hg²⁺), gadolinium (Gd³⁺), ferrous ion (Fe²⁺), Zinc (Zn²⁺), and ferric ion (Fe³⁺). This is the first report using CDs as optical sensing probe for the detection of Gd³⁺, and for detection of Fe³⁺ with fluorescence "turn on". More significantly, with these versatile and fascinating properties, we applied mPD-CDs for intracellular ion detection in living cells like Hep G2 and S. cerevisiae, and zebra fish. Altogether, mPD-CDs displayed great potential for multicolor cell imaging and the multiple ion detection in vitro and in vivo, presenting a promising strategy for in-situ ultrasensitive sensing of multiple metal ions in the environment and the biological systems.

Yellow-Emitting Carbon Dots for Selective Fluorescence Imaging of Lipid Droplets in Living Cells

This study shows a one-pot preparation of carbon dots by a solvothermal method in ethylene glycol. The carbon dots show yellow-colored fluorescence emission in water. The carbon dots showed distinct preference to be present in the hydrophobic environment which was evident from their efficient transfer from aqueous phase to organic phase. They were also found to locate themselves in the vesicle bilayer and micelle core. This inherent lipophilic character of these carbon dots has been successfully utilized for the selective imaging of lipid droplets inside the living cells. The selective imaging of lipid droplets was confirmed by similar staining patterns with other staining dyes and the starvation study.

Hydrosoluble Perylene Monoimide-Based Telomerase Inhibitors with Diminished Cytotoxicity

Telomerase is essential for the immortality characteristics of most cancers. Telomerase-specific inhibitors should render cancer cells to replicative senescence without acute cytotoxicity. Perylene-based G-quadruplex (G4) ligands are widely studied as telomerase inhibitors. Most reported perylene-based G4 ligands are perylene diimides (PDIs), which often suffer from self-aggregation in aqueous solutions. Previously, we found that PM2, a perylene monoimide (PMI), exhibited better solubility, G4 binding affinity, and telomerase inhibition than PIPER, the prototypic PDI. However, the acute cytotoxicity of PM2 was about 20-30 times more than PIPER in cancer cells. In this report, we replaced the piperazine side chain of PM2 with ethylenediamine to yield PM3 and replaced the N,N-diethylethylenediamine side chain of PM2 with the 1-(2-aminoethyl) piperidine to yield PM5. We found that asymmetric PMIs with two basic side chains (PM2, PM3, and PM5) performed better than PIPER (the prototypic PDI), in terms of hydrosolubility, G4 binding, in vitro telomerase inhibition, and suppression of human telomerase reverse transcriptase (hTERT) expression and telomerase activity in A549 cells. However, PM5 was 7-10 times less toxic than PM2 and PM3 in three cancer cell lines. We conclude that replacing the N,N-diethylethylenediamine side chain with the 2-aminoethylpiperidine on PMIs reduces the cytotoxicity in cancer cells without impacting G4 binding and telomerase inhibition. This study paves the way for synthesizing new PMIs with drug-like properties for selective telomerase inhibition.

Evaluation of chemotherapeutic response in living cells using subcellular Organelle‒Selective amphipathic carbon dots

Monitoring of structural changes in subcellular organelles is critical to evaluate the chemotherapeutic response of cells. However, commercial organelle selective fluorophores are easily photobleached, and thus are unsuitable for real-time and long-term observation. We have developed photostable carbon-dot liposomes (CDsomes)-based fluorophores for organellar and suborganellar imaging to circumvent these issues. The CDs synthesized through a mild pyrolysis/hydrolysis process exhibit amphipathic nature and underwent self-assembly to form liposome-like structures (CDsomes). The controlled hydrophilicity or hydrophobicity-guided preparation of CDsomes are used to selectively and rapidly (<1 min) stain nucleolus, cytoplasm, and membrane. In addition, the CDsomes offer universal high-contrast staining not only in fixed cells but also in living cells, allowing real-time observation and morphological identification in the specimen. The as-prepared CDsomes exhibit excitation-dependent fluorescence, and are much more stable under photoirradiation (e.g., ultraviolet light) than traditional subcellular dyes. Interestingly, the CDsomes can be transferred to daughter cells by diluting the particles, enabling multigenerational tracking of suborganelle for up to six generations, without interrupting the staining pattern. Therefore, we believe that the ultra-photostable CDsomes with high biocompatibility, and long-term suborganellar imaging capabilities, hold a great potential for screening and evaluating therapeutic performance of various chemotherapeutic drugs.

An insight into the potentials of carbon dots for in vitro live-cell imaging: recent progress, challenges, and prospects

Carbon dots (CDs) are a strong alternative to conventional fluorescent probes for cell imaging due to their brightness, photostability, tunable fluorescence emission, low toxicity, inexpensive preparation, and chemical diversity. Improving the targeting efficiency by modulation of the surface functional groups and understanding the mechanisms of targeted imaging are the most challenging issues in cell imaging by CDs. Firstly, we briefly discuss important features of fluorescent CDs for live-cell imaging application in this review. Then, the newest modulated CDs for targeted live-cell imaging of whole-cell, cell organelles, pH, ions, small molecules, and proteins are elaborately discussed, and their challenges in these fields are explained.

Carbon Dot Therapeutic Platforms: Administration, Distribution, Metabolism, Excretion, Toxicity, and Therapeutic Potential

Ultrasmall nanoparticles are often grouped under the broad umbrella term of "nanoparticles" when reported in the literature. However, for biomedical applications, their small sizes give them intimate interactions with biological species and endow them with unique functional physiochemical properties. Carbon quantum dots (CQDs) are an emerging class of ultrasmall nanoparticles which have demonstrated considerable biocompatibility and have been employed as potent theragnostic platforms. These particles find application for increasing drug solubility and targeting, along with facilitating the passage of drugs across impermeable membranes (i.e., blood brain barrier). Further functionality can be triggered by various environmental conditions or external stimuli (i.e., pH, temperature, near Infrared (NIR) light, ultrasound), and their intrinsic fluorescence is valuable for diagnostic applications. The focus of this review is to shed light on the therapeutic potential of CQDs and identify how they travel through the body, reach their site of action, administer therapeutic effect, and are excreted. Investigation into their toxicity and compatibility with larger nanoparticle carriers is also examined. The future of CQDs for theragnostic applications is promising due to their multifunctional attributes and documented biocompatibility. As nanomaterial platforms become more commonplace in clinical treatments, the commercialization of CQD therapeutics is anticipated.

Highly Photostable Carbon Dots from Citric Acid for Bioimaging

Bioimaging supported by nanoparticles requires low cost, highly emissive and photostable systems with low cytotoxicity. Carbon dots (C-dots) offer a possible solution, even if controlling their properties is not always straightforward, not to mention their potentially simple synthesis and the fact that they do not exhibit long-term photostability in general. In the present work, we synthesized two C-dots starting from citric acid and tris (hydroxymethyl)-aminomethane (tris) or arginine methyl ester dihydrochloride. Cellular uptake and bioimaging were tested in vitro using murine neuroblastoma and ovine fibroblast cells. The C-dots are highly biocompatible, and after 24 h of incubation with the cells, 100% viability was still observed. Furthermore, the C-dots synthesized using tris have an average dimension of 2 nm, a quantum yield of 37%, high photostability and a zeta potential (ζ) around −12 mV. These properties favor cellular uptake without damaging cells and allow for very effective bioimaging.

Dynamic Visualization of Endoplasmic Reticulum Stress in Living Cells via a Two-Stage Cascade Recognition Process

The endoplasmic reticulum (ER) is crucial for the regulation of multiple cellular processes, such as cellular responses to stress and protein synthesis, folding, and posttranslational modification. Nevertheless, monitoring ER physiological activity remains challenging due to the lack of powerful detection methods. Herein, we built a two-stage cascade recognition process to achieve dynamic visualization of ER stress in living cells based on a fluorescent carbon dot (CD) probe, which is synthesized by a facile one-pot hydrothermal method without additional modification. The fluorescent CD probe enables two-stage cascade ER recognition by first accumulating in the ER as the positively charged and lipophilic surface of the CD probe allows its fast crossing of multiple membrane barriers. Next, the CD probe can specifically anchor on the ER membrane via recognition between boronic acids and o-dihydroxy groups of mannose in the ER lumen. The two-stage cascade recognition process significantly increases the ER affinity of the CD probe, thus allowing the following evaluation of ER stress by tracking autophagy-induced mannose transfer from the ER to the cytoplasm. Thus, the boronic acid-functionalized cationic CD probe represents an attractive tool for targeted ER imaging and dynamic tracking of ER stress in living cells.

A multifunctional chemical toolbox to engineer carbon dots for biomedical and energy applications

Photoluminescent carbon nanoparticles, or carbon dots, are an emerging class of materials that has recently attracted considerable attention for biomedical and energy applications. They are defined by characteristic sizes of <10 nm, a carbon-based core and the possibility to add various functional groups at their surface for targeted applications. These nanomaterials possess many interesting physicochemical and optical properties, which include tunable light emission, dispersibility and low toxicity. In this Review, we categorize how chemical tools impact the properties of carbon dots. We look for pre- and postsynthetic approaches for the preparation of carbon dots and their derivatives or composites. We then showcase examples to correlate structure, composition and function and use them to discuss the future development of this class of nanomaterials.

Intracellular Trafficking of Cationic Carbon Dots in Cancer Cell Lines MCF-7 and HeLa-Time Lapse Microscopy, Concentration-Dependent Uptake, Viability, DNA Damage, and Cell Cycle Profile

Fluorescent carbon dots (CDs) are potential tools for the labeling of cells with many advantages such as photostability, multicolor emission, small size, rapid uptake, biocompatibility, and easy preparation. Affinity towards organelles can be influenced by the surface properties of CDs which affect the interaction with the cell and cytoplasmic distribution. Organelle targeting by carbon dots is promising for anticancer treatment; thus, intracellular trafficking and cytotoxicity of cationic CDs was investigated. Based on our previous study, we used quaternized carbon dots (QCDs) for treatment and monitoring the behavior of two human cancer cell MCF-7 and HeLa lines. We found similarities between human cancer cells and mouse fibroblasts in the case of QCDs uptake. Time lapse microscopy of QCDs-labeled MCF-7 cells showed that cells are dying during the first two hours, faster at lower doses than at higher ones. QCDs at a concentration of 100 µg/mL entered into the nucleus before cellular death; however, at a dose of 200 µg/mL, blebbing of the cellular membrane occurred, with a subsequent penetration of QCDs into the nuclear area. In the case of HeLa cells, the dose-depended effect did not happen; however, the labeled cells were also dying in mitosis and genotoxicity occurred nearly at all doses. Moreover, contrasted intracellular compartments, probably mitochondria, were obvious after 24 h incubation with 100 µg/mL of QCDs. The levels of reactive oxygen species (ROS) slightly increased after 24 h, depending on the concentration, thus the genotoxicity was likely evoked by the nanomaterial. A decrease in viability did not reach IC 50 as the DNA damage was probably partly repaired in the prolonged G0/G1 phase of the cell cycle. Thus, the defects in the G2/M phase may have allowed a damaged cell to enter mitosis and undergo apoptosis. The anticancer effect in both cell lines was manifested mainly through genotoxicity.

Monitoring protein conformational changes using fluorescent nanoantennas

Understanding the relationship between protein structural dynamics and function is crucial for both basic research and biotechnology. However, methods for studying the fast dynamics of structural changes are limited. Here, we introduce fluorescent nanoantennas as a spectroscopic technique to sense and report protein conformational changes through noncovalent dye-protein interactions. Using experiments and molecular simulations, we detect and characterize five distinct conformational states of intestinal alkaline phosphatase, including the transient enzyme-substrate complex. We also explored the universality of the nanoantenna strategy with another model protein, Protein G and its interaction with antibodies, and demonstrated a rapid screening strategy to identify efficient nanoantennas. These versatile nanoantennas can be used with diverse dyes to monitor small and large conformational changes, suggesting that they could be used to characterize diverse protein movements or in high-throughput screening applications.

Nanomaterials: Synthesis and Applications in Theranostics

Nanomaterials are endowed with unique features and essential properties suitable for employing in the field of nanomedicine. The nanomaterials can be classified as 0D, 1D, 2D, and 3D based on their dimensions. The nanomaterials can be malleable and ductile and they can be drawn into wires and sheets. Examples of nanomaterials are quantum dots (0D), nanorods, nanowires (1D), nanosheets (2D), and nanocubes (3D). These nanomaterials can be synthesized using top-down and bottom-up approaches. The achievements of 0D and 1D nanomaterials are used to detect trace heavy metal (e.g., Pb2+) and have higher sensitivity with the order of five as compared to conventional sensors. The achievements of 2D and 3D nanomaterials are used as diagnostic and therapeutic agents with multifunctional ability in imaging systems such as PET, SPECT, etc. These imaging modalities can be used to track the drug in living tissues. This review comprises the state-of-the-art of the different dimensions of the nanomaterials employed in theranostics. The nanomaterials with different dimensions have unique physicochemical properties that can be utilized for therapy and diagnosis. The multifunctional ability of the nanomaterials can have a distinct advantage that is used in the field of theranostics. Different dimensions of the nanomaterials would have more scope in the field of nanomedicine.

In Vivo Biodistribution, Clearance, and Biocompatibility of Multiple Carbon Dots Containing Nanoparticles for Biomedical Application

Current research on the use of carbon dots for various biological systems mainly focuses on the single carbon dots, while particles that contain multiple carbon dots have scarcely been investigated. Here, we assessed multiple carbon dots-crosslinked polyethyleneimine nanoparticles (CDs@PEI) for their in vivo biodistribution, clearance, biocompatibility, and cellular uptake. The in vivo studies demonstrate three unique features of the CDs@PEI nanoparticles: (1) the nanoparticles possess tumor-targeting ability with steady and prolonged retention time in the tumor region. (2) The nanoparticles show hepatobiliary excretion and are clear from the intestine in feces. (3) The nanoparticles have much better biocompatibility than the polyethyleneimine passivated single carbon dots (PEI-CD). We also found that pegylated CDs@PEI nanoparticles can be effectively taken up by the cells, which the confocal laser scanning microscope can image under different excitation wavelengths (at 405, 488, and 800 nm). These prior studies provide invaluable information and new opportunities for this new type of intrinsic photoluminescence nanoparticles in carbon dot-based biomedical applications.

Targeted design of green carbon dot-CA-125 aptamer conjugate for the fluorescence imaging of ovarian cancer cell

Aptamer-Carbon Dot (CD) bioconjugation is an attractive target-tracking strategy in detecting cell surface antigens. This study describes an effective imaging paradigm for CA-125 antigen imaging. Our experience encompasses green CD synthesis and characterization, CD-capture probe conjugation through covalent bonding, the hybridization linkage of CD-probe to aptamer and their coupling confirmation, and fluorescent targeted imaging of ovarian cancer cells. As a result, the synthesized CDs from lemon extract by hydrothermal reaction show average size of 2 nm with maximum fluorescence intensity at excitation/emission 360/450 nm. CD-probe construction was provided by functional group interactions of CD and probe via EDC/NHS chemistry. The linkage of CD-probe to aptamer was conducted by Watson-Crick nucleotide pairing. The assessment of CD-probe and CD-probe-aptamer fabrication was validated by the increase in surface roughness through AFM analysis, the diminish of fluorescence intensity of CD after bioconjugation, and particle size growth of the construct. Conjugates with negligible cytotoxicity, appropriate zeta potential, and good aptamer release were applied in cellular imaging. This targeted diagnosis method was employed the four reported DNA aptamers toward fluorescence intensity. The DOV-3 aptamer showed more qualified detection over other aptamer conjugates during fluorescent microscopy analysis. In conclusion, the CD-probe-aptamer conjugate applications as toxic-free method can open new horizons in fluorescent nano-imaging in the field of targeted cancer cell diagnosis.

Research Progress in the Synthesis of Targeting Organelle Carbon Dots and Their Applications in Cancer Diagnosis and Treatment

With increasing knowledge about diseases at the histological, cytological to sub-organelle level, targeting organelle therapy has gradually been envisioned as an approach to overcome the shortcomings of poor specificity and multiple toxic side effects on tissues and cell-level treatments using the currently available therapy. Organelle carbon dots (CDs) are a class of functionalized CDs that can target organelles. CDs can be prepared by a "synchronous in situ synthesis method" and "asynchronous modification method." The superior optical properties and good biocompatibility of CDs can be preserved, and they can be used as targeting particles to carry drugs into cells while reducing leakage during transport. Given the excellent organelle fluorescence imaging properties, targeting organelle CDs can be used to monitor the physiological metabolism of organelles and progression of human diseases, which will provide advanced understanding and accurate diagnosis and targeted treatment of cancers. This study reviews the methods used for preparation of targeting organelle CDs, mechanisms of accurate diagnosis and targeted treatment of cancer, as well as their application in the area of cancer diagnosis and treatment research. Finally, the current difficulties and prospects for targeting organelle CDs are prospected.

Tunable Organelle Imaging by Rational Design of Carbon Dots and Utilization of Uptake Pathways

Employing one-step hydrothermal treatment of o-phenylenediamine and lysine to exploit their self- and copolymerization, four kinds of CDs (ECDs, NCDs, GCDs, and LCDs) are synthesized, possessing different surface groups (CH₃, C-O-C, NH₂, and COOH) and lipophilicity which endow them with various uptake pathways to achieve tunable organelle imaging. Specifically, highly lipophilic ECDs with CH₃ group and NCDs with C-O-C group select passive manner to target to endoplasmic reticulum and nucleus, respectively. Amphiphilic GCDs with CH₃, C-O-C and NH₂ groups prefer caveolin-mediated endocytosis to locate at Golgi apparatus. Highly hydrophilic LCDs with CH₃, NH₂ and COOH groups are involved in clathrin-mediated endocytosis to localize in lysosomes. Besides, imaging results of cell division, three-dimensional reconstruction and living zebrafish demonstrate that the obtained CDs are promising potential candidates for specific organelle-targeting imaging.

Engineering Mitochondriotropic Carbon Dots for Targeting Cancer Cells

Aiming to understand and enhance the capacity of carbon dots (CDs) to transport through cell membranes and target subcellular organelles—in particular, mitochondria—a series of nitrogen-doped CDs were prepared by the one-step microwave-assisted pyrolysis of citric acid and ethylenediamine. Following optimization of the reaction conditions for maximum fluorescence, functionalization at various degrees with alkylated triphenylphosphonium functional groups of two different alkyl chain lengths afforded a series of functionalized CDs that exhibited either lysosome or mitochondria subcellular localization. Further functionalization with rhodamine B enabled enhanced fluorescence imaging capabilities in the visible spectrum and allowed the use of low quantities of CDs in relevant experiments. It was thus possible, by the appropriate selection of the alkyl chain length and degree of functionalization, to attain successful mitochondrial targeting, while preserving non-toxicity and biocompatibility. In vitro cell experiments performed on normal as well as cancer cell lines proved their non-cytotoxic character and imaging potential, even at very low concentrations, by fluorescence microscopy. Precise targeting of mitochondria is feasible with carefully designed CDs that, furthermore, are specifically internalized in cells and cell mitochondria of high transmembrane potential and thus exhibit selective uptake in malignant cells compared to normal cells.

Lipid phase dependent distinct emission behaviour of hydrophobic carbon dots: C-dot based membrane probes

We observe a unique distinct emission behaviour of hydrophobic carbon dots (H-CDs) embedded within the ordered and the disordered phase of a lipid membrane. The H-CDs exhibit blue emission in the disordered phase, however, they exhibit an intense red emission in the ordered phase of the lipid bilayer. The H-CDs have the potential ability to probe membrane dynamics like previously reported organic dyes. To the best of our knowledge, this is the first report of a CD-based membrane probe.