Biocompatibility and Bioimaging Potential of Fruit-Based Carbon Dots

Turn-Off Fluorescence Sensor for the Detection of Ferric Ion in Water Using Green Synthesized Wrightia coccinea Carbon Quantum Dot

The current study report that the production of carbon quantum dots from Wrightia coccinea (WC) leaves using an eco-friendly, one-pot process. The structural, morphological, and optical characteristics of the CDs made from W. coccinea leaves by hydrothermal treatment at 200 °C for six hours were assessed using a variety of spectroscopic and electron microscopy techniques. The average size of CD was found to be approximately 5 nm using transmission electron microscopy (TEM) and the quantum yield of the produced CD was 15.6%. The synthesized CDs demonstrated extraordinary sensing capacity with a detection limit of 0.511 µM for ferric ion detection. The impact of varying pH levels on the fluorescence behavior of CD was thoroughly investigated. The maximum fluorescence intensity was examined at pH 3. Therefore, to detect Fe3+ ions as best as possible, the pH of the entire solution was adjusted to a value of 3. Furthermore, the pH-dependent fluorescence feature of CDs can be exploited by pH-sensitive fluorescence sensors. In the future, this might provide an added advantage for pH-based fluorescence sensor applications.

Tailor-made molecular imprints for biological event intervention

Molecular imprints, which are crosslinked architectures containing specific molecular recognition cavities for targeting compounds, have recently transitioned from in vitro diagnosis to in vivo treatment. In current application scenarios, it has become an important topic to create new biomolecular recognition pathways through molecular imprinting, thereby inhibiting the pathogenesis and regulating the development of diseases. This review starts with a pathological analysis, mainly focusing on the corresponding artificial enzymes, enzyme inhibitors and antibody mimics with enhanced functions that are created by molecular imprinting strategies. Recent advances are highlighted in the use of molecular imprints as tailor-made nanomedicines for the prevention of three major diseases: metabolic syndrome, cancer, and bacterial/viral infections.

Carbon Dots and Their Polymeric Nanocomposites: Insight into Their Synthesis, Photoluminescence Mechanisms, and Recent Trends in Sensing Applications

Carbon dots (CDs), a novel class of carbon-based nanoparticles, have received a lot of interest recently due to their exceptional mechanical, chemical, and fluorescent properties, as well as their excellent photostability and biocompatibility. CDs' emission properties have already found a variety of potential applications, in which bioimaging and sensing are major highlights. It is widely acknowledged that CDs' fluorescence and surface conditions are closely linked. However, due to the structural complexity of CDs, the specific underlying process of their fluorescence is uncertain and yet to be explained. Because of their low toxicity, robust and wide optical absorption, high chemical stability, rapid transfer characteristics, and ease of modification, CDs have been recognized as promising carbon nanomaterials for a variety of sensing applications. Thus, following such outstanding properties of CDs, they have been mixed and imprinted onto different polymeric components to achieve a highly efficient nanocomposite with improved functional groups and properties. Here, in this review, various approaches and techniques for the preparation of polymer/CDs nanocomposites have been elaborated along with the individual characteristics of CDs. CDs/polymer nanocomposites recently have been highly demanded for sensor applications. The insights from this review are detailed sensor applications of polymer/CDs nanocomposites especially for detection of different chemical and biological analytes such as metal ions, small organic molecules, and several contaminants.

Multifunctional Carbon Dots for Biomedical Applications: Diagnosis, Therapy, and Theranostic

Designing suitable nanomaterials is an ideal strategy to enable early diagnosis and effective treatment of diseases. Carbon dots (CDs) are luminescent carbonaceous nanoparticles that have attracted considerable attention. Through facile synthesis, they process properties including tunable light emission, low toxicity, and light energy transformation, leading to diverse applications as optically functional materials in biomedical fields. Recently, their potentials have been further explored, such as enzyme-like activity and ability to promote osteogenic differentiation. Through refined synthesizing strategies carbon dots, a rich treasure trove for new discoveries, stand a chance to guide significant development in biomedical applications. In this review, the authors start with a brief introduction to CDs. By presenting mechanisms and examples, the authors focus on how they can be used in diagnosing and treating diseases, including bioimaging failure of tissues and cells, biosensing various pathogenic factors and biomarkers, tissue defect repair, anti-inflammation, antibacterial and antiviral, and novel oncology treatment. The introduction of the application of integrated diagnosis and treatment follows closely behind. Furthermore, the challenges and future directions of CDs are discussed. The authors hope this review will provide critical perspectives to inspire new discoveries on CDs and prompt their advances in biomedical applications.

An Overview of the Potential of Food-Based Carbon Dots for Biomedical Applications

Food-based carbon dots (CDs) hold significant importance across various fields, ranging from biomedical applications to environmental and food industries. These CDs offer unique advantages over traditional carbon nanomaterials, including affordability, biodegradability, ease of operation, and multiple bioactivities. This work aims to provide a comprehensive overview of recent developments in food-based CDs, focusing on their characteristics, properties, therapeutic applications in biomedicine, and safety assessment methods. The review highlights the potential of food-based CDs in biomedical applications, including antibacterial, antifungal, antivirus, anticancer, and anti-immune hyperactivity. Furthermore, current strategies employed for evaluating the safety of food-based CDs have also been reported. In conclusion, this review offers valuable insights into their potential across diverse sectors and underscores the significance of safety assessment measures to facilitate their continued advancement and application.

Green synthesis of gardenia seeds-based carbon dots for bacterial imaging and antioxidant activity in aqueous and oil samples

In this work, luminescent carbon dots with gardenia seeds as carbon precursors (GCDs) were synthesized using a one-step mild pyrolysis process and were then used as probes for imaging of bacterial (Escherichia coli). The GCDs showed a strong emission at 430 nm when excited at 370 nm. The relative fluorescence quantum yield of GCDs was found to be 1.13% in an aqueous medium. Rapid internalization of the GCDs by bacteria was confirmed by three colors (blue, green, and yellow) images that were obtained using confocal fluorescence microscopy. In addition, GCDs were noted to exhibit potent scavenging activities against DPPH˙, ˙OH, and ˙O2- free radicals. GCDs were also assayed as antioxidants in an oil sample by volumetric determination of the peroxide value. Thus, GCDs exhibited good antioxidant properties both in aqueous and oil media. In addition, a free fatty acid quantification kit in the presence of GCDs showed enhanced fluorescence detection of palmitic acid with a remarkably good limit of detection of 0.08 μM, which is lower than that in the absence of GCDs (0.76 μM). The proposed fluorescence method was then successfully used to determine the concentration of palmitic acid spiked in milk powder samples, with spiked recoveries of 82.6-109.6% and relative standard deviations of 0.9-4.6%.

Carbon Dots: Opportunities and Challenges in Cancer Therapy

Recently, carbon dots (CDs) have been actively studied and reported for their various properties. In particular, the specific characteristics of carbon dots have been considered as a possible technique for cancer diagnosis and therapy. This is also a cutting-edge technology that offers fresh ideas for treating various disorders. Though carbon dots are still in their infancy and have not yet shown their value to society, their discovery has already resulted in some noteworthy advancements. The application of CDs indicates conversion in natural imaging. Photography using CDs has demonstrated extraordinary appropriateness in bio-imaging, the discovery of novel drugs, the delivery of targeted genes, bio-sensing, photodynamic therapy, and diagnosis. This review seeks to provide a comprehensive understanding of CDs, including their benefits, characteristics, applications, and mode of action. In this overview, many CD design strategies will be highlighted. In addition, we will discuss numerous studies on cytotoxic testing to demonstrate the safety of CDs. The current study will address the production method, mechanism, ongoing research, and application of CDs in cancer diagnosis and therapy.

Green Carbon Dots: Applications in Development of Electrochemical Sensors, Assessment of Toxicity as Well as Anticancer Properties

Carbon dots are one of the most promising nanomaterials which exhibit a wide range of applications in the field of bioimaging, sensing and biomedicine due to their ultra-small size, high photostability, tunable fluorescence, electrical properties, etc. However, green carbon dots synthesized from several natural and renewable sources show some additional advantages, such as favorable biocompatibility, wide sources, low cost of production and ecofriendly nature. In this review, we will provide an update on the latest research of green carbon dots regarding their applications in cancer therapy and in the development of electrochemical sensors. Besides, the toxicity assessment of carbon dots as well as the challenges and future direction of research on their anticancer and sensing applications will be discussed.

Facile and Green Synthesis of Novel Fluorescent Carbon Quantum Dots and Their Silver Heterostructure: An In Vitro Anticancer Activity and Imaging on Colorectal Carcinoma

Carbon dots (CQDs) have been widely investigated as prime candidates for developing a tumor theranostic platform due to their tunable fluorescence emission and excitation, high water solubility, good photostability, and biocompatibility. Among the CQDs, natural CQDs are an emerging class of nanomaterials in the carbon family. Herein, highly fluorescent carbon quantum dots (CQDs) were synthesized from orange juice using a one-step hydrothermal method and characterized by different techniques. After that, CQD/Ag heterostructures were synthesized by the reduction of silver salt, in particular silver nitrate (AgNO₃) solution using sodium borohydride (NaBH₄) in different ratios. The photostability and characterization of CQD/Ag heterostructures were investigated. At last, a comparative cellular toxicity measurement was done to select the superior CQD/Ag heterostructure in the human colorectal carcinoma (HCT 116) cell line along with the imaging property. The detailed cell death signaling was also observed in the HCT 116 cell line via the ROS-dependent mitochondrial-mediated pathway, where Akt (RAC-α serine/threonine-protein kinase) played a important role.

Nanoformulation of Curcuma longa Root Extract and Evaluation of Its Dissolution Potential

Medicinal plants have been widely used for therapeutic purposes for a long time, but they have been found to have some major issues such as low water solubility and bioavailability. In the present study, the nanoformulation of Curcuma longa L. plant extract was prepared to enhance its dissolution potential and biological activities. For the formulation of the nanosuspension, an ethanolic extract of C. longa was prepared through Soxhlet extraction using the nanoformulation technique. The nanosuspensions were formulated using four different stabilizers, namely sodium lauryl sulfate (SLS), hydroxy propyl methyl cellulose (HPMC), poly(vinyl alcohol) (PVA), and polysorbate-80 (P-80). The scanning electron microscopy (SEM), polydispersity index, and ζ potential were used for characterization of the nanoformulation. Among all of these, the surfactant stabilizer SLS was found to be the best. The average particle size of the selected optimized nanosuspension was found to be 308.2 nm with a polydispersity index (PDI) value of 0.330. The ζ potential value of the optimized nanosuspension was recorded at -33.3 mV. The SEM image indicated that the particles were slightly agglomerated, which may have occurred during lyophilization of the nanosuspension. The highest dissolution rate recorded at pH = 7 was 192.32 μg/mL, which indicates pH = 7 as the most appropriate condition for the dissolution of the C. longa nanosuspension. The antioxidant, antimicrobial, and antifungal activities of the optimized nanosuspension were also determined with regard to the coarse plant extract. The study findings suggested that the nanoprecipitation approach helps in enhancing the dissolution potential and biological activities of C. longa root extract.

A Perspective on Using Organic Molecules Composing Carbon Dots for Cancer Treatment

Fluorescent Carbon dots (CDs) derived from biologically active sources have shown enhanced activities compared to their precursors. With their prominent potentiality, these small-sized (<10nm) nanomaterials could be easily synthesized from organic sources either by bottom-up or green approach. Their sources could influence the functional groups present on the CDs surfaces. A crude source of organic molecules has been used to develop fluorescent CDs. In addition, pure organic molecules were also valuable in developing practical CDs. Physiologically responsive interaction of CDs with various cellular receptors is possible due to the robust functionalization on their surface. In this review, we studied various literatures from the past ten years that reported the potential application of carbon dots as alternatives in cancer chemotherapy. The selective cytotoxic nature of some of the CDs towards cancer cell lines suggests the role of surface functional groups towards selective interaction, which results in over-expressed proteins characteristic of cancer cell lines. It could be inferred that cheaply sourced CDs could selectively bind to overexpressed proteins in cancer cells with the ultimate effect of cell death induced by apoptosis. In most cases, CDs-induced apoptosis directly or indirectly follows the mitochondrial pathway. Therefore, these nanosized CDs could serve as alternatives to the current kinds of cancer treatments that are expensive and have numerous side effects.

High reactive oxygen species produced from fluorescence carbon dots for anticancer and photodynamic therapies: A review

High-photoluminescence carbon dots (CDs) were synthesized from various sources and various methods using two approaches, namely bottom up and top down, with emission-dependent excitation wavelength. Electronic transition from the higher-occupied molecular orbital (HOMO) state to the lowest-unoccupied molecular orbital(LUMO) state, surface defect states, wider excitation spectrum, higher quantum yield, efficient energy transfer, and element doping affected the fluorescence properties of CDs. Using 102 references listed in this review, the authors studied the relationship between fluorescence mechanism and reactive oxygen species (ROS) produced for photodynamic therapy (PDT) and materials anticancer applications. We described how the radical atom or ROS work as anticancer therapy and PDT and described the chemical reaction of high-resolution fluorescence CDs. We summarized experimental techniques that are used for producing CDs and discussed their characteristics. Finally, conclusions and future prospects in this field are also discussed. The important characteristics of CD-based design for high ROS may usher in new prospects and challenges for high efficiency and stability of PDT and anticancer therapy. In conclusion, we have provided perspectives and challenges of the future development of CD s.

Biocompatible carbonized iodine-doped dots for contrast-enhanced CT imaging

Background

Computed tomography (CT) imaging has been widely used for the diagnosis and surveillance of diseases. Although CT is attracting attention due to its reasonable price, short scan time, and excellent diagnostic ability, there are severe drawbacks of conventional CT contrast agents, such as low sensitivity, serious toxicity, and complicated synthesis process. Herein, we describe iodine-doped carbon dots (IDC) for enhancing the abilities of CT contrast agents.

Method

IDC was synthesized by one-pot hydrothermal synthesis for 4 h at 180 ℃ and analysis of its structure and size distribution with UV–Vis, XPS, FT-IR, NMR, TEM, and DLS. Furthermore, the CT values of IDC were calculated and compared with those of conventional CT contrast agents (Iohexol), and the in vitro and in vivo toxicities of IDC were determined to prove their safety.

Results

IDC showed improved CT contrast enhancement compared to iohexol. The biocompatibility of the IDC was verified via cytotoxicity tests, hemolysis assays, chemical analysis, and histological analysis. The osmotic pressure of IDC was lower than that of iohexol, resulting in no dilution-induced contrast decrease in plasma.

Conclusion

Based on these results, the remarkable CT contrast enhancement and biocompatibility of IDC can be used as an effective CT contrast agent for the diagnosis of various diseases compared with conventional CT contrast agents.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40824-022-00277-3.

How to evaluate the potential toxicity of therapeutic carbon nanomaterials? A comprehensive study of carbonized nanogels with multiple animal toxicity test models

Carbon-based nanomaterials have great potential in medical applications, especially in the treatment of infectious diseases and even tumors. However, to safely execute the application of carbon nanomaterials in human treatments, conducting safety assessments and establishing suitable evaluation criteria are necessary. In this study, lysine-carbonized nanogels (Lys-CNGs) that display antibacterial and antiviral abilities were employed in a comprehensive evaluation of their toxicity profiles through assessments in different animal models and growth stages. It was observed that zebrafish at the embryo and eleutheroembryo stages experienced significant toxic effects at a concentration of 15-fold the recommended dosage (0.5 ppm), whereas adult zebrafish following long-term consumption of fodder containing Lys-CNGs presented no adverse effects. Further microbiota analysis indicated that Lys-CNGs did not cause significant changes in the composition of the intestinal bacteria. In contrast, in the toxicity assessments with mammalian animal models, the Lys-CNGs showed no adverse effects, such as weight loss, dermal irritation, and skin sensitization responses in rabbits and guinea pigs, even at a high dose of 2000 mg/kg body weight. Our study revealed that Lys-CNGs have different toxic effects on different growth stages of zebrafish. Researchers in this field should carefully consider the implications of these toxicity profiles during the development of therapeutic carbon-based nanomaterials and for comparison of studies.

Green synthesis of multifunctional carbon quantum dots: An approach in cancer theranostics

Carbon quantum dots (CQDs) have gained significant growing attention in the recent past due to their peculiar characteristics including smaller size, high surface area, photoluminescence, chemical stability, facile synthesis and functionalization possibilities. They are carbon nanostructures having less than 10 nm size with fluorescent properties. In recent years, the scientific community is curiously adopting biomass precursors for the preparation of CQDs over the chemical compounds. These biomass sources are sustainable, eco-friendly, inexpensive, widely available and convert waste into valuable materials. Hence in our work the fundamental understating of diverse fabrication methodologies of CQDs, and the types of raw materials employed in recent times, are all examined and correlated comprehensively. Their unique combination of remarkable properties, together with the ease with which they can be fabricated, makes CQDs as promising materials for applications in diverse biomedical fields, in particular for bio-imaging, targeted drug delivery and phototherapy for cancer treatment. The mechanism for luminescence is of considerable significance for leading the synthesis of CQDs with tunable fluorescence emission. Therefore, it is aimed to explore and provide an updated review on (i) the recent progress on the different synthesis methods of biomass-derived CQDs, (ii) the contribution of surface states or functional groups on the luminescence origin and (iii) its potential application for cancer theranostics, concentrating on their fluorescence properties. Finally, we explored the challenges in modification for the synthesis of CQDs from biomass derivatives and the future scope of CQDs in phototherapy for cancer theranostics.

Carbon dots: a novel platform for biomedical applications

Carbon dots (CDs) are a recently synthesised class of carbon-based nanostructures known as zero-dimensional (0D) nanomaterials, which have drawn a great deal of attention owing to their distinctive features, which encompass optical properties (e.g., photoluminescence), ease of passivation, low cost, simple synthetic route, accessibility of precursors and other properties. These newly synthesised nano-sized materials can replace traditional semiconductor quantum dots, which exhibit significant toxicity drawbacks and higher cost. It is demonstrated that their involvement in diverse areas of chemical and bio-sensing, bio-imaging, drug delivery, photocatalysis, electrocatalysis and light-emitting devices consider them as flawless and potential candidates for biomedical application. In this review, we provide a classification of CDs within their extended families, an overview of the different methods of CDs preparation, especially from natural sources, i.e., environmentally friendly and their unique photoluminescence properties, thoroughly describing the peculiar aspects of their applications in the biomedical field, where we think they will thrive as the next generation of quantum emitters. We believe that this review covers a niche that was not reviewed by other similar publications.

Carbon Dots: Synthesis, Properties and Applications

Carbon dots (CDs) are known as the rising star of carbon-based nanomaterials and, by virtue of their unique structure and fascinating properties, they have attracted considerable interest in different fields such as biological sensing, drug delivery, photodynamic therapy, photocatalysis, and solar cells in recent years. Particularly, the outstanding electronic and optical properties of the CDs have attracted increasing attention in biomedical and photocatalytic applications owing to their low toxicity, biocompatibility, excellent photostability, tunable fluorescence, outstanding efficient up-converted photoluminescence behavior, and photo-induced electron transfer ability. This article reviews recent progress on the synthesis routes and optical properties of CDs as well as biomedical and photocatalytic applications. Furthermore, we discuss an outlook on future and potential development of the CDs based biosensor, biological dye, biological vehicle, and photocatalysts in this booming research field.

Carbon dots for cancer nanomedicine: a bright future

Cancer remains one of the main causes of death in the world. Early diagnosis and effective cancer therapies are required to treat this pathology. Traditional therapeutic approaches are limited by lack of specificity and systemic toxicity. In this scenario, nanomaterials could overcome many limitations of conventional approaches by reducing side effects, increasing tumor accumulation and improving the efficacy of drugs. In the past few decades, carbon nanomaterials (i.e., fullerenes, carbon nanotubes, and carbon dots) have attracted significant attention of researchers in various scientific fields including biomedicine due to their unique physical/chemical properties and biological compatibility and are among the most promising materials that have already changed and will keep changing human life. Recently, because of their functionalization and stability, carbon nanomaterials have been explored as a novel tool for the delivery of therapeutic cancer drugs. In this review, we present an overview of the development of carbon dot nanomaterials in the nanomedicine field by focusing on their synthesis, and structural and optical properties as well as their imaging, therapy and cargo delivery applications.

Carbon dots-embedded N-acetylneuraminic acid and glucuronic acid-imprinted polymers for targeting and imaging of cancer cells

Diagnosis, treatment, and prediction of cancer progression require new targeting agents to specifically target cell surface receptors. Herein, we demonstrated fluorescent carbon quantum dots-molecularly imprinted polymer (CQD-MIP) for selective targeting and imaging of cancer cells. Carbon quantum dots (CQDs) were synthesized and characterized. The synthesized CQDs had average size of 1.5 nm and show intense fluorescence emission at wavelength of 450 nm with excitation at 370 nm. CQD-MIP nanoparticles imprinted with N-acetylneuraminic acid and glucuronic acid were prepared and characterized. CQD-MIPs were successfully applied for selective targeting and imaging of MCF-7, HepG-2, and NIH-3T3 cell lines. Non-imprinted polymer (NIP) showed no binding properties toward a target molecule. Non-imprinted polymer (NIP) and non-cancerous human cell lines were used for controlling the imprinting and targeting effects, respectively. Acceptable results were obtained with imprinted polymers on cancer cells.

Toxic or Not Toxic, That Is the Carbon Quantum Dot's Question: A Comprehensive Evaluation with Zebrafish Embryo, Eleutheroembryo, and Adult Models

Carbon quantum dots (CQDs) are emerging novel nanomaterials with a wide range of applications and high biocompatibility. However, there is a lack of in-depth research on whether CQDs can cause acute or long-term adverse reactions in aquatic organisms. In this study, two different types of CQDs prepared by ammonia citrate and spermidine, namely CQDAC and CQDSpd, were used to evaluate their biocompatibilities. In the fish embryo acute toxicity test (FET), the LD50 of CQDAC and CQDSpd was about 500 and 100 ppm. During the stage of eleutheroembryo, the LD50 decreased to 340 and 55 ppm, respectively. However, both CQDs were quickly eliminated from embryo and eleutheroembryo, indicating a lack of bioaccumulation. Long-term accumulation of CQDs was also performed in this study, and adult zebrafish showed no adverse effects in 12 weeks. In addition, there was no difference in the hatchability and deformity rates of offspring produced by adult zebrafish, regardless of whether they were fed CQDs or not. The results showed that both CQDAC and CQDSpd have low toxicity and bioaccumulation to zebrafish. Moreover, the toxicity assay developed in this study provides a comprehensive platform to assess the impacts of CQDs on aquatic organisms in the future.

Carbon dots derived from Fusobacterium nucleatum for intracellular determination of Fe3+ and bioimaging both in vitro and in vivo

Intracellular Fe3+ amount is one of the critical determinants of human health. The development of simple and effective probes for the quantitative detection of Fe3+in vivo is of great significance for the early diagnosis of disease or disorder associated with iron deficiency or overload. In this study, remarkable carbon dots, which can serve as a biosensor for efficient intracellular Fe3+ detection, were synthesized by hydrothermal carbonization of Fusobacterium nucleatum, an anaerobic bacterium. The achieved F. nucleatum-carbon dots (Fn-CDs) possessed the features of strong fluorescence, high stability and excellent biocompatibility. The obtained Fn-CDs could easily internalize into both plant cells and human cells with excellent ability for cell tracking and biomedical labeling. The fluorescence of Fn-CDs could still remain for another 24 hours after penetrating into cells. Furthermore, the fluorescent Fn-CDs were very sensitive to the presence of Fe3+ ions even in cells, exhibiting great promising applications in in vivo detection of Fe3+ ions. In addition, the Fn-CDs posed no harm to the mice, being circulated and excreted within a short time, making the Fn-CDs an excellent candidate for bioimaging and biosensing in vivo.

Leonardos I, Stalikas CD. Metabolomic Profiling Unveils the Impact of Non-Doped and Heteroatom-Doped Carbon Nanodots on Zebrafish (Danio rerio) Embryos

Recently, concern has been raised over the transport, transformation, and fate of carbon nanodots (CNDs) after their release into the environment. Their toxicity towards organisms and humans has recently been addressed as an important issue. In this study, a metabolomic approach was employed to obtain an insight into the effect of CNDs (either pristine or doped with nitrogen and nitrogen/sulfur) on zebrafish. Embryos were exposed to concentrations corresponding to lethal concentration (LC) LC₅₀ (550, 400, and 150 μg mL⁻¹), LC_50/2 (275, 200, and 75 μg mL⁻¹), and LC_50/4 (138, 100, and 38 μg mL⁻¹) of the three CNDs (non-doped, N-doped, and N,S-codoped, respectively) to scrutinize the interactions of the CNDs with the larvae. Numerous differences in the metabolic pathways were recorded in all cases. Seven metabolic pathways were detected in the control larvae. When the larvae were exposed to concentrations equal to LC₅₀, LC_50/2, and LC_50/4 of non-doped CNDs, 12, 12, and 3 metabolic pathways were detected, respectively. In the case of N-doped CNDs, 4, 7, and 4 pathways were detected, while in the case of N,S-codoped CNDs, 8, 5, and 5 pathways were detected when exposed to concentrations of LC₅₀, LC_50/2, and LC_50/4, respectively. In all cases, certain metabolic pathways were altered while others were either down-regulated or up-regulated. Some of these changes include the activation of alanine, aspartate, and glutamate metabolism, aminoacyl-tRNA biosynthesis, butanoate metabolism, D-glutamine, and D-glutamate metabolism, glutathione metabolism, selenoamino acid metabolism, valine, leucine, and isoleucine degradation pathways. Moreover, the deactivation of starch and sucrose metabolism, the glycine, serine, and threonine metabolism, among others, were recorded. Our findings underline the importance to further study the impact of CNDs on marine organisms. As zebrafish has been shown to share many similarities with humans in bioprocesses and genome, it can be assumed that CNDs may also pose a threat to human health.

Actin-binding carbon dots selectively target glioblastoma cells while sparing normal cells

Curcumin, a pleiotropic signalling molecule from Curcuma longa, is reported to be effective against multiple cancers. Despite its promising effect, curcumin had failed in clinical trials due to its low aqueous solubility, stability and poor bioavailability. While several approaches are being attempted to overcome the limitations, the improved solubility observed with curcumin-derived carbon dots appeared to be a strategy worth exploring. To assess if the carbon dots possess bio-activity similar to curcumin, we synthesized carbon dots (CurCD) from curcumin and ethylenediamine. Unlike curcumin, the as-synthesized curcumin carbon dots exhibited excellent solubility, excitation-dependent emission and photostability. The anti-cancer activity evaluated with glioblastoma cells using the well-established in vitro models indicated its comparable/enhanced activity over curcumin. Besides, the selective affinity of CurCD to the actin filament, indicated it's prospective to serve as a marker of actin filaments. In addition, the non-toxic effects observed in normal cells and fish embryos indicated CurCD was more biocompatible than curcumin. While this work reveals the superior properties of CurCD over curcumin, it provides a new approach to explore other plant derived molecules with similar limitations like curcumin.

Carbon dots: A novel trend in pharmaceutical applications

Carbon quantum dots (CQDs, C-dots, or CDs), are generally small carbon nanoparticles having a size less than 10nm. Carbon dots (CDs) were accidentally discovered during the purification of single-walled carbon nanotubes through preparative electrophoresis in 2004. Carbon is an organic material having poor water solubility that emits less fluorescence. However, CDs have good aqueous solubility and excellent fluorescent property, hence more attention has been given to the synthesis of CDs and their applications in chemistry and allied sciences. CDs being easily accessible for in-house synthesis, simpler fabrication as per compendial requirements are wisely accepted. In addition, since CDs are biocompatible, of low toxicity, and of biodegradable nature, they appear as a promising tool for the health care sector. Furthermore, owing to their capabilities of expressing significant interaction with biological materials, and their excellent photoluminescence (PL), CDs have been emerging as novel pioneered nanoparticles useful for pharmaceutical and theranostic applications. Also, CDs are more eco-friendly in synthesis and therefore can be favorably consumed as alternatives in the further development of biological, environmental, and food areas. A massive study has been performed dealing with different approaches which are adopted for CDs synthesis and their applications as, filters for the separation of pollutants from polluted water, food safety, toxicological studies, and optical properties, etc. While still less emphasis is given on the applications of CDs in pharmaceuticals like for sustained and targeted drug delivery systems, theranostic study, etc. Hence, in the present review, we are exploring CQDs as a boon to pharmaceutical concerns.

Carbon Dots as a Sustainable New Platform for Organic Light Emitting Diode

Over the past 10 years, carbon dots (CDs) synthesized from renewable raw materials have received considerable attention in several fields for their unique photoluminescent properties. Moreover, the synthesis of CDs fully responds to the principles of circular chemistry and the concept of safe-by-design. This review will focus on the different strategies for incorporation of CDs in organic light-emitting devices (OLEDs) and on the study of the impact of CDs properties on OLED performance. The main current research outcomes and highlights are summarized to guide users towards full exploitation of these materials in optoelectronic applications.

Natural carbon-based quantum dots and their applications in drug delivery: A review

Natural carbon based quantum dots (NCDs) are an emerging class of nanomaterials in the carbon family. NCDs have gained immense acclamation among researchers because of their abundance, eco-friendly nature, aqueous solubility, the diverse functionality and biocompatibility when compared to other conventional carbon quantum dots (CDs).The presence of different functional groups on the surface of NCDs such as thiol, carboxyl, hydroxyl, etc., provides improved quantum yield, physicochemical and optical properties which promote bioimaging, sensing, and drug delivery. This review provides comprehensive knowledge about NCDs for drug delivery applications by outlining the source and rationale behind NCDs, different routes of synthesis of NCDs and the merits of adopting each method. Detailed information regarding the mechanism behind the optical properties, toxicological profile including biosafety and biodistribution of NCDs that are favourable for drug delivery are discussed. The drug delivery applications of NCDs particularly as sensing and real-time tracing probe, antimicrobial, anticancer, neurodegenerative agents are reviewed. The clinical aspects of NCDs are also reviewed as an initiative to strengthen the case of NCDs as potent drug delivery agents.

Sensor and Bioimaging Studies Based on Carbon Quantum Dots: The Green Chemistry Approach

Since carbon quantum dots have high photoluminescent efficiency, it has been a desired material in sensor and bioimaging applications. In recent years, the green chemistry approach has been preferred and the production of quantum dots has been reported in many studies using different precursors from natural, abundant, or waste sources. Hydrothermal, chemical oxidation, microwave supported, ultrasonic, solvothermal, pyrolysis, laser etching, solid-state, plasma, and electrochemical methods have been reported in the literature. In this review article, green chemistry strategies for carbon quantum dot synthesis is summarized and compared with conventional methods using methodologic and statistical data. Furthermore, a detailed discussion on sensor and bioimaging applications of carbon quantum dots produced with green synthesis approaches are presented with a special focus on the last decade.

Plant Part-Derived Carbon Dots for Biosensing

Carbon dots (CDs) are a new cluster of carbon atoms with particle size less than 10 nm. CDs also exhibit interesting fluorescence (FL) properties. CDs are attractive because of their fascinating characteristics including low toxicity, good water solubility, and tremendous biocompatibility. Recently, CDs have been investigated as biosensors for numerous target analytes. Meanwhile, the utilization of cheap and renewable natural resources not only fulfills the pressing requirement for the large-scale synthesis of CDs but also encourages the establishment of sustainable applications. The preparation of CDs using natural resources, i.e., plants, offers several advantages as it is inexpensive, eco-friendly, and highly available in the surroundings. Plant parts are readily available natural resources as the starting materials to produce CDs with different characteristics and attractive applications. Several review articles are now available covering the synthesis, properties, and applications of CDs. However, there is no specific and focused review literature discussing plant part-derived CDs for biosensing applications. To handle this gap, we provide a review of the progress of CDs derived from various plant parts with their synthesis methods, optical properties, and biosensing applications in the last five years. We highlight the synthesis methods and then give an overview of their optical properties and applications as biosensors for various biomolecules and molecules in biological samples. Finally, we discuss some future perspectives for plant part-derived CDs for better material development and applications.