Biomass-derived carbon dots with pharmacological activity for biomedicine: Recent advances and future perspectives

Carbon dots (CDs), a type of nanoparticle with excellent optical properties, good biocompatibility, and small size, are finding increasing application across the fields of biology and biomedicine. In recent years, biomass-derived CDs with pharmacological activity (BP-CDs) derived from herbal medicines (HMs), HMs extracts and other natural products with demonstrated pharmaceutical activity have attracted particular attention. Herein, we review recent advances in the development of BP-CDs, covering the selection of biomass precursors, different methods used for the synthesis of BP-CDs from natural sources, and the purification of BP-CDs. Additionally, we summarize the many remarkable properties of BP-CDs including optical properties, biocompatibility and pharmaceutical efficacy. Moreover, the antibacterial, antiviral, anticancer, biosensing, bioimaging, and other applications of BP-CDs are reviewed. Thereafter, we discuss the advantages and disadvantages of BP-CDs and Western drug-derived CDs, highlighting the excellent performance of BP-CDs. Finally, based on the current state of research on BP-CDs, we suggest several aspects of BP-CDs that urgently need to be addressed and identify directions that should be pursued in the future. This comprehensive review on BP-CDs is expected to guide the precise design, preparation, and future development of BP-CDs, thereby advancing the application of BP-CDs in biomedicine.

Fluorescent Polylactic acid composite incorporating lignin-based carbon quantum dots for sustainable 4D printing applications

Fluorescent 4D printing materials, as innovative materials that combine fluorescent characteristics with 4D printing technology, have attracted widespread interest and research. In this study, green lignin-derived carbon quantum dots (CQDs) were used as the fluorescent module, and renewable poly(propylene carbonate) polyurethane (PPCU) was used for toughening. A new low-cost fluorescent polylactic acid (PLA) composite filament for 4D printing was developed using a simple melt extrusion method. The strength of the prepared composite was maintained at 32 MPa, while the elongation at break increased 8-fold (34 % increase), demonstrating excellent shape fixed ratio (∼99 %), recovery ratio (∼92 %), and rapid shape memory recovery speed. The presence of PPCU prevented fluorescence quenching of the CQDs in the PLA matrix, allowing the composite to emit bright green fluorescence under 365 nm ultraviolet light. The composite exhibited shear thinning behavior and had an ideal melt viscosity for 3D printing. The results obtained demonstrated the versatility of these easy-to-manufacture and low-cost filaments, opening up a novel and convenient method for the preparation of strong, tough, and multifunctional PLA materials, increasing their potential application value.

CARBON DOTS: Bioimaging and Anticancer Drug Delivery

Cancer, responsible for approximately 10 million lives annually, urgently requires innovative treatments, as well as solutions to mitigate the limitations of traditional chemotherapy, such as long-term adverse side effects and multidrug resistance. This review focuses on Carbon Dots (CDs), an emergent class of nanoparticles (NPs) with remarkable physicochemical and biological properties, and their burgeoning applications in bioimaging and as nanocarriers in drug delivery systems for cancer treatment. The review initiates with an overview of NPs as nanocarriers, followed by an in-depth look into the biological barriers that could affect their distribution, from barriers to administration, to intracellular trafficking. It further explores CDs' synthesis, including both bottom-up and top-down approaches, and their notable biocompatibility, supported by a selection of in vitro, in vivo, and ex vivo studies. Special attention is given to CDs' role in bioimaging, highlighting their optical properties. The discussion extends to their emerging significance as drug carriers, particularly in the delivery of doxorubicin and other anticancer agents, underscoring recent advancements and challenges in this field. Finally, we showcase examples of other promising bioapplications of CDs, emergent owing to the NPs flexible design. As research on CDs evolves, we envisage key challenges, as well as the potential of CD-based systems in bioimaging and cancer therapy.

Tumor diagnosis using carbon-based quantum dots: Detection based on the hallmarks of cancer

Carbon-based quantum dots (CQDs) have been shown to have promising application value in tumor diagnosis. Their use, however, is severely hindered by the complicated nature of the nanostructures in the CQDs. Furthermore, it seems impossible to formulate the mechanisms involved using the inadequate theoretical frameworks that are currently available for CQDs. In this review, we re-consider the structure-property relationships of CQDs and summarize the current state of development of CQDs-based tumor diagnosis based on biological theories that are fully developed. The advantages and deficiencies of recent research on CQDs-based tumor diagnosis are thus explained in terms of the manifestation of nine essential changes in cell physiology. This review makes significant progress in addressing related problems encountered with other nanomaterials.

Carbon-Based Nanostructures as Emerging Materials for Gene Delivery Applications

Gene therapeutics are promising for treating diseases at the genetic level, with some already validated for clinical use. Recently, nanostructures have emerged for the targeted delivery of genetic material. Nanomaterials, exhibiting advantageous properties such as a high surface-to-volume ratio, biocompatibility, facile functionalization, substantial loading capacity, and tunable physicochemical characteristics, are recognized as non-viral vectors in gene therapy applications. Despite progress, current non-viral vectors exhibit notably low gene delivery efficiency. Progress in nanotechnology is essential to overcome extracellular and intracellular barriers in gene delivery. Specific nanostructures such as carbon nanotubes (CNTs), carbon quantum dots (CQDs), nanodiamonds (NDs), and similar carbon-based structures can accommodate diverse genetic materials such as plasmid DNA (pDNA), messenger RNA (mRNA), small interference RNA (siRNA), micro RNA (miRNA), and antisense oligonucleotides (AONs). To address challenges such as high toxicity and low transfection efficiency, advancements in the features of carbon-based nanostructures (CBNs) are imperative. This overview delves into three types of CBNs employed as vectors in drug/gene delivery systems, encompassing their synthesis methods, properties, and biomedical applications. Ultimately, we present insights into the opportunities and challenges within the captivating realm of gene delivery using CBNs.

Carbon quantum dots derived from polysaccharides: Chemistry and potential applications

Since the beginning of 21th century, nanoscience and nanotechnology become the most promising topics in various fields, attributing to the superior characters of nanoscaled structures. The conventional quantum dots are substituted with new family of luminescent nanostructures, owing to their interchanged optical properties, low-cost of fabrication, biocompatibility, non-toxicity, ecofriendly, hydrophilicity and superior chemical stability. Carbon quantum dots (CQDs) were recently investigated for their simple synthesis, bio-consonance, and different revelation applicability. Obeying the green chemistry aspects, this review demonstrates an overview about CQDs generated from polysaccharides in brief, with a background on CQDs discovery, chemical composition, green synthesis via exploitation of different polysaccharides (cellulose, starch, pectin, chitin, etc) as biocompatible/biodegradable abundant biopolymers. Additionally, applications of CQDs originated from polysaccharides in environmental purposes, textiles industry and medical activities were also presented.

Novel Strategies Using Sagacious Targeting for Site-Specific Drug Delivery in Breast Cancer Treatment: Clinical Potential and Applications

For more than a decade, researchers have been working to achieve new strategies and smart targeting drug delivery techniques and technologies to treat breast cancer (BC). Nanotechnology presents a hopeful strategy for targeted drug delivery into the building of new therapeutics using the properties of nanomaterials. Nanoparticles are of high regard in the field of diagnosis and the treatment of cancer. The use of these nanoparticles as an encouraging approach in the treatment of various cancers has drawn the interest of researchers in recent years. In order to achieve the maximum therapeutic effectiveness in the treatment of BC, combination therapy has also been adopted, leading to minimal side effects and thus an enhancement in the quality of life for patients. This review article compares, discusses and criticizes the approaches to treat BC using novel design strategies and smart targeting of site-specific drug delivery systems.

Pyrimidine-5-carbonitrile derivatives as sprout for CQDs proveniences: Antitumor and anti-inflammatory potentiality

A comparative study is proposed to show the effect of variation in the heteroatoms in the main skeleton of CQDs proveniences, on their affinity for nucleation of CQDs, as anti-inflammatory and anticancer drugs. Heterocyclic-based CQDs sprout was successfully exploited for preparation of three CQDs proveniences, named as; 2-(2,5-dimethoxyphenyl)-4,6-dioxo-6,11-dihydro-4H-pyrimido[2,1-b] quinazoline-3-carbonitrile (compound A), 2-(2,5-dimethoxyphenyl)-4,6-dioxo-4H,6H-benzo[e]pyrimido[2,1-b][1,3]oxazine-3-carbonitrile (compound S) and 2-(2,5-dimethoxyphenyl)-4,6-dioxo-4H,6H-benzo[e]pyrimido[2,1-b][1,3] thiazine-3-carbonitrile (compound T). Chemical formulas of CQDs proveniences & CQDs were verified via FTIR, 1HNMR, 13CNMR & XRD. Particle size of TM-CQDs, A-CQDs, S-CQDs & T-CQDs were estimated to be 3.7 ± 1.4, 4.6 ± 1.6, 5.9 ± 1.6 nm and 3.0 ± 1.3 nm, respectively. All of CQDs proveniences & CQDs were examined for their affinity as anti-inflammatory drugs via Griess assay. CQDs ingrained from TM (TM-CQDs) were detected with the highest NO inhibition% by increasing its concentration from 10 up to 100 μM to be 40 % to 89 %, respectively. Moreover, their anti-tumor performance against MCF-7: breast Adenocarcinoma cell line was approved via sulforhodamine B assay, whereas, IC50 was evaluated for TM-CQDs, A-CQDs, S-CQDs and T-CQDs to be 38.16, 36.09, 100 and 100 μg/ml, respectively.

Carbon Nanomaterial-Based Hydrogels as Scaffolds in Tissue Engineering: A Comprehensive Review

Carbon-based nanomaterials (CBNs) are a category of nanomaterials with various systems based on combinations of sp2 and sp3 hybridized carbon bonds, morphologies, and functional groups. CBNs can exhibit distinguished properties such as high mechanical strength, chemical stability, high electrical conductivity, and biocompatibility. These desirable physicochemical properties have triggered their uses in many fields, including biomedical applications. In this review, we specifically focus on applying CBNs as scaffolds in tissue engineering, a therapeutic approach whereby CBNs can act for the regeneration or replacement of damaged tissue. Here, an overview of the structures and properties of different CBNs will first be provided. We will then discuss state-of-the-art advancements of CBNs and hydrogels as scaffolds for regenerating various types of human tissues. Finally, a perspective of future potentials and challenges in this field will be presented. Since this is a very rapidly growing field, we expect that this review will promote interdisciplinary efforts in developing effective tissue regeneration scaffolds for clinical applications.

Green synthesis of fluorescent carbon nanodots from sage leaves for selective anticancer activity on 2D liver cancer cells and 3D multicellular tumor spheroids

Carbon nanodots, a family of carbon-based nanomaterials, have been synthesized through different methods from various resources, affecting the properties of the resulting product and their application. Herein, carbon nanodots (CNDs) were synthesized with a green and simple hydrothermal method from sage leaves at 200 °C for 6 hours. The obtained CNDs are well dispersed in water with a negative surface charge (ζ-potential = -11 mV) and an average particle size of 3.6 nm. The synthesized CNDs showed concentration-dependent anticancer activity toward liver cancer (Hep3B) cell lines and decreased the viability of the cancer cells to 23% at the highest used concentration (250 μg ml-1 of CNDs). More interestingly, the cytotoxicity of the CNDs was tested in normal liver cell lines (LX2) revealed that the CNDs at all tested concentrations didn't affect their viability including at the highest concentration showing a viability of 86.7%. The cellular uptake mechanisms of CNDs were investigated and they are thought to be through energy-dependent endocytosis and also through passive diffusion. The main mechanisms of endocytosis were lipid and caveolae-mediated endocytosis. In addition, the CNDs have hindered the formation of 3D spheroids from the Hep3B hepatocellular carcinoma cell line. Hence, it would be concluded that the synthesized CNDs from sage are more highly selective to liver cancer cells than normal ones. The CNDs' cancer-killing ability would be referred to as the production of reactive oxygen species.

Carbon Dots Derived from Traditional Chinese Medicines with Bioactivities: A Rising Star in Clinical Treatment

In the field of carbon nanomaterials, carbon dots (CDs) have become a preferable choice in biomedical applications. Based on the concept of green chemistry, CDs derived from traditional Chinese medicines (TCMs) have attracted extensive attention, including TCM charcoal drugs, TCM extracts, and TCM small molecules. The design and preparation of CDs from TCMs (TCMs-CDs) can improve the inherent characteristics of TCMs, such as solubility, particle size distribution, and so on. Compared with other precursor materials, TCMs-CDs have outstanding intrinsic bioactivities and potential pharmacological effects. However, the research of TCMs-CDs in biomedicine is not comprehensive, and their mechanisms have not been understood deeply either. In this review, we will provide concise insights into the recent development of TCMs-CDs, with a major focus on their preparation, formation, precursors, and bioactivities. Then we will discuss the perfect transformation from TCMs to TCMs-CDs. Finally, we discuss the opportunities and challenges for the application of TCMs-CDs in clinical treatment.

Progress in drug delivery and diagnostic applications of carbon dots: a systematic review

Carbon dots (CDs), which have particle size of less than 10 nm, are carbon-based nanomaterials that are used in a wide range of applications in the area of novel drug delivery in cancer, ocular diseases, infectious diseases, and brain disorders. CDs are biocompatible, eco-friendly, easy to synthesize, and less toxic with excellent chemical inertness, which makes them very good nanocarrier system to deliver multi-functional drugs effectively. A huge number of researchers worldwide are working on CDs-based drug delivery systems to evaluate their versatility and efficacy in the field of pharmaceuticals. As a result, there is a tremendous increase in our understanding of the physicochemical properties, diagnostic and drug delivery aspects of CDs, which consequently has led us to design and develop CDs-based theranostic system for the treatment of multiple disorders. In this review, we aim to summarize the advances in application of CDs as nanocarrier including gene delivery, vaccine delivery and antiviral delivery, that has been carried out in the last 5 years.

An Efficient Green Approach to Constructing Adenine Sulfate-Derived Multicolor Sulfur- and Nitrogen-Codoped Carbon Dots and Their Bioimaging Applications

A cost-effective and environmentally friendly approach is proposed for producing N- and S-codoped multicolor-emission carbon dots (N- and S-codoped MCDs) at a mild reaction temperature (150 °C) and relatively short time (3 h). In this process, adenine sulfate acts as a novel precursor and doping agent, effectively reacting with other reagents such as citric acid, para-aminosalicylic acid, and ortho-phenylenediamine, even during solvent-free pyrolysis. The distinctive structures of reagents lead to the increased amount of graphitic nitrogen and sulfur doping in the N- and S-codoped MCDs. Notably, the obtained N- and S-codoped MCDs exhibit considerable fluorescence intensities, and their emission color can be adjusted from blue to yellow. The observed tunable photoluminescence can be attributed to variations in the surface state and the amount of N and S contents. Furthermore, due to the favorable optical properties, good water solubility and biocompatibility, and low cytotoxicity, these N- and S-codoped MCDs, especially green carbon dots, are successfully applied as fluorescent probes for bioimaging. The affordable and environmentally friendly synthesis method employed to create N- and S-codoped MCDs, combined with their remarkable optical properties, offers a promising avenue for their use in various fields, particularly in biomedical applications.

Nitrogen and copper-doped saffron-based carbon dots: Synthesis, characterization, and cytotoxic effects on human colorectal cancer cells

AIM

Doped carbon dots (CDs) have attracted tremendous attention in cancer therapy. We aimed to synthesize copper, nitrogen-doped carbon dots (Cu, N-CDs) from saffron and investigated their effects on HCT-116 and HT-29 colorectal cancer (CRC) cells.

MAIN METHODS

CDs were synthesized by hydrothermal method and characterized by transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-visible (UV-Vis) absorption spectroscopy, and fluorescence spectroscopy. HCT-116 and HT-29 cells were incubated with saffron, N-CDs, and Cu, N-CDs for 24 and 48 h for cell viability. Cellular uptake and intracellular reactive oxygen species (ROS) were evaluated by immunofluorescence microscopy. Oil Red O staining was used to monitor lipid accumulation. Apoptosis was evaluated using acridine orange/propidium iodide (AO/PI) staining and quantitative real-time polymerase chain reaction (Q-PCR) assay. The expression of miRNA-182 and miRNA-21 was measured by Q-PCR, while the generation of nitric oxide (NO) and lysyl oxidase (LOX) activity was calculated by colorimetric methods.

KEY FINDINGS

CDs were successfully prepared and characterized. Cell viability decreased in the treated cells dose- and time-dependently. HCT-116 and HT-29 cells uptook Cu, N-CDs with a high level of ROS generation. The Oil Red O staining showed lipid accumulation. Concomitant with an up-regulation of apoptotic genes (p < 0.05), AO/PI staining showed increased apoptosis in the treated cells. In comparison to control cells, NO generation, and miRNA-182 and miRNA-21 expression significantly changed in the Cu, N-CDs treated cells (p < 0.05).

SIGNIFICANCE

The results indicated that Cu, N-CDs could inhibit CRC cells through the induction of ROS generation and apoptosis.

Natural resources for sustainable synthesis of nanomaterials with anticancer applications: A move toward green nanomedicine

Today, researchers have focused on the application of environmentally-benign and sustainable micro- and nanosystems for drug delivery and cancer therapy. Compared to conventional chemotherapeutics, advanced micro- and nanosystems designed by applying abundant, natural, and renewable feedstocks have shown biodegradability, biocompatibility, and low toxicity advantages. However, important aspects of toxicological assessments, clinical translational studies, and suitable functionalization/modification still need to be addressed. Herein, the benefits and challenges of green nanomedicine in cancer nanotherapy and targeted drug delivery are cogitated using nanomaterials designed by exploiting natural and renewable resources. The application of nanomaterials accessed from renewable natural resources, comprising metallic nanomaterials, carbon-based nanomaterials, metal-organic frameworks, natural-derived nanomaterials, etc. for targeted anticancer drug delivery and cancer nanotherapy are deliberated, with emphasis on important limitations/challenges and future perspectives.

Carbon Dots Derived from Tea Polyphenols as Photosensitizers for Photodynamic Therapy

Photodynamic therapy (PDT) has become an emerging cancer treatment method. Choosing the photosensitizer (PS) compounds is one of the essential factors that can influence the PDT effect and action. Carbon dots (CDs) have shown great potential as photosensitizers in PDT of cancers due to their excellent biocompatibility and high generation of reactive oxygen species (ROS). Here, we used tea polyphenol as raw material for synthesized tea polyphenol carbon dots (T-CDs) that show dual emission bands of red and blue fluorescence and can efficiently generate hydroxyl radicals (OH) under mildly visible irradiation with a LED light (400-500 nm, 15 mW cm^-2). The extremely low cytotoxicity and excellent biocompatibility of T-CDs without light irradiation were tested using MTT and hemolytic assay. Further, T-CDs have been shown by in vivo experiments, using a mouse breast cancer cell line (4T1) subcutaneously injected in the back of the mouse buttock as a model, to effectively inhibit the tumor cell proliferation in solid tumors and show an excellent PDT effect. In addition, pathological sections of the mice tissues after further treatment showed that the T-CDs had no apparent impact on the major organs of the mice and did not produce any side effect lesions. This work demonstrates that the as-synthesized T-CDs has the potential to be used as a PS in cancer treatment.

Research progress on Walnut oil: Bioactive compounds, health benefits, extraction methods, and medicinal uses

Walnut oil is extracted from walnut kernels (Juglans regia Linne) or iron walnut kernels (Juhlans sigillata Dode). The percentage of oil in walnuts is 52%-70%. The main constituents in oil are fatty acids, phenols, sterols, squalene, melatonin, vitamins, and minerals. Many extraction methods such as supercritical carbon dioxide extraction, maceration, modified "bligh and dyer extraction," aqueous enzymatic extraction, ultrasonic extraction, soxhlet extraction, and cold-press extraction methods are reported in the literature. Walnut oil showed anti-inflammatory, antitumor, antioxidant, immunomodulatory, neuroprotective, cardioprotective, antidiabetic, and antihyperlipidemic activities. The reported data in the literature suggest that walnut oil has many health benefits. This review summarizes the extraction methods, bioactive constituents, health benefits, and pharmacological actions of walnut oil. PRACTICAL APPLICATIONS: Walnut oil is a natural vegetable oil of significant importance due to their nutritional, and intelligence-boosting benefits. Several factors, including the processing parameters and the phytochemical profile, affect walnut oil products' flavor and color. In addition, storage environment of walnut oil can also affect walnut oil quality. Apart from the predominant ingredient fatty acids, the chemical composition of walnut oil comprises phenols, sterols, squalene, melatonin, vitamins, and minerals. These bioactive compounds are of potential value owing to their health-promoting benefits, including antioxidant, antitumor, and cholesterol-lowering effects. Many chemical constituents were isolated from walnut oil; however, all the compounds are not explored for their possible medicinal value. Thus, clinical studies, exploration of the therapeutic potential and the molecular mechanisms of all the compounds, and development of convenient dosage forms either for therapeutic or functional food purposes are warranted.

Carbon nanoparticles induce DNA repair and PARP inhibitor resistance associated with nanozyme activity in cancer cells

Background

Quantum nanodots especially carbon nanoparticles (CNPs) have been widely studied in biomedicine in imaging, and drug delivery, but anti-cancer mechanisms remain elusive.

Methods

Here, we investigated a type of cell death induced by food (beet, soybean) derived CNPs in cancer cells and tested whether CNPs induced DNA damage and resistant to anti-cancer agent PARP inhibitor (PARPi) could be overcome by quantum calculations, TEM, AFM, FT-IR, soft agar assay, and cytotoxicity assay.

Results

At high doses, CNPs derived from beet lead to a pop-like apoptosis (Carbopoptosis) in cancer cells. Quantum mechanical calculations confirmed CNPs binding with phosphate groups as well as DNA bases. At low doses, CNPs develop PARPi drug resistance through interactions between CNPs and PARPi. A synergistic drug effect was achieved with the combination of phosphatase inhibitor (PPi), PARPi, and CNPs. This is corroborated by the fact that sulfur modulated CNPs which exhibit super high phosphatase nanozyme activity abrogated the CNPs induced colony formation in anchorage-independent cancer cell growth.

Conclusion

Thus, our data suggest the CNPs intrinsic nanozyme activity of phosphatase may crosstalk with drug resistance, which can be reversed upon modulations.

Biowaste-Derived Carbon Dots: A Perspective on Biomedical Potentials

Today, sustainable and natural resources including biowastes have been considered attractive starting materials for the fabrication of biocompatible and biodegradable carbon dots (CDs) due to the benefits of availability, low cost, biorenewability, and environmentally benign attributes. These carbonaceous nanomaterials have been widely explored in the field of sensing/imaging, optoelectronics, photocatalysis, drug/gene delivery, tissue engineering, regenerative medicine, and cancer theranostics. Designing multifunctional biowaste-derived CDs with a high efficacy-to-toxicity ratio for sustained and targeted drug delivery, along with imaging potentials, opens a new window of opportunity toward theranostic applications. However, crucial challenges regarding the absorption/emission wavelength, up-conversion emission/multiphoton fluorescence mechanisms, and phosphorescence of these CDs still need to be addressed to attain the maximum functionality and efficacy. Future studies ought to focus on optimizing the synthesis techniques/conditions, evaluating the influence of nucleation/growth process on structures/properties, controlling their morphology/size, and finding the photoluminescence mechanisms. Reproducibility of synthesis techniques is another critically important factor that needs to be addressed in the future. Herein, the recent developments related to the biowaste-derived CDs with respect to their biomedical applications are deliberated, focusing on important challenges and future perspectives.

Strict Twice Iterative Optimization Strategy to Synthesize Ultrabright Fluorescent Carbon Dots for UV and pH Dual-Encryption Fluorescent Ink

In this work, ultrabright fluorescent carbon dots (U-CDs) were synthesized by using a strict twice iterative optimization strategy. Their relative photoluminescence (PL) quantum yield is close to 100%, exceeding most of the reported fluorescent CDs and greatly boosting the practical applications of fluorescent CDs in many fields. Then serving as fluorescent anti-counterfeiting ink was taken as an example to briefly introduce the application of the U-CDs. The PL emission of the U-CDs is quenched at the range of pH < 4 or pH > 11 and restored at the range of pH = 5-10. This pH-sensitive PL feature allows the U-CDs to be used as fluorescent ink for pH and UV dual information encryption. The written or printed information is invisible under daylight but visible under UV light. After acid treatment or alkali treatment, the information is invisible even under a UV lamp but visible after neutralization treatment. This work provides a standardized scheme for optimizing the synthesis conditions of fluorescent CDs and paves the way for large-scale production of high-performance fluorescent CDs.

An Overview of Synthetic Methods and Applications of Photoluminescent Properties of Carbon Quantum Dots

Carbon quantum dots (CQDs) are promising carbonaceous nanomaterials fortuitously discovered in 2004. CQDs are the rising stars in the nanotechnology ensemble because of their unique properties and widespread applications in sensing, imaging, medicine, catalysis, and optoelectronics. CQDs are notable for their excellent solubility and effective luminescence, and as a result, they are also known as carbon nanolights. Many strategies are used for the efficient and economical preparation of CQDs; however, CQDs prepared from waste or green sustainable methods have greater requirements due to their safety and ease of synthesis. Sustainable chemical strategies for CQDs have been developed, emphasizing green synthetic methodologies based on "top-down" and "bottom-up" approaches. This review summarizes many such studies relevant to the development of sustainable methods for photoluminescent CQDs. Furthermore, we have emphasized recent advances in CQDs' photoluminescent applications in chemical and biological fields. Finally, a brief overview of synthetic processes utilizing the green source and their associated applications are tabulated, providing a clear understanding of the new optoelectronic materials.

Chinese Medicinal Herb-Derived Carbon Dots for Common Diseases: Efficacies and Potential Mechanisms

The management of hemorrhagic diseases and other commonly refractory diseases (including gout, inflammatory diseases, cancer, pain of various forms and causes) are very challenging in clinical practice. Charcoal medicine is a frequently used complementary and alternative drug therapy for hemorrhagic diseases. However, studies (other than those assessing effects on hemostasis) on charcoal-processed medicines are limited. Carbon dots (CDs) are quasi-spherical nanoparticles that are biocompatible and have high stability, low toxicity, unique optical properties. Currently, there are various studies carried out to evaluate their efficacy and safety. The exploration of using traditional Chinese medicine (TCM) -based CDs for the treatment of common diseases has received great attention. This review summarizes the literatures on medicinal herbs-derived CDs for the treatment of the difficult-to-treat diseases, and explored the possible mechanisms involved in the process of treatment.

Nanoparticles: Excellent Materials Yet Dangerous When They Become Airborne

Since the rise and rapid development of nanoscale science and technology in the late 1980s, nanomaterials have been widely used in many areas including medicine, electronic products, crafts, textiles, and cosmetics, which have provided a lot of convenience to people's life. However, while nanomaterials have been fully utilized, their negative effects, also known as nano pollution, have become increasingly apparent. The adverse effects of nanomaterials on the environment and organisms are mainly based on the unique size and physicochemical properties of nanoparticles (NPs). NPs, as the basic unit of nanomaterials, generally refer to the ultrafine particles whose spatial scale are defined in the range of 1-100 nm. In this review, we mainly introduce the basic status of the types and applications of NPs, airborne NP pollution, and the relationship between airborne NP pollution and human diseases. There are many sources of airborne NP pollutants, including engineered nanoparticles (ENPs) and non-engineered nanoparticles (NENPs). The NENPs can be further divided into those generated from natural activities and those produced by human activities. A growing number of studies have found that exposure to airborne NP pollutants can cause a variety of illnesses, such as respiratory diseases, cardiovascular diseases, and neurological disorders. To deal with the ever increasing numbers and types of NPs being unleashed to the air, we believe that extensive research is needed to provide a comprehensive understanding of NP pollution hazards and their impact mechanisms. Only in this way can we find the best solution and truly protect the safety and quality of life of human beings.

Carbon dots for virus detection and therapy

Recent experience with the COVID-19 pandemic should be a lesson learnt with respect to the effort we have to invest in the development of new strategies for the treatment of viral diseases, along with their cheap, easy, sensitive, and selective detection. Since we live in a globalized world where just hours can play a crucial role in the spread of a virus, its detection must be as quick as possible. Thanks to their chemical stability, photostability, and superior biocompatibility, carbon dots are a kind of nanomaterial showing great potential in both the detection of various virus strains and a broad-spectrum antiviral therapy. The biosensing and antiviral properties of carbon dots can be tuned by the selection of synthesis precursors as well as by easy post-synthetic functionalization. In this review, we will first summarize current options of virus detection utilizing carbon dots by either electrochemical or optical biosensing approaches. Secondly, we will cover and share the up-to-date knowledge of carbon dots' antiviral properties, which showed promising activity against various types of viruses including SARS-CoV-2. The mechanisms of their antiviral actions will be further adressed as well. Finally, we will discuss the advantages and distadvantages of the use of carbon dots in the tangled battle against viral infections in order to provide valuable informations for further research and development of new virus biosensors and antiviral therapeutics.

Carbon Nanodots Inhibit Oxidized Low Density Lipoprotein-Induced Injury and Monocyte Adhesion to Endothelial Cells Through Scavenging Reactive Oxygen Species

Oxidized low density lipoprotein (Ox-LDL) is a known biomarker of inflammation and atherosclerosis, a leading cause of death worldwide. As a new class of nanomaterials, carbon nanodots (CNDs) are widely used in bioimaging, diagnostics, and drug delivery. However, there is no current report on how these CNDs affect the cardiovascular system, particularly their potential in mediating endothelial inflammatory dysfunction. This study examined effects of CNDs on Ox-LDL-mediated endothelial dysfunction. CNDs significantly inhibited Ox-LDL-mediated adhesion of monocytes to human microvascular endothelial cells (HMEC-1), in human microvascular endothelial cells (HMEC-1). CNDs significantly inhibited Ox-LDL-mediated adhesion of monocytes to endothelial cells, which is an essential step in the development of atherosclerosis. Further, CNDs significantly inhibited OxLDL-induced expression of interleukin-8 (IL-8), a vital cytokine on monocyte adhesion to the endothelial cells. These results demonstrate CNDs possess anti-inflammatory properties. CNDs also protect cells against Ox-LDL-induced cytotoxicity. Electron paramagnetic resonance (EPR) spectroscopy studies demonstrated direct reactive oxygen species-scavenging by CNDs. This result indicates that the anti-inflammatory properties of CNDs are most likely due to their direct scavenging of reactive oxygen species. Animal studies involving mice did not show any morphological or physical changes between the CNDs and control groups. Our study provides evidence of potential of CNDs in reducing Ox-LDL-mediated inflammation and cytotoxicity in HMEC-1.

Imaging-Guided Chemo-Photothermal Polydopamine Carbon Dots for EpCAM-Targeted Delivery toward Liver Tumor

We demonstrate a versatile nanoparticle with imaging-guided chemo-photothermal synergistic therapy and EpCAM-targeted delivery of liver tumor cells. EpCAM antibody (anti-EpCAM) and Pt(IV) were grafted onto the polydopamine carbon dots (PDA-CDs) by the amidation reaction. The EpCAM antibody of particles enables the targeted interaction with liver progenitor cells due to their overexpressed EpCAM protein. The tetravalent platinum prodrug [Pt(IV)] induces apoptosis with minimum toxic side effects through the interaction between cisplatin and tumor cell DNA. The nanoparticles displayed stable photothermal property and considerable anti-tumor therapeutic effect in vivo. Coupling with cellular imaging due to their fluorescence property, anti-EpCAM@PDA-CDs@Pt(IV) offers a convenient and effective platform for imaging-guided chemo-photothermal synergistic therapy toward liver cancers in the near future.

Selective mediation of ovarian cancer SKOV3 cells death by pristine carbon quantum dots/Cu2O composite through targeting matrix metalloproteinases, angiogenic cytokines and cytoskeleton

It was shown that some nanomaterials may have anticancer properties, but lack of selectivity is one of challenges, let alone selective suppression of cancer growth by regulating the cellular microenvironment. Herein, we demonstrated for the first time that carbon quantum dots/Cu2O composite (CQDs/Cu2O) selectively inhibited ovarian cancer SKOV3 cells by targeting cellular microenvironment, such as matrix metalloproteinases, angiogenic cytokines and cytoskeleton. The result was showed CQDs/Cu2O possessed anticancer properties against SKOV3 cells with IC50 = 0.85 μg mL-1, which was approximately threefold lower than other tested cancer cells and approximately 12-fold lower than normal cells. Compared with popular anticancer drugs, the IC50 of CQDs/Cu2O was approximately 114-fold and 75-fold lower than the IC50 of commercial artesunate (ART) and oxaliplatin (OXA). Furthermore, CQDs/Cu2O possessed the ability to decrease the expression of MMP-2/9 and induced alterations in the cytoskeleton of SKOV3 cells by disruption of F-actin. It also exhibited stronger antiangiogenic effects than commercial antiangiogenic inhibitor (SU5416) through down-regulating the expression of VEGFR2. In addition, CQDs/Cu2O has a vital function on transcriptional regulation of multiple genes in SKOV3 cells, where 495 genes were up-regulated and 756 genes were down-regulated. It is worth noting that CQDs/Cu2O also regulated angiogenesis-related genes in SKOV3 cells, such as Maspin and TSP1 gene, to suppress angiogenesis. Therefore, CQDs/Cu2O selectively mediated of ovarian cancer SKOV3 cells death mainly through decreasing the expression of MMP-2, MMP-9, F-actin, and VEGFR2, meanwhile CQDs/Cu2O caused apoptosis of SKOV3 via S phase cell cycle arrest. These findings reveal a new application for the use of CQDs/Cu2O composite as potential therapeutic interventions in ovarian cancer SKOV3 cells.

Antitumor/antiviral carbon quantum dots based on carrageenan and pullulan

Requirement for medication from pathogenic human viruses and cancer diseases are urgently considered, while, numerous reports were focused on investigating easily manufactured and excellently effective therapeutic reagents. Herein, CQDs were prepared with size of 2.1 nm from both of carrageenan and pullulan. CQDs nucleated from pullulan showed higher anti-proliferative effects against cancer cells, while, treatment with 100 μg/mL of CQDs colloids originated from pullulan and carrageenan separately resulted in diminishing of cancer cell viability percent to be 42.1 & 58.7%, respectively. Plaque reduction assay was also affirmed that, 2.5 μg/L of both of pullulan and carrageenan based CQDs exhibited viral inhibition with percent of 44.3& 59.5%, respectively. As a conclusion, pullulan showed seniority over carrageenan in nucleation of CQDs with higher anticancer activities. While, estimation of antiviral performance of the prepared CQDs confirmed the priority of carrageenan compared to pullulan in preparation of CQDs as antiviral laborer.

Normal breast epithelial MCF-10A cells to evaluate the safety of carbon dots

The human normal breast cell line MCF-10A is being widely used as a model in toxicity studies due to its structural similarity to the normal human mammary epithelium. Over the years, application of carbon dots (C-dots) in biomedicine has been increasing due to their photoluminescence properties, biocompatibility, biosafety and possible applications in bioimaging and as drug carriers. In this work we prepared three different C-dots from the same set of carbon and nitrogen precursors (citric acid and urea, respectively) via three distinct bottom-up synthetic routes and their safety was tested against the normal breast cell line MCF-10A. The characterization results demonstrated a similar size range and composition for all the C-dots. The MCF-10A cells were treated with different concentrations of C-dots for 24, 48 and 72 h to evaluate the cell viability over time. For the 24 h incubation, there were no significant decreases in the viability of the MCF-10A cells. For the 48 h treatment, there was a significant decrease in the viability of the cells treated with calcination-based C-dots, but without significant cellular viability changes for microwave and hydrothermal-based C-dots. For 72 h, cells treated with hydrothermal-based C-dots have the most promising viability profile. Also, compared with paclitaxel, these C-dots have a safety profile very close to that of an antineoplastic in non-tumor cells. Our results suggest that these new C-dots have potential as imaging candidates or biosensing tools as well as drug carriers, and further investigation in animal models is needed for future application in medicine.

Green synthesis of water-soluble fluorescent carbon dots from rosemary leaves: Applications in food storage capacity, fingerprint detection, and antibacterial activity

Blue fluorescent carbon dots are synthesized via a one-step hydrothermal method using rosemary leaves as a carbon source. The obtained carbon dots are characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-Vis, FTIR, and fluorescence spectrometry. The results show that carbon dots gave a maximum emission peak at 422 nm when excited at 332 nm. The average particle diameter of the synthesized spherical carbon dots is found to be 16.13 nm with a 4.6-nm standard deviation. The diameters of the produced carbon dots vary, as is evident from standard deviation heights, resulting in multicolor emission spectra. The fruit storage experiment is carried out by investigating the qualitative antioxidant ability of the produced carbon dots. The results obtained for polyvinyl alcohol–carbon dot–coated samples differ remarkably compared to polyvinyl alcohol–coated samples only. The polyvinyl alcohol–carbon dot composition is used in latent fingerprint detection applications. In analyses made on a glass surface, fingerprints cannot be monitored on the glass surface with the polyvinyl alcohol layer under ultraviolet light, while they are observed on the surface covered with the polyvinyl alcohol–carbon dot composition. Moreover, biological activity against Gram-positive, Gram-negative, and yeast strains are investigated.

Innovatory role of nanomaterials as bio-tools for treatment of cancer

Conventional treatment modes like chemotherapy, thermal and radiations aimed at cancerous cells eradication are marked by destruction pointing the employment of nanomaterials as sustainable and auspicious materials for saving human lives. Cancer has been deemed as the second leading cause of death on a global scale. Nanomaterials employment in cancer treatment is based on the utilization of their inherent physicochemical characteristics in addition to their modification for using as nano-carriers and nano-vehicles eluted with anti-cancer drugs. Current work has reviewed the significant role of different types of nanomaterials in cancer therapeutics and diagnostics in a systematic way. Compilation of review has been done by analyzing voluminous investigations employing ERIC, MEDLINE, NHS Evidence and Web of Science databases. Search engines used were Google scholar, Jstore and PubMed. Current review is suggestive of the remarkable performance of nanomaterials making them candidates for cancer treatment for substitution of destructive treatment modes through investigation of their physicochemical characteristics, utilization outputs and long term impacts in patients.

DNA-damage and cell cycle arrest initiated anti-cancer potency of super tiny carbon dots on MCF7 cell line

While carbon-based materials have spearheaded numerous breakthroughs in biomedicine, they also have procreated many logical concerns on their overall toxicity. Carbon dots (CDs) as a respectively new member have been extensively explored in nucleus directed delivery and bioimaging due to their intrinsic fluorescence properties coupled with their small size and surface properties. Although various in vitro/in vivo studies have shown that CDs are mostly biocompatible, sufficient information is lacking regarding genotoxicity of them and underlying mechanisms. This study aims to analyze the real-time cytotoxicity of super tiny CDs (2.05 ± 0.22 nm) on human breast cancer cells (MCF7) and human primary dermal fibroblast cell cultures (HDFa) by xCELLigence analysis system for further evaluating their genotoxicity and clastogenicity to evaluate the anti-tumor potential of CDs on breast adenocarcinoma. As combined with flow cytometry studies, comet assay and cytokinesis-block micronucleus assay suggest that the CDs can penetrate to the cell nuclei, interact with the genetic material, and explode DNA damage and G0/G1 phase arrest in cancer cells even at very low concentrations (0.025 ppm) which provide a strong foundation for the design of potentially promising CD-based functional nanomaterials for DNA-damage induced treatment in cancer therapy.

The Differential Effect of Carbon Dots on Gene Expression and DNA Methylation of Human Embryonic Lung Fibroblasts as a Function of Surface Charge and Dose

This study presents a toxicological evaluation of two types of carbon dots (CD), similar in size (<10 nm) but differing in surface charge. Whole-genome mRNA and miRNA expression (RNAseq), as well as gene-specific DNA methylation changes, were analyzed in human embryonic lung fibroblasts (HEL 12469) after 4 h and 24 h exposure to concentrations of 10 and 50 µg/mL (for positive charged CD; pCD) or 10 and 100 µg/mL (for negative charged CD, nCD). The results showed a distinct response for the tested nanomaterials (NMs). The exposure to pCD induced the expression of a substantially lower number of mRNAs than those to nCD, with few commonly differentially expressed genes between the two CDs. For both CDs, the number of deregulated mRNAs increased with the dose and exposure time. The pathway analysis revealed a deregulation of processes associated with immune response, tumorigenesis and cell cycle regulation, after exposure to pCD. For nCD treatment, pathways relating to cell proliferation, apoptosis, oxidative stress, gene expression, and cycle regulation were detected. The expression of miRNAs followed a similar pattern: more pronounced changes after nCD exposure and few commonly differentially expressed miRNAs between the two CDs. For both CDs the pathway analysis based on miRNA-mRNA interactions, showed a deregulation of cancer-related pathways, immune processes and processes involved in extracellular matrix interactions. DNA methylation was not affected by exposure to any of the two CDs. In summary, although the tested CDs induced distinct responses on the level of mRNA and miRNA expression, pathway analyses revealed a potential common biological impact of both NMs independent of their surface charge.

Extraction of Graphene Nanostructures from Colocasia esculenta and Nelumbo nucifera Leaves and Surface Functionalization with Tin Oxide: Evaluation of Their Antibacterial Properties

Expeditious evolution of antimicrobial resistance in recent years has been identified as a growing concern by various health organizations around the world. Herein, facile and environmentally benign production of highly antibacterial carbonaceous nanomaterials from Colocasia esculenta and Nelumbo nucifera leaves is reported. After carbonization and oxidative treatment, smaller graphene domains are formed in Colocasia esculenta derivatives, whereas larger sheetlike structures are observed in the case of Nelumbo nucifera. Smaller particle size makes quantum confinement effects more prominent, as is evident in fine-tuning of the photoluminescence emission after each stage of treatment. The influence of precursor materials on the antibacterial properties of the nanosystems is also demonstrated. When microbiocidal activity was tested against model bacteria Pseudomonas aeruginosa, the nanocomposite derived from Colocasia esculenta leaves showed higher activity than the antibiotic drug clarithromycin (control) with a measured zone of inhibition of 40±0.5 mm. This is one of the highest values reported in comparison with plant-based carbon-silver nanosystems. Quantitative analysis revealed that the nanocomposite obtained from Colocasia esculenta leaves has antimicrobial efficacy equivalent to those of commercial antibiotic drugs and is able to eradicate bacteria at much lower concentrations than that obtained from Nelumbo nucifera leaves.

Highly Efficient Electron Transfer in a Carbon Dot-Polyoxometalate Nanohybrid

Using solar radiation to fuel catalytic processes is often regarded as the solution to our energy needs. However, developing effective photocatalysts that are active under visible light has proven to be difficult, often due to the toxicity, instability, and high cost of suitable catalysts. We engineered a novel photoactive nanomaterial obtained by the spontaneous electrostatic coupling of carbon nanodots with [P₂W₁₈O₆₂]^6-, a molecular catalyst belonging to the class of polyoxometalates. While the former are used as photosensitizers, the latter was chosen for its ability to catalyze reductive reactions such as dye decomposition and water splitting. We find the electron transfer within the nanohybrid to be so efficient that a charge-separated state is formed within 120 fs from photon absorption. These results are a cornerstone in the engineering of a new class of nanodevices, which are nontoxic, are inexpensive, and can carry out solar-driven catalytic processes.

Fluorescent Carbon Dots for Selective Labeling of Subcellular Organelles

With the recent advancement in understanding and control of the structure and optical properties of fluorescent carbon dots (CDs), they have been shown to be valuable in biolabeling of bacteria, tumor cells, tissues, and organelles. Their extremely small size and tunable functional properties coupled with ultrastable fluorescence enable CDs to be used for easy and effective labeling of various organelles. In addition, CDs with advantages of easy preparation and functionalization with recognition elements and/or drugs have emerged as nanocarriers for organelle-targeted drug delivery. In this review, we mainly discuss the applications of fluorescent CDs for the labeling of organelles, including lysosome, nucleoli, nucleus, endoplasmic reticulum, and mitochondria. We highlight the importance of the surface properties (functional groups, hydrophobicity/hydrophilicity, charges, zwitterions) and the size of CDs for labeling. Several interesting examples are provided to highlight the potential and disadvantages of CDs for labeling organelles. Strategies for the preparation of CDs for specific labeling of organelles are suggested. With the edge in preparation of diverse CDs, their potential in labeling and drug delivery is highly expected.

Nitrogen-doped carbon quantum dots-decorated 2D graphitic carbon nitride as a promising photocatalyst for environmental remediation: A study on the importance of hybridization approach

Growing concerns of water pollution by dye pollutants from the textile industry has led to vast research interest to find green solutions to address this issue. In recent years, heterogeneous photocatalysis has harvested tremendous attention from researchers due to its powerful potential applications in tackling many important energy and environmental challenges at a global level. To fully utilise the broad spectrum of solar energy has been a common aim in the photocatalyst industry. This study focuses on the development of an efficient, highly thermal and chemical stable, environmentally friendly and metal-free graphitic carbon nitride (g-C₃N₄) to overcome the problem of fast charge recombination which hinders photocatalytic performances. Nitrogen-doped carbon quantum dots (NCQDs) known for its high electronic and optical functionality properties is believed to achieve photocatalytic enhancement by efficient charge separation through forming heterogeneous interfaces. Hence, the current work focuses on the hybridisation of NCQDs and g-C₃N₄ to produce a composite photocatalyst for methylene blue (MB) degradation under LED light irradiation. The optimal hybridisation method and the mass loading required for maximum attainable MB degradation were systematically investigated. The optimum photocatalyst, 1 wt% NCQD/g-C₃N₄ composite was shown to exhibit a 2.6-fold increase in photocatalytic activity over bare g-C₃N₄. Moreover, the optimum sample displayed excellent stability and durability after three consecutive degradation cycles, retaining 91.2% of its original efficiency. Scavenging tests were also performed where reactive species, photon-hole (h⁺) was identified as the primary active species initiating the pollutant degradation mechanism. The findings of this study successfully shed light on the hybridisation methods of NCQDs which improve existing g-C₃N₄ photocatalyst systems for environmental remediation by utilising solar energy.