Swarming carbon dots for folic acid mediated delivery of doxorubicin and biological imaging

Innovative tumor interstitial fluid-triggered carbon dot-docetaxel nanoassemblies for targeted drug delivery and imaging of HER2-positive breast cancer

In this study, we have developed an innovative pH-triggered nanomedicine delivery system, targeting HER2-positive breast cancer cells for effective low-cost, imaging-guided drug delivery and precise therapy. The key feature of this system lies in its unique tumor interstitial fluid microenvironment-responsive drug release behavior which achieved tumor site-specific drug delivery. Our in vitro experiments demonstrated that the carbon dot-integrated material achieves more efficient DTX release (96.13 % at 72 h) in the tumor interstitial fluid microenvironment (pH 6.5), thereby boosting drug concentration at the tumor site and enhancing therapeutic efficacy. Further cell experiments confirmed the system's significant inhibitory effect on HER2-positive tumor cells SKBR3 in a pH 6.5 environment, and apoptosis assays indicating a notable increase in early cell apoptosis (from 8.39 % to 24.61 % compared with pH 7.4). Furthermore, the integration of HER2 aptamer within the carbon dot-based system enables targeted recognition and binding to tumor cells, ensuring more precise delivery of DTX while minimizing potential side effects. Crucially, the carbon dots in this system emit superior red fluorescence (the QY = 47.64 % excited at 535 nm compared with Rodamine 6G), enabling real-time visualization of the drug delivery process. This feature provides valuable feedback on treatment effectiveness, facilitating necessary adjustments. The small size (1.88 ± 0.48 nm) of carbon dots significantly improved their ability to penetrate biological barriers, while their low toxicity (no significant cell toxicity under 350 μg/mL) contributed to the formulation's outstanding biocompatibility. Overall, this carbon dot-enhanced drug delivery system offers immense potential for enhancing drug efficacy, minimizing side effects, and providing real-time treatment monitoring, thus proposing a innovate strategy for breast cancer therapy.

Carbon Dots: Synthesis, Characterizations, and Recent Advancements in Biomedical, Optoelectronics, Sensing, and Catalysis Applications

Carbon nanodots (CNDs), a fascinating carbon-based nanomaterial (typical size 2-10 nm) owing to their superior optical properties, high biocompatibility, and cell penetrability, have tremendous applications in different interdisciplinary fields. Here, in this Review, we first explore the superiority of CNDs over other nanomaterials in the biomedical, optoelectronics, analytical sensing, and photocatalysis domains. Beginning with synthesis, characterization, and purification techniques, we even address fundamental questions surrounding CNDs such as emission origin and excitation-dependent behavior. Then we explore recent advancements in their applications, focusing on biological/biomedical uses like specific organelle bioimaging, drug/gene delivery, biosensing, and photothermal therapy. In optoelectronics, we cover CND-based solar cells, perovskite solar cells, and their role in LEDs and WLEDs. Analytical sensing applications include the detection of metals, hazardous chemicals, and proteins. In catalysis, we examine roles in photocatalysis, CO2 reduction, water splitting, stereospecific synthesis, and pollutant degradation. With this Review, we intend to further spark interest in CNDs and CND-based composites by highlighting their many benefits across a wide range of applications.

Synthesis of 2-amino-terephthalic acid crosslinked chitosan/bentonite hydrogel; an efficient adsorbent for anionic dyes and laccase

This research article presents the fabrication of NH2-terephthalic acid crosslinked chitosan-bentonite composite, which adopted a facile synthesis approach and offered efficient adsorption capacity for organic dyes. A novel hydrogel material named CB 5:1 demonstrated remarkable adsorption for anionic dyes (Congo red (CR) and brilliant blue (BB)) while showing a negligible affinity for cationic dyes. Adsorption isotherm studies revealed the adsorption capacity of 4950 mg/g and 2053 mg/g (per g of composite's dry weight) for CR and BB following the Langmuir adsorption model. Kinetics and thermodynamic studies were also conducted while the adsorption of anionic dyes in the presence of metal ions, cationic dyes, anionic dyes, and in simulated water remained unaffected. Laccase, an industrially important enzyme, was also immobilized on CB 5:1 to achieve enzyme stability and reusability, resulting in a staggering immobilization capacity (4782 mg/g) at pH 6.0. Laccase immobilized product was employed to perform dye degradation (> 90 % for CR and > 75 % for BB), and the reusability was tested. Overall, our crosslinked product proved appealing for removing high concentrations of anionic organic dyes from polluted water and could be envisaged for practical use.

Preparation of Multicolor Fluorescent Carbon Dots Based on Catechol and o-Phthalaldehyde

As the foremost category of carbon materials, carbon dots (CDs) have been extensively applied in many domains because of their special fluorescence features and outstanding biocompatibility. However, in early studies of fluorescent CDs, as the fluorescence wavelength of most CDs was restricted to the blue or green region and was excitation dependent, the application of CDs was limited. In this study, three representative CDs, fluorescing yellow, green, and blue, were synthesized under alkaline, neutral, and acidic circumstances, respectively, while using a hydrothermal method in which catechol and phthalaldehyde acted as carbon sources and methanol functioned as the reaction solvent. The carbon nuclei of the three fluorescent CDs all had comparable graphite structures. The diversity of photoluminescence (PL) emission from these three CDs was attributed mainly to the different sizes of the sp² conjugated structures among them. Mixing synthesized CDs with epoxy resin, three colors (yellow, green, and blue) of LED using CIE coordinates (0.40, 0.44), (0.33, 0.46), and (0.21, 0.22), respectively, were successfully prepared.

Interaction between carbon dots from folic acid and their cellular receptor: a qualitative physicochemical approach

According to the World Health Organization, the number of cancers (all cancers, both sexes, all ages and worldwide) in 2020 reached a total of 19 292 789 new cases leading to 9 958 133 deaths during the same period. Many cancers could be cured if detected early. Preventing cancer and detecting it early are two essential strategies for controlling this pathology. For this purpose, several strategies have been described for imaging cancer cells. One of them is based on the use of carbon nanoparticles called carbon dots, tools of physical chemistry. The literature describes that cancer cells can be imaged using carbon dots obtained from folic acid and that the in cellulo observed photoluminescence probably results from the interaction of these nanoparticles with the folic acid-receptor, a cell surface protein overexpressed in many malignant cells. However, this interaction has never been directly demonstrated yet. We investigated it, for the first time, using (i) freshly synthesized and fully characterized carbon dots, (ii) folate binding protein, a folic acid-receptor model protein and (iii) fluorescence spectroscopy and isothermal titration calorimetry, two powerful methods for detecting molecular interactions. Our results even highlight a selective interaction between these carbon made nano-objects and their biological target.

Effects of plastic-derived carbon dots on germination and growth of pea (Pisum sativum) via seed nano-priming

Seed nano-priming is a promising technology employed in the agronomic field to promote seed germination and plant growth. However, the effects of carbon dots (CDs) on plant development via seed nano-priming remain unclear. In the present study, CDs synthesized from non-biodegradable plastic wastes were adopted as a nano-priming agent for pea (Pisum sativum) seed treatment. The results demonstrated positive effects of seed priming at all CD concentrations (0.25-2 mg/mL), including accelerated seed germination rate, increased shoot and root elongation, biomass accumulation, and root moisture level compared to the control groups. Surface erosion of seed coat was observed after CD priming, which effectively promoted seed imbibition capability. CD penetration, internalization, and translocation were confirmed using transmission electron microscopy. Furthermore, the CD-plant interaction significantly enhanced seed antioxidant enzyme activity, as well as augmented root vigor, chlorophyll content, and carbohydrate content. These findings exhibit great potential of waste-derived CDs as nano-priming agents for seed germination and seedling development in a cost-effective and sustainable manner.

Could artificial intelligence revolutionize the development of nanovectors for gene therapy and mRNA vaccines?

Gene therapy enables the introduction of nucleic acids like DNA and RNA into host cells, and is expected to revolutionize the treatment of a wide range of diseases. This growth has been further accelerated by the discovery of CRISPR/Cas technology, which allows accurate genomic editing in a broad range of cells and organisms in vitro and in vivo. Despite many advances in gene delivery and the development of various viral and non-viral gene delivery vectors, the lack of highly efficient non-viral systems with low cellular toxicity remains a challenge. The application of cutting-edge technologies such as artificial intelligence (AI) has great potential to find new paradigms to solve this issue. Herein, we review AI and its major subfields including machine learning (ML), neural networks (NNs), expert systems, deep learning (DL), computer vision and robotics. We discuss the potential of AI-based models and algorithms in the design of targeted gene delivery vehicles capable of crossing extracellular and intracellular barriers by viral mimicry strategies. We finally discuss the role of AI in improving the function of CRISPR/Cas systems, developing novel nanobots, and mRNA vaccine carriers.

Quercetin conjugated fluorescent nitrogen-doped carbon dots for targeted cancer therapy application

In this work, we report the development of nitrogen-doped carbon dots (NDCDs) as a drug carrier using quercetin (QC) as a model drug for anti-cancer drug delivery application. NDCDs were prepared by a simple hydrothermal method using Luffa acutangula as a carbon source. The characterization of QC-NDCDs was done by UV-vis spectroscopy, fluorescence spectroscopy, zeta potential measurements, high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and Raman spectroscopy. The as-synthesized NDCDs have a small particle size with hydroxyl and nitrogen-containing groups (pyridinic and amide groups), enhancing the fluorescence properties, and were obtained in a good quantum yield (14%). Furthermore, the in vitro alamarBlue® assay revealed that the NDCDs-QC conjugate was nontoxic to colon cancer cells. This NDCDs-QC conjugate is able to kill cancer cells in the NDCDs-QC form compared to free QC as confirmed by in vitro MTT assay results. Thus, the developed NDCDs conjugate can be used as a promising drug delivery and bio-imaging vehicle in cancer therapy.

Carbon dots with intrinsic theranostic properties for photodynamic therapy of oral squamous cell carcinoma

Carbon dots (CDs) are one of the carbon-based materials with remarkable optical properties, good water dispersibility and high biocompatibility. However, few studies have emphasized the intrinsic photodynamic and anticancer properties of CDs. Herein, we used CDs as photosensitizers to explore their photodynamic therapy (PDT) effect on oral squamous cell carcinoma (OSCC) cells. The obtained CDs had an effective cellular internalization capacity and possessed good biocompatibility in both CAL-27 and UM1 cells. After irradiation, the CDs showed obvious photodynamic effects on the test cells, which were confirmed by apoptosis analysis. In addition, the CDs exhibited excellent intracellular ROS generation under irradiation, and the subsequent induced cell death may be related to a lysosome-associated pathway.

Covalent and Noncovalent Loading of Doxorubicin by Folic Acid-Carbon Dot Nanoparticles for Cancer Theranostics

With special properties such as excellent fluoresce features, low toxicity, good biocompatibility, permeability, and easy clearance from the body, carbon dot (CD)-based nanoparticles (NPs) have the potential to deliver drugs and use in vivo diagnostics through molecular imaging. In this work, folic acid-CD (FA-CD) NPs were prepared to deliver doxorubicin (Dox) covalently and noncovalently as cancer theranostics. FA was conjugated to the surface of CDs for targeting cancer cells with overexpressing folate receptors. CDs prepared with various amounts of precursors lead to their associated NPs with different photoluminescence properties and drug release profiles. The loading of Dox and its releasing data depends on the linkage of drug Dox to FA-CD and CD composition. All NPs were characterized by UV-vis, Fourier transform infrared spectroscopy, and dynamic light scattering. The noncovalent FA-CD-Dox NPs were preferred with a simple preparation process, excellent photoluminescence, and in vitro drug release properties. The noncovalent FA-CD-Dox showed the best efficacy against MDA-MB-231 compared to the CD-Dox and covalent FA-CD-Dox.

Comparative photoluminescence study of nitrogen doped carbon dots co-doped with boron and sulphur

Although different studies in carbon dots (CDs) were reported based on heteroatom doping, most of them have focussed on the enhancement of fluorescence properties. Herein we report a comparative study of both fluorescence and room-temperature phosphorescence (RTP) of nitrogen-sulphur doped CDs (N-S CDs) and N, B doped CDs (N-B CDs) with N doped CDs (N CDs). The CDs employed in the study were synthesized through microwave-assisted pyrolysis. Among the doped CDs, sulphur doped CDs showed high fluorescence quantum yield. Upon irradiation, the aqueous dispersion of the CDs demonstrated blue fluorescence; and further, by incorporating the CDs in potash alum matrix, blue fluorescence, as well as green phosphorescence was observed. The phosphorescence lifetime measurements indicated that the N-S CDs exhibit a longer emission lifetime and red-shifted emission in contrast to other samples, which might be attributed to the presence of a greater proportion of surface states on N-S CDs.

Structure-Activity Relationship of Carbon Nitride Dots in Inhibiting Tau Aggregation

Due to the numerous failed clinical trials of anti-amyloid drugs, microtubule associated protein tau (MAPT) now stands out as one of the most promising targets for AD therapy. In this study, we report for the first time the structure-dependent MAPT aggregation inhibition of carbon nitride dots (CNDs). CNDs have exhibited great promise as a potential treatment of Alzheimer's disease (AD) by inhibiting the aggregation of MAPT. In order to elucidate its structure-activity relationship, CNDs were separated via column chromatography and five fractions with different structures were obtained that were characterized by multiple spectroscopy methods. The increase of surface hydrophilic functional groups is consistent with the increase of polarity from fraction 1 to 5. Particle sizes (1-2 nm) and zeta potentials (~-20 mV) are similar among five fractions. With the increase of polarity from fraction 1 to 5, their MAPT aggregation inhibition capacity was weakened. This suggests hydrophobic interactions between CNDs and MAPT, validated via molecular dynamics simulations. With a zebrafish blood-brain barrier (BBB) model, CNDs were observed to cross the BBB through passive diffusion. CNDs were also found to inhibit the generation of multiple reactive oxygen species, which is an important contributor to AD pathogenesis.

Facile preparation of aqueous-soluble fluorescent polyethylene glycol functionalized carbon dots from palm waste by one-pot hydrothermal carbonization for colon cancer nanotheranostics

Carbon dots (CDs) are categorized as an emerging class of zero-dimension nanomaterials having high biocompatibility, photoluminescence, tunable surface, and hydrophilic property. CDs, therefore, are currently of interest for bio-imaging and nano-medicine applications. In this work, polyethylene glycol functionalized CDs (CD-PEG) were prepared from oil palm empty fruit bunch by a one-pot hydrothermal technique. PEG was chosen as a passivating agent for the enhancement of functionality and photoluminescence properties of CDs. To prepare the CDs-PEG, the effects of temperature, time, and concentration of PEG were investigated on the properties of CDs. The as-prepared CDs-PEG were characterized by several techniques including dynamic light scattering, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, fluorescence spectroscopy, Raman spectroscopy, Fourier-transform infrared spectroscopy and Thermogravimetric analysis. The as-prepared CDs under hydrothermal condition at 220 °C for 6 h had spherical morphology with an average diameter of 4.47 nm. Upon modification, CDs-PEG were photo-responsive with excellent photoluminescence property. The CDs-PEG was subsequently used as a drug carrier for doxorubicin [DOX] delivery to CaCo-2, colon cancer cells in vitro. DOX was successfully loaded onto CDs-PEG surface confirmed by FT-IR and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometer (MALDI-TOF/MS) patterns. The selective treatment of CDs-PEG-DOX against the colorectal cancer cells, , relative to normal human fibroblast cells was succesfully demonstrated.

Colorimetric detection of ATP by inhibiting the Peroxidase-like activity of carbon dots

Adenosine triphosphate (ATP) is the main energy currency for cells and an important biomolecule involved in cellular reactions, whose abnormal levels are closely related to physical disease, thus it is extremely important to establish a convenient, fast and simple ATP monitoring method. Toward this end, we developed a facile method for colorimetric detection of ATP on the basis of the inhibiting effect of ATP on the peroxidase-like activity of carbon dots (CDs). The detection principle of this method was utilizing the peroxidase-like activity of CDs, which catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H₂O₂ to generate blue products. However, the introduction of ATP in the system can inhibit the generation of blue products, so ATP can be colorimetric detected. This method exhibited high sensitivity with a detection limit of 34 nM and a wide linear range (0.050-2.0 μM). The as-proposed colorimetric ATP sensor was capable of detecting ATP in real samples accurately.

On-site, rapid, and facile determination of gentamicin using a fluorescent resonance energy transfer sensor constructed from nitrogen-carbon quantum dots functionalized by 4,5-imidazole dicarboxylic acid

In this paper, NC QDs were obtained from agricultural waste (wheat straw), functionalized by 4,5-imidazole dicarboxylic acid and used to detect gentamicin in aqueous solution. The NC QDs were characterized by HRTEM, XPS, UV-Vis, etc. The fluorescence properties of the functionalized NC QDs for GEN detection were studied at λ_em = 385 nm. The fluorescence intensity showed a good linear relationship with the GEN concentration of samples (I = 343.10 + 30.07C, R² = 0.9896) for GEN concentrations ranging from 0 to 2.9 × 10^-4 mol/L. The sensing mechanism was found to be fluorescence resonance energy transfer (FRET) between the functionalized NC QDs and GEN. The results indicated that the method had good repeatability for GEN detection. The technology could be extended to biological detection.

Synthesis of highly fluorescent, amine-functionalized carbon dots from biotin-modified chitosan and silk-fibroin blend for target-specific delivery of antitumor agents

Carbon dots (CDs) have been a promising theranostic tool with high biocompatibility and a tailorable fluorescence profile. Herein, we report the synthesis of highly fluorescent amine-functionalized CDs from low molecular weight chitosan (LMWC) and silk-fibroin (SF) blends. The synthesized CDs were quasi-spherical in shape with a size of 3 ± 1.5 nm. A significant increase in fluorescent intensity and quantum yield was achieved upon increasing the SF content due to nitrogen doping. For inducing target specificity to cancer cells, biotin was covalently conjugated to the CDs, and the conjugation was determined by FTIR spectroscopy. The conjugate was further loaded with 5-fluorouracil (5-FU) as a model anti-cancer drug. The MTT assay showed increased cytotoxicity of the conjugated CDs in cancer cells compared to normal cells. The live-cell imaging in MCF-7 cell lines showed bright blue-colored fluorescence and increased internalization of the conjugated CDs than the non-conjugate ones due to receptor-mediated endocytosis.

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-dot doped, transfer-free, low-temperature, high mobility graphene using microwave plasma CVD

Microwave plasma chemical vapor deposition is a well-known method for low-temperature, large-area direct graphene growth on any insulating substrate without any catalysts.

Designing of a pH-activatable carbon dots as a luminescent nanoprobe for recognizing folate receptor-positive cancer cells

During recent years, cancer has been recognized as a well-known disorder all over the world. One of the important factors to tackle this problem better than past decades is early diagnosis that takes into practice by state-of-the-art visual equipment for detection cancer cells. Herein, in this research, we synthesized carbon dots with pH-dependent behavior from a green source by hydrothermal method with high quantum yield and blue fluorescence. Folic acid-conjugated carbon dots by an efficient and optimal conjugation method were set upped which determined cancer cells visually. These synthesized and conjugated nanoparticles entered into the cancer cells more comprehensive than normal cells by receptor-mediated endocytosis and could distinguish cancer cells from normal ones by fluorescence imaging. Ultimately, synthesized nanoparticles in this research can be considered as an efficient fluorescent nanoprobe for cancer pre-diagnosis.

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.

Self-Targeting of Carbon Dots into the Cell Nucleus: Diverse Mechanisms of Toxicity in NIH/3T3 and L929 Cells

It is important to understand the nanomaterials intracellular trafficking and distribution and investigate their targeting into the nuclear area in the living cells. In our previous study, we firstly observed penetration of nonmodified positively charged carbon dots decorated with quaternary ammonium groups (QCDs) into the nucleus of mouse NIH/3T3 fibroblasts. Thus, in this work, we focused on deeper study of QCDs distribution inside two healthy mouse NIH/3T3 and L929 cell lines by fluorescence microspectroscopy and performed a comprehensive cytotoxic and DNA damage measurements. Real-time penetration of QCDs across the plasma cell membrane was recorded, concentration dependent uptake was determined and endocytic pathways were characterized. We found out that the QCDs concentration of 200 µg/mL is close to saturation and subsequently, NIH/3T3 had a different cell cycle profile, however, no significant changes in viability (not even in the case with QCDs in the nuclei) and DNA damage. In the case of L929, the presence of QCDs in the nucleus evoked a cellular death. Intranuclear environment of NIH/3T3 cells affected fluorescent properties of QCDs and evoked fluorescence blue shifts. Studying the intracellular interactions with CDs is essential for development of future applications such as DNA sensing, because CDs as DNA probes have not yet been developed.

Photoluminescent Nanomaterials for Medical Biotechnology

Creation of various photoluminescent nanomaterials has significantly expanded the arsenal of approaches used in modern biomedicine. Their unique photophysical properties can significantly improve the sensitivity and specificity of diagnostic methods, increase therapy effectiveness, and make a theranostic approach to treatment possible through the application of nanoparticle conjugates with functional macromolecules. The most widely used nanomaterials to date are semiconductor quantum dots; gold nanoclusters; carbon dots; nanodiamonds; semiconductor porous silicon; and up-conversion nanoparticles. This paper considers the promising groups of photoluminescent nanomaterials that can be used in medical biotechnology: in particular, for devising agents for optical diagnostic methods, sensorics, and various types of therapy.

Molecular Dynamics Simulations of the pH-Dependent Adsorption of Doxorubicin on Carbon Quantum Dots

In this work, the combined effect of the amount of oxygen-containing groups on the carbon quantum dot (CQD) surface and the pH level on the interaction mechanism between an anticancer drug and a carrier has been studied. Molecular dynamics simulations of loading and release of doxorubicin (DOX) molecules on the CQD surface at pH = 7.4 and pH = 5 were carried out, followed by binding free energy calculations with steered molecular dynamics. The results indicate that the CQDs-DOX interaction strength increases with the surface coverage and pH, as well as that the electrostatic interaction between DOX and CQDs plays a significant role in the drug-loading process. This effect was partly attributed to the different surface orientations of the DOX molecular fragments. The obtained results provide the microscopic picture of DOX loading and release on/from the CQDs, which may be critical for the development of advanced CQD-based targeted drug delivery systems.

Carbon dots-based nanocarrier system with intrinsic tumor targeting ability for cancer treatment

Doxorubicin (DOX) is a traditional broad-spectrum antitumor drug, which has a wide range of clinical applications, but has no tumor non-specificity. Nanoparticles have been explored as drug delivery agents to enhance the therapeutic efficacy and reduce toxic and side effects. Carbon dots (CDs), a carbon-based nanomaterial, has many unique advantages such as easy synthesis, good biocompatibility, and low toxicity. In this study, folic acid was used as raw material to prepare new CDs, and DOX was loaded on the surface of CDs through electrostatic interaction. The prepared nano-drugs CDs/DOX could effectively release DOX under mild acidic pH stimulation. Cell imaging showed that CDs/DOX could transport doxorubicin (DOX) to cancer cells and make them accumulated in nucleus freely. Flow cytometry tests and cellular toxicity assay together confirmed that CDs/DOX could target tumor cells with high expression of folate receptor and increase anti-tumor activity. The therapeutic effect on 4T1 tumor-bearing mice model indicated that CDs/DOX could alleviate DOX-induced toxicity, effectively inhibit tumor growth, and prolong the survival time. Hence, such a targeting nanocarrier is likely to be a candidate for cancer treatment.

Synthesis, characterization and biocompatibility studies of carbon quantum dots from Phoenix dactylifera

In the present study, Carbon Quantum Dots (CQDs) were synthesized from Phoenix dactylifera (Date palm fruit) using microwave-assisted pyrolysis and were characterized for its various properties. The synthesized CQD sample exhibited a narrow absorbance peak at 270 nm in UV-Vis spectrum that indicated generation of narrow sized particles. The FTIR analysis of the crude CQDs and dialysed sample revealed the various functional groups involved in the formation of CQDs. TEM data revealed the nature of CQDs to be quasi-spherical and spatially distributed. Biocompatibility of the CQDs was studied using various model systems. CQDs displayed no cytotoxic and anti-clonogenic property when exposed to WRL-68 cell line whereas a slight toxicity was evident in HT1080 post 24 h of incubation suggesting the tremendous potential of the CQDs in the synergistic killing of cancer cells. Phytotoxicity assessment in four different seedlings revealed the non-toxic nature of CQDs. Further these CQDs were found to possess high biocompatibility imposing no inhibition in microbial growth and zilch effect on the development of zebrafish embryos. Thus these CQDs can find immense potential applications in fields of biomedicine as biomolecule detection, drug carriers, fluorescent tracers and in controlling the drug release.

Graphene quantum dots based on maltose as a high yield photocatalyst for efficient photodegradation of imipramine in wastewater samples

PURPOSE

In this work, for the first time, graphene quantum dots (GQDs) based on maltose were fabricated as a new photocatalytic material to the photodegradation of imipramine (as a persistence organic pollutant) under light irradiation.

METHODS

The synthesized GQDs were characterized by different instrumentation approaches such as X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), nitrogen adsorption/desorption, and transmission electron microscopy (TEM). A Box-Behnken design (BBD) and the response surface methodology (RSM) were applied for the optimization of different factors that affect the overall photocatalytic yield.

RESULTS

Under the optimized conditions (pH of the sample solution: 2.0; photocatalyst dosage: 0.1 mg mL^-1; UV exposure time: 80 min), the highest achievable reduction efficiency was obtained about 80%. The stability and reusability of the synthesized photocatalytic material were investigated in four reaction cycles (80 min), which showed only a 15% photo-activity loss after the fourth photocatalytic runs.

CONCLUSIONS

The proposed method was successfully applied to degrade the mentioned drug in the real wastewater samples by about 70%. Regarding the mentioned advantages by the proposed method, this new kind of photocatalytic material possesses a strong potential for photodegradation of pollutants in industrial wastewater samples.

GRAPHICAL ABSTRACT

Photodegradation of imipramine using graphene quantum dots based on maltose.

Recent advances in the modification of carbon-based quantum dots for biomedical applications

Carbon-based quantum dots (CDs) are mainly divided into two sub-groups; carbon quantum dots (CQDs) and graphene quantum dots (GQDs), which exhibit outstanding photoluminescence (PL) properties, low toxicity, superior biocompatibility and facile functionalization. Regarding these features, they have been promising candidates for biomedical science and engineering applications. In this work, we reviewed the efforts made to modify these zero-dimensional nano-materials to obtain the best properties for bio-imaging, drug and gene delivery, cancer therapy, and bio-sensor applications. Five main surface modification techniques with outstanding results are investigated, including doping, surface functionalization, polymer capping, nano-composite and core-shell structures, and the drawbacks and challenges in each of these methods are discussed.

Recent advances in nanoscale materials for antibody-based cancer theranostics

The quest for advanced management tools or options of various cancers has been on the rise to efficiently reduce their risks of mortality without the demerits of conventional treatments (e.g., undesirable side effects of the medications on non-target tissues, non-targeted distribution, slow clearance of the administered drugs, and the development of drug resistance over the duration of therapy). In this context, nanomaterials-antibody conjugates can offer numerous advantages in the development of cancer theranostics over conventional delivery systems (e.g., highly specific and enhanced biodistribution of the drug in targeted tissues, prolonged systemic circulation, low toxicity, and minimally invasive molecular imaging). This review comprehensively discusses and evaluates recent advances in the application of nanomaterial-antibody bioconjugates for cancer theranostics for the further advancement in the control of diverse cancerous diseases. Further, discussion is expanded to cover the various challenges and limitations associated with the design and development of nanomaterial-antibody conjugates applicable towards better management of cancer.

Electron/energy co-transfer behavior and reducibility of Cu-chlorophyllin-bonded carbon-dots

Cu-chlorophyllin-bonded carbon dots (CCPh-CDs) have been synthesized at room temperature, and the energy/electron co-transfer behavior between Cu-chlorophyllin molecules (CCPh) and carbon dots (CDs) is investigated via various techniques. The mean diameters of CDs and CCPh-CDs are 2.8 nm and 3.1 nm, respectively, measured by HRTEM. The absorption spectra of CCPh-CDs show two parts: the absorptions of CDs and CCPh are in the wavelength range of 300–500 nm. The PL spectra of CCPh-CDs exhibit very weak intensities, and with the decreasing of CCPh content on CDs, the corresponding intensity increases. Luminescent decay spectra show that the PL decay times of CCPh and CCPh-CDs with the highest CCPh content are single-exponentially fitted to be 3.20 ns and 12.64 ns, respectively. Furthermore, based on the electron transfer and reducibility of CCPh-CDs, Ag/Ag₂O nanoparticles with a mean diameter of 10 nm can be easily prepared at room temperature under ultraviolet irradiation. The PL measurement result reveals that both electron transfer and FRET behavior take place from CCPh-CDs to Ag.

Cu-chlorophyllin-bonded carbon dots (CCPh-CDs) with/without Ag/Ag₂O (CCPh-CD-Ag) were obtained and investigated by optical measurements and luminescence decay spectroscopy.

Photocatalytic activation of peroxymonosulfate by surface-tailored carbon quantum dots

In this study, carbon quantum dots (CQDs) were synthesized by a low-cost and scalable approach and the oxygen functional groups were fine-tuned by chemical post-treatment. It was found that the CQDs could be applied as visible-light-responsive photocatalysts for activation of peroxymonosulfate (PMS) and remediation of aqueous organic dyes. Phenylhydrazine modified CQDs (CQDs-PH) presented high efficiency for degradation of methylene blue due to selective removal of carboxylic groups and inhibited recombination of photogenerated electron-hole pairs. The effects of catalyst dosage, species and concentrations of dyes, and initial pH values on the photodegradation efficiency were systematically investigated and the alkaline condition facilitates the separation of photoinduced charge carriers and promotes the dye decoloration. The reactive oxygen species produced in the photocatalysis were identified by radical quenching tests and the mechanism was elucidated. Superoxide radicals were generated from PMS activation via electron transfer from CQDs and played the primary role in organic oxidation. In addition, photogenerated holes on the valence band of CQDs also participated in the dye decomposition.

Enhanced-fluorescent imaging and targeted therapy of liver cancer using highly luminescent carbon dots-conjugated foliate

Carbon dots (CDs) have shown great potential in drug delivery and biological imaging applications. In this work, a doxorubicin (DOX) delivery carrier and imaging probe for liver cancer-targeted therapy was designed based on CDs with high fluorescence quantum yield (97%), aiming to enhance the antitumor activity and imaging efficiency. Folic acid (FA), which showed high expression in hepatoma cells, was used as targeting components to modify CDs (FA-CDs), and then FA-CDs-DOX was obtained by loading DOX. Results show that CDs and FA-CDs have good biocompatibility, and the DOX release from FA-CDs-DOX is targeted and selective. Confocal microscope demonstrates that FA-CDs-DOX has excellent ability of fluorescence imaging in liver cancer cells. The imaging in vivo shows the fluorescence intensity of FA-CDs-DOX is strong enough to penetrate tumor tissue and skin, further verifying its enhanced-fluorescent imaging effects. Tumor inhibition in vivo indicates that the targeting ability of FA-CDs-DOX is significantly higher than that of free DOX, showing obvious better therapeutic effect. To sum up, the targeted and fluorescent drug delivery system based on CDs with high fluorescence quantum yield show an excellent imaging in vivo and tumor inhibition effect, which provide a novel strategy for promoting the potential clinical application of CDs in liver cancer treatment.

Direct conjugation of distinct carbon dots as Lego-like building blocks for the assembly of versatile drug nanocarriers

As a promising drug nanocarrier, carbon dots (CDs) have exhibited many excellent properties. However, some properties such as bone targeting and crossing the blood-brain barrier (BBB) only apply to a certain CD preparation with limited drug loading capacity. Therefore, it is significant to conjugate distinct CDs to centralize many unique properties on the novel drug nanocarrier. Considering that CDs have abundant and tunable surface functionalities, in this study, a direct conjugation was initiated between two distinct CD models, black CDs (B-CDs) and gel-like CDs (G-CDs) via an amidation reaction. As a result of conjugation at a mass ratio of 5:3 (B-CDs to G-CDs) and a two-step purification process, the conjugate, black-gel CDs (B-G CDs) (5:3) inherited functionalities from both CDs and obtained an enhanced thermostability, aqueous stability, red-shifted photoluminescence (PL) emission, and a figure-eight shape with a width and length of 3 and 6 nm, respectively. In addition, the necessity of high surface primary amine (NH₂) content in the CD conjugation was highlighted by replacing G-CDs with other CDs with lower surface NH₂ content. Meanwhile, the carboxyl groups (COOH) on G-CDs were not enough to trigger self-conjugation between G-CDs. Moreover, the drug loading capacity was enhanced by 54.5% from B-CDs to B-G CDs (5:3). Furthermore, when the mass ratio of B-CDs to G-CDs was decreased from 5:30, 5:100 to 5:300, the obtained nanostructures revealed a great potential of CDs as Lego-like building blocks. Also, bioimaging of zebrafish demonstrated that various B-G CDs exhibited properties of both bone targeting and crossing the BBB, which are specific properties of B-CDs and G-CDs, respectively.

Carbon Dots Conjugated with Vascular Endothelial Growth Factor for Protein Tracking in Angiogenic Therapy

One of the challenges of using growth factors for tissue regeneration is to monitor their biodistributions and delivery to injured tissues for minimally invasive detection. In the present study, tracking of human vascular endothelial growth factor (VEGF) was achieved by chemically linking it to photoluminescent carbon dots (CDs). Carbon dots were synthesized by the hydrothermal method and, subsequently, conjugated with VEGF using carbodiimide coupling. ELISA and western blot analysis revealed that VEGF-conjugated CDs preserve the binding affinity of VEGF to its antibodies. We also show that VEGF-conjugated CDs maintain the functionality of VEGF for tube formation and cell migration. The VEGF-conjugated CDs were also used for in vitro imaging of human umbilical vein endothelial cells. The results of this work suggest that cell-penetrating VEGF-conjugated CDs can be used for growth factor protein tracking in therapeutic and tissue engineering applications.

A glance over doxorubicin based-nanotherapeutics: From proof-of-concept studies to solutions in the market

Cancer is one of the leading causes of death worldwide and, as such, efforts are being done to find new chemotherapeutic drugs or, alternatively, novel approaches for the delivery of old ones. In this scope, when used as vehicles for drugs, nanomaterials may potentially maximize the efficacy of the treatment and reduce its side effects, for example by a change in drug's pharmacokinetics, cell targeting and/or specific stimuli-responsiveness. This is the case of doxorubicin (DOX) that presents a broad spectrum of activity and is one of the most widely used chemotherapeutic drugs as first-line treatment. Indeed, DOX is a very interesting example of a drug for which several nanosized delivery systems have been developed over the years. While it is true that some of these systems are already in the market, it is also true that research on this subject remains very active and that there is a continuing search for new solutions. In this sense, this review takes the example of doxorubicin, not so much with the focus on the drug itself, but rather as a case study around which very diverse and imaginative nanotechnology approaches have emerged.

Regulating the properties of carbon dots via a solvent-involved molecule fusion strategy for improved sensing selectivity

Carbon dots (CDs) were prepared by a solvent-involved molecular fusion strategy using o-phenylenediamine (OPD) as the carbon source and formamide as the reaction solvent. The CDs possessed not only the functional groups inherited from the carbon source and the reaction solvent, but also numerous C=N groups in the structure, resulting from the Schiff base reaction between -NH₂ of OPD and C=O of formamide. These functional groups endowed the final CDs with a favorable soft-base property, leading to the high tolerance level toward hard-acid type metal ions and prominent detection selectivity toward Ag⁺. Moreover, the obtained CDs displayed outstanding biocompatibility and low cytotoxicity, and demonstrated potential as an effective photoluminescence probe for intercellular Ag⁺ and Cys imaging, preventing the interference of autofluorescence from living tissues. This study focused on the solvent-involved molecular fusion strategy could provide new insights into the design of novel carbon-based nanostructures and optimization of the structure-property relationship of CDs.