Fluorescent carbon dots driven from ayurvedic medicinal plants for cancer cell imaging and phototherapy

Recent advancements and prospects in carbon-based nanomaterials derived from biomass for environmental remediation applications

The conversion of waste biomass into a value-added carbonaceous nanomaterial highlights the appealing power of biomass valorization. The advantages of using sustainable and cheap biomass precursors exhibit the tremendous opportunity for boosting energy production and their application in environmental remediation processes. This review emphasis the development and production of carbon-based nanomaterials derived from biomass, which possess favourable characteristics such as biocompatibility and photoluminescence. The advantages and limitations of various nanomaterials synthesised from different precursors were also discussed with insights into their physicochemical properties. The surface morphology of the porous nanomaterials is also explored along with their characteristic properties like regenerative nature, non-toxicity, ecofriendly nature, unique surface area, etc. The incorporation of various functional groups confers superiority of these materials, resulting in unique and advanced functional properties. Further, the use of these biomass derived nanomaterials was also explored in different applications like adsorption, photocatalysis and sensing of hazardous pollutants, etc. The challenges and outcomes obtained from different carbon-based nanomaterials are briefly outlined and discussed in this review.

Route-dependent tailoring of carbon dot release in alginate hydrogel beads (HB-Alg@WTR-CDs): A versatile platform for biomedical applications

The present investigation explores the different pathways for development of waste tea residue carbon dots (WTR-CDs) loading into hydrogel matrix for WTR-CDs releasing probe. Fluorescent WTR-CDs incorporated into hydrogel matrix were synthesized by valorisation of kitchen waste tea by simple carbonization method (λem = 450 nm, ΦWTR-CDs =18.45 %). Biopolymeric alginate-based hydrogel beads (HB-Alg) were prepared by simple extrusion method. Three routes (ex-situ/in-situ) were employed for loading of WTR-CDs into hydrogel matrix. Successful synthesis of WTR-CDs and its loading into hydrogel matrix was confirmed via various characterization techniques. Developed protocol was employed for stimuli-responsive cumulative release of WTR-CDs study (pH = 3.0, 7.4, 9.0) was monitored over 7 days. Results suggests that, the HB-Alg@WTR-CDs-A system with in-situ loaded WTR-CDs have sustained release due to ionic interaction of WTR-CDs with crosslinked polymer network, whereas in HB-Alg@WTR-CDs-B, WTR-CDs loaded in wet-beads having burst release in which loosely bound WTR-CDs into hydrogel cavities releases rapidly. While, in case of HB-Alg@WTR-CDs-C, lowest release was observed due to weakly surface bound WTR-CDs, low loading and shrinkage of pores into dry-beads. Radical scavenging activity was studied and shown antioxidant properties of WTR-Powder, WTR-CDs and HB-Alg@WTR-CDs-A,B,C. Cytotoxicity of all systems was checked via CAM assay and significant growth in blood vascularization with no loss of chick embryo confirming the released WTR-CDs are biocompatible. Successful investigation and summarization of results ensure that, waste-valorisation, simple, sustainable, and smart hydrogel systems with different routes of WTR-CDs loading have opened a window to understand the mechanistic pathways in release behaviour. This robust approach for improvement of smarter and biocompatible materials can be fruitfully applicable in advanced, controlled and stimuli responsive delivery probes.

Biogenic synthesis of highly fluorescent carbon dots using Azadirachta indica leaves: An eco-friendly approach with enhanced photocatalytic degradation efficiency towards Malachite green

A simpler and efficient method has been developed for the green synthesis of highly fluorescent carbon dots (CDs) from Azadirachta Indica leaves. The surface morphology of developed CDs has shown the existence of spherical particles in the size range of 3-8 nm with superior biocompatibility and high quantum yield value i.e. 42.3%. The particles exhibited a highly fluorescent and crystalline nature along with a bandgap value of 4.02 eV. The prepared CDs served as a factorial design for the sensing and degradation of Malachite green among other dyes. The main perspective of the current finding is that the designed catalyst exhibits excellent sensing results towards Malachite green with a limit of detection i.e. 0.144 μM in the concentration range of 0-50 μM. Moreover, the UV triggered results of photocatalysis illustrated a good dye removal efficacy by developed CDs with an average of 90.73, 98.25, 52 and 6.13% degradation in Methylene blue (MB), Malachite green (MG), Rhodamine 6G (Rh 6G) and Methyl orange (MO) upon 70 min of irradiation with mercury lamp. Additionally, the proton NMR, FTIR and FESEM results of the recycled samples also confirm the complete degradation of MG dye with the application of N-CDs.

Photothermal performance of a novel carbon dot and its conjugate with disulfiram for prostate cancer PC3 cell therapy

Aim: To develop and employ a copper, sulfur, nitrogen-carbon quantum dot (C,S,N-CQD) multifunctional platform for synergistic cancer therapy, combining chemotherapy and photothermal treatment with in vitro cancer cell imaging. Materials & methods: Cu,S,N-CQDs were synthesized hydrothermally, loaded with disulfiram (DSF), and characterized through UV-Vis spectrophotometry, photoluminescence, Fourier-transform infrared spectroscopy, high-resolution transmission electron microscopy, dynamic light scattering, x-ray diffraction and EDAX. Results: Cu,S,N-CQD exhibited 5.5% absolute fluorescence quantum yield, 46.0% photothermal conversion efficiency and excellent stability. The release of DSF-loaded Cu,S,N-CQD, photothermal performance, and IC50 on PC3 prostate cancer cells, were evaluated. The impact of cellular glutathione on nanocarrier performance was investigated. Conclusion: Cu,S,N-CQD as a photothermal agent and DSF carrier showed synergy (combination index: 0.71) between chemotherapy and photothermal therapy. The nanocarrier simultaneously employed for in vitro cancer cell imaging due to its unique fluorescence properties.

Modeling of carbon dioxide fixation by microalgae using hybrid artificial intelligence (AI) and fuzzy logic (FL) methods and optimization by genetic algorithm (GA)

In this study, we are reporting a novel prediction model for forecasting the carbon dioxide (CO₂) fixation of microalgae which is based on the hybrid approach of adaptive neuro-fuzzy inference system (ANFIS) and genetic algorithm (GA). The CO₂ fixation rate of various algal strains was collected and the cultivation conditions of the microalgae such as temperature, pH, CO₂ %, and amount of nitrogen and phosphorous (mg/L) were taken as the input variables, while the CO₂ fixation rate was taken as the output variable. The optimization of ANFIS parameters and the formation of the optimized fuzzy model structure were performed by genetic algorithm (GA) using MATLAB in order to achieve optimum prediction capability and industrial applicability. The best-fitting model was figured out using statistical analysis parameters such as root mean square error (RMSE), coefficient of regression (R²), and average absolute relative deviation (AARD). According to the analysis, GA-ANFIS model depicted a greater prediction capability over ANFIS model. The RMSE, R², and AARD for GA-ANFIS were observed to be 0.000431, 0.97865, and 0.044354 in the training phase and 0.00056, 0.98457, and 0.032156 in the testing phase, respectively, for the GA-ANFIS Model. As a result, it can be concluded that the proposed GA-ANFIS model is an efficient technique having a very high potential to accurately predict the CO₂ fixation rate.

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

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

Seed germination studies on Chickpeas, Barley, Mung beans and Wheat with natural biomass and plastic waste derived C-dots

Agronomical providence of nanoparticles in enhancing food productivity has brought new revolution in agricultural sector. However, the comprehensive ingenuity of their synergetic impact on environment and living flora and fauna is still poorly explored. The current study endeavours to tackle this apprehension by systematically exploring the agronomical paradigm of six different types of C-dots derived from natural biomass and plastic waste on the four different types of seeds viz. black chick peas (Cicer arietinum), barley (Hordeum vulgare), mung beans (Vigna radiata) and wheat (Triticum aestivum) at room temperature. C-dots have displayed a dose responsive effect (250 to 5000 mg/L) on the growth of chosen seeds, including the elongation of root length and coleoptile length. The development of seedlings under atmospheric conditions exhibited excellent physiological stability in presence of synthesized C-dots for all types of seeds with concentrations as high as 3000 mg/L for dry seed. The direct exposure of C-dots resulted in enhanced growth as compared to the water exposure and considered as the most important novel aspect of present work. The developed C-dots provide more nutrient content and easy penetration to the seeds due to their enhanced surface area and very small size. The germination and Vigor index have also been augmented in presence of C-dots after 7 days of exposure. C-dots have affected the chlorophyll content in mung beans as a function of time and concentration. The developed C-dots possess excellent biocompatible behaviour and help in the complete growth of the different types of seeds which suggest their enhanced utilization in the agronomical field. This is one of the detailed studies, which explore the impact of C-dots on widely used food crops with the non-toxic and biocompatible C-dots. The information achieved herein will allow the usage of C-dots as a capable nanopriming agent for the natural germination of seeds.

Folic Acid-Modified Cerium-Doped Carbon Dots as Photoluminescence Sensors for Cancer Cells Identification and Fe(III) Detection

Carbon dots (CDs) are a new class of carbon-based luminescence materials with fascinating properties. They have been given great expectations on superseding traditional semiconductor quantum dots due to their good dispersity and stability, relatively low toxicity, superior resistance to photobleaching, and excellent biocompatibility. The diversified luminescence properties of CDs are largely due to the synthetic strategies and precursors. In view of those described above, this study has explored the possibility to establish a facile one-step hydrothermal method for the one-pot synthesis of folic acid-modified cerium-doped CDs (Ce-CDs-FA), which could be further utilized as a sensitive fluorescent nanoprobe for biosensing. This investigation demonstrates that the Ce-CDs-FA nanocomposites have nice biocompatibility and bright fluorescent properties, which can be readily utilized to detect cancer cells through recognizing overexpressing folate receptors by virtue of folic acid. Meanwhile, it is noted that the Fe3+ ion can actualize a specific and hypersensitive quenching effect for these Ce-CDs-FA nanocomposites, which can be further explored for special ion recognition, including iron ions. It raises the possibility that the as-prepared Ce-CDs-FA nanocomposites could be extended as a dual fluorescence sensor for targeted cell imaging and Fe3+ ion detection.

A Strategic Review on Carbon Quantum Dots for Cancer-Diagnostics and Treatment

The understanding of the genesis of life-threatening cancer and its invasion calls for urgent development of novel technologies for real-time observations, early diagnosis, and treatment. Quantum dots (QDs) grabbed the spotlight in oncology owing to their excellent photostability, bright fluorescence, high biocompatibility, good electrical and chemical stability with minimum invasiveness. Recently, carbon QDs (CQDs) have become popular over toxic inorganic QDs in the area of bioimaging, biosensing, and drug delivery. Further, CQDs derived from natural sources like biomolecules and medicinal plants have drawn attention because of their one-pot, low-cost and ease of synthesis, along with remarkable tunable optical properties and biocompatibility. This review introduces the synthesis and properties of CQDs derived from natural sources, focusing on the applicability of CQD-based technologies as nano-theranostics for the diagnosis and treatment of cancer. Furthermore, the current issues and future directions for the transformation of CQDs-based nanotechnologies to clinical applications are highlighted.

Growth of MWCNTs from Azadirachta indica oil for optimization of chromium(VI) removal efficiency using machine learning approach

The main objective of the present study is to develop artificial neural networks (ANN) to predict the adsorption efficiency of multi-walled carbon nanotubes (MWCNTs) on Cr(VI) removal. Polydisperse MWCNTs were synthesized at 750 °C on alumina supported Fe-Co-Mo catalyst using CVD (chemical vapor deposition)-assisted spray pyrolysis of Azadirachta indica (Neem) oil under inert Argon (Ar) atmosphere. Growth of MCWNTs with inner diameters between 9 and 14 nm was corroborated by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction analysis (XRD), and Raman spectral evidence assessments. The metal-ion adsorbent capacity (Cr-VI) of the as such prepared MWCNTs was examined for industrial purposes. Different parameters such as adsorption isotherms, kinetics, and thermodynamic parameters were analyzed for the removal of metal ions with MWCNTs. The results of isotherm, kinetic, and thermodynamic study indicated that the process suited well with Langmuir isotherm, pseudo second-order kinetics, and followed endothermic reaction, respectively. The effects of parameters such as adsorbent dosage, concentration of chromium ion (Cr-VI), pH, and contact time were studied to optimize the maximum removal of Cr(VI). In order to optimize the process conditions using Artificial Neural Networks, Box-Behnken design (BBD) was used to design the batch adsorption experiments, and the resulting datasets were used as the input for ANN. To predict the adsorption efficiency, various ANN architectures were examined using different training algorithms, number of neurons in the hidden layer, and the transfer function for the hidden and output layers. A neural network structure with Levenberg-Marquardt (LM) training algorithm, 14 hidden neurons, and tangent sigmoid transfer function at the hidden layer and logarithmic sigmoid transfer function at the output layer furnished the best level of prediction results. Comparing with experimental data, the optimal model capitulated mean square error (MSE),and correlation coefficient (R²) of 0.0324 and 0.99512, respectively. The results showed that ANN is well-organized in predicting the adsorption efficiency of MWCNTs for Cr(VI) metal ion removal process.

Carbon-Based Materials in Photodynamic and Photothermal Therapies Applied to Tumor Destruction

Within phototherapy, a grand challenge in clinical cancer treatments is to develop a simple, cost-effective, and biocompatible approach to treat this disease using ultra-low doses of light. Carbon-based materials (CBM), such as graphene oxide (GO), reduced GO (r-GO), graphene quantum dots (GQDs), and carbon dots (C-DOTs), are rapidly emerging as a new class of therapeutic materials against cancer. This review summarizes the progress made in recent years regarding the applications of CBM in photodynamic (PDT) and photothermal (PTT) therapies for tumor destruction. The current understanding of the performance of modified CBM, hybrids and composites, is also addressed. This approach seeks to achieve an enhanced antitumor action by improving and modulating the properties of CBM to treat various types of cancer. Metal oxides, organic molecules, biopolymers, therapeutic drugs, among others, have been combined with CBM to treat cancer by PDT, PTT, or synergistic therapies.

Natural Carbon Nanodots: Toxicity Assessment and Theranostic Biological Application

This review outlines the methods for preparing carbon dots (CDs) from various natural resources to select the process to produce CDs with the best biological application efficacy. The oxidative activity of CDs mainly involves photo-induced cell damage and the destruction of biofilm matrices through the production of reactive oxygen species (ROS), thereby causing cell auto-apoptosis. Recent research has found that CDs derived from organic carbon sources can treat cancer cells as effectively as conventional drugs without causing damage to normal cells. CDs obtained by heating a natural carbon source inherit properties similar to the carbon source from which they are derived. Importantly, these characteristics can be exploited to perform non-invasive targeted therapy on human cancers, avoiding the harm caused to the human body by conventional treatments. CDs are attractive for large-scale clinical applications. Water, herbs, plants, and probiotics are ideal carbon-containing sources that can be used to synthesize therapeutic and diagnostic CDs that have become the focus of attention due to their excellent light stability, fluorescence, good biocompatibility, and low toxicity. They can be applied as biosensors, bioimaging, diagnosis, and treatment applications. These advantages make CDs attractive for large-scale clinical application, providing new technologies and methods for disease occurrence, diagnosis, and treatment research.

Bioinspired Camellia japonica carbon dots with high near-infrared absorbance for efficient photothermal cancer therapy

Since carbon dots (CDs) exhibit excellent biocompatibility, low cytotoxicity, near-infrared (NIR) absorbance, and superior photostability, many types of CDs are considered as powerful candidates for photothermal therapy (PTT) applications. However, the development of a desirable CD is still difficult due to insufficient photothermal conversion, thus resulting in the use of high laser power densities at a high dose of CDs for the PTT effect. Herein, bioinspired sulfur-doped CDs (S-CDs) with strong NIR absorbance were prepared from Camellia japonica flowers via a facile hydrothermal method for enhancing the photothermal conversion efficiency. The as-prepared S-CDs exhibited various advantages including cost-effective preparation, good water-solubility, high biocompatibility, intense NIR absorption, and excellent photothermal effect with robust photostability. Most importantly, the optimal low dose of S-CDs (45 μg mL^-1) successfully led to efficient PTT performance with a high photothermal conversion efficiency (55.4%) under moderate laser power (808 nm, 1.1 W cm^-2) for safe and effective cancer therapy.

Applications of natural product-derived carbon dots in cancer biology

Natural products have contributed conspicuously to the development of innovative nanomedicines. Hence, the interface between nanomaterial science and plant natural products may bestow comprehensive diagnostic and therapeutic strategies for tackling diseases such as cancer and neurological disorders. Natural product-derived carbon dots (NPdCDs) have revealed noteworthy attributes in the fields of cancer theranostics, microbial imaging, drug sensing and drug delivery. As plants consist of a cocktail of bioactive phytomolecules, the NPdCDs can be anticipated to have medicinal properties, biocompatibility, photo-stability and easy functionalization. NPdCDs have wide-ranging applications. The primary objective of this review is to comment on recent developments in the use of NPdCDs, with special reference to their application in cancer biology. The future of the use of NPdCDs has also been considered.

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

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

Biomass-derived nanocarbon materials for biological applications: challenges and prospects

Biomass-derived nanocarbons (BNCs) have attracted significant research interests due to their promising economic and environmental benefits. Following their extensive uses in physical and chemical research domains, BNCs are now growing in biological applications. However, their practical biological applications are still in their infancy, requiring critical evaluations and strategic directions, which are provided in this review. The carbonization of biomass sources and major types of BNCs are introduced, encompassing carbon nanodots, nanofibres, nanotubes, and graphenes. Next, essential biological uses of BNCs, antibacterial/antibiofilm materials (nanofibres and nanodots) and bioimaging agents (predominantly nanodots), are summarized. Furthermore, the future potential of BNCs, for designing wound dressing/healing materials, water and air disinfection platforms, and microbial electrochemical systems, is discussed. We reach the conclusion that a crucial challenge is the structural control of BNCs. Furthermore, a key knowledge gap for realizing practical biological applications is the lack of systematic comparisons of BNCs with nanocarbons of synthetic origin in the current literature. Although we did not attempt to perform an exhaustive literature survey, the evaluation of the existing results indicates that BNCs are promising as easily accessible materials for various biomedically and environmentally relevant applications.

Green Synthesis of Full-Color Fluorescent Carbon Nanoparticles from Eucalyptus Twigs for Sensing the Synthetic Food Colorant and Bioimaging

Full-color fluorescent carbon nanoparticles (CNPs) are produced by a facile and green hydrothermal method followed by the differential washing technique. Eucalyptus twigs are used as a precursor to synthesize multiemissive light blue, blue, green, and red CNPs. Brilliant Blue FCF (BB) is a widely used synthetic food colorant, which is toxic for the human body, when consumed beyond the permitted limit. Herein, we demonstrate light blue CNPs as a sensor for selective and sensitive detection of BB via a fluorescence quenching mechanism with a limit of detection of 200 nM. Temperature-dependent fluorescence and 1H NMR studies confirmed the mechanism as combined dynamic and static quenching. To demonstrate the practical efficacy of the sensor, BB is effectively detected and estimated in selected food samples procured from the market. Moreover, the biocompatibility of light blue and blue CNPs is examined and confirmed by performing a cytotoxicity assay on MDA-MB-231 cell lines. Subsequently, the cellular imaging study is also carried out to explore the internalization process of the CNPs as a function of concentration. To the best of our knowledge, this is the first time that Eucalyptus twigs, a natural source of high abundance, are used as raw materials and valorized for sensing artificial food color and bioimaging purposes.

Highly fluorescent carbon dots derived from Mangifera indica leaves for selective detection of metal ions

In this study, we report an inexpensive, green, and one-pot synthesis method for highly fluorescent carbon quantum dots (CQDs) using mango (Mangifera indica: M. indica) leaves to develop an efficient sensing platform for metal ions. The CQDs synthesized from M. indica leaves via pyrolysis treatment at 300 °C for 3 h were characterized by various spectroscopic and electron microscopy techniques for their structural, morphological, and optical properties. Accordingly, the synthesized CQDs showed an absorption peak at 213 nm to confirm the p-p* transition of the carbon core state, while the CQD particles were spherical with a size less than 10 nm. The prepared CQDs showed excellent fluorescent properties with blue emission spectra (around 525 nm) upon excitation at 435 nm. The synthesized CQDs had the prodigious sensing potential to detect Fe²⁺ ions in water with a limit of detection of 0.62 ppm. Additionally, their sensing capability was tested using a real sample (e.g., Livogen tablet). Moreover, the synthesized CQDs showed substantial stability over a long period (three months). Thus, this study provides an inexpensive and facile method for CQD-based sensing of Fe²⁺ ions with a photoluminescence quenching mechanism.