Carbon dot unravels accumulation of triterpenoid in Evolvulus alsinoides hairy roots culture by stimulating growth, redox reactions and ANN machine learning model prediction of metabolic stress response.

Evolvulus alsinoides, a therapeutically valuable shrub can provide consistent supply of secondary metabolites (SM) with pharmaceutical significance. Nonetheless, because of its short life cycle, fresh plant material for research and medicinal diagnostics is severely scarce throughout the year. The effects of exogenous carbon quantum dot (CD) application on metabolic profiles, machine learning (ML) prediction of metabolic stress response, and SM yields in hairy root cultures of E. alsinoides were investigated and quantified. The range of the particle size distribution of the CDs was between 3 and 7 nm. The CDs EPR signal and spin trapping experiments demonstrated the formation of O2-•spin-adducts at (g = 2.0023). Carbon dot treatment increased the levels of hydrogen peroxide and malondialdehyde concentrations as well as increased antioxidant enzyme activity. CD treatments (6 µg mL-1) significantly enhanced the accumulation of squalene and stigmasterol (7 and 5-fold respectively). The multilayer perceptron (MLP) algorithm demonstrated remarkable prediction accuracy (MSE value = 1.99E-03 and R2 = 0.99939) in both the training and testing sets for modelling. Based on the prediction, the maximum oxidative stress index and enzymatic activities were highest in the medium supplemented with 10 µg mL-1 CDs. The outcome of this study indicated that, for the first time, using CD could serve as a novel elicitor for the production of valuable SM. MLP may also be used as a forward-thinking tool to optimize and predict SM with high pharmaceutical significance. This study would be a touchstone for understanding the use of ML and luminescent nanomaterials in the production and commercialization of important SM.

Preparation of Fe,Co,P-Codoping Peroxidase-like Green-Emitting Carbon Dots and Its Application in Monitoring the Freshness of Aquatic Products.

Carbon dot (CD) nanozymes with excellent fluorescence properties and mimetic enzyme activity have exhibited great potential in monitoring the freshness of meat products. This paper reports the synthesis of Fe, Co, and P codoped CD nanozymes (quantum yields = 48.76%) through a one-step hydrothermal route. The product showed green fluorescence and peroxidase (POD) activity. Because the fluorescence intensity and emission wavelength of prepared CDs change with pH, a pH sensor has been developed to monitor the pH change caused by volatile biogenic amines during the spoilage process of aquatic products. Moreover, this CD biosensor has been used to realize the sensitive and visual detection of hypoxanthine (Hx, the marker of the spoilage of aquatic products) based on the inhibitory effect of Hx upon the POD activity of CDs. This study provides a new strategy for preparing high-quality CD nanozymes and its application in low-cost and visual monitoring of the freshness of aquatic products.

Intelligent Carbon Dots with Switchable Photo-Activated Oxidase-Mimicking Activity and pH Responsive Antioxidant Activity Adaptive to the Wound Microenvironment for Selective Antibacterial Therapy.

Intelligent antibacterial agent with controllable activities adaptive to the wound microenvironment is appealing to reduce drug resistance and enhance antibacterial efficiency. In this study, celery is chosen as the carbon source to construct celery-based carbon dots (CECDs) with double activities, i.e., reactive oxygen species (ROS)-production and ROS-clearance activities. The ROS-production capability of CECDs is dependent on the oxidase (OXD)-mimicking activity, which is only photo-activated and thus artificially controlled by light to avoid the production of excess ROS. Meanwhile, the optimal OXD-mimicking activity occurrs at the pH of 5, close to microenvironmental pH at the bacterial infection site, which will enhance the antibacterial efficacy. On the other hand, CECDs exhibit the antioxidant activity at the neutral or weak alkaline pH, which will assist the healing of the wound. Thus, the conversion of ROS-production and ROS-clearance ability of CECDs can be dynamically and intelligently switched automatically with microenvironmental pH at different stages of treatment (from acid to neutral/weak basic). The proposed CECDs exert adorable selective antibacterial activity against Gram-positive bacteria and satisfactory therapeutic effect on bacteria infected mice. This study paves a new avenue to design the intelligent antibacterial nanoagent sensitive to the infected microenvironmental condition, reducing drug resistance and assisting precise medicine.

A carbon dot nanozyme hydrogel enhances pulp regeneration activity by regulating oxidative stress in dental pulpitis.

Preserving pulp viability and promoting pulp regeneration in pulpitis have attracted widespread attention. Restricted by the oxidative stress microenvironment of dental pulpitis, excessive reactive oxygen and nitrogen species (RONS) trigger uncontrolled inflammation and exacerbate pulp tissue destruction. However, modulating redox homeostasis in inflamed pulp tissue to promote pulp regeneration remains a great challenge. Herein, this work proposes an effective antioxidative system (C-NZ/GelMA) consisting of carbon dot nanozymes (C-NZ) with gelatin methacryloyl (GelMA) to modulate the pulpitis microenvironment for dental pulp regeneration by utilizing the antioxidant properties of C-NZ and the mechanical support of an injectable GelMA hydrogel. This system effectively scavenges RONS to normalize intracellular redox homeostasis, relieving oxidative stress damage. Impressively, it can dramatically enhance the polarization of regenerative M2 macrophages. This study revealed that the C-NZ/GelMA hydrogel promoted pulp regeneration and dentin repair through its outstanding antioxidant, antiapoptotic, and anti-inflammatory effects, suggesting that the C-NZ/GelMA hydrogel is highly valuable for pulpitis treatment.

TWO IN ONE GRAM NEGATIVE ANTIBACTERIAL AGENT AND ORGANIC DYE PHOTOCATALYST FROM GREEN OCIMUM SANCTUM-BASED CO-DOPED CARBON DOT SILVER NANOCOMPOSITE.

This study reports, successful synthesis of Oxygen(O) and Nitrogen(N) co-doped Ocimum Sanctum plant-based or tulsi carbon dots-silver nanoparticle nanocomposites (TCD-AgNP) for the development of an efficient, highly active, low-cost fingerprint antibacterial agent against gram-negative organisms and a highly efficient photocatalyst for the degradation of methylene blue (MB).  The novelty and advantage of this study is the development of highly stable, blue fluorescent, high quantum yield (40%) environmental -friendly TCD-AgNP nanocomposite through reduction method by using green TCDs. Spectrochemical characteristics of synthesized TCDs and TCD-AgNP nanocomposites were investigated through UV-Vis absorbance, Photoluminescence (PL) spectroscopy, Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and Zeta potential measurements confirming excellent fluorescence, unique stability and effective O and N doping. High-resolution transmission electron microscopy (HR-TEM) images confirms that the synthesized TCDs and TCD-AgNP nanocomposites were spherical in shape with an average size of 6.3 nm and 11.5 nm respectively. The antibacterial studies proved that TCD-AgNP nanocomposites ware highly effective against Gram-negative (Serratia marcescens, E. coli, and Pseudomonas aeruginosa) microbial organisms. Besides, TCD-AgNP nanocomposite was used as a photocatalyst for the degradation of MB (10 ppm) under sunlight irradiation for regular intervals of time at room temperature with a photodegradation efficiency of 95.63%.

Copper doped carbon dots modified bacterial cellulose with enhanced antibacterial and immune regulatory functions for accelerating wound healing.

The microenvironment of wound healing is susceptible to bacterial infection, chronic inflammation, oxidative stress, and inadequate angiogenesis, requiring the development of innovative wound dressings with antibacterial, anti-inflammatory, antioxidant, and angiogenic capabilities. This research crafted a new multifunctional bacterial cellulose composite membrane infused with copper-doped carbon dots (BC/Cu(II)-RCDs). Findings validated the successful loading of copper-doped carbon dots onto the BC membrane via hydrogen bonding interactions. Compared to the pure BC membrane, the BC/Cu(II)-RCDs composite membrane exhibited significantly enhanced hydrophilicity, tensile properties, and thermal stability. Diverse in vitro assays demonstrated excellent biocompatibility and antibacterial activity of BC/Cu(II)-RCDs composite membranes, alongside their ability to expedite the inflammatory phase and stimulate angiogenesis. In vivo trials corroborated the membrane's ability to foster epithelial regeneration, collagen deposition, and tissue regrowth in full-thickness skin wounds in rats while also curbing inflammation in infected full-thickness skin wounds. More importantly, the treatment of the BC/Cu(II)-RCDs composite membrane may result in the activation of VEGF and MAPK signaling proteins, which are key players in cell migration, angiogenesis, and skin tissue development. In essence, the developed BC/Cu(II)-RCDs composite membrane shows promise for treating infected wounds and serves as a viable alternative material for medicinal bandages.

On the glow of cremated remains: long-lived green photo-luminescence of heat-treated human bones.

The long-lived green luminescence of human bone (that has been heated to 600 °C for a short duration) is attributed to a carbon quantum dot material (derived from collagen) encapsulated and protected by an inorganic matrix (derived from bone apatite) and is more intense in dense rigid and crystalline parts of (healthy) human bones. The strong collagen-apatite interaction results (upon decomposition) in a protective inorganic environment of the luminescent centers allowing long-lived triplet-based emission of a carbon (quantum) dot-like material at room temperature, as well as resilience against oxidation between 550 and 650 °C. The graphitic black phase (obtained upon heating around 400 °C) is a precursor to the luminescent carbon-based material, that is strongly interacting with the crystalline inorganic matrix. Human bone samples that have been heated to 600 °C were subjected to steady-state and time-resolved spectroscopy. Excitation-emission matrix (EEM) luminescence spectroscopy revealed a broad range of excitation and emission wavelengths, indicating a heterogeneous system with a broad density of emissive states. The effect of low temperature on the heat-treated bone was studied with Cryogenic Steady State Luminescence Spectroscopy. Cooling the bone to 80 K leads to a slight increase in total emission intensity as well as an intensity increase towards to red part of the spectrum, incompatible with a defect state model displaying luminescent charge recombination in the inorganic matrix. Time-resolved spectroscopy with an Optical Multichannel Analyzer (OMA) and Time Correlated Single Photon Counting (TCSPC) of these samples showed that the decay could be fitted with a multi-exponential decay model as well as with second-order decay kinetics. Confocal Microscopy revealed distinct (plywood type) structures in the bone and high intensity-fast decay areas as well as a spatially heterogeneous distribution of green and (fewer) red emissive species. The use of the ATTO 565 dye aided in bone-structure visualization by chemical adsorption. Conceptually our data interpretation corresponds to previous reports from the material science field on luminescent powders.

Green fabrication of biomass-derived carbon dots and bio-based coatings: Potential of enhancing postharvest quality on Chinese flowering cabbage.

The objective of this study was to develop a bio-nanocomposite coating (CQSC) by combining chitosan quaternary ammonium salt (CQAS) and sericin (SC) with biomass-derived carbon dots (CDs) to extend the shelf life of Chinese flowering cabbage (CFC). The effects of different concentrations of CDs (0.2, 0.4, 0.6, 0.8, and 1.0 mg/mL) on the physicochemical, structural, and functional activity of nanocomposite particles were evaluated. CQAS exhibited strong inhibitory effects against Escherichia coli and Bacillus subtilis. Moreover, the application of CQSC on CFC significantly reduced mass losses, slowed the increase in lignin content, maintained ascorbic acid and chlorophyll levels, inhibited the growth of microorganisms, and preserved the unique texture and aroma of CFC during storage at 10 °C compared with uncoated CFC. The results will contribute to the further development of CDs coatings to improve the postharvest preservation effect of fruits and vegetables.

Adsorption and detection of praseodymium ion by ion-imprinted polymer with ultra-low sensitivity.

A novel kind of carbon dot (CD) was prepared by one-step hydrothermal microwave assisted method using L-tryptophan and L-tartaric acid as raw materials. Monodisperse poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) microspheres were utilized as the matrix, with praseodymium (Pr) ion (Pr3+) as the template, methacrylic acid as the functional monomer, and 5-amino-8-hydroxyquinoline (5-AHQ) acts as the ligand. A composite microsphere of ion-imprinted polymer (IIP) and CD (noted CD@IIP) was prepared by surface-initiated atom transfer radical polymerization (SI-ATRP). For comparison, IIP without CD (Pr-IIP) and non-imprinted polymer (NIP) were also prepared. Through static adsorption experiments, it was  determined that the saturated adsorption amount of CD@IIP is 47.19 mg g-1, that of Pr-IIP is 54.49 mg g-1, while that of NIP is only 24.32 mg g-1. Dynamic adsorption experiments showed that the equilibrium of three kinds of materials was reached within 30 min. Particularly, CD@IIP could emit two fluorescence peaks at 325 nm and 421 nm under ultraviolet irradiation, and exhibited excellent selectivity and fluorescence quenching effect on Pr3+. The fluorescence response of Pr3+ in the range 0-400 µmol L-1 was determined by ratiometric fluorescence method, offering a two-stage model and robust linear regression coefficient. These results demonstrated that CD@IIP exhibited selective adsorption ability for Pr3+, and a sensitive, rapid and simple method for detection of Pr3+ was successfully developed.

Carbon dots-facilitated on-demand dissolution of Ca-alginate hydrogel via site-specific mineralization for wound healing.

On-demand dissolution of hydrogels has shown much potential in easy and pain-free removal of wound dressings. This work firstly describes a type of carbon dots (CDs) for dissolving Ca-alginate hydrogel via site-specific mineralization method. The CDs were characterized by two features, which included presence of primary/secondary amine groups and generation of calcium crystals with Ca2+. Especially, the amount of primary/secondary amine groups on CDs played key role in determining whether hydrogel could be dissolved. When there were sufficient primary/secondary amine groups, the mineralization occurred on CDs rather than alginates due to the hydrogen bond between primary/secondary amine and carboxyl of alginates. Thereby, this promoted the gel-sol transition through Ca2+ capture from the hydrogels. Moreover, antibacterial test revealed Ca2+ capture from cell walls, while in vivo test revealed hypoxia relief due to porous structures of the renewed hydrogels. Overall, CDs with sufficient primary/secondary amine groups could dissolve Ca-alginate hydrogel through site-specific mineralization method, accompanying by additional functions of antibacterial and hypoxia relief.