Bioactive carbon dots as antibacterial neural interface for neuron recording

In this study, multifunctional fluorescent carbon dots (CDs) were synthesized using a one-pot hydrothermal carbonization reaction, with the naturally-occurring porphyra polysaccharide (PPS) serving as a single carbon source for the first time and ethylenediamine (Ed) acting as the surface passivation agent. The resulting CDs enjoyed a high quantum yield (56.3%), excitation-dependent fluorescence, small size (<10 nm), spherical shape, uniform distribution, positive surface charge, low cytotoxicity and excellent ability to condense macromolecular plasmid DNA. The synthesized CDs were employed for neuronal induction from ectodermal mesenchymal stem cells for the first time via highly efficient non-viral gene delivery. The optimal combination of factors (Ascl1 and Brn2) was selected from seven different combinations out of Ascl1, Brn2 and Sox2 according to the expression of neuronal markers (Tuj1, Map2 and Tau). The results of qRT-PCR demonstrated that the CDs possessed a significantly higher transfection efficiency than the commercially available transfection reagents PEI (25 kDa) and Lipofectamine2000. Moreover, the CDs/pDNA nanoparticles exhibited more efficient neuronal differentiation of the EMSCs than the AT-RA-containing induction medium. Furthermore, the CDs/pDNA nanoparticles could enter cells via both caveolae- and clathrin-mediated endocytosis. Taken together, the natural polysaccharide PPS-derived CDs enriched the current application of CDs by employing the CDs as a novel non-viral gene carrier for neuronal differentiation of adult stem cells, which held great promise in tissue engineering and bioimaging.

Increasing the production of renewable energy will be critical to achieving global sustainability goals in the coming decades. Biofuels derived from microalgae have great potential to contribute to this production. However, cultivating algae with sufficient neutral lipid content, while maintaining high growth rates, is a continual challenge in making algal-derived biofuels a reality. Previous work has shown that exposure to polymer-functionalized carbon dots can increase the lipid content of the microalgae Raphidocelis subcapitata. This study investigates this finding, aiming to determine the mechanisms underlying this effect and if altering nanoparticle surface charge mediates the mechanism of action of the carbon dots used. Carbon dots with both negative and positive surface charges were added to microalgal cultures, and the impacts of this exposure were analyzed using high-content imaging, growth measurements, and chlorophyll content measurements. Results indicate that positively charged carbon dots induce a nano-specific increase in lipid content but also cause decreases in growth. Additionally, the mechanism of action of each nanoparticle was examined by conducting a morphological comparison to treatments with known mechanisms of action. This analysis showed that negatively charged carbon dots cause similar impacts to R. subcapitata as nitrogen deprivation. Nitrogen deprivation is known to increase lipid content in microalgae. The findings of this study suggest that carbon dots may have surface charge dependent effects on the lipid metabolism of R. subcapitata. Future work should consider the use of carbon dots with varied surface charge densities for enhancing algae biofuel production in bioreactors.

Microbial inhibition and biosensing with multifunctional carbon dots: Progress and perspectives

Design of an efficient fluorescent nanoplatform carrier for hydrophobic drugs along with green carbon dot: Possible application in cancer image-guided drug therapy

Gram-positive bacteria are one of the most common pathogens causing severe and acute infection, and hospital infection caused by Gram-positive bacteria have increased significantly. Also, as antibiotics have been widely used, abusing of antibiotics is becoming an increasingly serious problem which is followed by dangerous drug resistance. Here, we developed a series of cationic carbon dots (CDs) with high-performance as antibacterial agents by using tartaric acid and m-aminophenol as precursors. The surface charge of these CDs can be regulated from +4.5 ± 0.42 mV to +33.2 ± 0.99 mV by increasing the contents of pyridine N and pyrrolic N in CDs. Further antibacterial experiments show that 250 μg mL-1 of CDs with +33.2 ± 0.99 mV can selectively kill Gram-positive bacteria and the antibacterial efficiency can reach approximately >99%. These CDs with positive surface charge can be selectively absorbed on the cell walls of Staphylococcus aureus (S. aureus) via electrostatic interaction and then disturb their physiological metabolism, eventually leading to bacterial death. The present work provides a novel method to adjust the surface charge of CDs and apply these CDs as alternative antibacterial agents.

Carbon dots (CDs) have attracted significant attention in the energy, environment, and biology fields due to their exceptional physicochemical properties. However, owing to the multifarious precursors and complex reaction mechanisms, the production of carbon dots from organic molecules is still a mysterious process. Inspired by the color change of sodium hydroxide ethanol solution after standing for some time, in this work, we thoroughly investigated the reaction mechanism from alcohol molecules to carbon dots through a lot of experiments and theoretical calculations, and it was found that the rate-controlling reaction is the formation of aldehydes, and it is also confirmed that there is a self-catalysis reaction, which can accelerate the conversion from alcohol to aldehyde, further facilitating the final formation of CDs. After the rate-controlling reaction of alcohol to aldehyde, under strongly alkaline conditions, an aldol reaction occurs to form unsaturated aldehydes, followed by further condensation and polymerization reactions to form long carbon chains, which are cross-linked and dehydrated to form carbon dots with a carbon core and surface functional groups. Additionally, it is found that the reaction can be largely accelerated with the assistance of electricity, which indicates the great prospect of industrial production. Furthermore, the obtained CDs with rich functional groups can be utilized as electrolyte additives to optimize the deposition behavior of Na metal, manifesting great potential towards safe and stable Na metal batteries.

The role of carbon dots in the life cycle of crops

We report on trans-membrane interactions between blue-emitting carbon dots (CDs) and fluorescein. Hydrophobic CDs with a positive surface charge are embedded as-synthesized in the lipophilic sheet of the bilayer membrane of large synthetic phospholipid vesicles. The vesicles are prepared by mixing DOPC phospholipids and lipid molecules that contain anionic fluorescein attached to their hydrophilic head. Due to attractive electrostatic interactions, the CDs and fluorescein conjoin within the vesicle membrane, which leads to photoluminescence enhancement of fluorescein and facilitates trans-membrane energy transfer between the CDs and the dye.

Objective:This review aims to explore the synthesis, characterization, and potential applications of carbon dots (CDs) derived from medicinal plants for cancer prevention, highlighting their role as a promising alternative in nanotechnological approaches.Methods:A comprehensive literature search was conducted to gather information on the synthesis methods, complex matrices, characterization techniques, and potential applications of CDs derived from medicinal plants in cancer therapy. Result:Carbon dots (CDs) have emerged as a subject of significant interest due to their favorable chemical and biological properties. Various precursors, including graphite, carbon black, and organic molecules, are utilized in the synthesis of CDs through chemical or physical methods. Notably, CDs derived from medicinal plants offer environmentally friendly alternatives, leveraging complex matrices such as aqueous, alcoholic, and hydroalcoholic extracts. This review emphasizes the green synthesis approaches, characterization techniques, and diverse applications of CDs, including drug transport, bioimaging, biosensing, and anti-cancer therapies. Furthermore, it highlights the advantages and disadvantages of different synthesis methods, aiding researchers in selecting appropriate techniques for continuous production.Conclusion: Carbon dots (CDs) represent a transformative advancement in nanotheranostics, offering a versatile platform for precise cancer diagnosis and therapy. With inherent anticancer properties, CDs hold promise in photodynamic therapy (PDT) and photothermal therapy (PTT), enabling precise tumor targeting while minimizing systemic toxicity. To address the limitations of standalone PDT and PTT, researchers are exploring multimodal treatment approaches integrating CDs. By leveraging the unique properties of CDs derived from medicinal plants, a new era of precision cancer therapy may be realized, emphasizing enhanced therapeutic outcomes and reduced adverse effects.

Porphyrin-based covalent organic framework as bioplatfrom for detection of vascular endothelial growth factor 165 through fluorescence resonance energy transfer

Advanced Functional Materials Solutions to Engineering the Neural Interface

Heteroatom co-doping (N, NS, NB) on carbon dots and their antibacterial and antioxidant properties

Brain‒computer interfaces (BCIs) exhibit significant potential for various applications, including neurofeedback training, neurological injury management, and language, sensory and motor rehabilitation. Neural interfacing electrodes are positioned between external electronic devices and the nervous system to capture complex neuronal activity data and promote the repair of damaged neural tissues. Implantable neural electrodes can record and modulate neural activities with both high spatial and high temporal resolution, offering a wide window for neuroscience research. Despite significant advancements over the years, conventional neural electrode interfaces remain insufficient for fully achieving these objectives, particularly in the context of long-term implantation. The primary limitation stems from the poor biocompatibility and mechanical mismatch between the interfacing electrodes and neural tissues, which induce a local immune response and scar tissue formation, thus decreasing the performance and useful lifespan. Therefore, neural interfaces should ideally exhibit appropriate stiffness and minimal foreign body reactions to mitigate neuroinflammation and enhance recording quality. This review provides an exhaustive analysis of the current understanding of the critical failure modes that may impact the performance of implantable neural electrodes. Additionally, this study provides a comprehensive overview of the current research on coating materials and design strategies for implanted neural interfaces and discusses the primary challenges currently facing long-term implantation of neural electrodes. Finally, we present our perspective and propose possible future research directions to improve implantable neural interfaces for BCIs.Graphical abstract

Carbon dots (CDs)with positive surface charges are consideredone of the encouraging nanomedications for antibacterial applications.However, due to the distinctive membrane structure of Gram-negativebacteria, cationic CDs with relatively high concentrations are usuallyrequired for effective treatment, which might bring out serious safetyissues at high doses. Therefore, it is of substantial significanceto improve the killing efficiency of cationic CDs on Gram-negativebacteria at appropriately low concentrations. In this work, optimizedcationic CDs (bPEI25 000-CDs) were prepared viaa hydrothermal method with citric acid and branched PEI25000, which offered a positive surface potential, elimination abilitiesagainst Escherichia coli, and relativelyhigh biosafety. The optimized bPEI25 000-CDs canfurther assemble with the clinical photodynamic therapy (PDT) drug5-aminolevulinic acid (5-ALA) through electrostatic interaction. Moreover,compared with bPEI25 000-CDs and 5-ALA, the bacterialsurvival rate was significantly reduced by the ALA-bPEI25 000-CD-induced PDT effect. Even when the dose of bPEI25 000-CD carrier was halved, the bacterial survival could be reduced by44.4% after light exposure compared to those incubated in the dark.The investigation of the bacterial morphology, membrane potential,and intracellular ROS production suggested that the enhanced antibacterialactivity may be due to the membrane dysfunction and cell damage resultingfrom the high interaction between positively charged ALA-bPEI25 000-CDs and the bacterial cell membrane. Meanwhile,the cationic ALA-bPEI25 000-CDs may facilitate thecellular uptake of 5-ALA, resulting in a more efficient PDT effect.In summary, the antibacterial strategy proposed in this study willprovide a novel approach for expanding the application of CD-basednanomedications.

Treating bone defects is a critical challenge in regenerative medicine. Carbon nanomaterials, with their unique physicochemical properties, offer significant potential for enhancing bone regeneration. In this study, we developed tartaric acid (TA)-based carbon dots (CDs) by synthesizing TA with branched polyethyleneimine (bPEI). These TA-bPEI CDs were systematically evaluated to determine their effects on osteogenic differentiation in human bone marrow-derived mesenchymal stem cells (BMSCs) and their capacity to repair calvarial defects in an in vivo model. Characterization of TA-bPEI CDs revealed a size of approximately 10 nm and a positive surface charge. The CDs exhibited fluorescence emission peaks between 464 and 506 nm under excitation wavelengths of 340-440 nm. Cytotoxicity assays demonstrated that TA-bPEI CDs maintained BMSC viability at concentrations up to 250 μg/ml. However, at concentrations of 500 μg/ml and above, apoptosis was induced. Treatment with TA-bPEI significantly enhanced osteogenic differentiation in vitro, as evidenced by increased expression of osteogenic-specific proteins such as Runx2, ALP, OCN and OPN. In vivo, the application of TA-bPEI CDs in a mouse calvarial defect model promoted robust new bone formation, reduced defect gaps, and improved bone morphometric parameters, including bone volume fraction and trabecular thickness. These results suggest that TA-bPEI CDs enhance osteogenesis by directly stimulating osteogenic differentiation and upregulating osteogenesis-specific genes. This study demonstrates the high potential of TA-bPEI CDs as a novel nanomaterial for bone regeneration applications.