Preparation of blue-color-emitting graphene quantum dots and their in vitro and in vivo toxicity evaluation

Graphene quantum dots induced performance enhancement in memristors

With the rapid development of information technology, the demand for miniaturization, integration, and intelligence of electronic devices is growing rapidly. As a key device in the non-von Neumann architecture, memristors can perform computations while storing data, enhancing computational efficiency and reducing power consumption. Memristors have become pivotal in driving the advancement of artificial intelligence (AI) and Internet of Things technologies. Combining the electronic properties of graphene with the size effects of quantum dots, graphene quantum dot (GQD)-based memristors exhibit potential applications in constructing brain-inspired neuromorphic computing systems and achieving AI hardware acceleration, making them a focal point of research interest. This review provides an overview of the preparation, mechanism, and application of GQD-based memristors. Initially, the structure, properties, and synthesis methods of GQDs are introduced in detail. Subsequently, the memristive mechanisms of GQD-based memristors are presented from three perspectives: the metal conductive filament mechanism, the electron trapping and detrapping mechanism, and the oxygen vacancy conductive filament mechanism. Furthermore, the different application scenarios of GQD-based memristors in both digital and analog types are summarized, encompassing information storage, brain-like artificial synapses, visual perception systems, and brain-machine interfaces. Finally, the challenges and future development prospects of GQD-based memristors are discussed.

Graphene Quantum Dots from Natural Carbon Sources for Drug and Gene Delivery in Cancer Treatment

Cancer therapy is constantly evolving, with a growing emphasis on targeted and efficient treatment options. In this context, graphene quantum dots (GQDs) have emerged as promising agents for precise drug and gene delivery due to their unique attributes, such as high surface area, photoluminescence, up-conversion photoluminescence, and biocompatibility. GQDs can damage cancer cells and exhibit intrinsic photothermal conversion and singlet oxygen generation efficiency under specific light irradiation, enhancing their effectiveness. They serve as direct therapeutic agents and versatile drug delivery platforms capable of being easily functionalized with various targeting molecules and therapeutic agents. However, challenges such as achieving uniform size and morphology, precise bandgap engineering, and scalability, along with minimizing cytotoxicity and the environmental impact of their production, must be addressed. Additionally, there is a need for a more comprehensive understanding of cellular mechanisms and drug release processes, as well as improved purification methods. Integrating GQDs into existing drug delivery systems enhances the efficacy of traditional treatments, offering more efficient and less invasive options for cancer patients. This review highlights the transformative potential of GQDs in cancer therapy while acknowledging the challenges that researchers must overcome for broader application.

Lights and Dots toward Therapy-Carbon-Based Quantum Dots as New Agents for Photodynamic Therapy

The large number of deaths induced by carcinoma and infections indicates that the need for new, better, targeted therapy is higher than ever. Apart from classical treatments and medication, photodynamic therapy (PDT) is one of the possible approaches to cure these clinical conditions. This strategy offers several advantages, such as lower toxicity, selective treatment, faster recovery time, avoidance of systemic toxic effects, and others. Unfortunately, there is a small number of agents that are approved for usage in clinical PDT. Novel, efficient, biocompatible PDT agents are, thus, highly desired. One of the most promising candidates is represented by the broad family of carbon-based quantum dots, such as graphene quantum dots (GQDs), carbon quantum dots (CQDs), carbon nanodots (CNDs), and carbonized polymer dots (CPDs). In this review paper, these new smart nanomaterials are discussed as potential PDT agents, detailing their toxicity in the dark, and when they are exposed to light, as well as their effects on carcinoma and bacterial cells. The photoinduced effects of carbon-based quantum dots on bacteria and viruses are particularly interesting, since dots usually generate several highly toxic reactive oxygen species under blue light. These species are acting as bombs on pathogen cells, causing various devastating and toxic effects on those targets.

Interactions of Nanoparticles with Macrophages and Feasibility of Drug Delivery for Asthma

Understanding the interaction between nanoparticles and immune cells is essential for the evaluation of nanotoxicity and development of nanomedicines. However, to date, there is little data on the membrane microstructure and biochemical changes in nanoparticle-loaded immune cells. In this study, we observed the microstructure of nanoparticle-loaded macrophages and changes in lipid droplets using holotomography analysis. Quantitatively analyzing the refractive index distribution of nanoparticle-loaded macrophages, we identified the interactions between nanoparticles and macrophages. The results showed that, when nanoparticles were phagocytized by macrophages, the number of lipid droplets and cell volume increased. The volume and mass of the lipid droplets slightly increased, owing to the absorption of nanoparticles. Meanwhile, the number of lipid droplets increased more conspicuously than the other factors. Furthermore, alveolar macrophages are involved in the development and progression of asthma. Studies have shown that macrophages play an essential role in the maintenance of asthma-related inflammation and tissue damage, suggesting that macrophage cells may be applied to asthma target delivery strategies. Therefore, we investigated the target delivery efficiency of gold nanoparticle-loaded macrophages at the biodistribution level, using an ovalbumin-induced asthma mouse model. Normal and severe asthma models were selected to determine the difference in the level of inflammation in the lung. Consequently, macrophages had increased mobility in models of severe asthma, compared to those of normal asthma disease. In this regard, the detection of observable differences in nanoparticle-loaded macrophages may be of primary interest, as an essential endpoint analysis for investigating nanomedical applications and immunotheragnostic strategies.

Spectroscopic investigation on the binding interactions between graphene quantum dots and carbonic anhydrase

As a new member of the nanomaterials family, ultrasmall graphene quantum dots (GQDs) have shown broad application prospects in the field of biomedicine, but the analysis of their biological effects at the molecular level is yet limited. Herein, carbonic anhydrase (CA) was selected as a model protein to assess the interactions between GQDs and biomacromolecules. A range of spectroscopic techniques were employed to systematically investigate the binding interactions between GQDs and CA and the catalytic function of CA in the presence of GQDs was evaluated. Experimental results showed that GQDs could quench the intrinsic fluorescence of CA and the concentration dependent quenching efficiency exhibited an obvious deviation from the linear plot, indicating a static binding mode. Further investigation suggested that van der Waal interactions and hydrogen bonding were the main driving forces. Additionally, circular dichroism measurement showed that the binding of GQDs induced slight conformational changes of CA. The catalytic capability assessment proved that these binding interactions resulted in the reduction of the biological functions of CA. This comprehensive study provided important insight into the interaction of GQDs with biomacromolecules, which would be crucial for the further applications of GQDs and other nanomaterials in the biomedical field.

The cytotoxicity of core-shell or non-shell structure quantum dots and reflection on environmental friendly: A review

Quantum dots are widely applicated into bioindustry and research owing to its superior properties such as broad excitation spectra, narrow bandwidth emission spectra and high resistance to photo-bleaching. However, the toxicity of quantum dots should not be underestimated and aroused widespread concern. The surface properties and size of quantum dots are critical relevant properties on toxicity. Then, the core/shell structure becomes one common way to affect the activity of quantum dots such as enhance biocompatibility and stability. Except those toxicity it induced, the problem it brought into the environment such as the degradation of quantum dot similarly becomes a hot issue. This review initially took a brief scan of current research on the cytotoxicity of QDs and the mechanism behind that over the past five years. Mainly discussion concentrated on the diversity of structure on quantum dots whether played a key role on the cytotoxicty of quantum dots. It also discussed the role of different shells with metal or nonmetal cores and the influence on the environment.

Fluorescent Carbon Dots from Nerium oleander: Effects of Physical Conditions and the Extract Types

In this original research, the synthesis of carbon nanodots (CDs) from two different solvent extracts of Nerium oleander by the thermal method was investigated under various physical conditions such as pH, reaction temperature, ionic strength, and surface passivation agent (polyethylene glycol, PEG) presence in the reaction media. The effects of extract types and physical conditions on CDs formation were characterized by UV-Visible spectrophotometry, fluorescence spectrophotometry, Fourier transform infrared spectroscopy and dynamic light scattering analysis. Fluorescent CDs were obtained from PEG included reaction media. Additionally, the enhanced fluorescence intensity correlated with ascending reaction temperature was reported. The hydrodynamic particle size of CDs in aqueous solution was determined between ~1 and 235 nm with negative surface potential in the range of -6 mV and -28 mV. Moreover, CDs synthesized from aqueous extract mostly resulted in smaller size than that of ethanol extract based ones. The impact of surface passivation with PEG on the fluorescence feature of CDs was verified. For the relevant extracts of Oleander, CDs synthesized from PEG included formulations at pH 5 and NaCl free reaction media found as better alternatives than CDs synthesized under other conditions taking account their effect on fluorescence feature, hydrodynamic size and etc. Graphical Abstract.