The permeability and transport mechanism of graphene quantum dots (GQDs) across the biological barrier

Cholesterol mediates the potential adverse influence of graphene quantum dots on placental lipid membrane model

Nanomaterial-biomembrane interactions constitute a critical biological process in assessing the toxicity of such materials in theoretical studies. However, many investigations simplify these interactions by using membrane models containing only one or a few lipid types, deviating significantly from the complexity of real membrane compositions. In particular, cholesterol, a ubiquitous lipid essential for regulating membrane fluidity and closely linked to various diseases, is often overlooked. Consequently, the role of cholesterol in nanomaterial-biomembrane interactions remains poorly understood. In this study, we employ molecular dynamics (MD) simulations to explore the effect of graphene quantum dots (GQDs) on a realistic placental lipid membrane model, aiming to elucidate the role of cholesterol in these interactions. Our MD results reveal that both GQD monomers and clusters can spontaneously insert into the placental lipid membrane model, driven by strong van der Waals interaction energy. Further analyses indicate that cholesterol and POPC lipids primarily contribute to interfacial interactions. Notably, cholesterol can be squeezed into the bilayer interface, forming a unique structure where it is sandwiched between the GQD cluster and the membrane's bottom leaflet. More significantly, cholesterol, together with the GQD cluster, exhibits free lateral movement, suggesting a strong affinity of cholesterol for GQD clusters. These findings highlight the critical role of cholesterol in mediating GQD insertion into the biomembrane. Structural analyses of the membrane further demonstrate deformation of the placental lipid membrane model during GQD penetration. Finally, free energy calculations confirm that the insertion of both GQD monomers and clusters into the placental lipid membrane model is energetically favorable. Overall, this study not only sheds new light on the potential harmful effects of GQDs on realistic placental membranes but also provides the first theoretical evidence of the pivotal role of cholesterol in nanomaterial-biomembrane interactions, contributing to a deeper understanding of nanomaterial-cell membrane interactions.

Enhancing Gene Delivery to Breast Cancer with Highly Efficient siRNA Loading and pH-Responsive Small Extracellular Vesicles

Small extracellular vesicles (sEVs) are promising nanocarriers for drug delivery to treat a wide range of diseases due to their natural origin and innate homing properties. However, suboptimal therapeutic effects, attributed to ineffective targeting, limited lysosomal escape, and insufficient delivery, remain challenges in effectively delivering therapeutic cargo. Despite advances in sEV-based drug delivery systems, conventional approaches need improvement to address low drug-loading efficiency and to develop surface functionalization techniques for precise targeting of cells of interest, all while preserving the membrane integrity of sEVs. We report an enhanced gene delivery system using multifunctional sEVs for highly efficient siRNA loading and delivery. The integration of chiral graphene quantum dots enhanced the loading capacity while preserving the structural integrity of the sEVs. Additionally, lysosomal escape is facilitated by functionalizing sEVs with pH-responsive peptides, fully harnessing the inherent homing effect of sEVs for targeted and precise delivery. These sEVs achieved a 1.74-fold increase in cytosolic cargo delivery compared to unmodified sEVs, resulting in substantial gene silencing of around 73%. Our approach has significant potential to advance sEV-based gene delivery in order to accelerate clinical progress.

Combination therapy enhances efficacy and overcomes toxicity of metal-based anti-diabetic agent

BACKGROUND AND PURPOSE

Metal-based therapeutic agents are limited by the required concentration of metal-based agents. Hereby, we determined if combination with 17β-oestradiol (E2) could reduce such levels and the therapy still be effective in type 2 diabetes mellitus (T2DM).

EXPERIMENTAL APPROACH

The metal-based agent (vanadyl acetylacetonate [VAC])- 17β-oestradiol (E2) combination is administered using the membrane-permeable graphene quantum dots (GQD), the vehicle, to form the active GQD-E2-VAC complexes, which was characterized by fluorescence spectra, infrared spectra and X-ray photoelectron spectroscopy. In db/db type 2 diabetic mice, the anti-diabetic effects of GQD-E2-VAC complexes were evaluated using blood glucose levels, oral glucose tolerance test (OGTT), serum insulin levels, homeostasis model assessment (homeostasis model assessment of insulin resistance [HOMA-IR] and homeostasis model assessment of β-cell function [HOMA-β]), histochemical assays and western blot.

KEY RESULTS

In diabetic mice, GQD-E2-VAC complex had comprehensive anti-diabetic effects, including control of hyperglycaemia, improved insulin sensitivity, correction of hyperinsulinaemia and prevention of β-cell loss. Co-regulation of thioredoxin interacting protein (TXNIP) activation by the combination of metal complex and 17β-oestradiol contributed to the enhanced anti-diabetic effects. Furthermore, a potent mitochondrial protective antioxidant, coniferaldehyde, significantly potentiates the protective effects of GQD-E2-VAC complexes.

CONCLUSION AND IMPLICATIONS

A metal complex-E2 combinatorial approach achieved simultaneously the protection of β cells and insulin enhancement at an unprecedented low dose, similar to the daily intake of dietary metals in vitamin supplements. This study demonstrates the positive effects of combination and multi-modal therapies towards type 2 diabetes treatment.

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.

Facile synthesis of carbon dots via pyrolysis and their application in photocatalytic degradation of rhodamine B (RhB)

Carbon Quantum dot (CQDs) is one of the newest materials in carbon-based nanomaterials. It is pertinent to study the synthesis and the application of these carbon dots. Here we have studied the effect of precursor on the optical, morphological, and photocatalytic properties of CQDs. We have synthesized CQDs using pyrolysis method using the precursors citric acid, urea, polyethyleneimine. We have synthesized two samples: CQD-S1; synthesized using urea and polyethyleneimine, and CQD-S2; synthesized using citric acid and polyethyleneimine. In optical properties study two distinct peaks have been obtained at 243 nm and 345 nm for CQD-S1, and at 265 nm and 335 nm for CQD-S2. In fluorescence study, the maximum emission was found at excitation wavelength of 340 nm for CQD-S1 and at excitation wavelength of 350 nm for CQD-S2. In morphological studies, Transmission Electron Microscope (TEM) revealed particle size of sample CQD-S1 and CQD-S2 were 1.91 nm and 1.61 nm, respectively. EDX confirmed the elemental composition in both samples. The rhodamine B (RhB) dye degradation percentages in dark and under visible and UV light were found to 6, 13, and 98.4% respectively for CQD-S1. Similarly, dye degradation for CQD-S2 were 7, 11, and 99.63%, respectively. Effective degradation of photocatalysis performed under UV-light within 100 min using mineralization process.

A review on synthesis, properties, and biomedical applications of graphene quantum dots (GQDs)

A new type of 0-dimensional carbon-based materials called graphene quantum dots (GQDs) is gaining significant attention as a non-toxic and eco-friendly nanomaterial. GQDs are nanomaterials composed of sp2hybridized carbon domains and functional groups, with their lateral size less than 10 nm. The unique and exceptional physical, chemical, and optical properties arising from the combination of graphene structure and quantum confinement effect due to their nano-size make GQDs more intriguing than other nanomaterials. Particularly, the low toxicity and high solubility derived from the carbon core and abundant edge functional groups offer significant advantages for the application of GQDs in the biomedical field. In this review, we summarize various synthetic methods for preparing GQDs and important factors influencing the physical, chemical, optical, and biological properties of GQDs. Furthermore, the recent application of GQDs in the biomedical field, including biosensor, bioimaging, drug delivery, and therapeutics are discussed. Through this, we provide a brief insight on the tremendous potential of GQDs in biomedical applications and the challenges that need to be overcome in the future.

Unraveling the potential of graphene quantum dots against Mycobacterium tuberculosis infection

Introduction

The emergence of drug-resistant Mycobacterium tuberculosis (Mtb) strains has underscored the urgent need for novel therapeutic approaches. Carbon-based nanomaterials, such as graphene oxide (GO), have shown potential in anti-TB activities but suffer from significant toxicity issues.

Methods

This study explores the anti-TB potential of differently functionalized graphene quantum dots (GQDs) - non-functionalized, L-GQDs, aminated (NH2-GQDs), and carboxylated (COOH-GQDs) - alone and in combination with standard TB drugs (isoniazid, amikacin, and linezolid). Their effects were assessed in both axenic cultures and in vitro infection models.

Results

GQDs alone did not demonstrate direct mycobactericidal effects nor trapping activity. However, the combination of NH2-GQDs with amikacin significantly reduced CFUs in in vitro models. NH2-GQDs and COOH-GQDs also enhanced the antimicrobial activity of amikacin in infected macrophages, although L-GQDs and COOH-GQDs alone showed no significant activity.

Discussion

The results suggest that specific types of GQDs, particularly NH2-GQDs, can enhance the efficacy of existing anti-TB drugs. These nanoparticles might serve as effective adjuvants in anti-TB therapy by boosting drug performance and reducing bacterial counts in host cells, highlighting their potential as part of advanced drug delivery systems in tuberculosis treatment. Further investigations are needed to better understand their mechanisms and optimize their use in clinical settings.

Photothermal therapy using graphene quantum dots

The rapid development of powerful anti-oncology medicines have been possible because of advances in nanomedicine. Photothermal therapy (PTT) is a type of treatment wherein nanomaterials absorb the laser energy and convert it into localized heat, thereby causing apoptosis and tumor eradication. PTT is more precise, less hazardous, and easy-to-control in comparison to other interventions such as chemotherapy, photodynamic therapy, and radiation therapy. Over the past decade, various nanomaterials for PTT applications have been reviewed; however, a comprehensive study of graphene quantum dots (GQDs) has been scantly reported. GQDs have received huge attention in healthcare technologies owing to their various excellent properties, such as high water solubility, chemical stability, good biocompatibility, and low toxicity. Motivated by the fascinating scientific discoveries and promising contributions of GQDs to the field of biomedicine, we present a comprehensive overview of recent progress in GQDs for PTT. This review summarizes the properties and synthesis strategies of GQDs including top-down and bottom-up approaches followed by their applications in PTT (alone and in combination with other treatment modalities such as chemotherapy, photodynamic therapy, immunotherapy, and radiotherapy). Furthermore, we also focus on the systematic study of in vitro and in vivo toxicities of GQDs triggered by PTT. Moreover, an overview of PTT along with the synergetic application used with GQDs for tumor eradication are discussed in detail. Finally, directions, possibilities, and limitations are described to encourage more research, which will lead to new treatments and better health care and bring people closer to the peak of human well-being.

Surface-Engineered Monocyte Immunotherapy Combined Graphene Quantum Dots Effective Against Solid Tumor Targets

Introduction

The immunosuppressive tumor microenvironment (TME) of solid tumors inhibits most drug delivery system-based nanomaterials from achieving deep penetration in tumor tissue and interferes with T cell activity in terms of differentiation and exhaustion, which is becoming a critical therapy hurdle for solid tumors. Therefore, developing a therapeutic strategy with abilities of rapid establishment of tumor-targeted cells, elimination of immune obstacles, and enhanced active immunization is very important, while is still a big challenge.

Methods

A new strategy was explored to enhance immune therapy via the conjugation of microRNA155 (miR) to the surface of therapeutic monocyte with graphene quantum dots (GQDs).

Results

TME was reversed using surface-engineered monocyte immunotherapy via reprogramming pro-tumoral M2 TAMs into antitumor M1, and thus tumor elimination was dramatically enhanced.

Conclusion

Such a surface-engineered monocyte immunotherapy has been demonstrated to be well tolerated to intravenous administration and bio-compatible, showing the potential to be extended for the solid tumor treatment.

Delivering the Promise of Gene Therapy with Nanomedicines in Treating Central Nervous System Diseases

Central Nervous System (CNS) diseases, such as Alzheimer's diseases (AD), Parkinson's Diseases (PD), brain tumors, Huntington's disease (HD), and stroke, still remain difficult to treat by the conventional molecular drugs. In recent years, various gene therapies have come into the spotlight as versatile therapeutics providing the potential to prevent and treat these diseases. Despite the significant progress that has undoubtedly been achieved in terms of the design and modification of genetic modulators with desired potency and minimized unwanted immune responses, the efficient and safe in vivo delivery of gene therapies still poses major translational challenges. Various non-viral nanomedicines have been recently explored to circumvent this limitation. In this review, an overview of gene therapies for CNS diseases is provided and describes recent advances in the development of nanomedicines, including their unique characteristics, chemical modifications, bioconjugations, and the specific applications that those nanomedicines are harnessed to deliver gene therapies.

Molecular Dynamics Simulation of Transport Mechanism of Graphene Quantum Dots Through Different Cell Membranes

Exploring the mechanisms underlying the permeation of graphene quantum dots (GQDs) through different cell membranes is key for the practical application of GQDs in medicine. Here, the permeation process of GQDs through different lipid membranes was evaluated using molecular dynamics (MD) simulations. Our results showed that GQDs can easily permeate into 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) lipid membranes with low phospholipid molecule densities but cannot permeate into 1-palmitoyl-2-oleoyl phosphatidylethanolamine (POPE) lipid membranes with high phospholipid densities. Free energy calculation showed that a high-energy barrier exists on the surface of the POPE lipid membrane, which prevents GQDs from entering the cell membrane interior. Further analysis of the POPE membrane structure showed that sparsely arranged phospholipid molecules of the low-density lipid membrane facilitated the entry of GQDs into the interior of the membrane, compared to compactly arranged molecules in the high-density lipid membrane. Our simulation study provides new insights into the transmembrane transport of GQDs.

Graphene quantum dots: A review on the effect of synthesis parameters and theranostic applications

The rising demand for early-stage diagnosis of diseases such as cancer, diabetes, neurodegenerative can be met with the development of materials offering high sensitivity and specificity. Graphene quantum dots (GQDs) have been investigated extensively for theranostic applications owing to their superior photostability and high aqueous dispersibility. These are attractive for a range of biomedical applications as their physicochemical and optoelectronic properties can be tuned precisely. However, many aspects of these properties remain to be explored. In the present review, we have discussed the effect of synthetic parameters upon their physicochemical characteristics relevant to bioimaging. We have highlighted the effect of particle properties upon sensing of biological molecules through 'turn-on' and 'turn-off' fluorescence and generation of electrochemical signals. After describing the effect of surface chemistry and solution pH on optical properties, an inclusive view on application of GQDs in drug delivery and radiation therapy has been given. Finally, a brief overview on their application in gene therapy has also been included.

Rational design of large flat nitrogen-doped graphene oxide quantum dots with green-luminescence suitable for biomedical applications

Rational synthesis and simple methodology for the purification of large (35-45 nm in lateral size) and flat (1.0-1.5 nm of height) nitrogen-doped graphene oxide quantum dots (GOQDs) are presented. The methodology allows robust metal-free and acid-free preparation of N-GOQDs with a yield of about 100% and includes hydrothermal treatment of graphene oxide with hydrogen peroxide and ammonia. It was demonstrated that macroscopic impurities can be separated from N-GOQD suspension by their coagulation with 0.9% NaCl solution. Redispersible in water and saline solutions, particles of N-GOQDs were characterized using tip-enhanced Raman spectroscopy (TERS), photoluminescent, XPS, and UV-VIS spectroscopies. The size and morphology of N-GOQDs were studied by dynamic light scattering, AFM, SEM, and TEM. The procedure proposed allows nitrogen-doped GOQDs to be obtained, having 60-51% of carbon, 34-45% of oxygen, and up to 7.2% of nitrogen. The N-GOQD particles obtained in two hours of synthesis contain only pyrrolic defects of the graphene core. The fraction of pyridine moieties grows with the time of synthesis, while the fraction of quaternary nitrogen declines. Application of TERS allows demonstration that the N-GOQDs consist of a graphene core with an average crystallite size of 9 nm and an average distance between nearest defects smaller than 3 nm. The cytotoxicity tests reveal high viability of the monkey epithelial kidney cells Vero in the presence of N-GOQDs in a concentration below 60 mg L-1. The N-GOQDs demonstrate green luminescence with an emission maximum at 505 nm and sedimentation stability in the cell culture medium.

Graphene Quantum Dot-Based Optical Sensing Platform for Aflatoxin B1 Detection via the Resonance Energy Transfer Phenomenon

An optical sensing platform for the detection of an important mycotoxin, aflatoxin B1 (AFB1), in the absence of a bioactive environment is explored. In this work, a fluorescence-based sensing technique was designed by combining graphene quantum dots (GQDs) and AFB1 via fluorescence quenching, where AFB1 acts as the quencher of GQD fluorescence. GQDs were synthesized through a single-step hydrothermal reaction from the leaves of "curry tree" (Murraya Koenigii) at 200 °C. The fluorescent GQDs were quenched by AFB1 (quencher), which itself is detecting the analyte. Hence, this study reports the direct sensing of the mycotoxin AFB1 without the involvement of inhibitors or biological entities. The possible mode of quenching is the nonradiative resonance energy transfer between the GQDs and the AFB1 molecules. This innovative sensor could detect AFB1 in the range from 5 to 800 ng mL^-1 with a detection limit of 0.158 ng mL^-1. The interferent study was also carried out in the presence of different mycotoxins and carbohydrates (d-fructose, cellulose, and starch), which demonstrated the high selectivity and robustness of the sensor in the complex sample matrix. The recovery percentage of the spiked samples was also calculated to be up to 106.8%. Thus, this study reports the first GQD based optical sensor for AFB1.

Graphene Quantum Dot Assisted Translocation of Daunomycin through an Ordered Lipid Membrane: A Study by Fluorescence Lifetime Imaging Microscopy and Resonance Energy Transfer

Daunomycin (DN) is a well-known chemotherapy drug frequently used in treating acute myeloid and lymphoblastic leukemia. It needs to be delivered to the therapeutic target by a delivering agent that beats the blood-brain barrier. DN is known to be specifically located at the membrane surface and scantly to the bilayer. Penetration of DN into the membrane bilayer depends on the molecular packing of the lipid. It does not travel promptly to the interior of the cells and needs a carrier to serve the purpose. Here, we have demonstrated, by fluorescence lifetime imaging spectroscopy (FLIM) and resonance energy transfer (RET) phenomenon, that ultrasmall graphene quantum dots (GQDs) can be internalized into the aqueous pool of giant unilamellar vesicles (GUVs) made from dipalmitoylphosphatidylcholine (DPPC) lipids, which, in turn, help in fast translocation of DN through the membrane without any delivery vehicle.

Bioactive Graphene Quantum Dots Based Polymer Composite for Biomedical Applications

Today, nanomedicine seeks to develop new polymer composites to overcome current problems in diagnosing and treating common diseases, especially cancer. To achieve this goal, research on polymer composites has expanded so that, in recent years, interdisciplinary collaborations between scientists have been expanding day by day. The synthesis and applications of bioactive GQD-based polymer composites have been investigated in medicine and biomedicine. Bioactive GQD-based polymer composites have a special role as drug delivery carriers. Bioactive GQDs are one of the newcomers to the list of carbon-based nanomaterials. In addition, the antibacterial and anti-diabetic potentials of bioactive GQDs are already known. Due to their highly specific surface properties, π-π aggregation, and hydrophobic interactions, bioactive GQD-based polymer composites have a high drug loading capacity, and, in case of proper correction, can be used as an excellent option for the release of anticancer drugs, gene carriers, biosensors, bioimaging, antibacterial applications, cell culture, and tissue engineering. In this paper, we summarize recent advances in using bioactive GQD-based polymer composites in drug delivery, gene delivery, thermal therapy, thermodynamic therapy, bioimaging, tissue engineering, bioactive GQD synthesis, and GQD green resuscitation, in addition to examining GQD-based polymer composites.

Microemulsion Based Nanostructures for Drug Delivery

Most of the active pharmaceutical compounds are often prone to display low bioavailability and biological degradation represents an important drawback. Due to the above, the development of a drug delivery system (DDS) that enables the introduction of a pharmaceutical compound through the body to achieve a therapeutic effect in a controlled manner is an expanding application. Henceforth, new strategies have been developed to control several parameters considered essential for enhancing delivery of drugs. Nanostructure synthesis by microemulsions (ME) consist of enclosing a substance within a wall material at the nanoscale level, allowing to control the size and surface area of the resulting particle. This nanotechnology has shown the importance on targeted drug delivery to improve their stability by protecting a bioactive compound from an adverse environment, enhanced bioavailability as well as controlled release. Thus, a lower dose administration could be achieved by minimizing systemic side effects and decreasing toxicity. This review will focus on describing the different biocompatible nanostructures synthesized by ME as controlled DDS for therapeutic purposes.

Nanomedicine and graphene-based materials: advanced technologies for potential treatments of diseases in the developing nervous system

The interest in graphene-based nanomaterials (GBNs) application in nanomedicine, in particular in neurology, steadily increased in the last decades. GBNs peculiar physical-chemical properties allow the design of innovative therapeutic tools able to manipulate biological structures with subcellular resolution. In this review, we report GBNs applications to the central nervous system (CNS) when these nanomaterials are engineered as potential therapeutics to treat brain pathologies, with a focus on those of the pediatric age. We revise the state-of-the art studies addressing the impact of GBNs in the CNS, showing that the design of GBNs with different dimensions and chemical compositions or the use of specific administration routes and doses can limit unwanted side effects, exploiting GBNs efficacy in therapeutic approaches. These features favor the development of GBNs-based multifunctional devices that may find applications in the field of precision medicine for the treatment of disorders in the developing CNS. In this framework, we address the suitability of GBNs to become successful therapeutic tools, such as drug nano-delivery vectors when being chemically decorated with pharmaceutical agents and/or other molecules to obtain a high specific targeting of the diseased area and to achieve a controlled release of active molecules. IMPACT: The translational potential of graphene-based nanomaterials (GBNs) can be used for the design of novel therapeutic approaches to treat pathologies affecting the brain with a focus on the pediatric age. GBNs can be chemically decorated with pharmaceutical agents and molecules to obtain a highly specific targeting of the diseased site and a controlled drug release. The type of GBNs, the selected functionalization, the dose, and the way of administration are factors that should be considered to potentiate the therapeutic efficacy of GBNs, limiting possible side effects. GBNs-based multifunctional devices might find applications in the precision medicine and theranostics fields.

Graphene quantum dot antioxidant and proautophagic actions protect SH-SY5Y neuroblastoma cells from oxidative stress-mediated apoptotic death

We investigated the ability of graphene quantum dot (GQD) nanoparticles to protect SH-SY5Y human neuroblastoma cells from oxidative/nitrosative stress induced by iron-nitrosyl complex sodium nitroprusside (SNP). GQD reduced SNP cytotoxicity by preventing mitochondrial depolarization, caspase-2 activation, and subsequent apoptotic death. Although GQD diminished the levels of nitric oxide (NO) in SNP-exposed cells, NO scavengers displayed only a slight protective effect, suggesting that NO quenching was not the main protective mechanism of GQD. GQD also reduced SNP-triggered increase in the intracellular levels of hydroxyl radical (^•OH), superoxide anion (O₂^•-), and lipid peroxidation. Nonselective antioxidants, ^•OH scavenging, and iron chelators, but not superoxide dismutase, mimicked GQD cytoprotective activity, indicating that GQD protect cells by neutralizing ^•OH generated in the presence of SNP-released iron. Cellular internalization of GQD was required for optimal protection, since a removal of extracellular GQD by extensive washing only partly diminished their protective effect. Moreover, GQD cooperated with SNP to induce autophagy, as confirmed by the inhibition of autophagy-limiting Akt/PRAS40/mTOR signaling and increase in autophagy gene transcription, protein levels of proautophagic beclin-1 and LC3-II, formation of autophagic vesicles, and degradation of autophagic target p62. The antioxidant activity of GQD was not involved in autophagy induction, as antioxidants N-acetylcysteine and dimethyl sulfoxide failed to stimulate autophagy in SNP-exposed cells. Pharmacological inhibitors of early (wortmannin, 3-methyladenine) or late stages of autophagy (NH₄Cl) efficiently reduced the protective effect of GQD. Therefore, the ability of GQD to prevent the in vitro neurotoxicity of SNP depends on both ^•OH/NO scavenging and induction of cytoprotective autophagy.

Design of carboxylated single-walled carbon nanotubes as highly efficient inhibitors against Aβ40 fibrillation based on the HyBER mechanism

Misfolding and the subsequent self-assembly of amyloid-β protein (Aβ) is very important in the occurrence of Alzheimer's disease (AD). Thus, inhibition of Aβ aggregation is currently an effective method to alleviate and treat AD. Herein, a carboxylated single-walled carbon nanotube (SWCNT-COOH) was rationally designed based on the hydrophobic binding-electrostatic repulsion (HyBER) mechanism. The inhibitory effect of SWCNT-COOH on Aβ fibrillogenesis was first studied. Based on the results of thioflavin T fluorescence and atomic force microscopy imaging assays, it was shown that SWCNT-COOH can not only effectively inhibit Aβ aggregation, but also depolymerize the mature fibrils of Aβ. In addition, its inhibitory action will be affected by the content of carboxyl groups. Moreover, the influence of SWCNT-COOH on cytotoxicity induced by Aβ was investigated by the MTT method. It was found that SWCNT-COOH can produce an anti-Aβ neuroprotective effect in vitro. Molecular dynamics simulations showed that SWCNT-COOH significantly destroyed the overall and internal structural stability of an Aβ40 trimer. Moreover, SWCNT-COOH interacted strongly with the N-terminal region, turn region and C-terminal region of the Aβ40 trimer via hydrogen bonds, salt bridges and π-π interactions, which triggered a large structural disturbance of the Aβ40 trimer, reduced the β-sheet content of the Aβ40 trimer and led to more disorder in these regions. All the above data not only reveal the suppressive effect of SWCNT-COOH on Aβ aggregation, but also reveal its inhibitory mechanism, which provides a useful clue to exploit anti-Aβ drugs in the future.

Carbon Dots: A Future Blood-Brain Barrier Penetrating Nanomedicine and Drug Nanocarrier

Drug delivery across the blood-brain barrier (BBB) is one of the biggest challenges in modern medicine due to the BBB's highly semipermeable property that limits most therapeutic agents of brain diseases to enter the central nervous system (CNS). In recent years, nanoparticles, especially carbon dots (CDs), exhibit many unprecedented applications for drug delivery. Several types of CDs and CD-ligand conjugates have been reported successfully penetrating the BBB, which shows a promising progress in the application of CD-based drug delivery system (DDS) for the treatment of CNS diseases. In this review, our discussion of CDs includes their classification, preparations, structures, properties, and applications for the treatment of neurodegenerative diseases, especially Alzheimer's disease (AD) and brain tumor. Moreover, abundant functional groups on the surface, especially amine and carboxyl groups, allow CDs to conjugate with diverse drugs as versatile drug nanocarriers. In addition, structure of the BBB is briefly described, and mechanisms for transporting various molecules across the BBB and other biological barriers are elucidated. Most importantly, recent developments in drug delivery with CDs as BBB-penetrating nanodrugs and drug nanocarriers to target CNS diseases especially Alzheimer's disease and brain tumor are summarized. Eventually, future prospects of the CD-based DDS are discussed in combination with the development of artificial intelligence and nanorobots.

Mitochondria-targeted graphene for advanced cancer therapeutics

There have been numerous efforts to develop targeted therapies for treating cancer. The non-specificity of 'classical' cytotoxic chemotherapy drugs and drug resistance remain major challenges in cancer dormancy. Mitochondria-targeted therapy is an alternative strategy for the treatment of numerous cancer types and is heavily dependent on the ability of the anticancer drugs to reach the tumor mitochondria in a safe and selective manner. Over the past two decades, research efforts have provided mechanistic insights into the roles of mitochondria in cancer progression and therapies that specifically target cancer mitochondria. Given that several nanotechnology-driven strategies aimed at therapeutically targeting mitochondrial dysfunction are still in their infancy, this review considers the cross-disciplinary nature of this area and focuses on the design and development of mitochondria-targeted graphene (mitoGRAPH), its immense potential, and future use for selective targeting of cancer mitochondria. This review also provides novel insights into the strategies for preparing mitoGRAPH to destroy the cell powerhouse in a targeted fashion. Targeting mitochondria with graphene may represent an important therapeutic approach that transforms therapeutic interventions. STATEMENT OF SIGNIFICANCE: Mitochondria-targeted therapy represents a major advance for treating several medical conditions. At this time, no nanoparticles (NPs) or nanocarriers are clinically available, which are capable of spatial targeting and controlled delivery of drugs to mitochondria. NPs-based approaches have revolutionized the field of targeted therapy and have demonstrated efficacy for delivering drugs selectively to mitochondria. These NPs show limited results in pre-clinical animal models due to their adverse side effects and inadequate therapeutic outcomes. Over the past decade, graphene has emerged as a potential anticancer agent and has shown great potential in targeting tumor mitochondria in a safe and targeted fashion. This review considers recent advances in the use of mitochondria-targeted graphene (mitoGRAPH) in chemotherapy, photodynamic therapy, photothermal therapy, and combination therapies.

Quantum dots as a theranostic approach in Alzheimer's disease: a systematic review

Aim: Quantum dots (QDs) are nanoparticles that have an emerging application as theranostic agents in several neurodegenerative diseases. The advantage of QDs as nanomedicine is due to their unique optical properties that provide high sensitivity, stability and selectivity at a nanoscale range. Objective: To offer renewed insight into current QD research and elucidate its promising application in Alzheimer's disease (AD) diagnosis and therapy. Methods: A comprehensive literature search was conducted in PubMed and Google Scholar databases that included the following search terms: 'quantum dots', 'blood-brain barrier', 'cytotoxicity', 'toxicity' and 'Alzheimer's disease'; PRISMA guidelines were adhered to. Results: Thirty-four publications were selected to evaluate the ability of QDs to cross the blood-brain barrier, potential toxicity and current AD diagnostic and therapeutic applications. Conclusion: QD's unique optical properties and versatility to conjugate to various biomolecules, while maintaining a nanoscale size, render them a promising theranostic tool in AD.

A review on the cytotoxicity of graphene quantum dots: from experiment to simulation

Graphene quantum dots (GQDs) generate intrinsic fluorescence and improve the aqueous stability of graphene oxide (GO) while maintaining wide chemical adaptability and high adsorption capacity. Despite GO's remarkable advantages in bio-imaging, bio-sensing, and other biomedical applications, many experiments and simulations have focused on the biosafety of GQDs. Here, we review the findings on the biosafety of GQDs from experiments; then, we review the results from simulated interactions with biological membranes, DNA molecules, and proteins; finally, we examine the intersection between experiments and simulations. The biosafety results from simulations are explained in detail. Based on the literature and our experiments, we also discuss the trends toward GQDs with better biosafety.

Construction of graphene quantum dots-decorated EGFR cell membrane chromatography for screening active components from Peucedanum praeruptorum Dunn

A novel stability-enhanced graphene quantum dot (GQD)-decorated epidermal growth factor receptor (EGFR) cell membrane chromatography was constructed to study the potential application of GQDs in bioaffinity chromatography, and to screen active components acting on EGFR from traditional Chinese medicine (TCM). The carboxyl groups on the surface of GQDs reacted with the amino groups of the amino-silica gel (SiO₂-NH₂) to form a covalent bond, thereby preparing the GQD-decorated silica gel (SiO₂-GQDs). The EGFR cell membrane was further immobilized on the SiO₂-GQDs through the same covalent binding method to obtain the GQD-decorated cell membrane stationary phase (SiO₂-GQDs-CMSP). In this way, the cell membrane was firmly immobilized on the decorated silica carrier. The life span and stability of the GQD-decorated cell membrane chromatographic (SiO₂-GQDs-CMC) column were both enhanced, and the optimal immobilization conditions of the EGFR cell membrane were also determined. This model was then verified by establishing a SiO₂-GQDs-CMC online liquid chromatography-ion trap-time-of-flight (LC-IT-TOF) system to screen possible active components in Peucedanum praeruptorum Dunn. As a result, praeruptorin B (Pra-B) was screened out, and its inhibitory effect against EGFR cell growth was evaluated by the cell counting kit-8 (CCK-8) assay. Molecular docking assay was also conducted to further estimate the interaction between Pra-B and EGFR. Overall, this research indicated that GQDs may be a promising nanomaterial to be used in prolonging the life span of the CMC column, and Pra-B could be a potential EGFR inhibitor so as to treat cancer.

The membrane axis of Alzheimer's nanomedicine

Alzheimer's disease (AD) is a major neurological disorder impairing its carrier's cognitive function, memory and lifespan. While the development of AD nanomedicine is still nascent, the field is evolving into a new scientific frontier driven by the diverse physicochemical properties and theranostic potential of nanomaterials and nanocomposites. Characteristic to the AD pathology is the deposition of amyloid plaques and tangles of amyloid beta (Aβ) and tau, whose aggregation kinetics may be curbed by nanoparticle inhibitors via sequence-specific targeting or nonspecific interactions with the amyloidogenic proteins. As literature implicates cell membrane as a culprit in AD pathogenesis, here we summarize the membrane axis of AD nanomedicine and present a new rationale that the field development may greatly benefit from harnessing our existing knowledge of Aβ-membrane interaction, nanoparticle-membrane interaction and Aβ-nanoparticle interaction.

Influence of the digestive process on intestinal toxicity of polystyrene microplastics as determined by in vitro Caco-2 models

The digestive tract is an important target organ for microplastics (MPs). However, little is known about the effects of digestive treatment on the intestinal toxicity of MPs. In this study, an in vitro digestive process was applied to transform 100 nm and 5 μm polystyrene microplastics (PS-MPs). Intestinal toxicities of original PS-MPs and transformed PS-MPs (t-PS-MPs) were determined using an in vitro Caco-2 monolayer model. Results showed that the digestive process did not alter the chemical constitution of PS-MPs, but formed a corona on the surface of PS-MPs. The 100 nm PS-MPs showed higher intestinal toxicity than 5 μm PS-MPs. Digestive treatment relieved cytotoxicity and transport function disorder of the Caco-2 monolayer induced by the original PS-MPs. Moreover, the combined toxicities of PS-MPs and arsenic were also decreased by digestive treatment. However, the in vitro digestive process increased the proinflammatory effects of PS-MPs. The formation of a corona on the PS-MP surface, which lead to a change in size, Zeta potential, and adsorbed compounds, might induce the above influence of digestive treatment. Our study suggests that direct cytotoxicity assays of PS-MPs might misestimate their intestinal effects, which provide new lights to the toxicity evaluation of PS-MPs by oral exposure.

Enhanced Chemotherapy for Glioblastoma Multiforme Mediated by Functionalized Graphene Quantum Dots

Glioblastoma is the most aggressive and lethal brain cancer. Current treatments involve surgical resection, radiotherapy and chemotherapy. However, the life expectancy of patients with this disease remains short and chemotherapy leads to severe adverse effects. Furthermore, the presence of the blood–brain barrier (BBB) makes it difficult for drugs to effectively reach the brain. A promising strategy lies in the use of graphene quantum dots (GQDs), which are light-responsive graphene nanoparticles that have shown the capability of crossing the BBB. Here we investigate the effect of GQDs on U87 human glioblastoma cells and primary cortical neurons. Non-functionalized GQDs (NF-GQDs) demonstrated high biocompatibility, while dimethylformamide-functionalized GQDs (DMF-GQDs) showed a toxic effect on both cell lines. The combination of GQDs and the chemotherapeutic agent doxorubicin (Dox) was tested. GQDs exerted a synergistic increase in the efficacy of chemotherapy treatment, specifically on U87 cells. The mechanism underlying this synergy was investigated, and it was found that GQDs can alter membrane permeability in a manner dependent on the surface chemistry, facilitating the uptake of Dox inside U87 cells, but not on cortical neurons. Therefore, experimental evidence indicates that GQDs could be used in a combined therapy against brain cancer, strongly increasing the efficacy of chemotherapy and, at the same time, reducing its dose requirement along with its side effects, thereby improving the life quality of patients.

Graphene Quantum Dots' Surface Chemistry Modulates the Sensitivity of Glioblastoma Cells to Chemotherapeutics

Recent evidence has shown that graphene quantum dots (GQDs) are capable of crossing the blood-brain barrier, the barrier that reduces cancer therapy efficacy. Here, we tested three alternative GQDs' surface chemistries on two neural lineages (glioblastoma cells and mouse cortical neurons). We showed that surface chemistry modulates GQDs' biocompatibility. When used in combination with the chemotherapeutic drug doxorubicin, GDQs exerted a synergistic effect on tumor cells, but not on neurons. This appears to be mediated by the modification of membrane permeability induced by the surface of GQDs. Our findings highlight that GQDs can be adopted as a suitable delivery and therapeutic strategy for the treatment of glioblastoma, by both directly destabilizing the cell membrane and indirectly increasing the efficacy of chemotherapeutic drugs.

Unravelling the Potential of Graphene Quantum Dots in Biomedicine and Neuroscience

Quantum dots (QDs) are semiconducting nanoparticles that have been gaining ground in various applications, including the biomedical field, thanks to their unique optical properties. Recently, graphene quantum dots (GQDs) have earned attention in biomedicine and nanomedicine, thanks to their higher biocompatibility and low cytotoxicity compared to other QDs. GQDs share the optical properties of QD and have proven ability to cross the blood-brain barrier (BBB). For this reason, GQDs are now being employed to deepen our knowledge in neuroscience diagnostics and therapeutics. Their size and surface chemistry that ease the loading of chemotherapeutic drugs, makes them ideal drug delivery systems through the bloodstream, across the BBB, up to the brain. GQDs-based neuroimaging techniques and theranostic applications, such as photothermal and photodynamic therapy alone or in combination with chemotherapy, have been designed. In this review, optical properties and biocompatibility of GQDs will be described. Then, the ability of GQDs to overtake the BBB and reach the brain will be discussed. At last, applications of GQDs in bioimaging, photophysical therapies and drug delivery to the central nervous system will be considered, unraveling their potential in the neuroscientific field.

Bridge between Temperature and Light: Bottom-Up Synthetic Route to Structure-Defined Graphene Quantum Dots as a Temperature Probe In Vitro and in Cells

Owing to their unique superiorities in chemical and photoluminescence (PL) stability, low toxicity, biocompatibility, and easy functionalization, graphene quantum dots (GQDs) are widely used in cell imaging, probes, and sensors. However, further development and deeper research of GQDs are restricted by their imprecise and complex structure and accompanying controversial PL mechanism. In this work, two kinds of structure-defined water-soluble GQDs, with different oxidation degrees, are synthesized from molecules using bottom-up syntheses methods. After being studied by a series of characterizations, their optical properties, functional groups, molecular weight, and structural information were obtained. The optical properties of GQDs could be optimized by controlling their oxidation degree. The PL mechanism of GQDs was investigated by comparing their structure and properties. Furthermore, robust, stable, and precise temperature probes were designed using the GQDs, which exhibited an excellent wide response range, covering the whole physiology temperature range, from 0 to 60 °C in water. Moreover, the GQDs were successfully applied as temperature-responsive fluorescence probes in the HeLa cell line. These works laid a solid foundation for further applications of GQDs as biological thermoprobes and selectively temperature detectors in vitro cellular and in vivo.

Vanadium coordination compounds loaded on graphene quantum dots (GQDs) exhibit improved pharmaceutical properties and enhanced anti-diabetic effects

Vanadium compounds are promising anti-diabetic agents, and graphene quantum dots (GQDs) are emerging as potential drug delivery systems to improve drug solubility in water and membrane transport. Using highly dispersible and water-soluble GQDs, we herein prepared a novel GQD-VO (p-dmada) complex, in which vanadium coordination compounds [VO(p-dmada)] were packed closely on one side of the GQD sheets possibly via the π-π stacking mechanism. The in vitro tests showed that GQD-VO(p-dmada) exhibited membrane permeability (Papp) as good as that of GQDs with reduced cytotoxicity. In vivo tests on type 2 diabetic mice demonstrated that GQD-VO(p-dmada) exhibited a delayed glucose lowering profile but more profound effects on insulin enhancement and β-cell protection after three-week treatment compared to VO(p-dmada) alone. In addition, GQD alone was observed for the first time to effectively lower the blood lipid levels of the db/db mice. Overall, GQD-VO(p-dmada) showed improved pharmacokinetic performance and hypoglycemic effects, and using GQD as a nanoplatform for drug delivery may provide vast opportunities for the further design of metal-based pharmaceutical agents.

The role of electrostatic potential polarization in the translocation of graphene quantum dots across membranes

Graphene quantum dots (GQDs) have shown promising potential applications in the field of biomedicine. To date, understanding the GQD-cell membrane interactions remains a key issue in developing their biomedical applications, such as targeted drug delivery and bio-imaging. In this study, we mainly shed light on the mechanism of how to control the interactions between GQDs and membranes by tuning the electrostatic potential (EP) of GQDs. Charge distributions at the edge sites were adjusted to mimic the modified EP of GQDs, given that the physicochemical properties of GQDs are usually regulated and determined by the grafted groups and doped atoms at edges. We found that the dynamics of GQDs in the GQD-membrane system can be regulated effectively by modulating the EP of GQDs, which is not only determined by the direct GQD-cell interactions but also by the GQD-water interactions. GQDs with non- or less-polarized EP are hydrophobic, and they can easily translocate into the inner membrane from the bulk water because of the decreased GQD-POPC van der Waals interactions and the favorable dehydration process. In the case of a GQD with more polarized EP, the nanomaterial prefers to adsorb onto the membrane surface due to the strong electrostatic attraction between the GQD and lipid headgroups, and especially, the high dehydration free energy of GQDs can even lead to transient detachment from the surface. These findings would be helpful to understand the interactions between GQD-based nanomaterials and cell membranes, facilitating the rational design of GQD-related biomedicines.

Differential properties and effects of fluorescent carbon nanoparticles towards intestinal theranostics

Given the potential applications of fluorescent carbon nanoparticles in biomedicine, the relationship between their chemical structure, optical properties and biocompatibility has to be investigated in detail. In this work, different types of fluorescent carbon nanoparticles are synthesized by acid treatment, sonochemical treatment, electrochemical cleavage and polycondensation. The particle size ranges from 1 to 6 nm, depending on the synthesis method. Nanoparticles that were prepared by acid or sonochemical treatments from graphite keep a crystalline core and can be classified as graphene quantum dots. The electrochemically produced nanoparticles do not clearly show the graphene core, but it is made of heterogeneous aromatic structures with limited size. The polycondensation nanoparticles do not have CC double bonds. The type of functional groups on the carbon backbone and the optical properties, both absorbance and photoluminescence, strongly depend on the nanoparticle origin. The selected types of nanoparticles are compatible with human intestinal cells, while three of them also show activity against colon cancer cells. The widely different properties of the nanoparticle types need to be considered for their use as diagnosis markers and therapeutic vehicles, specifically in the digestive system.

Role of surface oxygen-containing functional groups of graphene oxide quantum dots on amyloid fibrillation of two model proteins

There are many reports demonstrating that various derivatives of carbon nanoparticles are effective inhibitors of protein aggregation. As surface structural features of nanoparticles play a key role on modulating amyloid fibrillation process, in the present in vitro study, bovine insulin and hen egg white lysozyme (HEWL) were selected as two model proteins to investigate the reducing effect of graphene oxide quantum dots (GOQDs) on their assembly under amyloidogenic conditions. GOQDs were prepared through direct pyrolysis of citric acid, and the reduction step was carried out using ascorbic acid. The prepared nanoparticles were characterized by UV-Vis, X-ray photoelectron, and FT-IR spectroscopies, transmission electron and atomic force microscopies, zeta potential measurement, and Nile red fluorescence assay. They showed the tendencies to modulate the assembly of the proteins through different mechanisms. While GOQDs appeared to have the capacity to inhibit fibrillation, the presence of reduced GOQDs (rGOQDs) was found to promote protein assembly via shortening the nucleation phase, as suggested by ThT fluorescence data. Moreover, the structures produced in the presence of GOQDs or rGOQDs were totally nontoxic. We suggest that surface properties of these particles may be part of the differences in their mechanism(s) of action.

In vitro study of transportation of porphyrin immobilized graphene oxide through blood brain barrier

Blood brain barrier (BBB), a barrier formed by endothelial cells, separates the brain from the circulatory system and protects the stability of central neural system normally, however, it also results in low permeability of vast majority of drugs for brain disease therapy. In this work, the cytotoxicity, uptake and transportation of 2D graphene nanosheet through BBB were investigated in in vitro models of BBB constructed by human brain microvascular endothelia cells (hBMECs). Permeability of two types of graphene nanosheet, including graphene oxide (GO) and porphyrin conjugated graphene oxide (PGO) through BBB were studied. With hydrophobic chemicals conjugation on its surface, permeability of PGO was greatly improved compared to GO. Furthermore, transportation behavior of assorted sizes of PGO obtained by differential velocity centrifugation through BBB was also explored, revealing that PGO with larger size has higher permeability than smaller-size PGO. The significant improved permeability of 2D graphene nanosheet through BBB compared to traditional drugs provides promising applications in drug delivery and disease therapy for brain disease in the near future.

Graphene quantum dots unraveling: Green synthesis, characterization, radiolabeling with 99mTc, in vivo behavior and mutagenicity

Graphene is one of the crystalline forms of carbon, along with diamond, graphite, carbon nanotubes, and fullerenes, and is considered as a revolutionary and innovating product. The use of a graphene-based nanolabels is one of the latest and most prominent application of graphene, especially in the field of diagnosis and, recently, in loco radiotherapy when coupled with radioisotopes. However, its biological behavior and mutagenicity in different cell or animal models, as well as the in vivo functional activities, are still unrevealed. In this study we have developed by a green route of synthesizing graphene quantum dots (GQDs) and characterized them. We have also developed a methodology for direct radiolabeling of GQDs with radioisotopes.Finally; we have evaluated in vivo biological behavior of GQDs using two different mice models and tested in vitro mutagenicity of GQDs. The results have shown that GQDs were formed with a size range of 160-280 nm, which was confirmed by DRX and Raman spectroscopy analysis, corroborating that the green synthesis is an alternative, environmentally friendly way to produce graphene. The radiolabeling test has shown that stable radiolabeled GQDs can be produced with a high yield (>90%). The in vivo test has demonstrated a ubiquitous behavior when administered to healthy animals, with a high uptake by liver (>26%) and small intestine (>25%). Otherwise, in an inflammation/VEGF hyperexpression animal model (endometriosis), a very peculiar behavior of GQDs was observed, with a high uptake by kidneys (over 85%). The mutagenicity test has demonstrated A:T to G:C substitutions suggesting that GQDs exhibits mutagenic activity.

Label-free tracking of nanosized graphene oxide cellular uptake by confocal Raman microscopy

Graphene oxide (GO), a partially oxidized two-dimensional allotrope of carbon, is an attractive nanocarrier for cancer diagnostics and therapy. The nanometer-sized GO is known to permeate cell membranes. Herein we studied the cellular uptake pathways of GO nanoflakes by cancer and non-cancerous cell lines. By employing confocal Raman imaging, we were able to track the GO cellular uptake in living cells (C33 and MDCK) without any additional fluorescent or plasmonic labels. This specific progress in label-free Raman imaging of GO facilitates the monitoring of nanoflakes at the cellular level.

The Inhibitory Effect of Hydroxylated Carbon Nanotubes on the Aggregation of Human Islet Amyloid Polypeptide Revealed by a Combined Computational and Experimental Study

Fibrillar deposits formed by the aggregation of the human islet amyloid polypeptide (hIAPP) are the major pathological hallmark of type 2 diabetes mellitus (T2DM). Inhibiting the aggregation of hIAPP is considered the primary therapeutic strategy for the treatment of T2DM. Hydroxylated carbon nanoparticles have received great attention in impeding amyloid protein fibrillation owing to their reduced cytotoxicity compared to the pristine ones. In this study, we investigated the influence of hydroxylated single-walled carbon nanotubes (SWCNT-OHs) on the first step of hIAPP aggregation: dimerization by performing explicit solvent replica exchange molecular dynamics (REMD) simulations. Extensive REMD simulations demonstrate that SWCNT-OHs can dramatically inhibit interpeptide β-sheet formation and completely suppress the previously reported β-hairpin amyloidogenic precursor of hIAPP. On the basis of our simulation results, we proposed that SWCNT-OH can hinder hIAPP fibrillation. This was further confirmed by our systematic turbidity measurements, thioflavin T fluorescence, circular dichroism (CD), transmission electron microscope (TEM), and atomic force microscopy (AFM) experiments. Detailed analyses of hIAPP-SWCNT-OH interactions reveal that hydrogen bonding, van der Waals, and π-stacking interactions between hIAPP and SWCNT-OH significantly weaken the inter- and intrapeptide interactions that are crucial for β-sheet formation. Our collective computational and experimental data reveal not only the inhibitory effect but also the inhibitory mechanism of SWCNT-OH against hIAPP aggregation, thus providing new clues for the development of future drug candidates against T2DM.

Rho GTPases in A549 and Caco-2 cells dominating the endocytic pathways of nanocarbons with different morphologies

Introduction

Endocytosis of nanomaterials is the first step of nano-bio interaction and current regulation is mostly by nanomaterials but seldom by intracellular signaling proteins.

Materials and methods

Herein, we synthesized tubular nanocarbon (oxMWCNT) and lamellar-like nanocarbon (oxGRAPHENE) and formulated their aqueous dispersion. A549 and Caco-2 cells were selected as the models of tumor and intestinal epithelial cells, respectively. After knocking down three members of Rho GTPases (Cdc42, Rac1, RhoA) in these two cell lines, their silencing effects on the uptake pathways of nanomaterials with different morphologies were investigated.

Results

An unexpected finding was that the knock-down led to opposite uptake trends in different types of cells. The endocytosis of carbon nanomaterials increased in Caco-2 cells when Rho GTPases were inactivated, while that in A549 cells decreased. For nanomaterials with different shapes, the involved GTPase member of Rho family, or regulating protein molecule, was different. Concretely, Cdc42 and Rac1 were involved in oxMWCNT endocytosis, while all three GTPases participated in oxGRAPHENE internalization. More interestingly, such difference induced different uptake pathways, namely, the cellular uptake of oxMWCNT was clathrin-mediated and oxGRAPHENE was caveolin-modulated, both with the involvement of dynamin.

Conclusion

In conclusion, this study provides new insights for the potential intervention in nano-bio interplay.

Tuning the optical properties of graphene quantum dots for biosensing and bioimaging

This review highlights new insights into the various strategies used to tune the optical features of graphene quantum dots, and their use as attractive and powerful probes for bio-sensing/imaging.

Investigation of the effects of carbon-based nanomaterials on A53T alpha-synuclein aggregation using a whole-cell recombinant biosensor

The aggregation of alpha-synuclein (αS), natively unstructured presynaptic protein, is a crucial factor leading to the pathogenesis of Parkinson’s disease (PD) and other related disorders. Recent studies have shown prefibrillar and oligomeric intermediates of αS as toxic to the cells. Herein, split-luciferase complementation assay is used to design a “signal-on” biosensor to monitor oligomerization of A53T αS inside the cells. Then, the effect of carbon-based nanomaterials, such as graphene quantum dots (GQDs) and graphene oxide quantum dots (GOQDs), on A53T αS oligomerization in vitro and in living cells is investigated. In this work, for the first time, it was found that GQDs at a concentration of 0.5 μg/mL can promote A53T αS aggregation by shortening the nucleation process, which is the key rate-determining step of fibrillation, thereby making a signal-on biosensor. While these nanomaterials may cross the blood–brain barrier because of their small sizes, the interaction between αS and GQDs may contribute to PD etiology.

Knowledge gaps between nanotoxicological research and nanomaterial safety

With the wide research and application of nanomaterials in various fields, the safety of nanomaterials attracts much attention. An increasing number of reports in the literature have shown the adverse effects of nanomaterials, representing the quick development of nanotoxicology. However, many studies in nanotoxicology have not reflected the real nanomaterial safety, and the knowledge gaps between nanotoxicological research and nanomaterial safety remain large. Considering the remarkable influence of biological or environmental matrices (e.g., biological corona) on nanotoxicity, the situation of performing nanotoxicological experiments should be relevant to the environment and humans. Given the possibility of long-term and low-concentration exposure of nanomaterials, the reversibility of and adaptation to nanotoxicity, and the transgenerational effects should not be ignored. Different from common pollutants, the specific analysis methodology for nanotoxicology need development and exploration furthermore. High-throughput assay integrating with omics was highlighted in the present review to globally investigate nanotoxicity. In addition, the biological responses beyond individual levels, special mechanisms and control of nanotoxicity deserve more attention. The progress of nanotoxicology has been reviewed by previous articles. This review focuses on the blind spots in nanotoxicological research and provides insight into what we should do in future work to support the healthy development of nanotechnology and the evaluation of real nanomaterial safety.

Single layer nano graphene platelets derived from graphite nanofibres

Solutions of calibrated nanographenides (negatively charged nanographenes) are obtained by dissolution of graphite nanofibre intercalation compounds (GNFICs). Deposits show homogeneous unfolded nanographene platelets of 1 to 2 layers thickness and 10 nm lateral size, evidenced by atomic force microscopy and Raman spectroscopy. Upon oxidation, nanographenide solutions exhibit strong photoluminescence.