The in vitro and in vivo toxicity of graphene quantum dots

Nitrogen-doped carbon quantum dot regulates cell proliferation and differentiation by endoplasmic reticulum stress

Quantum dots have diverse biomedical applications, from constructing biological infrastructures like medical imaging to advancing pharmaceutical research. However, concerns about human health arise due to the toxic potential of quantum dots based on heavy metals. Therefore, research on quantum dots has predominantly focused on oxidative stress, cell death, and other broader bodily toxicities. This study investigated the toxicity and cellular responses of mouse embryonic stem cells (mESCs) and mouse adult stem cells (mASCs) to nitrogen-doped carbon quantum dots (NCQDs) made of non-metallic materials. Cells were exposed to NCQDs, and we utilized a fluorescent ubiquitination-based cell system to verify whether NCQDs induce cytotoxicity. Furthermore, we validated the differentiation-inducing impact of NCQDs by utilizing embryonic stem cells equipped with the Oct4 enhancer-GFP reporter system. By analyzing gene expression including Crebzf, Chop, and ATF6, we also observed that NCQDs robustly elicited endoplasmic reticulum (ER) stress. We confirmed that NCQDs induced cytotoxicity and abnormal differentiation. Interestingly, we also confirmed that low concentrations of NCQDs stimulated cell proliferation in both mESCs and mASCs. In conclusion, NCQDs modulate cell death, proliferation, and differentiation in a concentration-dependent manner. Indiscriminate biological applications of NCQDs have the potential to cause cancer development by affecting normal cell division or to fail to induce normal differentiation by affecting embryonic development during pregnancy. Therefore, we propose that future biomedical applications of NCQDs necessitate comprehensive and diverse biological studies.

Unravelling the toxicity of carbon nanomaterials - From cellular interactions to mechanistic understanding

The application of carbon nanomaterials in diverse fields has substantially increased their demand for commercial usage. Within the earliest decade, the development of functional materials has further increased the significance of this element. Despite the advancements recorded, the potential harmful impacts of embracing carbon nanomaterials for biological applications must be balanced against their advantages. Interestingly, many studies have neglected the intriguing and dynamic cellular interaction of carbon nanomaterials and the mechanistic understanding of their property-driven behaviour, even though common toxicity profiles have been reported. Reiterating the toxicity issue, several researchers conclude that these materials have minimal toxicity and may be safe for contact with biological systems at certain dosages. Here, we aim to provide a report on the significance of some of the properties that influence their toxicity. After that, a description of the implication of nanotoxicology in humans and living systems, revealing piece by piece their exposure routes and possible risks, will be provided. Then, an extensive discussion of the mechanistic puzzle modulating the interface between various human cellular systems and carbon nanomaterials such as carbon nanotubes, carbon dots, graphene, fullerenes, and nanodiamonds will follow. Finally, this review also sheds light on the organization that handles the risk associated with nanomaterials.

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.

Retinal Degeneration Response to Graphene Quantum Dots: Disruption of the Blood-Retina Barrier Modulated by Surface Modification-Dependent DNA Methylation

Graphene quantum dots (GQDs) are used in diverse fields from chemistry-related materials to biomedicines, thus causing their substantial release into the environment. Appropriate visual function is crucial for facilitating the decision-making process within the nervous system. Given the direct interaction of eyes with the environment and even nanoparticles, herein, GQDs, sulfonic acid-doped GQDs (S-GQDs), and amino-functionalized GQDs (A-GQDs) were employed to understand the potential optic neurotoxicity disruption mechanism by GQDs. The negatively charged GQDs and S-GQDs disturbed the response to light stimulation and impaired the structure of the retinal nuclear layer of zebrafish larvae, causing vision disorder and retinal degeneration. Albeit with sublethal concentrations, a considerably reduced expression of the retinal vascular sprouting factor sirt1 through increased DNA methylation damaged the blood-retina barrier. Importantly, the regulatory effect on vision function was influenced by negatively charged GQDs and S-GQDs but not positively charged A-GQDs. Moreover, cluster analysis and computational simulation studies indicated that binding affinities between GQDs and the DNMT1-ligand binding might be the dominant determinant of the vision function response. The previously unknown pathway of blood-retinal barrier interference offers opportunities to investigate the biological consequences of GQD-based nanomaterials, guiding innovation in the industry toward environmental sustainability.

Graphene Quantum Dots Inhibit Lipid Peroxidation in Biological Membranes

Excessive reactive oxygen species (ROS) in cellular environments leads to oxidative stress, which underlies numerous diseases, including inflammatory diseases, neurodegenerative diseases, cardiovascular diseases, and cancer. Oxidative stress can be particularly damaging to biological membranes such as those found in mitochondria, which are abundant with polyunsaturated fatty acids (PUFAs). Oxidation of these biological membranes results in concomitant disruption of membrane structure and function, which ultimately leads to cellular dysfunction. Graphene quantum dots (GQDs) have garnered significant interest as a therapeutic agent for numerous diseases that are linked to oxidative stress. Specifically, GQDs have demonstrated an ability to protect mitochondrial structure and function under oxidative stress conditions. However, the fundamental mechanisms by which GQDs interact with membranes in oxidative environments are poorly understood. Here, we used C11-BODIPY, a fluorescent lipid oxidation probe, to develop quantitative fluorescence assays that determine both the extent and rate of oxidation that occurs to PUFAs in biological membranes. Based on kinetics principles, we have developed a generalizable model that can be used to assess the potency of antioxidants that scavenge ROS in the presence of biological membranes. By augmenting our fluorescence assays with 1H NMR spectroscopy, the results demonstrate that GQDs scavenge nascent hydroxyl and peroxyl ROS that interact with membranes and that GQDs are potent inhibitors of ROS-induced lipid oxidation in PUFA-containing biological membranes. The antioxidant potency of GQDs is comparable to or even greater than established antioxidant molecules, such as ascorbic acid and Trolox. This work provides mechanistic insights into the mitoprotective properties of GQDs under oxidative stress conditions, as well as a quantitative framework for assessing antioxidant interactions in biological membrane systems.

Advances in Black Phosphorus Quantum Dots for Cancer Research: Synthesis, Characterization, and Applications

In the past few years, there has been notable advancement in nanotechnology, leading to the development of new materials with potential uses in the medical field, especially in cancer diagnosis, imaging, and therapy. Black phosphorus quantum dots (BPQDs) are one of the emerging nanomaterials that have generated interest due to their unique properties and potential in biomedical applications. This review aims to give a detailed overview of how BPQDs are synthesized, characterized, and utilized. The synthesis methods of BPQDs are discussed, with a focus on obtaining size-controlled and high-quality BPQDs. Two main approaches, top-down exfoliation and bottom-up techniques, are described. Despite advancements in synthesis, there are challenges hindering the practical application of BPQDs, such as poor dispersion and short durability. To address these issues, techniques to enhance biocompatibility and reduce potential toxicity, such as surface modifications, are discussed. BPQDs have potential in bioimaging as they offer higher resolution and sensitivity compared with traditional imaging agents. Their small size and expansive surface area make them suitable for drug delivery systems, enabling the effective incorporation of therapeutic substances. By functionalizing BPQDs with targeting ligands, they can selectively bind to cancer cells or tissue, making them ideal for targeted therapies. Moreover, BPQDs can serve as biosensors to detect biomarkers in bodily fluids, further expanding their biomedical applications. However, before they can be successfully translated into clinical settings, further research is needed to optimize the synthesis methods of BPQDs and evaluate their long-term safety profiles. Nonetheless, with ongoing research and development, the medical uses of BPQDs are expected to expand.

Application of Photoactive Compounds in Cancer Theranostics: Review on Recent Trends from Photoactive Chemistry to Artificial Intelligence

According to the World Health Organization (WHO) and the International Agency for Research on Cancer (IARC), the number of cancer cases and deaths worldwide is predicted to nearly double by 2030, reaching 21.7 million cases and 13 million fatalities. The increase in cancer mortality is due to limitations in the diagnosis and treatment options that are currently available. The close relationship between diagnostics and medicine has made it possible for cancer patients to receive precise diagnoses and individualized care. This article discusses newly developed compounds with potential for photodynamic therapy and diagnostic applications, as well as those already in use. In addition, it discusses the use of artificial intelligence in the analysis of diagnostic images obtained using, among other things, theranostic agents.

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.

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.

Compounding Methylene Blue with Selenium-decorated Graphene Quantum Dots to Improve Singlet Oxygen Production for Photodynamic Therapy Application

Graphene quantum dots (GQDs) are known as suitable material to be applied in different fields such as photodynamic therapy (PDT). Herein, GQDs were synthesized by the pyrolysis method and then decorated with selenium (Se). Afterward, they were combined with methylene blue (MB) to increase singlet oxygen generation as well as to apply them more effectively in the PDT method. Furthermore, GQDs were investigated by transmission electron microscope (TEM), photoluminescence spectrum (PL), Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM), reactive oxygen species (ROS) measurement, and cytotoxicity measurement. GQDs showed no dependence on the excitation wavelength. The result of ROS measurement proves that the combination of GQD-Se and MB increases singlet oxygen production. Moreover, afterglow measurement approved the beneficial effect of GQD-Se on even deep and near skin tumor treatment. Cytotoxicity measurements under dark conditions, cell viability, and the side effects on human cells were determined by (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) (MTT) assay. Our findings show that under dark conditions, even high concentrations of nanoparticles have no significant effect on cell viability. These findings and the high biocompatibility of GQDs indicate the effective application of GQD-Se-MB in PDT.

Potential toxicity of graphene (oxide) quantum dots via directly covering the active site of anterior gradient homolog 2 protein

Graphene quantum dots (GQDs) have attracted significant attention in biomedicine, while extensive investigations have revealed a reverse regarding the potential biotoxicity of GQDs. In order to supplementing the understanding of the toxicity profile of GQDs, this study employs a molecular dynamics (MD) simulation approach to systematically investigate the potential toxicity of both GQDs and Graphene Oxide Quantum Dots (GOQDs) on the Anterior Gradient Homolog 2 (AGR2) protein, a key protein capable of protecting the intestine. We construct two typical simulation systems, in which an AGR2 protein is encircled by either GQDs or GOQDs. The MD results demonstrate that both GQDs and GOQDs can directly make contact with and even cover the active site (specifically, the Cys81 amino acid) of the AGR2 protein. This suggests that GQDs and GOQDs have the capability to inhibit or interfere with the normal biological interaction of the AGR2 active site with its target protein. Thus, GQDs and GOQDs exhibit potential detrimental effects on the AGR2 protein. Detailed analyses reveal that GQDs adhere to the Cys81 residue due to van der Waals (vdW) interaction forces, whereas GOQDs attach to the Cys81 residue through a combination of vdW (primary) and Coulomb (secondary) interactions. Furthermore, GQDs aggregation typically adsorb onto the AGR2 active site, while GOQDs adsorb to the active site of AGR2 one by one. Consequently, these findings shed new light on the potential adverse impact of GQDs and GOQDs on the AGR2 protein via directly covering the active site of AGR2, providing valuable molecular insights for the toxicity profile of GQD nanomaterials.

Polyethylenimine-modified graphene quantum dots promote endothelial cell proliferation

Endothelial cell proliferation plays an important role in angiogenesis and treatment of related diseases. The aim of this study was to evaluate the effect of polyethylenimine (PEI)-modified graphene quantum dots (GQDs) gene vectors on endothelial cell proliferation. The GQDs-cationic polymer gene vectors were synthesized by amidation reaction, and used to deliver pZNF580 gene to Human umbilical vein endothelial cells (HUVECs) for promoting their proliferation. The chemical modification of GQDs can adjust gene vectors' surface properties and charge distribution, thereby enhancing their interaction with gene molecules, which could effectively compress the pZNF580 gene. The CCK-8 assay showed that the cell viability was higher than 80% at higher vector concentration (40 μg/mL), demonstrating that the GQDs-cationic polymer gene vectors and their gene complex nanoparticles (NPs) having low cytotoxicity. The results of the live/dead cell double staining assay were consistent with those of the CCK-8 assay, in which the cell viability of the A-GQDs/pZNF580 (94.38 ± 6.39%), C-GQDs-PEI- polylactic acid-co-polyacetic acid (PLGA)/pZNF580 (98.65 ± 6.60%) and N-GQDs-PEI-PLGA/pZNF580 (90.08 ± 1.60%) groups was significantly higher than that of the Lipofectamine 2000/pZNF580 (71.98 ± 3.53%) positive treatment group. The results of transfection and western blot experiments showed that the vector significantly enhanced the delivery of plasmid to HUVECs and increased the expression of pZNF580 in HUVECs. In addition, the gene NPs better promote endothelial cell migration and proliferation. The cell migration rate and proliferation ability of C-GQDs-PEI-PLGA/pZNF580 and N-GQDs-PEI-PLGA/pZNF580 treatment groups were higher than those of Lipofectamine 2000/pDNA treatment group. Modified GQDs possess the potential to serve as efficient gene carriers. They tightly bind gene molecules through charge and other non-covalent interactions, significantly improving the efficiency of gene delivery and ensuring the smooth release of genes within the cell. This innovative strategy provides a powerful means to promote endothelial cell proliferation.

A potent multifunctional ZIF-8 nanoplatform developed for colorectal cancer therapy by triple-delivery of chemo/radio/targeted therapy agents

BACKGROUND

Multimodal cancer therapy has garnered significant interest due to its ability to target tumor cells from various perspectives. The advancement of novel nano-delivery platforms represents a promising approach for improving treatment effectiveness while minimizing detrimental effects on healthy tissues.

METHODS

This study aimed to develop a multifunctional nano-delivery system capable of simultaneously delivering an anti-cancer drug, a radiosensitizer agent, and a targeting moiety (three-in-one) for the triple combination therapy of colorectal cancer (CRC). This unique nano-platform, called Apt-PEG-DOX/ZIF-8@GQD, encapsulated both doxorubicin (DOX) and graphene quantum dots (GQDs) within the zeolitic imidazolate framework-8 (ZIF-8). To enhance the safety and anti-cancer potential of the platform, heterobifunctional polyethylene glycol (PEG) and an epithelial cell adhesion molecule (EpCAM) aptamer were conjugated with the system, resulting in the formation of targeted Apt-PEG-DOX/ZIF-8@GQD NPs. The physical and chemical characteristics of Apt-PEG-DOX/ZIF-8@GQD were thoroughly examined, and its therapeutic efficacy was evaluated in combination with radiotherapy (RT) against both EpCAM-positive HT-29 and EpCAM-negative CHO cells. Furthermore, the potential of Apt-PEG-DOX/ZIF-8@GQD as a tumor-specific, radio-enhancing, non-toxic, and controllable delivery system for in vivo cancer treatment was explored using immunocompromised C57BL/6 mice bearing human HT-29 tumors.

RESULTS

The large surface area of ZIF-8 (1013 m2 g-1) enabled successful loading of DOX with an encapsulation efficiency of approximately ∼90%. The synthesis of Apt-PEG-DOX/ZIF-8@GQD resulted in uniform particles with an average diameter of 100 nm. This targeted platform exhibited rapid decomposition under acidic conditions, facilitating an on-demand release of DOX after endosomal escape. In vitro experiments revealed that the biocompatible nano-platform induced selective toxicity in HT-29 cells by enhancing X-ray absorption. Moreover, in vivo experiments demonstrated that the therapeutic efficacy of Apt-PEG-ZIF-8/DOX@GQD against HT-29 tumors was enhanced through the synergistic effects of chemotherapy, radiotherapy, and targeted therapy, with minimal side effects.

CONCLUSION

The combination of Apt-PEG-DOX/ZIF-8@GQD with RT as a multimodal therapy approach demonstrated promising potential for the targeted treatment of CRC and enhancing therapeutic effectiveness. The co-delivery of DOX and GQD using this nano-platform holds great promise for improving the outcome of CRC treatment.

Graphene quantum dots blocking the channel egresses of cytochrome P450 enzyme (CYP3A4) reveals potential toxicity

Graphene quantum dots (GQDs) have garnered significant attention, particularly in the biomedical domain. However, extensive research reveals a dichotomy concerning the potential toxicity of GQDs, presenting contrasting outcomes. Therefore, a comprehensive understanding of GQD biosafety necessitates a detailed supplementation of their toxicity profile. In this study, employing a molecular dynamics (MD) simulation approach, we systematically investigate the potential toxicity of GQDs on the CYP3A4 enzyme. We construct two distinct simulation systems, wherein a CYP3A4 protein is enveloped by either GQDs or GOQDs (graphene oxide quantum dots). Our results elucidate that GQDs come into direct contact with the bottleneck residues of Channels 2a and 2b of CYP3A4. Furthermore, GQDs entirely cover the exits of Channels 2a and 2b, implying a significant hindrance posed by GQDs to these channels and consequently leading to toxicity towards CYP3A4. In-depth analysis reveals that the adsorption of GQDs to the exits of Channels 2a and 2b is driven by a synergistic interplay of hydrophobic and van der Waals (vdW) interactions. In contrast, GOQDs only partially obstruct Channel 1 of CYP3A4, indicating a weaker influence on CYP3A4 compared to GQDs. Our findings underscore the potential deleterious impact of GQDs on the CYP3A4 enzyme, providing crucial molecular insights into GQD toxicology.

Utilizing Atmospheric Carbon Dioxide and Sunlight in Graphene Quantum Dot-Based Nano-Biohybrid Organisms for Making Carbon-Negative and Carbon-Neutral Products

Increasing emissions of greenhouse gases compounded with legacy emissions in the earth's atmosphere poses an existential threat to human survival. One potential solution is creating carbon-negative and carbon-neutral materials, specifically for commodities used heavily throughout the globe, using a low-cost, scalable, and technologically and economically feasible process that can be deployed without the need for extensive infrastructure or skill requirements. Here, we demonstrate that nickel-functionalized graphene quantum dots (GQDs) can effectively couple to nonphotosynthetic bacteria at a cellular, molecular, and optoelectronic level, creating nanobiohybrid organisms (nanorgs) that enable the utilization of sunlight to convert carbon dioxide, air, and water into high-value-added chemicals such as ammonia (NH3), ethylene (C2H4), isopropanol (IPA), 2,3-butanediol (BDO), C11-C15 methyl ketones (MKs), and degradable bioplastics poly hydroxybutyrate (PHB) with high efficiency and selectivity. We demonstrate a high turnover number (TON) of up to 108 (mol of product per mol of cells), ease of application, facile scalability (demonstrated using a 30 L tank in a lab), and sustainable generation of carbon nanomaterials from recovered bacteria for creating nanorgs without the use of any toxic chemicals or materials. These findings can have important implications for the further development of sustainable processes for making carbon-negative materials using nanorgs.

Photostability and phototoxicity of graphene quantum dots interacting with red blood cells

Here we discuss fluorescent properties of graphene quantum dots (GQDs) interacting with the membranes of red blood cells. We report the results of spectroscopic, microscopic, and photon-counting measurements of the GQDs in different surroundings for uncovering specific features of the GQD fluorescence, and describe two observed phenomena important for implementation of the GQDs as fluorescent labels and agents for drug delivery. Firstly, the GQDs can suffer from photodegradation but also can be stabilized in the presence of antioxidants (reduced glutathione, N-acetylcysteine, or 1,4-hydroquinone). Secondly, GQDs can accumulate in red blood cell membranes without compromising the viability of the cells but also can induce hemolysis in the presence of visible light. We discuss mechanisms and regimes of the photodegradation, stabilization, interaction of the GQDs with red blood cell membranes, and hemolysis. Notably, photohemolysis for the case is dependent on the light dose and GQD concentration but not caused by the production of reactive oxygen species.

Polyphenolic Carbon Quantum Dots with Intrinsic Reactive Oxygen Species Amplification for Two-Photon Bioimaging and In Vivo Tumor Therapy

Recent studies indicate that mitochondrial dysfunctions and DNA damage have a critical influence on cell survival, which is considered one of the therapeutic targets for cancer therapy. In this study, we demonstrated a comparative study of the effect of polyphenolic carbon quantum dots (CQDs) on in vitro and in vivo antitumor efficacy. Dual emissive (green and yellow) shape specific polyphenolic CQDs (G-CQDs and Y-CQDs) were synthesized from easily available nontoxic precursors (phloroglucinol), and the antitumor property of the as-synthesized probe was investigated as compared to round-shaped blue emissive CQDs (B-CQDs) derived from well-reported precursor citric acid and urea. The B-CQDs had a nuclei-targeting property, and G-CQDs and Y-CQDs had mitochondria-targeting properties. We have found that the polyphenol containing CQDs (at a dose of 100 μg mL-1) specifically attack mitochondria by excess accumulation, altering the metabolism, inhibiting branching pattern, imbalanced Bax/Bcl-2 homeostasis, and ultimately generating oxidative stress levels, leading to oxidative stress-induced cell death in cancer cells in vitro. We show that G-CQDs are the main cause of oxidative stress in cancer cells because of their ability to produce sufficient •OH- and 1O2 radicals, evidenced by electron paramagnetic resonance spectroscopy and a terephthalic acid test. Moreover, the near-infrared absorption properties of the CQDs were exhibited in two-photon (TP) emission, which was utilized for TP cellular imaging of cancer cells without photobleaching. The in vivo antitumor test further discloses that intratumoral injection of G-CQDs can significantly augment the treatment efficacy of subcutaneous tumors without any adverse effects on BalB/c nude mice. We believe that shape-specific polyphenolic CQD-based nanotheranostic agents have a potential role in tumor therapy, thus proving an insight on treatment of malignant cancers.

Plasma-Enabled Graphene Quantum Dot Hydrogel-Magnesium Composites as Bioactive Scaffolds for In Vivo Bone Defect Repair

Bioactive and mechanically stable metal-based scaffolds are commonly used for bone defect repair. However, conventional metal-based scaffolds induce nonuniform cell growth, limiting damaged tissue restoration. Here, we develop a plasma nanotechnology-enhanced graphene quantum dot (GQD) hydrogel-magnesium (Mg) composite scaffold for functional bone defect repair by integrating a bioresource-derived nitrogen-doped GQD (NGQD) hydrogel into the Mg ZK60 alloy. Each scaffold component brings major synergistic advantages over the current alloy-based state of the art, including (1) mechanical support of the cortical bone and calcium deposition by the released Mg2+ during degradation; (2) enhanced uptake, migration, and distribution of osteoblasts by the porous hydrogel; and (3) improved osteoblast adhesion and proliferation, osteogenesis, and mineralization by the NGQDs in the hydrogel. Through an in vivo study, the hybrid scaffold with the much enhanced osteogenic ability induced by the above synergy promotes a more rapid, uniform, and directional bone growth across the hydrogel channel, compared with the control Mg-based scaffold. This work provides insights into the design of multifunctional hybrid scaffolds, which can be applied in other areas well beyond the demonstrated bone defect repair.

In vitro and in vivo toxicity of carbon dots with different chemical compositions

Carbon dots (CDs) are easy-obtained nanoparticles with wide range of biological activity; however, their toxicity after prolonged exposure is poorly investigated. So, in vitro and in vivo toxicity of CDs with the surfaces enriched with hydroxylated hydrocarbon chains and methylene groups (CD_GE), carboxyl and phenol groups accompanied with nitrogen (CD_3011), trifluoromethyl (CDF19) or toluidine and aniline groups (CDN19) were aimed to be discovered. CDs' in vitro toxicity was assessed on A549 cells (real-time cell analysis of impedance, fluorescence microscopy) after 24 h of incubation, and we observed no changes in cell viability and morphology. CDs' in vivo toxicity was assessed on C57Bl6 mice after multiple dosages (5 mg/kg subcutaneously) for 14 days. Lethality (up to 50%) was observed in CDN19 and CD_3011 groups on different days of dosing, accompanied by toxicity signs in case of CD_3011. There were no changes in serum biochemical parameters except Urea (increased in CDF19 and CD_3011 groups), nor substantial kidney, liver, and spleen injuries. The most impactful for all organs were also CD_3011 and CDF19, causing renal tubule injury and liver blood supply violation. Thus, CDs with a surface enriched with oxygen- and nitrogen-containing functional groups might be toxic after multiple everyday dosing, without, however, significant damages of internal organs in survived animals.

Recent advances in 3D printable conductive hydrogel inks for neural engineering

Recently, the 3D printing of conductive hydrogels has undergone remarkable advances in the fabrication of complex and functional structures. In the field of neural engineering, an increasing number of reports have been published on tissue engineering and bioelectronic approaches over the last few years. The convergence of 3D printing methods and electrically conducting hydrogels may create new clinical and therapeutic possibilities for precision regenerative medicine and implants. In this review, we summarize (i) advancements in preparation strategies for conductive materials, (ii) various printing techniques enabling the fabrication of electroconductive hydrogels, (iii) the required physicochemical properties of the printed constructs, (iv) their applications in bioelectronics and tissue regeneration for neural engineering, and (v) unconventional approaches and outlooks for the 3D printing of conductive hydrogels. This review provides technical insights into 3D printable conductive hydrogels and encompasses recent developments, specifically over the last few years of research in the neural engineering field.

Potential of graphene-based nanomaterials for cardiac tissue engineering

Cardiovascular diseases are the primary cause of death worldwide. Despite significant advances in pharmacological treatments and surgical interventions to restore heart function after myocardial infarction, it can progress to heart failure due to the restricted inherent potential of adult cardiomyocytes to self-regenerate. Hence, the evolution of new therapeutic methods is critical. Nowadays, novel approaches in tissue engineering have assisted in restoring biological and physical specifications of the injured myocardium and, hence, cardiac function. The incorporation of a supporting matrix that could mechanically and electronically support the heart tissue and stimulate the cells to proliferate and regenerate will be advantageous. Electroconductive nanomaterials can facilitate intracellular communication and aid synchronous contraction via electroactive substrate creation, preventing the issue of arrhythmia in the heart. Among a wide range of electroconductive materials, graphene-based nanomaterials (GBNs) are promising for cardiac tissue engineering (CTE) due to their outstanding features including high mechanical strength, angiogenesis, antibacterial and antioxidant properties, low cost, and scalable fabrication. In the present review, we discuss the effect of applying GBNs on angiogenesis, proliferation, and differentiation of implanted stem cells, their antibacterial and antioxidant properties, and their role in improving the electrical and mechanical properties of the scaffolds for CTE. Also, we summarize the recent research that has applied GBNs in CTE. Finally, we present a concise discussion on the challenges and prospects.

The mechanical, optical, and thermal properties of graphene influencing its pre-clinical use in treating neurological diseases

Rapid progress in nanotechnology has advanced fundamental neuroscience and innovative treatment using combined diagnostic and therapeutic applications. The atomic scale tunability of nanomaterials, which can interact with biological systems, has attracted interest in emerging multidisciplinary fields. Graphene, a two-dimensional nanocarbon, has gained increasing attention in neuroscience due to its unique honeycomb structure and functional properties. Hydrophobic planar sheets of graphene can be effectively loaded with aromatic molecules to produce a defect-free and stable dispersion. The optical and thermal properties of graphene make it suitable for biosensing and bioimaging applications. In addition, graphene and its derivatives functionalized with tailored bioactive molecules can cross the blood-brain barrier for drug delivery, substantially improving their biological property. Therefore, graphene-based materials have promising potential for possible application in neuroscience. Herein, we aimed to summarize the important properties of graphene materials required for their application in neuroscience, the interaction between graphene-based materials and various cells in the central and peripheral nervous systems, and their potential clinical applications in recording electrodes, drug delivery, treatment, and as nerve scaffolds for neurological diseases. Finally, we offer insights into the prospects and limitations to aid graphene development in neuroscience research and nanotherapeutics that can be used clinically.

Activatable Graphene Quantum-Dot-Based Nanotransformers for Long-Period Tumor Imaging and Repeated Photodynamic Therapy

Photodynamic therapy (PDT) is considered as an emerging therapeutic modality against cancer with high spatiotemporal selectivity because the utilized photosensitizers (PSs) are only active and toxic upon light irradiation. To maximize its effectiveness, PDT is usually applied repetitively for ablating various tumors. However, the total overdose of PSs from repeated administrations causes severe side effects. Herein, acidity-activated graphene quantum dots-based nanotransformers (GQD NT) are developed as PS vehicles for long-period tumor imaging and repeated PDT. Under the guidance of Arg-Gly-Asp peptide, GQD NT targets to tumor tissues actively, and then loosens and enlarges in tumor acidity, thus promising long tumor retention. Afterwards, GQD NT transforms into small pieces for better penetration in tumor. Upon laser irradiation, GQD NT generates mild hyperthermia that enhances cell membrane permeability and further promotes the PSs uptake. Most intriguingly, the as-prepared GQD NT not only "turns-on" fluorescence/magnetic resonance signals, but also achieves efficient repeated PDT. Notably, the total PSs dose is reduced to 3.5 µmol kg^-1 , which is 10-30 times lower than that of other reported works. Overall, this study exploits a smart vehicle to enhance accumulation, retention, and release of PSs in tumors through programmed deformation, thus overcoming the overdose obstacle in repeated PDT.

Graphene quantum dots enhance the osteogenic differentiation of PDLSCs in the inflammatory microenvironment

BACKGROUND AND OBJECTIVE

Graphene quantum dots (GQDs), a type of carbon-based nanomaterial, have remarkable biological, physical, and chemical properties. This study investigated the biological mechanisms of the proliferation and osteogenic differentiation of human periodontal ligament stem cells (PDLSCs) induced by GQDs in an inflammatory microenvironment.

MATERIALS AND METHODS

PDLSCs were cultured in osteogenic-induced medium with various concentrations of GQDs in standard medium or medium mimicking a proinflammatory environment. The effects of GQDs on the proliferation and osteogenic differentiation activity of PDLSCs were tested by CCK-8 assay, Alizarin Red S staining, and qRT‒PCR. In addition, Wnt/β-catenin signalling pathway-related gene expression was measured by qRT‒PCR.

RESULTS

Compared with the control group, the mRNA expression levels of ALP, RUNX2, and OCN and the number of mineralized nodules were all increased in PDLSCs after treatment with GQDs. Moreover, during the osteogenic differentiation of PDLSCs, the expression levels of LRP6 and β-catenin, which are Wnt/β-catenin signalling pathway-related genes, were upregulated.

CONCLUSION

In the inflammatory microenvironment, GQDs might promote the osteogenic differentiation ability of PDLSCs by activating the Wnt/β-catenin signalling pathway.

Surface Area of Graphene Governs Its Neurotoxicity

Due to their unique physicochemical properties, graphene and its derivatives are widely exploited for biomedical applications. It has been shown that graphene may exert different degrees of toxicity in in vivo or in vitro models when administered via different routes and penetrated through physiological barriers, subsequently being distributed within tissues or located within cells. In this study, in vitro neurotoxicity of graphene with different surface areas (150 and 750 m²/g) was examined on dopaminergic neuron model cells. SH-SY5Y cells were treated with graphene possessing two different surface areas (150 and 750 m²/g) in different concentrations between 400 and 3.125 μg/mL, and the cytotoxic and genotoxic effects were investigated. Both sizes of graphene have shown increased cell viability in decreasing concentrations. Cell damage increased with higher surface area. Lactate dehydrogenase (LDH) results have concluded that the viability loss of the cells is not through membrane damage. Neither of the two graphene types showed damage through lipid peroxidation (MDA) oxidative stress pathway. Glutathione (GSH) values increased within the first 24 and 48 h for both types of graphene. This increase suggests that graphene has an antioxidant effect on the SH-SY5Y model neurons. Comet analysis shows that graphene does not show genotoxicity on either surface area. Although there are many studies on graphene and its derivatives on their use with different cells in the literature, there are conflicting results in these studies, and most of the literature is focused on graphene oxide. Among these studies, no study examining the effect of graphene surface areas on the cell was found. Our study contributes to the literature in terms of examining the cytotoxic and genotoxic behavior of graphene with different surface areas.

Treatment for Myocardial Infarction: In Vivo Evaluation of Curcumin-Loaded PEGylated-GQD Nanoparticles

ABSTRACT

Curcumin (Cur) has been suggested as a complementary treatment for cardiovascular diseases. Its efficiency, however, is modest due to poor biocompatibility. This study examined the effects of curcumin loaded on polyethylene glycol-graphene quantum dots (Cur-PEG-GQDs) on hemodynamic and cardiac function in rats with myocardial infarction (MI). The study groups included control, MI, MI+Cur-3, MI + Cur-7, MI + Cur-15, MI + PEG-GQDs-5, MI + PEG-GQDs-10, MI + Cur-PEG-GQDs-5, and MI + Cur-PEG-GQDs-10. MI was established by left anterior descending artery ligation. Two weeks after intraperitoneal administration of vehicle, Cur, PEG-GQDs, and Cur-PEG-GQDs, blood pressure and heart contractility indices were measured. Triphenyl tetrazolium chloride, colorimetry, and clinical laboratory methods were used to measure the infarct size, the oxidant and antioxidant content, and the kidney and liver function parameters, respectively. In the MI animals, Cur-7, PEG-GQDs-10, Cur-PEG-GQDs-5, and Cur-PEG-GQDs-10 recovered systolic blood pressure, diastolic blood pressure, left ventricular systolic pressure, and ±dp/dt max disturbances and reduced myocardial infarct size, fibrosis, and left ventricular end-diastolic pressure. Curcumin lowered antioxidant markers and elevated 1 oxidant marker in the heart in a dose-dependent manner. Although Cur-PEG-GQDs-5 and Cur-PEG-GQDs-10 reduced curcumin's oxidative stress effects, the superoxide dismutase, glutathione peroxidase, and total antioxidant capacity levels were significantly lower in Cur-PEG-GQDs-5 and Cur-PEG-GQDs-10 groups compared with the MI group. Malondialdehyde levels were lower in Cur-PEG-GQDs-5 and -10 groups compared with the Cur-3, Cur-7, and Cur-15 groups. The glutathione/glutathione disulfide ratio improved in the groups treated by Cur-7, PEG-GQDs-10, Cur-PEG-GQDs-5, and Cur-PEG-GQDs-10. The findings indicated that Cur-PEG-GQDs mitigated MI-induced cardiac dysfunction. However, because of the increase in oxidative stress in the heart, nonclassic mechanisms may be involved in the beneficial effect of Cur-PEG-GQDs on MI-induced cardiac dysfunction.

Smart Nanomaterials in Cancer Theranostics: Challenges and Opportunities

Cancer is ranked as the second leading cause of death globally. Traditional cancer therapies including chemotherapy are flawed, with off-target and on-target toxicities on the normal cells, requiring newer strategies to improve cell selective targeting. The application of nanomaterial has been extensively studied and explored as chemical biology tools in cancer theranostics. It shows greater applications toward stability, biocompatibility, and increased cell permeability, resulting in precise targeting, and mitigating the shortcomings of traditional cancer therapies. The nanoplatform offers an exciting opportunity to gain targeting strategies and multifunctionality. The advent of nanotechnology, in particular the development of smart nanomaterials, has transformed cancer diagnosis and treatment. The large surface area of nanoparticles is enough to encapsulate many molecules and the ability to functionalize with various biosubstrates such as DNA, RNA, aptamers, and antibodies, which helps in theranostic action. Comparatively, biologically derived nanomaterials perceive advantages over the nanomaterials produced by conventional methods in terms of economy, ease of production, and reduced toxicity. The present review summarizes various techniques in cancer theranostics and emphasizes the applications of smart nanomaterials (such as organic nanoparticles (NPs), inorganic NPs, and carbon-based NPs). We also critically discussed the advantages and challenges impeding their translation in cancer treatment and diagnostic applications. This review concludes that the use of smart nanomaterials could significantly improve cancer theranostics and will facilitate new dimensions for tumor detection and therapy.

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.

Planted Graphene Quantum Dots for Targeted, Enhanced Tumor Imaging and Long-Term Visualization of Local Pharmacokinetics

While photoluminescent graphene quantum dots (GQDs) have long been considered very suitable for bioimaging owing to their protein-like size, superhigh photostability and in vivo long-term biosafety, their unique and crucial bioimaging applications in vivo remain unreachable. Herein, planted GQDs are presented as an excellent tool for in vivo fluorescent, sustainable and multimodality tumor bioimaging in various scenarios. The GQDs are in situ planted in the poly(ethylene glycol) (PEG) layer of PEGylated nanoparticles via a bottom-up molecular approach to obtain the NPs-GQDs-PEG nanocomposite. The planted GQDs show more than four times prolonged blood circulation and 7-8 times increased tumor accumulation than typical GQDs in vivo. After accessible specificity modification, the multifunctional NPs-GQDs-PEG provides targeted, multimodal molecular imaging for various tumor models in vitro or in vivo. Moreover, the highly photostable GQDs enable long-term, real-time visualization of the local pharmacokinetics of NPs in vivo. Planting GQDs in PEGylated nanomedicine offers a new strategy for broad in vivo biomedical applications of GQDs.

Engineered Graphene Quantum Dots as a Magnetic Resonance Signal Amplifier for Biomedical Imaging

The application of magnetic resonance imaging (MRI) nano-contrast agents (nano-CAs) has increasingly attracted scholarly interest owing to their size, surface chemistry, and stability. Herein, a novel T1 nano-CA (Gd(DTPA)-GQDs) was successfully prepared through the functionalization of graphene quantum dots with poly(ethylene glycol) bis(amine) and their subsequent incorporation into Gd-DTPA. Remarkably, the resultant as-prepared nano-CA displayed an exceptionally high longitudinal proton relaxivity (r₁) of 10.90 mM^-1 s^-1 (R² = 0.998), which was significantly higher than that of commercial Gd-DTPA (4.18 mM^-1 s^-1, R² = 0.996). The cytotoxicity studies indicated that the Gd(DTPA)-GQDs were not cytotoxic by themselves. The results of the hemolysis assay and the in vivo safety evaluation demonstrate the outstanding biocompatibility of Gd(DTPA)-GQDs. The in vivo MRI study provides evidence that Gd(DTPA)-GQDs exhibit exceptional performance as T1-CAs. This research constitutes a viable approach for the development of multiple potential nano-CAs with high-performance MR imaging capabilities.

Graphene quantum dots: A comprehensive overview

Because of their prospective applications and exceptional features, graphene quantum dots (GQDs) have gotten a lot of recognition as a new class of fluorescent carbon materials. One of the carbon family’s newest superstars is the GQD. Due to its exceptional optoelectrical qualities, it has sparked a lot of curiosity since its debut in 2008. Two of the most important traits are a band gap that is not zero, biocompatibility, and highly changeable characteristics. GQDs have several important characteristics. GQDs have shown potential in a variety of fields, for instance, catalysis, sensing, energy devices, drug delivery, bioimaging, photothermal, and photodynamic therapy. Because this area constantly evolves, it is vital to recognize emerging GQD concerns in the current breakthroughs, primarily since some specific uses and developments in the case of GQDs synthesis have not been thoroughly investigated through previous studies. The current results in the properties, synthesis, as well as benefits of GQDs are discussed in this review study. As per the findings of this research, the GQD’s future investigation is boundless, mainly if the approaching investigation focuses on purifying simplicity and environmentally friendly synthesis, as well as boosting photoluminescence quantum output and manufacturing output of GQDs.

Green Synthesis of Blue-Emitting Graphene Oxide Quantum Dots for In Vitro CT26 and In Vivo Zebrafish Nano-Imaging as Diagnostic Probes

Graphene oxide quantum dots (GOQDs) are prepared using black carbon as a feedstock and H₂O₂ as a green oxidizing agent in a straightforward and environmentally friendly manner. The process adopted microwave energy and only took two minutes. The GOQDs are 20 nm in size and have stable blue fluorescence at 440 nm. The chemical characteristics and QD morphology were confirmed by thorough analysis using scanning electron microscope (SEM), transmission electron microscope (TEM), atomic force microscope (AFM), Fourier transmission infra-red (FT-IR), and X-ray photoelectron spectroscopy (XPS). The biocompatibility test was used to evaluate the toxicity of GOQDs in CT26 cells in vitro and the IC₅₀ was found to be 200 µg/mL with excellent survival rates. Additional in vivo toxicity assessment in the developing zebrafish (Danio rerio) embryo model found no observed abnormalities even at a high concentration of 400 μg/mL after 96 h post fertilization. The GOQDs luminescence was also tested both in vitro and in vivo. They showed excellent internal distribution in the cytoplasm, cell nucleus, and throughout the zebrafish body. As a result, the prepared GOQDs are expected to be simple and inexpensive materials for nano-imaging and diagnostic probes in nanomedicine.

In vitro and in vivo toxicological evaluation of carbon quantum dots originating from Spinacia oleracea

Food-derived carbon quantum dots (CQDs) can relatively easily be synthesized and chemically manipulated for a broad spectrum of biomedical applications. However, their toxicity may hinder their actual use. Here, Spinacia oleracea-derived CQDs i.e., CQD-1 and CQD-2, were synthesized by means of different shredding methods and followed by a microwave-assisted hydrothermal approach. Subsequently, these CQDs were analyzed in vitro and in an in vivo mice model to test their biocompatibility and potential use as bioimaging agents and for activation of osteogenic differentiation. When comparing CQD-1 and CQD-2, it was found that CQD-1 exhibited 7.6 times higher photoluminescent (PL) emission intensity around 411 nm compared to CQD-2. Besides, it was found that the size distribution of CQD-1 was 2.05 ± 0.08 nm, compared with 2.14 ± 0.04 nm for CQD-2. Upon exposure to human bone marrow-derived mesenchymal stem cells (hBMSCs) in vitro, CQD-1 was endocytosed into the cytoplasm and significantly increased the differentiation of hBMSCs up to 10 μg mL^-1 after 7 and 14 days. Apparently, the presence of relatively low doses of CQD-1 showed virtually no toxic or histological effects in the major organs in vivo. In contrast, high doses of CQD-1 (1 mg mL^-1) caused cell death in vitro ranging from 35% on day 1 to 80% on day 3 post-exposure, and activated the apoptotic machinery and increased lymphocyte aggregates in the liver tissue. In conclusion, S. oleracea-derived CQDs have the potential for biomedical applications in bioimaging and activation of stem cells osteogenic differentiation. Therefore, it is postulated that CQD-1 from S. oleracea remains potential prospective material at appropriate doses and specifications.

Multifunctional 3D-printed bioceramic scaffolds: Recent strategies for osteosarcoma treatment

Osteosarcoma is the most prevalent bone malignant tumor in children and teenagers. The bone defect, recurrence, and metastasis after surgery severely affect the life quality of patients. Clinically, bone grafts are implanted. Primary bioceramic scaffolds show a monomodal osteogenesis function. With the advances in three-dimensional printing technology and materials science, while maintaining the osteogenesis ability, scaffolds become more patient-specific and obtain additional anti-tumor ability with functional agents being loaded. Anti-tumor therapies include photothermal, magnetothermal, old and novel chemo-, gas, and photodynamic therapy. These strategies kill tumors through novel mechanisms to treat refractory osteosarcoma due to drug resistance, and some have shown the potential to reverse drug resistance and inhibit metastasis. Therefore, multifunctional three-dimensional printed bioceramic scaffolds hold excellent promise for osteosarcoma treatments. To better understand, we review the background of osteosarcoma, primary 3D-printed bioceramic scaffolds, and different therapies and have a prospect for the future.

Applications of Carbon Dots for the Treatment of Alzheimer's Disease

There are currently approximately 50 million victims of Alzheimer's disease (AD) worldwide. The exact cause of the disease is unknown at this time, but amyloid plaques and neurofibrillary tangles in the brain are hallmarks of the disease. Current drug treatments for AD may slow the progression of the disease and improve the quality of life of patients, but they are often only minimally effective and are not cures. A major obstacle to developing and delivering more effective drug therapies is the presence of the blood-brain barrier (BBB), which prevents many compounds with therapeutic potential from reaching the central nervous system. Nanotechnology may provide a solution to this problem. Among the medical nanomaterials currently being studied, carbon dots (CDs) have attracted widespread attention because of their ability to cross the BBB, non-toxicity, and potential for drug/gene delivery.

Progress and challenges of graphene and its congeners for biomedical applications

Nanomaterials by virtue of their small size and enhanced surface area, present unique physicochemical properties that enjoy widespread applications in bioengineering, biomedicine, biotechnology, disease diagnosis, and therapy. In recent years, graphene and its derivatives have attracted a great deal of attention in various applications, including photovoltaics, electronics, energy storage, catalysis, sensing, and biotechnology owing to their exceptional structural, optical, thermal, mechanical, and electrical. Graphene is a two-dimensional sheet of sp2 hybridized carbon atoms of atomic thickness, which are arranged in a honeycomb crystal lattice structure. Graphene derivatives are graphene oxide (GO) and reduced graphene oxide (rGO), which are highly oxidized and less oxidized forms of graphene, respectively. Another form of graphene is graphene quantum dots (GQDs), having a size of less than 20 nm. Contemporary graphene research focuses on using graphene nanomaterials for biomedical purposes as they have a large surface area for loading biomolecules and medicine and offer the potential for the conjugation of fluorescent dyes or quantum dots for bioimaging. The present review begins with the synthesis, purification, structure, and properties of graphene nanomaterials. Then, we focussed on the biomedical application of graphene nanomaterials with special emphasis on drug delivery, bioimaging, biosensing, tissue engineering, gene delivery, and chemotherapy. The implications of graphene nanomaterials on human health and the environment have also been summarized due to their exposure to their biomedical applications. This review is anticipated to offer useful existing understanding and inspire new concepts to advance secure and effective graphene nanomaterials-based biomedical devices.

One-pot synthesis of robust dendritic sulfur quantum dots for two-photon fluorescence imaging and "off-on" detection of hydroxyl radicals and ascorbic acid

The straightforward preparation of fluorescent sulfur quantum dots (SQDs) with good photostability and biocompatibility and multifunction remains a challenge. Herein, a simple method to improve the performance of SQDs is reported, that is, using hyperbranched polyglycerol (HPG) as a ligand to direct the synthesis of dendritic HPG-SQD nanocomposites from cheap elemental sulfur. Thanks to the protection of HPG, the HPG-SQDs show much better biocompatibility and photostability as compared with the widely reported polyethylene glycol (PEG) ligand-capped SQDs (PEG-SQDs). In addition, the HPG-SQDs also present excellent aqueous solubility, stable fluorescence against environmental variation, good cell uptake capability, and strong single- and two-photon fluorescence. Moreover, the HPG-SQDs display sensitive and selective fluorescence "off-on" behavior to hydroxyl radicals (˙OH) and ascorbic acid (AA), respectively, and thereby hold potential as a fluorescent switch to detect ˙OH and AA. For the first time, the utilization of two-photon fluorescence of HPG-SQDs to monitor ˙OH and AA in cells is demonstrated in this study.

Quantum dots: The cutting-edge nanotheranostics in brain cancer management

Quantum dots (QDs) are semiconductor nanocrystals possessing unique optoelectrical properties in that they can emit light energy of specific tunable wavelengths when excited by photons. They are gaining attention nowadays owing to their all-around ability to allow high-quality bio-imaging along with targeted drug delivery. The most lethal central nervous system (CNS) disorders are brain cancers or malignant brain tumors. CNS is guarded by the blood-brain barrier which poses a selective blockade toward drug delivery into the brain. QDs have displayed strong potential to deliver therapeutic agents into the brain successfully. Their bio-imaging capability due to photoluminescence and specific targeting ability through the attachment of ligand biomolecules make them preferable clinical tools for coming times. Biocompatible QDs are emerging as nanotheranostic tools to identify/diagnose and selectively kill cancer cells. The current review focuses on QDs and associated nanoformulations as potential futuristic clinical aids in the continuous battle against brain cancer.

3D-Printing Graphene Scaffolds for Bone Tissue Engineering

Graphene-based materials have recently gained attention for regenerating various tissue defects including bone, nerve, cartilage, and muscle. Even though the potential of graphene-based biomaterials has been realized in tissue engineering, there are significantly many more studies reporting in vitro and in vivo data in bone tissue engineering. Graphene constructs have mainly been studied as two-dimensional (2D) substrates when biological organs are within a three-dimensional (3D) environment. Therefore, developing 3D graphene scaffolds is the next clinical standard, yet most have been fabricated as foams which limit control of consistent morphology and porosity. To overcome this issue, 3D-printing technology is revolutionizing tissue engineering, due to its speed, accuracy, reproducibility, and overall ability to personalize treatment whereby scaffolds are printed to the exact dimensions of a tissue defect. Even though various 3D-printing techniques are available, practical applications of 3D-printed graphene scaffolds are still limited. This can be attributed to variations associated with fabrication of graphene derivatives, leading to variations in cell response. This review summarizes selected works describing the different fabrication techniques for 3D scaffolds, the novelty of graphene materials, and the use of 3D-printed scaffolds of graphene-based nanoparticles for bone tissue engineering.

A Review on Graphene Quantum Dots for Electrochemical Detection of Emerging Pollutants

Graphene quantum dots which are known as zero-dimensional materials are gaining increasing attention from researchers all over the world. This is predicated upon their relatively unique chemiluminescent, fluorescent, electrochemiluminescent, and electronic properties. The precise mechanism of electrochemiluminescence continues to be a subject of debate in the research world, and this is important in identifying synthetic pathways for graphene quantum dots. Heavy metals and other emerging pollutants are global health and environmental concerns. Several studies have reported the sensitivity and limit of detection of graphene quantum dots up to the nano-, pico-, and femto- levels when used as sensors. This review seeks to bridge information gaps on the reported electrochemiluminescence chemosensors for emerging pollutants using graphene quantum dots under the sub-headings, synthesis, characterization, electrochemiluminescence chemosensor detection, and comparison with other detection methods.

Semiconductor quantum dots for photodynamic therapy: Recent advances

Photodynamic therapy is a promising cancer treatment that induces apoptosis as a result of the interactions between light and a photosensitizing drug. Lately, the emergence of biocompatible nanoparticles has revolutionized the prospects of photodynamic therapy (PDT) in clinical trials. Consequently, a lot of research is now being focused on developing non-toxic, biocompatible nanoparticle-based photosensitizers for effective cancer treatments using PDT. In this regard, semiconducting quantum dots have shown encouraging results. Quantum dots are artificial semiconducting nanocrystals with distinct chemical and physical properties. Their optical properties can be fine-tuned by varying their size, which usually ranges from 1 to 10 nm. They present many advantages over conventional photosensitizers, mainly their emission properties can be manipulated within the near IR region as opposed to the visible region by the former. Consequently, low intensity light can be used to penetrate deeper tissues owing to low scattering in the near IR region. Recently, successful reports on imaging and PDT of cancer using carbon (carbon, graphene based) and metallic (Cd based) based quantum dots are promising. This review aims to summarize the development and the status quo of quantum dots for cancer treatment.

Promising Therapeutic Strategies for Colorectal Cancer Treatment Based on Nanomaterials

Colorectal cancer (CRC) is a global health problem responsible for 10% of all cancer incidences and 9.4% of all cancer deaths worldwide. The number of new cases increases per annum, whereas the lack of effective therapies highlights the need for novel therapeutic approaches. Conventional treatment methods, such as surgery, chemotherapy and radiotherapy, are widely applied in oncology practice. Their therapeutic success is little, and therefore, the search for novel technologies is ongoing. Many efforts have focused recently on the development of safe and efficient cancer nanomedicines. Nanoparticles are among them. They are uniquewith their properties on a nanoscale and hold the potential to exploit intrinsic metabolic differences between cancer and healthy cells. This feature allows them to induce high levels of toxicity in cancer cells with little damage to the surrounding healthy tissues. Graphene oxide is a promising 2D material found to play an important role in cancer treatments through several strategies: direct killing and chemosensitization, drug and gene delivery, and phototherapy. Several new treatment approaches based on nanoparticles, particularly graphene oxide, are currently under research in clinical trials, and some have already been approved. Here, we provide an update on the recent advances in nanomaterials-based CRC-targeted therapy, with special attention to graphene oxide nanomaterials. We summarise the epidemiology, carcinogenesis, stages of the CRCs, and current nanomaterials-based therapeutic approaches for its treatment.

Recent advances in carbon-based nanomaterials for combating bacterial biofilm-associated infections

The prevalence of bacterial pathogens among humans has increased rapidly and poses a great threat to health. Two-thirds of bacterial infections are associated with biofilms. Recently, nanomaterials have emerged as anti-biofilm agents due to their enormous potential for combating biofilm-associated infections and infectious disease management. Among these, relatively high biocompatibility and unique physicochemical properties of carbon-based nanomaterials (CBNs) have attracted wide attention. This review presented the current advances in anti-biofilm CBNs. Different kinds of CBNs and their physicochemical characteristics were introduced first. Then, the various potential mechanisms underlying the action of anti-biofilm CBNs during different stages were discussed, including anti-biofouling activity, inhibition of quorum sensing, photothermal/photocatalytic inactivation, oxidative stress, and electrostatic and hydrophobic interactions. In particular, the review focused on the pivotal role played by CBNs as anti-biofilm agents and delivery vehicles. Finally, it described the challenges and outlook for the development of more efficient and bio-safer anti-biofilm CBNs.

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.