A graphene quantum dot-based FRET system for nuclear-targeted and real-time monitoring of drug delivery

Synthesis mechanism from graphene quantum dots to carbon nanotubes by ion-sputtering assisted chemical vapor deposition

We present the first work of the synthesis mechanism from graphene quantum dots (GQDs) to carbon nanotubes (CNTs) by an ion-sputtering assisted chemical vapor deposition. During the annealing process, a Pt thin film deposited by the ion-sputtering was dewetted and agglomerated to form many nanometer-sized particles, leading to Pt nanoparticles (PtNPs) that can act as catalysts for creating carbon allotropes. The shape of the allotropes can be effectively tailored from GQDs to CNTs by controlling three key parameters such as the dose of catalytic ions (D), amounts of carbon source (S), and thermal energy (T). In our work, it was clearly proved that the growth control from GQDs to CNTs has a comparably proportional relationship with D and S, but has a reverse proportional relationship with T. Furthermore, high-purity GQDs without any other by-products and the CNTs with the cap of PtNPs were generated. Their shapes were appropriately controlled, respectively, based on the established synthesis mechanism.

"Smart" drug delivery: A window to future of translational medicine

Chemotherapy is the mainstay of cancer treatment today. Chemotherapeutic drugs are non-selective and can harm both cancer and healthy cells, causing a variety of adverse effects such as lack of specificity, cytotoxicity, short half-life, poor solubility, multidrug resistance, and acquiring cancer stem-like characteristics. There is a paradigm shift in drug delivery systems (DDS) with the advent of smarter ways of targeted cancer treatment. Smart Drug Delivery Systems (SDDSs) are stimuli responsive and can be modified in chemical structure in response to light, pH, redox, magnetic fields, and enzyme degradation can be future of translational medicine. Therefore, SDDSs have the potential to be used as a viable cancer treatment alternative to traditional chemotherapy. This review focuses mostly on stimuli responsive drug delivery, inorganic nanocarriers (Carbon nanotubes, gold nanoparticles, Meso-porous silica nanoparticles, quantum dots etc.), organic nanocarriers (Dendrimers, liposomes, micelles), antibody-drug conjugates (ADC) and small molecule drug conjugates (SMDC) based SDDSs for targeted cancer therapy and strategies of targeted drug delivery systems in cancer cells.

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.

Graphene quantum dots based MnFe2O4@SiO2 magnetic nanostructure as a pH-sensitive fluorescence resonance energy transfer (FRET) system to enhance the anticancer effect of the drug

Among the various methods of targeted drug delivery, magnetic nanoparticles been considered for a long time due to local drug delivery, reduction of side effects, and controlled drug release. In this work, fluorescence resonance energy transfer (FRET) system MnFe₂O₄@SiO₂@ graphene quantum dots /DAU with 49.08 emu^-1 magnetism was prepared as pH-sensitive nanoplatform to enhance the anti-cancer effect of daunorubicin (DAU) drug (in the obtained FRET system, DAU act as acceptor molecule and graphene quantum dots act as donor molecule). The efficiency of the drug loaded on the nanoplatform in vitro is 78%. DAU drug release from nanoplatform at pHs of 7.4 and 5.5 during 48 h is 21% and 60%, respectively. Release sensitive to pH facilitates the application of prepared nanoplatform for DAU delivery. The results of MTT-assay and annexin V-FITC/PI show that MnFe₂O₄@SiO₂@ graphene quantum dots /DAU induces cell apoptosis by inhibiting the growth of more than 95% of MCF-7 cells. Also, according to the results, it was found that MnFe₂O₄@SiO₂@ graphene quantum dots /DAU can inhibit 66.65% cell cycle in the sub-G1 phase. Therefore, due to the anti-cancer activity of MnFe₂O₄@SiO₂@ graphene quantum dots /DAU, this biological nanoscale can be considered a candidate for drug delivery.

Fluorescence Resonance Energy Transfer Measurements in Polymer Science: A Review

Fluorescence resonance energy transfer (FRET) is a non-invasive characterization method for studying molecular structures and dynamics, providing high spatial resolution at nanometer scale. Over the past decades, FRET-based measurements are developed and widely implemented in synthetic polymer systems for understanding and detecting a variety of nanoscale phenomena, enabling significant advances in polymer science. In this review, the basic principles of fluorescence and FRET are briefly discussed. Several representative research areas are highlighted, where FRET spectroscopy and imaging can be employed to reveal polymer morphology and kinetics. These examples include understanding polymer micelle formation and stability, detecting guest molecule release from polymer host, characterizing supramolecular assembly, imaging composite interfaces, and determining polymer chain conformations and their diffusion kinetics. Finally, a perspective on the opportunities of FRET-based measurements is provided for further allowing their greater contributions in this exciting area.

PLGA-graphene quantum dot nanocomposites targeted against αvβ3 integrin receptor for sorafenib delivery in angiogenesis

Angiogenesis is a vital step in many severe diseases such as cancer, diabetic retinopathy, and rheumatoid arthritis. Sorafenib (SFB), a multi-tyrosine kinase inhibitor, has recently been shown to inhibit tumor progression and suppress angiogenesis. Its narrow therapeutic window, however, has limited its clinical application and therapeutic efficacy. Accordingly, in this study, a nanocomposite formulation comprising of graphene quantum dots (GQDs) and poly (D, l-lactide-co-glycolide) (PLGA) nanoparticles was functionalized with an integrin-targeting ligand (RGD peptide) to improve SFB delivery for the treatment of angiogenesis. Physicochemical and biological properties of the targeted nanocomposite were evaluated in terms of chemical structure, morphology, particle size, zeta potential, photoluminescence, and cell toxicity. The loading capacity of the nanocomposite was optimized at different drug-to-PLGA ratios. Drug release behavior was also investigated at 37 °C in pH = 7.4. The SFB-to-PLGA ratio of 1:3 was selected as the optimum condition which resulted in the encapsulation efficiency and encapsulation capacity of 68.93 ± 1.39 and 18.77 ± 0.46, respectively. Photoluminescence properties of GQD in nanocomposite were used to track the delivery system. The results indicated that conjugating targeting ligand could enhance cellular uptake of nanocomposite in cells overexpressing integrin receptors. In vivo anti-angiogenesis activity of targeted nanocomposite was investigated in chick chorioallantoic membrane (CAM). The findings showed that SFB loaded in the targeted nanocomposite reduced VEGF secretion in vitro and its anti-angiogenic effect surpass free SFB. Thanks to its unique therapeutic and bioimaging properties, the developed nanocomposite could be an effective drug delivery system for poorly water-soluble therapeutic agents.

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.

Insights into the Mechanism for Vertical Graphene Growth by Plasma-Enhanced Chemical Vapor Deposition

Vertically oriented graphene (VG) has attracted attention for years, but the growth mechanism is still not fully revealed. The electric field may play a role, but the direct evidence and exactly what role it plays remains unclear. Here, we conduct a systematic study and find that in plasma-enhanced chemical vapor deposition, the VG growth preferably occurs at spots where the local field is stronger, for example, at GaN nanowire tips. On almost round-shaped nanoparticles, instead of being perpendicular to the substrate, the VG grows along the field direction, that is, perpendicular to the particles' local surfaces. Even more convincingly, the sheath field is screened to different degrees, and a direct correlation between the field strength and the VG growth is observed. Numerical calculation suggests that during the growth, the field helps accumulate charges on graphene, which eventually changes the cohesive graphene layers into separate three-dimensional VG flakes. Furthermore, the field helps attract charged precursors to places sticking out from the substrate and makes them even sharper and turn into VG. Finally, we demonstrate that the VG-covered nanoparticles are benign to human blood leukocytes and could be considered for drug delivery. Our research may serve as a starting point for further vertical two-dimensional material growth mechanism studies.

Graphene quantum dots-porphyrins/phthalocyanines multifunctional hybrid systems: from interfacial dialogue to applications

Engineered well-ordered hybrid nanomaterials are at a symbolically pivotal point, just ahead of a long-anticipated human race transformation. Incorporating newer carbon nanomaterials like graphene quantum dots (GQDs) with tetrapyrrolic porphyrins...

Direct and Indirect Genotoxicity of Graphene Family Nanomaterials on DNA-A Review

Graphene family nanomaterials (GFNs), including graphene, graphene oxide (GO), reduced graphene oxide (rGO), and graphene quantum dots (GQDs), have manifold potential applications, leading to the possibility of their release into environments and the exposure to humans and other organisms. However, the genotoxicity of GFNs on DNA remains largely unknown. In this review, we highlight the interactions between DNA and GFNs and summarize the mechanisms of genotoxicity induced by GFNs. Generally, the genotoxicity can be sub-classified into direct genotoxicity and indirect genotoxicity. The direct genotoxicity (e.g., direct physical nucleus and DNA damage) and indirect genotoxicity mechanisms (e.g., physical destruction, oxidative stress, epigenetic toxicity, and DNA replication) of GFNs were summarized in the manuscript, respectively. Moreover, the influences factors, such as physicochemical properties, exposure dose, and time, on the genotoxicity of GFNs are also briefly discussed. Given the important role of genotoxicity in GFNs exposure risk assessment, future research should be conducted on the following: (1) developing reliable testing methods; (2) elucidating the response mechanisms associated with genotoxicity in depth; and (3) enriching the evaluation database regarding the type of GFNs, applied dosages, and exposure times.

Facile Synthesis of N-Doped Graphene Quantum Dots as Novel Transfection Agents for mRNA and pDNA

In the wake of the coronavirus disease 2019 (COVID-19) pandemic, global pharmaceutical companies have developed vaccines for the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Some have adopted lipid nanoparticles (LNPs) or viral vectors to deliver the genes associated with the spike protein of SARS-CoV-2 for vaccination. This strategy of vaccination by delivering genes to express viral proteins has been successfully applied to the mRNA vaccines for COVID-19, and is also applicable to gene therapy. However, conventional transfection agents such as LNPs and viral vectors are not yet sufficient to satisfy the levels of safety, stability, and efficiency required for the clinical applications of gene therapy. In this study, we synthesized N-doped graphene quantum dots (NGQDs) for the transfection of various genes, including messenger ribonucleic acids (mRNAs) and plasmid deoxyribonucleic acids (pDNAs). The positively charged NGQDs successfully formed electrostatic complexes with negatively charged mRNAs and pDNAs, and resulted in the efficient delivery and transfection of the genes into target cells. The transfection efficiency of NGQDs is found to be comparable to that of commercially available LNPs. Considering their outstanding stability even at room temperature as well as their low toxicity, NGQDs are expected to be novel universal gene delivery platforms that can outperform LNPs and viral vectors.

Multicompartment dendrimicelles with binary, ternary and quaternary core composition

Hierarchically built-up multicompartment nanoaggregate systems are of interest for, e.g., novel materials and medicine. Here we present a versatile strategy to generate and unambiguously characterize complex coacervate-core micelles by exploiting four different dendrimeric subcomponents as core-units. The resulting mesoscale structures have a hydrodynamic diameter of 50 nm and a core size of 33 nm, and host about thirty 6th generation polyamidoamine (PAMAM) dendrimers. We have used FRET (efficiency of ∼0.2) between fluorescein and rhodamine moieties immobilized on separate PAMAM dendrimers (G6-F and G6-R, respectively) to prove synchronous encapsulation in the micelle core. Tuning the proximity of the FRET pair molecules either by varying the G6-F : G6-R ratio, or by co-assembling non-functionalized dendrimer (G6-E) in the core, reveals the optimal FRET efficiency to occur at a minimum of 70% loading with G6-F and G6-R. Additional co-encapsulation of 6th generation gold dendrimer-encapsulated nanoparticles (G6-Au) in the micelle core shows a dramatic reduction of the FRET efficiency, which can be restored by chemical etching of the gold nanoparticles from within the micellar core with thiols, leaving the micelle itself intact. This study reveals the controlled co-assembly of up to four different types of subcomponents in one single micellar core and concomitantly shows the wide variety of structures that can be made with a well-defined basic set of subcomponents. It is straightforward to design related strategies, to incorporate inside one micellar core, e.g., even more than 4 different dendrimers, or other classes of (macro)molecules, with different functional groups, other FRET pairs or different encapsulated metal nanoparticles.

Trifunctional Graphene Quantum Dot@LDH Integrated Nanoprobes for Visualization Therapy of Gastric Cancer

Visualization technology has become a trend in tumor therapy in recent years. The superior optical properties of graphene quantum dots (GQDs) make them suitable candidates for tumor diagnosis, but their tumor targeting and drug-carrying capacities are still not ideal for treatment. Sulfur-doped graphene quantum dots (SGQDs) with stable fluorescence are prepared in a previous study. A reliable strategy by associating layered double hydroxides (LDHs) and etoposide (VP16) is designed for precise visualization therapy. Trifunctional LDH@SGQD-VP16 integrated nanoprobes can simultaneously achieve targeted aggregation, fluorescence visualization, and chemotherapy. LDH@SGQD-VP16 can accumulate in the tumor microenvironment, owing to pH-sensitive properties and long-term photostability in vivo, which can provide a basis for cancer targeting, real-time imaging, and effect tracking. The enhanced therapeutic and attenuated side effects of VP16 are demonstrated, and the apoptosis caused by LDH@SGQD-VP16 is ≈2.7 times higher than that of VP16 alone, in HGC-27 cells. This work provides a theoretical and experimental basis for LDH@SGQD-VP16 as a potential multifunctional agent for visualization therapy of gastric cancer.

Dual-Labeled Graphene Quantum Dot-Based Förster Resonance Energy Transfer Nanoprobes for Single-Molecule Localization Microscopy

Single-molecule localization microscopy (SMLM)-based super-resolution imaging techniques (e.g., photoactivated localization microscopy (PALM)/stochastic optical reconstruction microscopy (STORM)) require that the employed optical nanoprobes possess fluorescence intensity fluctuations under certain excitation conditions. Here, we present a dual-labeled graphene quantum dot (GQD)-based Förster resonance energy transfer (FRET) nanoprobe, which is suitable for SMLM imaging. The nanoprobe is constructed by attaching Alexa Fluor 488 (AF488) and Alexa Fluor 568 (AF568) dye molecules onto GQDs. Experimental results confirmed the FRET effect of the nanoprobes. Moreover, under a single 405 nm excitation, the FRET nanoprobe exhibits excellent blinking behavior. SMLM imaging of microtubules in MRC-5 cells is realized. The presented nanoprobe shows great potential in multicolor SMLM-based super-resolution imaging.

Biocompatible nucleus-targeted graphene quantum dots for selective killing of cancer cells via DNA damage

Graphene quantum dots (GQDs) are nano-sized graphene slices. With their small size, lamellar and aromatic-ring structure, GQDs tend to enter into the cell nucleus and interfere with DNA activity. Thus, GQD alone is expected to be an anticancer reagent. Herein, we developed GQDs that suppress the growth of tumor by selectively damaging the DNA of cancer cells. The amine-functionalized GQDs were modified with nucleus targeting TAT peptides (TAT-NGs) and further grafted with cancer-cell-targeting folic acid (FA) modified PEG via disulfide linkage (FAPEG-TNGs). The resulting FAPEG-TNGs exhibited good biocompatibility, nucleus uptake, and cancer cell targeting. They adsorb on DNA via the π-π and electrostatic interactions, which induce the DNA damage, the upregulation of the cell apoptosis related proteins, and the suppression of cancer cell growth, ultimately. This work presents a rational design of GQDs that induce the DNA damage to realize high therapeutic performance, leading to a distinct chemotherapy strategy for targeted tumor therapy.

Multifunctional and stimuli-responsive nanocarriers for targeted therapeutic delivery

INTRODUCTION

Nanocarrier-based delivery systems offer multiple benefits to overcome limitations of the traditional drug dosage forms, such as protection of the drug, enhanced bioavailability, targeted delivery to disease site, etc. Nanocarriers have exhibited tremendous successes in targeted delivery of therapeutics to the desired tissues and cells with improved bioavailability, high drug loading capacity, enhanced intracellular delivery, and better therapeutic effect. A specific design of stimuli-responsive nanocarriers allows for changing their structural and physicochemical properties in response to exogenous and endogenous stimuli. These nanocarriers show a promise in site specific controlled release of therapeutics under certain physiological conditions or external stimuli.

AREAS COVERED

This review highlights recent progresses on the multifunctional and stimuli-sensitive nanocarriers for targeted therapeutic drug delivery applications.

EXPERT OPINION

The progress from single functional to multifunctional nanocarriers has shown tremendous potential for targeted delivery of therapeutics. On our opinion, the future of targeted delivery of drugs, nucleic acids, and other substances belongs to the site-targeted multifunctional and stimuli-based nanoparticles with controlled release. Targeting of nanocarriers to the disease site enhance the efficacy of the treatment by delivering more therapeutics specifically to the affected cells and substantially limiting adverse side effects upon healthy organs, tissues, and cells.

Insights of doxorubicin loaded graphene quantum dots: Synthesis, DFT drug interactions, and cytotoxicity

Carbon nanomaterials (CNMs) such as graphene quantum dots (GQDs), graphene oxide nanosheets (GO), single and multiwalled carbon nanotubes (SWCNTs, MWCNTs) exhibit different drug loading capacities, release rates, and targeting abilities. This explains the reported discrepancy of their associated therapeutic efficiencies when used as drug carrier systems. In this study, for the first time, two different types of GQDs named GQDs1 and GQDs2 were synthesized, fully characterized, loaded with the chemotherapeutic Doxorubicin (DOX) and compared with other CNMs under the same conditions. The effects of shape (spheres, tubes and sheets), size (30-180 nm), and surface charge (-64.9 to -11.85 mv) of the synthesized CNMs on DOX loading and release efficiency as well as cytotoxicity against MCF-7 cells were investigated. Furthermore, the biosafety of the synthesized GQDs was studied both at the in vitro level using human WI-38 cells and at the in vivo level at low and high doses of 5 and 20 mg/Kg using healthy female Wister rats. Results revealed that GO nanosheets showed the highest DOX loading capacity reaching 2.85 mg/mg while GQDs1 exhibited the highest release rate of 78.1%. The in vitro cytotoxicity evaluation indicated that the smallest spherical nanomaterial among the tested CNMs, namely GQDs1 was the most efficient one on delivering DOX into the cells and inhibiting their proliferation. Regarding the biosafety, all CNMs displayed no noticeable cytotoxicity against WI-38, except for GQDs2. Moreover, hematological, biochemical and histological assessment of both kidneys and livers of treated rats assured the high biosafety level. We also present new insights on the first principle calculations investigating the adsorption of DOX on GO and GQDs. The calculations showed that DOX molecules adsorbed almost equally on both nanoforms, however, the flaky nature of our GO monolayers allowed for sandwich-like structures to exist making its loading capacity superior over GQDs. Based on this comprehensive study, GQDs is the most promising type of the tested CNMs to be used in further studies.

Cytotoxicity and Bioimaging Study for NHDF and HeLa Cell Lines by Using Graphene Quantum Pins

Herein, we report the synthesis of an interesting graphene quantum material called "graphene quantum pins (GQPs)". Morphological analysis revealed the interesting pin shape (width: ~10 nm, length: 50-100 nm) and spectral analysis elucidated the surface functional groups, structural features, energy levels, and photoluminescence properties (blue emission under 365 nm). The difference between the GQPs and graphene quantum dos (GQDs) isolated from the same reaction mixture as regards to their morphological, structural, and photoluminescence properties are also discussed along with the suggestion of a growth mechanism. Cytotoxicity and cellular responses including changes in biophysical and biomechanical properties were evaluated for possible biomedical applications of GQPs. The studies demonstrated the biocompatibility of GQPs even at a high concentration of 512 μg/mL. Our results suggest GQPs can be used as a potential bio-imaging agent with desired photoluminescence property and low cytotoxicity.

Clitoria ternatea Mediated Synthesis of Graphene Quantum Dots for the Treatment of Alzheimer's Disease

The main purpose of the present study was to synthesize graphene quantum dots (GQDs)from the flowers of Clitoria ternatea with the help of one-pot microwave-assisted green synthesis for the treatment of Alzheimer's disease. Further, the synthesized graphene quantum dots show a particle size of 10 nm ±1.3, a PDI of 0.354 ± 1.8, and a ζ potential of -46 ± 0.4, indicating the good stability of the quantum dots. With the help of scanning electron microscopy (SEM) and transfer electron microscopy (TEM) examination, the surface microscopic behavior of the synthesized quantum dots was determined. The presence of functional groups in the quantum dots was determined by Fourier-transform infrared spectroscopy (FTIR) study, the chemical state information on the sample was determined with the help of X-ray photoelectron spectroscopy (XPS), and the surface area of the dots was determined with the help of a surface area analyzer. With the help of a radial arm maze and water morris maze assay, the learning and memory capacity of the quantum dots was assessed, and the results show that the ctGQDs significantly decreased the transfer latency to reach the baited arm in 10.37 ± 1.65 s or to the hidden platform in 18.42 ± 0.99 s in 7 days. The synthesized quantum dots show more inhibition of the acetyl cholinesterase enzyme, i.e., 86.32 ± 1.52%, as compared to that of pure donepezil, i.e., 72.46 ± 2.21%. ctGQDs considerably increased the level of glutathione and protein and decreased the level of lipid peroxide and nitric oxide. The histopathological image of ctGQDs shows more preservation of small pyramidal cell and treats the disorganization of the cells. These results suggest that the quantum dots significantly crossed the blood-brain barrier since they were small in size and were effective in reducing Alzheimer-like symptoms in rodents, and thus, it can be concluded that Clitoria ternatea flowers can be used as an adjuvant in the treatment of Alzheimer's.

Sequentially-targeted biomimetic nano drug system for triple-negative breast cancer ablation and lung metastasis inhibition

As a breast cancer subtype with high mortality in women, the efficient treatment of Triple-negative breast cancer (TNBC) is still a challenge due to its unique metastatic mode and poor prognosis. In this study, we developed a biomimetic nanodelivery system (denoted as GTDC@M-R NPs) based on erythrocyte membrane (M)-camouflaged graphene oxide quantum dots (GOQDs, G) for TNBC therapy. The TAT (T) and RGD (R) peptides were used to endow targeting accumulation ability of Gamabufotalin (CS-6, C) and doxorubicin (DOX, D) in tumor tissue. In vitro assay indicated good biocompatibility, prolonged blood circulation time (3-fold longer than GT NPs), and effectively enhanced cell and nucleus targeting capability of this nanosystem. Fluorescence activated cell sorter (FACS) analysis indicated that the combination of DOX and CS-6 induced TNBC cell apoptosis more than 89 % under the ratio of 10:1. In vivo assay indicated that the accumulation of GTDC@M-R NPs in tumor sites increased about 2-fold compared to naked GTDC NPs, which was accompanied by high tumor apoptosis rates through blocking chemotherapy-activated cyclooxygenase-2 (COX-2) and enhancing DOX's anti-tumor activity of chemical drugs (85%). Moreover, comparing with the control, the average number of lung metastatic nodules in tumor-bearing mice reduced 84%, the molecular mechanism of which is related to the down expression of COX-2, matrix metalloproteinase 9 (MMP9) and vascular endothelial growth factor (VEGF). Taken together, our results proved that the developed GTDC@M-R NPs can inhibit the growth and suppress metastasis of TNBC, which broaden our insights into the application of combinational strategy for efficient TNBC therapy. STATEMENT OF SIGNIFICANCE: In this study, we developed a biomimetic nanodelivery system (denoted as GTDC@M-R NPs) based on erythrocyte membrane (M)-camouflaged graphene oxide quantum dots (GOQDs, G) for TNBC therapy. The TAT (T) and RGD (R) peptides were used to endow targeting accumulation ability of Gamabufotalin (CS-6, C) and doxorubicin (DOX, D) in tumor tissue. These GTDC@M-R NPs indicated synergistic chemotherapy against TNBC cells through the precise cell and nuclear targeting, immune escape, and improved DOX sensitivity. A effective inhibition of tumor growth and metastasis was achieved by inhibiting Bcl-2/BAX, COX-2 and VEGF related signal pathways. Our finding suggests that the developed GTDC@M-R NPs present great treating effects in the preclinical models of TNBC, which broaden our insights into the application of combinational strategy for efficient TNBC therapy.

Carbon and graphene quantum dots: a review on syntheses, characterization, biological and sensing applications for neurotransmitter determination

Neuro-transmitters have been considered to be essential biochemical molecules, which monitor physiological and behavioral function in the peripheral and central nervous systems. Thus, it is of high pharmaceutical and biological significance to analyze neuro-transmitters in the biological samples. So far, researchers have devised a lot of techniques for assaying these samples. It has been found that electro-chemical sensors possess features of robustness, selectivity, and sensitivity as well as real-time measurement. Graphene quantum dots (GQDs) and carbon QDs (CQDs) are considered some of the most promising carbon-based nanomaterials at the forefront of this research area. This is due to their characteristics including lower toxicity, higher solubility in various solvents, great electronic features, strong chemical inertness, high specific surface areas, plenty of edge sites for functionalization, and versatility, in addition to their ability to be modified via absorbent surface chemicals and the addition of modifiers or nano-materials. Hence in the present review, the synthesis methods of GQDs and CQDs has been summarized and their characterization methods also been analyzed. The applications of carbon-based QDs (GQDs and CQDs) in biological and sensing areas, such as biological imaging, drug/gene delivery, antibacterial and antioxidant activity, photoluminescence sensors, electrochemiluminescence sensors and electrochemical sensors, have also been discussed. This study then covers sensing features of key neurotransmitters, including dopamine, tyrosine, epinephrine, norepinephrine, serotonin and acetylcholine. Hence, issues and challenges of the GQDs and CQDs were analyzed for their further development.

Carbon and graphene quantum dots for biological and sensing applications of neurotransmitters.

Graphene quantum dot based materials for sensing, bio-imaging and energy storage applications: a review

Graphene quantum dots (GQDs) are an attractive nanomaterial consisting of a monolayer or a few layers of graphene having excellent and unique properties. GQDs are endowed with the properties of both carbon dots (CDs) and graphene. This review addresses applications of GQD based materials in sensing, bioimaging and energy storage. In the first part of the review, different approaches of GQD synthesis such as top-down and bottom-up synthesis methods have been discussed. The prime focus of this review is on green synthesis methods that have also been applied to the synthesis of GQDs. The GQDs have been discussed thoroughly for all the aspects along with their potential applications in sensors, biomedicine, and energy storage systems. In particular, emphasis is given to popular applications such as electrochemical and photoluminescence (PL) sensors, electrochemiluminescence (ECL) sensors, humidity and gas sensors, bioimaging, lithium-ion (Li-ion) batteries, supercapacitors and dye-sensitized solar cells. Finally, the challenges and the future perspectives of GQDs in the aforementioned application fields have been discussed.

Graphene quantum dots (GQDs) are an attractive nanomaterial consisting of a monolayer or a few layers of graphene having excellent and unique properties.

Daunomycin delivery by ultrasmall graphene quantum dots to DNA duplexes: understanding the dynamics by resonance energy transfer

Crystalline graphene quantum dots are shown to carry daunomycin to DNA via π–π stacking with the planar anthracenyl moiety of the drug.

A smart drug-delivery nanosystem based on carboxylated graphene quantum dots for tumor-targeted chemotherapy

Aim: Constructing a new drug-delivery system using carboxylated graphene quantum dots (cGQDs) for tumor chemotherapy in vivo. Materials & methods: A drug-delivery system was synthesized through a crosslink reaction of cGQDs, NH2-poly(ethylene glycol)-NH2 and folic acid. Results: A drug delivery system of folic acid-poly(ethylene glycol)-cGQDs was successfully constructed with ideal entrapment efficiency (97.5%) and drug-loading capacity (40.1%). Cell image indicated that the nanosystem entered into human cervical cancer cells mainly through macropinocytosis-dependent pathway. In vivo experiments showed the outstanding antitumor ability and low systemic toxicity of this nanodrug-delivery system. Conclusion: The newly developed drug-delivery system provides an important alternative for tumor therapy without causing systemic adverse effects.

Boosting Cancer Therapy with Organelle-Targeted Nanomaterials

The ultimate goal of cancer therapy is to eliminate malignant tumors while causing no damage to normal tissues. In the past decades, numerous nanoagents have been employed for cancer treatment because of their unique properties over traditional molecular drugs. However, lack of selectivity and unwanted therapeutic outcomes have severely limited the therapeutic index of traditional nanodrugs. Recently, a series of nanomaterials that can accumulate in specific organelles (nucleus, mitochondrion, endoplasmic reticulum, lysosome, Golgi apparatus) within cancer cells have received increasing interest. These rationally designed nanoagents can either directly destroy the subcellular structures or effectively deliver drugs into the proper targets, which can further activate certain cell death pathways, enabling them to boost the therapeutic efficiency, lower drug dosage, reduce side effects, avoid multidrug resistance, and prevent recurrence. In this Review, the design principles, targeting strategies, therapeutic mechanisms, current challenges, and potential future directions of organelle-targeted nanomaterials will be introduced.

Recent Advances on Graphene Quantum Dots: From Chemistry and Physics to Applications

Graphene quantum dots (GQDs) that are flat 0D nanomaterials have attracted increasing interest because of their exceptional chemicophysical properties and novel applications in energy conversion and storage, electro/photo/chemical catalysis, flexible devices, sensing, display, imaging, and theranostics. The significant advances in the recent years are summarized with comparative and balanced discussion. The differences between GQDs and other nanomaterials, including their nanocarbon cousins, are emphasized, and the unique advantages of GQDs for specific applications are highlighted. The current challenges and outlook of this growing field are also discussed.

Nitrogen-doped carbon dots as fluorescence ON-OFF-ON sensor for parallel detection of copper(ii) and mercury(ii) ions in solutions as well as in filter paper-based microfluidic device

Due to improper garbage disposal and rapid industrialization, concentrations of different metal ions are rising to toxic levels in natural water sources. Development of novel, selective and sensitive sensors for different metal ions is in high demand for rapid detection and remediation. Herein, we report nitrogen-doped carbon dots (NCDs) with high blue fluorescence, synthesized by a new one-step pyrolytic method using urea and ethylenediaminetetraacetic (EDTA) acid as precursors. The NCDs were used for parallel detection of Hg²⁺ and Cu²⁺ ions in aqueous medium through a fluorescence ON-OFF-ON process. The minimum detection limit for Hg²⁺ and Cu²⁺ were 6.2 nM and 2.304 nM, respectively, in aqueous medium, which is close to or below the allowed levels of Hg²⁺ and Cu²⁺ ions, i.e., 6 ppb and 2 ppm, respectively, in drinking water as per World Health Organisation (WHO). Hg²⁺ and Cu²⁺ ions were discriminated with vitamin C (ascorbic acid) and trisodium citrate by a fluorescence turn on process. A filter paper based microfluidic device loaded with NCDs, vitamin C and trisodium citrate was developed using candle wax channels on a filter paper as a proof of principle, projecting NCDs as a promising material for parallel detection of multiple metal ions. The device demonstrated herein is capable of detecting Hg²⁺ and Cu²⁺ ions up to 0.1 μM. This simple, low cost, disposable paper-based device will be very useful for rapid onsite analysis.

A Visible Codelivery Nanovaccine of Antigen and Adjuvant with Self-Carrier for Cancer Immunotherapy

Codelivery nanovaccines of antigens and adjuvants have achieved positive therapy for cancer immunotherapy. The insufficient immunogenicity of these vaccines leads to the difficulty of eliciting robust immune effects for immune clearance due to the inadequate loading efficiency, complex preparation processes, low safety concerns, and weak immune responses. Herein, a visible codelivery nanovaccine of an antigen and adjuvant based on self-cross-linked antigen nanoparticles (ovalbumin nanoparticles (ONPs)) combined with the adjuvant (CpG) for cancer immunotherapy was prepared using antigens themselves as carriers. ONPs not only provide sufficient antigens for continuous simulation of the immune response with high antigen loading efficiency but also serve as natural carriers of CpG. In vitro and in vivo experiments proved that ONPs-CpG can elicit a robust immune response including DC maturity, T cell activation, and IFN-γ production. ONPs-CpG induced strong tumor-specific immunity and exhibited remarkable antitumor immunotherapy effects in vivo using mouse models of lymphoma. Furthermore, to perform the precise vaccine delivery, the dual fluorescent codelivery nanovaccine was monitored in real time in vivo by the visible imaging method. With regard to migration tracking, fluorescence imaging allowed for both high resolution and sensitivity of visible detection based on the fluorescence of ONPs and CpG. The multifunctional nanovaccine could function as a robust platform for cancer immunotherapy and a visible system for antigen-adjuvant tracking.

Carbon-based quantum particles: an electroanalytical and biomedical perspective

Carbon-based quantum particles, especially spherical carbon quantum dots (CQDs) and nanosheets like graphene quantum dots (GQDs), are an emerging class of quantum dots with unique properties owing to their quantum confinement effect.

Transcriptomic response and perturbation of toxicity pathways in zebrafish larvae after exposure to graphene quantum dots (GQDs)

Graphene quantum dots (GQDs) are widely used for biomedical applications. Previously, the low-level toxicity of GQDs in vivo and in vitro has been elucidated, but the underlying molecular mechanisms remained largely unknown. Here, we employed the Illumina high-throughput RNA-sequencing to explore the whole-transcriptome profiling of zebrafish larvae after exposure to GQDs. Comparative transcriptome analysis identified 2116 differentially expressed genes between GQDs exposed groups and control. Functional classification demonstrated that a large proportion of genes involved in acute inflammatory responses and detoxifying process were significantly up-regulated by GQDs. The inferred gene regulatory network suggested that activator protein 1 (AP-1) was the early-response transcription factor in the linkage of a cascade of downstream (pro-) inflammatory signals with the apoptosis signals. Moreover, hierarchical signaling threshold determined the high sensitivity of complement system in zebrafish when exposed to the sublethal dose of GQDs. Further, 35 candidate genes from various signaling pathways were further validated by qPCR after exposure to 25, 50, and 100 μg/mL of GQDs. Taken together, our study provided a valuable insight into the molecular mechanisms of potential bleeding risks and detoxifying processes in response to GQDs exposure, thereby establishing a mechanistic basis for the biosafety evaluation of GQDs.

Antitumor effect of a Pt-loaded nanocomposite based on graphene quantum dots combats hypoxia-induced chemoresistance of oral squamous cell carcinoma

Background

Tumor microenvironment plays an important role in the chemoresistance of oral squamous cell carcinoma (OSCC). Hypoxia in the microenvironment is one of the important factors that contributes to OSCC chemoresistance; therefore overcoming hypoxia-mediated chemoresistance is one of the great challenges in clinical practice.

Methods

In this study, we developed a drug delivery system based on Pt-loaded, polyethylene glycol-modified graphene quantum dots via chemical oxidation and covalent reaction.

Results

Our results show that synthesized polyethylene glycol-graphene quantum dots-Pt (GPt) is about 5 nm in diameter. GPt sensitizes OSCC cells to its treatment in both normoxia and hypoxia conditions. Inductively coupled plasma-mass spectrometry assay shows that GPt enhances Pt accumulation in cells, which leads to a notable increase of S phase cell cycle arrest and apoptosis of OSCC cells in both normoxia and hypoxic conditions. Finally, compared with free cisplatin, GPt exhibits a strong inhibitory effect on the tumor growth with less systemic drug toxicity in an OSCC xenograft mouse tumor model.

Conclusion

Taken together, our results show that GPt demonstrates superiority in combating hypoxia-induced chemoresistance. It might serve as a novel strategy for future microenvironment-targeted cancer therapy.

Nanoparticle cellular uptake by dendritic wedge peptides: achieving single peptide facilitated delivery

Significant efforts are being undertaken to optimize the cargo carrying capacity and especially the cellular delivery efficiency of functionalized nanoparticles for applications in biological research and pharmacological delivery. One approach to increasing nanoparticle surface cargo display capacity is to decrease the number of moieties required for mediating cellular delivery by improving their efficiency. We describe a series of multivalent cell penetrating peptide (CPP) dendrimers that facilitate rapid cellular delivery of prototypical nanoparticle-semiconductor quantum dots (QDs). The modular CPP dendrimers were assembled through an innovative convergent oxime ligation strategy between (Arg₉)_n motifs and a dendritic QD-coordination scaffold. Dendrimeric peptides sequentially incorporate a terminal (His)₆ motif for metal-affinity QD coordination, a Pro₉ spacer, a branching poly-lysine scaffold, and wedged display of (Arg₉)_n binding motifs with n = 1×, 2×, 4×, 8×, 16× multivalency. QD dendrimer display capacity was estimated using structural simulations and QD-(Arg₉)_1-16 conjugates characterized by dynamic light scattering along with surface plasmon resonance-based binding assays to heparan sulfate proteoglycan surfaces. Cellular uptake via endocytosis was confirmed and peptide delivery kinetics investigated as a function of QD-(Arg₉)_1-16 conjugate exposure time and QD assembly ratio where cellular viability assays reflected no overt cytotoxicity. The ability of single dendrimer conjugates to facilitate cellular uptake was confirmed for QD-(Arg₉)_2-16 repeats along with the ability to deliver >850 kDa of protein cargo per QD. Minimizing the number of CPPs required for cellular uptake is critical for expanding nanoparticle cargo carrying capacity and can allow for inclusion of additional sensors, therapeutics and contrast agents on their surface.

Yolk-shell type nanoprobe with excellent fluorescence 'blinking' behavior for optical super resolution imaging

A new yolk-shell type nanoprobe for super-resolution imaging is demonstrated. Using the proposed nanoprobe and single molecule localization based super resolution imaging strategy, intracellular nanoparticle tracking and super-resolution imaging are realized. The localization precision is about 50 nm and single-molecule localization microscopy using the proposed nanoprobe requires only one single excitation laser and no specific imaging buffer.

Technical synthesis and biomedical applications of graphene quantum dots

Graphene quantum dots (GQDs) have generated enormous excitement because of their superiority in chemical inertness, biocompatibility and low toxicity. Due to quantum confinement and edge effects, GQDs have excellent properties, attracting extensive attention from scientists in the fields of chemistry, physics, materials science, biology, and other interdisciplinary sciences. In this review, we aim to present a comprehensive view on the synthesis of GQDs for biological applications. We highlight potential methods like acid oxidation, hydrothermal and solvothermal reactions, microwave-assisted methods, electrochemical oxidation, as well as pyrolysis and carbonization for the successful preparation of GQDs. Meanwhile, four representative types of biomedical application based on GQDs, bioimaging, biosensing, drug delivery, and antimicrobial materials, are introduced and discussed in detail. This work will be very useful for quickly gaining knowledge and experience for synthesizing various GQDs, and developing advanced strategies for creating novel functional GQD-based nanomaterials for further applications in biomedicine, materials science, analytical science, and optical nanodevices.

Development of a Novel Quantum Dots and Graphene Oxide Based FRET Assay for Rapid Detection of invA Gene of Salmonella

A novel, rapid and simple fluorescence resonance energy transfer (FRET) based Salmonella specific gene, invA, detection system was developed, in which quantum dots (QDs) and graphene oxide (GO) worked as fluorescent donor and quencher, respectively. By measuring the fluorescence intensity signal, the Salmonella specific invA gene could be sensitively and specifically detected with a limit of detection (LOD) of ∼4 nM of the invA gene in 20 min. The developed system has the potential to be used for Salmonella detection in food and environmental samples and further developed into a platform for detection of other bacterial pathogens.

Graphene quantum dot-based theranostic agents for active targeting of breast cancer

A novel GQD-complex was designed as a promising theranostic agent for the treatment of HER2-positive breast cancer.

Multifunctional graphene oxide for bioimaging: emphasis on biological research

Graphene oxide (GO) nanomaterials offer a wide range of bioimaging applicability. Almost complete quenching ability of fluorescence by GO and natural interaction of GO with single stranded nucleic acid made GO a useful and intriguing multifunctional nanoplatform both as a biosensor for in vitro microplate diagnostics and as a drug delivery carrier for targeted delivery. GO’s large surface area and strong near infrared absorbance contribute to enhancement of a therapeutic effect with abundant loading of drugs for possible photothermal and photodynamic therapy. Bioimaging capability of GO made it a good theranostic tool, while enabling tracing in vivo pharmacokinetics during concurrent treatment. Fluorescence, either signal on or off, Raman and surface-enhanced Raman scattering (SERs), photoacoustic, and radionuclide imaging modalities can be used for theranostic purposes using GO nanomaterials. In this review, we highlight current applications of GO for bioimaging that are classified into in vitro microplate, in vitro cellular and in vivo bioimaging.

Graphene quantum dots: multifunctional nanoplatforms for anticancer therapy

We review the recent advances in the application of GQDs as innovative nanoplatforms for anticancer therapy and bioimaging.

Thioacetamide-derived nitrogen and sulfur co-doped carbon nanoparticles used for label-free detection of copper(ii) ions and bioimaging applications

Thioacetamide-derived nitrogen and sulfur co-doped carbon nanoparticles as photoluminescent probes for the efficient detection of Cu²⁺ ions.