Graphene-Based Nanomaterials and Their Applications in Biosensors
- PMID: 30471026
- DOI: 10.1007/978-981-13-0445-3_4
Recently graphene has been drawing tremendous attention mainly due to its potential contributions to applications in biology, information technology and energy. Among these applications graphene-based biosensors have been particularly progressed caused in part by development of diverse derivatives of graphene such as graphene oxides (GOs) and graphene quantum dots (GQDs). In this chapter preparation and functionalization of the graphene and GOQs are described together with their optoelectronic properties. Recent progresses in graphene and GQD-based biosensors are also highlighted with emphasis on immunoassay which utilizes unique interaction between antigen and antibody, and oligonucleotide assay which utilizes hybridization process. Since electrical and optical features are the most prominent characteristics of graphene-based nanomaterials, biosensor systems will be focused on electrochemical and fluorescence-based detection scheme.
Keywords: Biosensor; Graphene; Graphene oxide; Graphene quantum dot; Immunoassay; Oligonucleotide.
Synthesis of fluorinated and nonfluorinated graphene quantum dots through a new top-down strategy for long-time cellular imaging
- 1 Laboratory of Chemical Biology and Division of Biological Inorganic Chemistry, State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022 (P.R. China); University of the Chinese Academy of Science, Beijing, 100039 (P.R. China).
- PMID: 25614445
- DOI: 10.1002/chem.201406345
Herein, a new strategy has been developed through combining a microwave-assisted technique with hydrothermal treatment to reduce graphene waste and improve production yield of graphene quantum dots (GQDs) prepared by top-down methods. By using fluorinated graphene oxide (FGO) as a raw material, fluorinated GQDs and nonfluorinated GQDs can be synthesized. Additionally, in the fluorinated GQDs, the protective shell supplied by fluorine improves the pH stability of photoluminescence and the strong electron-withdrawing group, -F, reduces the π-electron density of the aromatic structure; thus inhibiting reactivity toward singlet oxygen produced during irradiation and improving the photostability. Therefore, the as-prepared fluorinated GQDs with excellent photo- and pH stability are suitable for long-term cellular imaging.
Keywords: fluorescence; fluorine; graphene; imaging agents; quantum dots.
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Microwave assisted one-pot synthesis of graphene quantum dots as highly sensitive fluorescent probes for detection of iron ions and pH value
- PMID: 26838381
- DOI: 10.1016/j.talanta.2015.12.015
Recently, carbon nanomaterials have received considerable attention as fluorescent probes owing to their low toxicity, water solubility and stable photochemical properties. However, the development of graphene quantum dots (GQDs) is still on its early stage. In this work, GQDs were successfully synthesized by one-step microwave assisted pyrolysis of aspartic acid (Asp) and NH4HCO3 mixture. The as-prepared GQDs exhibited strongly blue fluorescence with high quantum yield up to 14%. Strong fluorescence quenching effect of Fe(3+) on GQDs can be used for its high selectivity detection among of general metal ions. The probe exhibited a wide linear response concentration range (0-50 μM) to Fe(3+) and the limit of detection (LOD) was calculated to be 0.26 μM. In addition, GQDs are also sensitive to the pH value in the range from 2 to 12 indicating a great potential as optical pH sensors. More importantly, the GQDs possess lower cellular toxicity and high photostability and can be directly used as fluorescent probes for cell imaging.
Keywords: Bioimaging; Detection of Fe(3+); Fluorescence; Graphene quantum dots; Sensor.
Copyright © 2015 Elsevier B.V. All rights reserved.
Graphene Quantum Dots: Synthesis and Applications
- 1 Department of Biomedical Engineering, University of Bridgeport, Bridgeport, CT, United States.
- 2 Department of Computer Science and Engineering, University of Bridgeport, Bridgeport, CT, United States.
- 3 Department of Biomedical Engineering, University of Bridgeport, Bridgeport, CT, United States; Department of Mechanical Engineering, University of Bridgeport, Bridgeport, CT, United States. Electronic address: email@example.com.
- PMID: 30244796
- DOI: 10.1016/bs.mie.2018.07.002
Graphene and its derivatives having at least one dimension in nanoscale range have attracted tremendous attention in recent years due to their unique electronic, optical, chemical, and mechanical properties. This chapter is about graphene quantum dots (GQDs) that are zero-dimensional graphene derivatives with one to few layers of graphene sheet having size range less than 20nm. This chapter is an overview of synthesis of GQDs by top-down and bottom-up approaches, as well as detailed methods of synthesis of GQDs by acidic oxidation of carbon fibers. Owing to their extremely small size, quantum confinement, edge effect, biocompatibility, low toxicity, photostability as well as water solubility they are excellent candidates for understanding biological systems and cellular processes at the molecular scale. These are also suitable nanomaterials to replace inorganic semiconducting nanoparticles (e.g., CdS, CdSe, ZnS, and Si) which are toxic to biological systems.
Keywords: Biomedical; Edge effect; Graphene; Graphene quantum dots; Inorganic semiconductors; Quantum confinement.
© 2018 Elsevier Inc. All rights reserved.
Applications of Graphene Quantum Dots in Biomedical Sensors
- 1 Technical University of Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany.
Free PMC article
Due to the proliferative cancer rates, cardiovascular diseases, neurodegenerative disorders, autoimmune diseases and a plethora of infections across the globe, it is essential to introduce strategies that can rapidly and specifically detect the ultralow concentrations of relevant biomarkers, pathogens, toxins and pharmaceuticals in biological matrices. Considering these pathophysiologies, various research works have become necessary to fabricate biosensors for their early diagnosis and treatment, using nanomaterials like quantum dots (QDs). These nanomaterials effectively ameliorate the sensor performance with respect to their reproducibility, selectivity as well as sensitivity. In particular, graphene quantum dots (GQDs), which are ideally graphene fragments of nanometer size, constitute discrete features such as acting as attractive fluorophores and excellent electro-catalysts owing to their photo-stability, water-solubility, biocompatibility, non-toxicity and lucrativeness that make them favorable candidates for a wide range of novel biomedical applications. Herein, we reviewed about 300 biomedical studies reported over the last five years which entail the state of art as well as some pioneering ideas with respect to the prominent role of GQDs, especially in the development of optical, electrochemical and photoelectrochemical biosensors. Additionally, we outline the ideal properties of GQDs, their eclectic methods of synthesis, and the general principle behind several biosensing techniques.
Keywords: biomedical applications; biosensors; electrochemical sensors; graphene quantum dots (GQDs); nanomaterials; optical sensors; photoelectrochemical sensors.
Graphene Quantum Dots as Flourishing Nanomaterials for Bio-Imaging, Therapy Development, and Micro-Supercapacitors
- 1 Technical University of Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany.
Free PMC article
Graphene quantum dots (GQDs) are considerably a new member of the carbon family and shine amongst other members, thanks to their superior electrochemical, optical, and structural properties as well as biocompatibility features that enable us to engage them in various bioengineering purposes. Especially, the quantum confinement and edge effects are giving GQDs their tremendous character, while their heteroatom doping attributes enable us to specifically and meritoriously tune their prospective characteristics for innumerable operations. Considering the substantial role offered by GQDs in the area of biomedicine and nanoscience, through this review paper, we primarily focus on their applications in bio-imaging, micro-supercapacitors, as well as in therapy development. The size-dependent aspects, functionalization, and particular utilization of the GQDs are discussed in detail with respect to their distinct nano-bio-technological applications.
Keywords: bio-imaging; graphene quantum dots (GQDs); micro-supercapacitors; nanomaterials; therapy development.
Graphene quantum dots derived from carbon fibers
Juan Peng 1 , Wei Gao, Bipin Kumar Gupta, Zheng Liu, Rebeca Romero-Aburto, Liehui Ge, Li Song, Lawrence B Alemany, Xiaobo Zhan, Guanhui Gao, Sajna Antony Vithayathil, Benny Abraham Kaipparettu, Angel A Marti, Takuya Hayashi, Jun-Jie Zhu, Pulickel M Ajayan Affiliations
- 1 Mechanical Engineering and Materials Science Department, Rice University, Houston, Texas 77005, USA.
- PMID: 22216895
- DOI: 10.1021/nl2038979
Graphene quantum dots (GQDs), which are edge-bound nanometer-size graphene pieces, have fascinating optical and electronic properties. These have been synthesized either by nanolithography or from starting materials such as graphene oxide (GO) by the chemical breakdown of their extended planar structure, both of which are multistep tedious processes. Here, we report that during the acid treatment and chemical exfoliation of traditional pitch-based carbon fibers, that are both cheap and commercially available, the stacked graphitic submicrometer domains of the fibers are easily broken down, leading to the creation of GQDs with different size distribution in scalable amounts. The as-produced GQDs, in the size range of 1-4 nm, show two-dimensional morphology, most of which present zigzag edge structure, and are 1-3 atomic layers thick. The photoluminescence of the GQDs can be tailored through varying the size of the GQDs by changing process parameters. Due to the luminescence stability, nanosecond lifetime, biocompatibility, low toxicity, and high water solubility, these GQDs are demonstrated to be excellent probes for high contrast bioimaging and biosensing applications.
© 2012 American Chemical Society
Structural features regulated photoluminescence intensity and cell internalization of carbon and graphene quantum dots for bioimaging
- PMID: 34579885
- DOI: 10.1016/j.msec.2021.112366
Carbon-based nanostructures with nanometer dimensions have been identified as potential photoluminescence probes for bioimaging due to their biocompatibility, tunable bandgap, and resistance to photobleaching. However, the influence of structural features of carbon quantum dots (CQDs) and graphene quantum dots (GQDs) in bioimaging has not been explored previously. In the present investigation, we elucidated the mechanism of higher PL in GQDs as compared to CQDs as a function of their structural features. TEM and AFM studies revealed that CQDs were spherical (size ~5 nm), while GQDs showed zigzag edges (size ~3 nm). Further, XRD and NMR studies confirmed that CQDs and GQDs show amorphous and crystalline structures with greater sp2 clusters, respectively. While both the QDs demonstrated multicolor fluorescence against variable excitations with similar lifetime, GQDs showed 7-fold higher QY than CQDs. Bioimaging studies in 2D cell culture, 3D tumoroids, and in vivo suggested a greater intensity of fluorescence in GQDs than CQDs. Additionally, rapid cell internalization was observed in GQDs owing to their positive surface potential by heterogeneous atomic (N and S) doping. Moreover, both CQDs and GQDs have demonstrated better time dependent stability for fluorescence properties. Taken together, the proposed mechanism elucidates the greater PL intensity in GQDs due to quantum confinement effect, crystallinity, and surface edge effects and is a better candidate for bioimaging amongst the carbon family.
Keywords: Bioimaging; Carbon quantum dots; Crystallinity; Graphene quantum dots; Photoluminescence; Quantum confinement effect.
Copyright © 2021 Elsevier B.V. All rights reserved.
Glowing graphene quantum dots and carbon dots: properties, syntheses, and biological applications
- 1 School of Chemical and Biomedical Engineering, Nanyang Technological University, 70 Nanyang Drive, 637457, Singapore.
- PMID: 25521301
- DOI: 10.1002/smll.201402648
The emerging graphene quantum dots (GQDs) and carbon dots (C-dots) have gained tremendous attention for their enormous potentials for biomedical applications, owing to their unique and tunable photoluminescence properties, exceptional physicochemical properties, high photostability, biocompatibility, and small size. This article aims to update the latest results in this rapidly evolving field and to provide critical insights to inspire more exciting developments. We comparatively review the properties and synthesis methods of these carbon nanodots and place emphasis on their biological (both fundamental and theranostic) applications.
Keywords: bioimaging; biosensing; carbon dots; graphene quantum dots; theranostics.
© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Carbon Nanodots as Peroxidase Nanozymes for Biosensing
- 1 Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand 247667, India. firstname.lastname@example.org.
- 2 Department of Chemistry, Government Post Graduate College, Champawat, Uttarakhand 262523, India. email@example.com.
Free PMC article
‘Nanozymes’, a term coined by Scrimin, Pasquato, and co-workers to describe nanomaterials with enzyme-like characteristics, represent an exciting and emerging research area in the field of artificial enzymes. Indubitably, the last decade has witnessed substantial advancements in the design of a variety of functional nanoscale materials, including metal oxides and carbon-based nanomaterials, which mimic the structures and functions of naturally occurring enzymes. Among these, carbon nanodots (C-dots) or carbon quantum dots (CQDs) offer huge potential due to their unique properties as compared to natural enzymes and/or classical artificial enzymes. In this mini review, we discuss the peroxidase-like catalytic activities of C-dots and their applications in biosensing. The scope intends to cover not only the C-dots but also graphene quantum dots (GQDs), doped C-dots/GQDs, carbon nitride dots, and C-dots/GQDs nanocomposites. Nevertheless, this mini review is designed to be illustrative, not comprehensive.
Keywords: biosensors; carbon nanodots; carbon nitride dots; carbon quantum dots; enzyme mimetics; graphene quantum dots; peroxidases; photoluminescence; tetramethylbenzidine.
Graphene-Based Nanomaterials as Efficient Peroxidase Mimetic Catalysts for Biosensing Applications: An Overview
Free PMC article
“Artificial enzymes”, a term coined by Breslow for enzyme mimics is an exciting and promising branch of biomimetic chemistry aiming to imitate the general and essential principles of natural enzymes using a variety of alternative materials including heterogeneous catalysts. Peroxidase enzymes represent a large family of oxidoreductases that typically catalyze biological reactions with high substrate affinity and specificity under relatively mild conditions and thus offer a wide range of practical applications in many areas of science. The increasing understanding of general principles as well as intrinsic drawbacks such as low operational stability, high cost, difficulty in purification and storage, and sensitivity of catalytic activity towards atmospheric conditions of peroxidases has triggered a dynamic field in nanotechnology, biochemical, and material science that aims at joining the better of three worlds by combining the concept adapted from nature with the processability of catalytically active graphene-based nanomaterials (G-NMs) as excellent peroxidase mimetic catalysts. This comprehensive review discusses an up-to-date synthesis, kinetics, mechanisms, and biosensing applications of a variety of G-NMs that have been explored as promising catalysts to mimic natural peroxidases.
Keywords: biosensing and diagnostics; enzyme mimetics; graphene; graphene oxide; graphene-based nanomaterials; heterogeneous catalysts; hydrogen peroxide; peroxidases; tetramethylbenzidine.
Deciphering a nanocarbon-based artificial peroxidase: chemical identification of the catalytically active and substrate-binding sites on graphene quantum dots
- 1 Laboratory of Chemical Biology and State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022 (China).
- 2 University of Chinese Academy of Science, Beijing, 100039 (China).
- 3 Laboratory of Chemical Biology and State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022 (China). firstname.lastname@example.org.
- PMID: 25940927
- DOI: 10.1002/anie.201500626
The design and construction of efficient artificial enzymes is highly desirable. Recent studies have demonstrated that a series of carbon nanomaterials possess intrinsic peroxidase activity. Among them, graphene quantum dots (GQDs) have a high enzymatic activity. However, the catalytic mechanism remains unclear. Therefore, in this report, we chose to decipher their peroxidase activity. By selectively deactivating the ketonic carbonyl, carboxylic, or hydroxy groups and investigating the catalytic activities of these GQD derivatives, we obtained evidence that the -C=O groups were the catalytically active sites, whereas the O=C-O- groups acted as substrate-binding sites, and -C-OH groups can inhibit the activity. These results were corroborated by theoretical studies. This work should not only enhance our understanding of nanocarbon-based artificial enzymes, but also facilitate the design and construction of other types of target-specific artificial enzymes.
Keywords: catalysis; graphene quantum dots; nanoparticles; peroxidase activity; reaction mechanisms.
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Graphene-palladium nanowires based electrochemical sensor using ZnFe2O4-graphene quantum dots as an effective peroxidase mimic
- PMID: 25441896
- DOI: 10.1016/j.aca.2014.08.054
We proposed an electrochemical DNA sensor by using peroxidase-like magnetic ZnFe2O4-graphene quantum dots (ZnFe2O4/GQDs) nanohybrid as a mimic enzymatic label. Aminated graphene and Pd nanowires were successively modified on glassy carbon electrode, which improved the electronic transfer rate as well as increased the amount of immobilized capture ssDNA (S1). The nanohybrid ZnFe2O4/GQDs was prepared by assembling the GQDs on the surface of ZnFe2O4 through a photo-Fenton reaction, which was not only used as a mimic enzyme but also as a carrier to label complementary ssDNA (S3). By synergistically integrating highly catalytically activity of nano-sized GQDs and ZnFe2O4, the nanohybrid possessed highly-efficient peroxidase-like catalytic activity which could produce a large current toward the reduction of H2O2 for signal amplification. Thionine was used as an excellent electron mediator. Compared with traditional enzyme labels, the mimic enzyme ZnFe2O4/GQDs exhibited many advantages such as environment friendly and better stability. Under the optimal conditions, the approach provided a wide linear range from 10(-16) to 5×10(-9) M and low detection limit of 6.2×10(-17) M. The remarkable high catalytic capability could allow the nanohybrid to replace conventional peroxidase-based assay systems. The new, robust and convenient assay systems can be widely utilized for the identification of other target molecules.
Keywords: Electrochemical sensor; Mimic enzymes; Palladium nanowires; ZnFe(2)O(4)–graphene quantum dots composites.
Copyright © 2014 Elsevier B.V. All rights reserved.
Recent Advances in the Cancer Bioimaging with Graphene Quantum Dots
- 1 State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, 100029 Beijing, China.
- 2 Hybrid Materials Interfaces Group, Faculty of Production Engineering, University of Bremen, D-28359 Bremen, Germany.
- PMID: 28240167
- DOI: 10.2174/0929867324666170223154145
Fluorescent graphene quantum dots (GQDs) have attracted increasing interest in cancer bioimaging due to their stable photoluminescence (PL), high stability, low cytotoxicity, and good biocompatibility. In this review, we present the synthesis and chemical modification of GQDs firstly, and then introduce their unique physical, chemical, and biological properties like the absorption, PL, and cytotoxicity of GQDs. Finally and most importantly, the recent applications of GQDs in cancer bioimaging are demonstrated in detail, in which we focus on the biofunctionalization of GQDs for specific cancer cell imaging and real-time molecular imaging in live cells. We expect this work would provide valuable guides on the synthesis and modification of GQDs with adjustable properties for various biomedical applications in the future.
Keywords: Graphene quantum dots; bioimaging; cytotoxicity; fluorescent graphene quantum; photoluminescence..
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Chiral Graphene Quantum Dots
Nozomu Suzuki 1 , Yichun Wang, Paolo Elvati, Zhi-Bei Qu, Kyoungwon Kim, Shuang Jiang, Elizabeth Baumeister, Jaewook Lee 2 , Bongjun Yeom, Joong Hwan Bahng, Jaebeom Lee 2 , Angela Violi, Nicholas A Kotov Affiliations
- PMID: 26743467
- DOI: 10.1021/acsnano.5b06369
Chiral nanostructures from metals and semiconductors attract wide interest as components for polarization-enabled optoelectronic devices. Similarly to other fields of nanotechnology, graphene-based materials can greatly enrich physical and chemical phenomena associated with optical and electronic properties of chiral nanostructures and facilitate their applications in biology as well as other areas. Here, we report that covalent attachment of l/d-cysteine moieties to the edges of graphene quantum dots (GQDs) leads to their helical buckling due to chiral interactions at the “crowded” edges. Circular dichroism (CD) spectra of the GQDs revealed bands at ca. 210-220 and 250-265 nm that changed their signs for different chirality of the cysteine edge ligands. The high-energy chiroptical peaks at 210-220 nm correspond to the hybridized molecular orbitals involving the chiral center of amino acids and atoms of graphene edges. Diverse experimental and modeling data, including density functional theory calculations of CD spectra with probabilistic distribution of GQD isomers, indicate that the band at 250-265 nm originates from the three-dimensional twisting of the graphene sheet and can be attributed to the chiral excitonic transitions. The positive and negative low-energy CD bands correspond to the left and right helicity of GQDs, respectively. Exposure of liver HepG2 cells to L/D-GQDs reveals their general biocompatibility and a noticeable difference in the toxicity of the stereoisomers. Molecular dynamics simulations demonstrated that d-GQDs have a stronger tendency to accumulate within the cellular membrane than L-GQDs. Emergence of nanoscale chirality in GQDs decorated with biomolecules is expected to be a general stereochemical phenomenon for flexible sheets of nanomaterials.
Keywords: biological activity; chiral excitons; chirality; circular dichroism; graphene quantum dots.
Graphene quantum dots functionalized β-cyclodextrin and cellulose chiral stationary phases with enhanced enantioseparation performance
- PMID: 31047665
- DOI: 10.1016/j.chroma.2019.04.053
Graphene quantum dots (GQD) functionalized β-cyclodextrin (β-CD) and cellulose silica composites were first prepared and applied in HPLC as chiral stationary phases (CSP) to investigate the effect of GQDs on chiral separation. Through comparing the enantioseparation performance of GQDs functionalized β-CD or cellulose CSPs and unmodified β-CD or cellulose CSPs, we found GQDs enhanced the enantioseparation performance of nature β-CD, β-CD-3,5-dimethylphenylcarbamate derivative and cellulose-3,5-dimethylphenylcarbamate derivative. Molecular modeling was applied to understand and theoretically study the enhancement mechanism of GQDs for enantioseparation. According to molecular simulation results, GQDs provide extra interactions such as hydrophobic, hydrogen bond and π-π interaction when chiral selector interacts with enantiomers, which enhances the chiral recognition ability indirectly. The molecular simulation results showed a good agreement with the experimental results. Our work reveals the enhancement performance of GQDs for chiral separation, it can be expected that GQDs-based chiral composites and chiral GQDs have great prospect in chiral separation and other research fields such as asymmetric synthesis, chiral catalysis, chiral recognition and drug delivery.
Keywords: Cellulose; Cyclodextrin; Enantioseparation; Graphene quantum dots; Molecular modeling.
Copyright © 2019 Elsevier B.V. All rights reserved.
Chiral magnetic hybrid materials constructed from macromolecules and their chiral applications
- PMID: 34231630
- DOI: 10.1039/d1nr01939b
Chirality is a fundamental and ubiquitous feature of living organisms in nature. Magnetic materials, in particular magnetic nanoparticles (MNPs), show some interesting properties such as large specific surface area, easy surface modification, magnetic responsivity and separation ability. Integrating MNPs with chirality in a single material will undoubtedly create a large number of advanced multi-functional materials. Despite the great advancements made in this area, there have been no review articles to summarize the relevant studies. The present work reviews the major progress recently made in constructing chiral magnetic hybrid materials (CMHMs) using macromolecules, which are classified based on the primary chiral macromolecular organic components, namely, biological polymers and synthetic polymers, and the applications of the resulting chiral hybrids in chiral research fields, including asymmetric catalysis, enzymatic resolution, chromatographic separation, enantioselective crystallization and enantioselective adsorption, are also summarized. The challenges and prospects of related research fields are proposed in the last section.