SNU Graphene Research Laboratory244 - Do Won...

Eur. J. Nanomed. 2017; aop

Review

Do Won Hwang, Byung Hee Hong and Dong Soo Lee*

Multifunctional graphene oxide for bioimaging: emphasis on biological researchDOI 10.1515/ejnm-2016-0036Received December 11, 2016; accepted February 1, 2017

Abstract: Graphene oxide (GO) nanomaterials offer a wide range of bioimaging applicability. Almost complete quenching ability of fluorescence by GO and natural inter-action 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 thera-nostic 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.

Keywords: bioimaging; cellular bioimaging; graphene oxide; in vitro diagnosis; in vivo theranostics.

IntroductionGraphene, the sp2 carbon structure-based single planar sheet isolated from multiple-layered graphite has received a lot of interest owing to its unique mechanical and elec-trical characteristics including foldable flexibility, con-ductivity, mechanical strength and transparency owing to or despite its single atom thickness (1–5). Its broad surface area (2630 m2/g) and strong elasticity enable graphene to load a variety of drugs or targeting agents while maintain-ing high stability. Investigators have already proposed graphene oxide (GO) for many biomedical applications exploiting its water solubility and biocompatibility (6, 7). The surface functionalization of GO also broadens and facilitates the application (8–10).

Thanks to the substantial advantages already men-tioned, GO has been explored widely for use either for diagnostic or therapeutic tools such as biosensors, as drug delivery carriers, as bioimaging agents and in therapeutics (11–16). The ultrafast electrical conductivity of graphene with its intrinsic electron-rich property has stirred the innovation to make an in vitro kit to detect nucleic acids and growth factor (17, 18). For example, the PPy-NDFLG-doped graphene sensor that is immobilized with the vas-cular endothelial growth factor (VEGF) VEGF aptamer led to the recognition of target molecules at a low concentra-tion (100 fM) (19). The dynamics of hormonal catechola-mine such as dopamine and Ca2 + molecules released from living neuroendocrine cells could be sensed on label-free reduced GO (RGO) field effect transistor (FET) devices (20).

Interestingly, the high near-infrared (NIR) absorb-ance capacity made GO useful as a therapeutic agent. Thioflavin-S (ThS)-immobilized GO specifically targeted amyloid beta aggregation and near infrared (NIR) irradia-tion could dissociate amyloid plaques by generating local heat while minimizing the side effects (21). This finding demonstrated the possibility that GO can also be used for photothermal ablation as a therapeutic for Alzheimer’s disease, which needs to be corroborated very soon.

Bioimaging refers to cutting edge technology of image-guided examination and interpretation of biologi-cal processes at the subcellular or cellular level. In vivo

*Corresponding author: Dong Soo Lee, M.D., Ph.D., Department of Nuclear Medicine, Seoul National University Hospital, 28 Yongon-Dong, Jongno-Gu, Seoul 110-744, Korea, Phone: + 82-2-2072-2501, Fax: + 82-2-2072-7690, E-mail: [email protected]; Seoul National University College of Medicine, Seoul, Korea; and Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul, KoreaDo Won Hwang: Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Korea; and Medical Research Center, Institute of Radiation Medicine, Seoul National University College of Medicine, Seoul, KoreaByung Hee Hong: Department of Chemistry, Seoul National University, Seoul, Korea

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2 Hwang et al.: Graphene oxide for bioimaging

bioimaging allows researchers to observe the in vivo char-acteristics or behavior of target biological materials of interest using markers or reporters to disclose where they are exactly localized and where they have accumulated, and when they are excreted in living subjects. Bioimaging helps provide information such as in vivo targeting effi-cacy or organ toxicity essential for new nanodrug devel-opment for clinical use (22, 23). In this review, we update the recent finding of bioimaging using GO for both in vitro and in vivo applications and focus mainly on in vitro microplate bioimaging, in vitro cellular bioimaging and in vivo bioimaging using graphene and GO.

In vitro microplate bioimaging using GORapid, simple and highly sensitive nanotechnologies are required for molecular diagnostics in clinical practice. Two superior characteristics of graphene, high affinity with ssDNA via π–π interactions and the fluorescence quenching effect in close proximity have made graphene suited for assessment of small amounts of biomolecules with high sensitivity. Nearly complete quenching of fluorescence by graphene minimizes the non-specific background signal. These properties render graphene nanomaterials more accurate and reliable biosensors in the biomedical field. A variety of research where gra-phene has been applied as simple and sensitive biosen-sors has been documented (24–28).

In bioimage-based in vitro sensing, Min’s group devel-oped the simple microplate sensing technique that exam-ined the endonuclease activity using a GO nanosheet (29). Linkage of fluorescence dye-labeled double stranded DNA with single stranded DNA allowed the detection of the endonuclease attacking double-single linkage site in which single stranded DNA attaches itself on the surface of GO, leading to fluorescence quenching by fluorescence resonance energy transfer (FRET). When endonuclease hydrolyzes the phosphodiester bond of the DNA mol-ecule, double-stranded DNA can be removed from GO to recover the fluorescence signal. By observing in vitro fluorescence plate images, they could quantify endonu-clease activity (and concentration) which was blocked specifically by adding the methylation group to the double stranded DNA portion. By the same token, they emphasized that the unique property of GO to bind only single stranded nucleic acid, but not double stranded nucleic acid could also allow the differential detection of hepatitis C virus-related helicase and severe acute

respiratory syndrome coronavirus (SARS CoV)-related helicase (30). This differential detection only needed the introduction of two different fluorescence probes which are quenched and recovered by being unwound only by a certain type of helicase. Because rapid mutagenesis in viruses lowers drug effectiveness with increasing drug resistance, the development of multiple drugs target-ing different virus-specific essential enzymes including helicase simultaneously would be a potential therapeu-tic strategy to boost therapeutic outcome. And, the high-throughput screening of ideal drugs inhibiting helicase using a graphene-based nanosensor could help to select the appropriate helicase inhibitors from small molecule compound libraries. A GO-based helicase assay will be essential for this purpose. Also, Fan’s group developed the interesting NGO-based molecular and cellular sensing platform for molecular diagnosis (31). The NGO-ENSap-tamer sensor which includes a 3D structured G-quadru-ple DNA probe sensitively and reproducibly identified the target proteins based on pattern recognition. The NGO-ENSaptamer sensing platform can differentiate the nine individual proteins including bovine serum albumin and hemoglobin. This NGO sensing technique expanded its capability further toward cellular targeting, clearly dis-criminating the five different human cell lines with high detection sensitivity.

GO was also used to design the potential immuno-biosensor platform for in vitro differential detection of viruses (32). Seo’s group made a signal-off system based on a fluorescent GO-array using an antigen-antibody reaction against a virus of interest which was a rotavirus. GO having a broad fluorescence emission peak (average 547 nm) was spotted onto amine-modified glass and a double antibodies sandwich immunoassay against rotavirus (one antibody labeled with GO array and the other antibody labeled with gold nanoparticles, AuNP, as a fluorescence quencher) was introduced to detect the amount of antigen, i.e. rotavirus. The high selectivity of rotavirus over poliovirus and variola virus was clearly visualized using the in vitro bioimaging technique (Figure 1). However, this method was dependent upon the antigenicity of the virus and the performance of anti-bodies against the virus of interest.

We expect that GO-based new diagnostic methods to examine multiple disease biomarkers using visible or quantitatively biosensing technology (33) could be har-nessed in clinical practice, thanks to the intrinsic advan-tage including low background and selectivity (graphene nanoprobe) and pave the way of using them as a point-of-care method at a bedside or in the clinic as simple and reliable biosensing devices.


Hwang et al.: Graphene oxide for bioimaging 3

In vitro cellular bioimaging using GO

Unlike in vitro microplate bioimaging, in cellular bioim-aging it should be considered that the cellular environ-ment has one critical barrier, the plasma lipid membrane. Generally, a variety of research has focused mainly on surface proteins of the cell membrane as a drug target. In the case of targeting cytoplasmic or intra-nuclear targets, the approach to intracellular molecules involved in dis-ease-triggering signals requires the cellular or nucleus membrane penetration of drugs or their corresponding probes. Many reports demonstrated that nanomaterials coated with positively charged molecules (e.g. polyethyl-eneimine, PEI) were ideal gene or drug delivery carriers into the cells. However, nanomaterials artificially modi-fied with a highly positive charged surface may cause undesirable interactions with negative charged intracel-lular proteins. GO has been recognized as a natural cell penetrating agent, which would be suitable for delivery of drugs into the cells of interest (34). Even though the exact underlying mechanism of cellular uptake of graphene has not yet been elucidated, a report revealed that graphene quantum dot (GQD) was taken up by the cells via caveolae-dependent endocytosis (35, 36). However, another study revealed that FITC-labeled polyethylene glycol (PEG)-GO were taken up by macropinocytosis, and further pathways of microtubule or clathrin-dependent pathways differently in hepatocyte or macrophage cell lines (36). One interest-ing study led by Zhou’s group (37) clearly represented the simulation-based computational method for interaction

of graphene nanosheet with the Escherichia coli mem-brane (Figure 2). The sharpened edge of the graphene nanosheet was docked on the membrane surface in a ver-tical position and the lipid molecule extraction motion in a hydrophobic interaction with the graphene surface was observed, providing insertion time information of the graphene nanosheet in E. coli membranes. These findings elucidating the interaction between graphene nanomate-rial and membrane surface could stimulate the cytotoxic-ity study as the well as antibacterial activity test.

Thus far, we can only say that GO internalization varies according to cell types, GO material types such as their size, charge, or surface composition. Indeed, the dif-ferent cellular localization pattern of QD-tagged rGO in a size dependent manner was clearly visualized by fluores-cence microscopy, showing 38 nm QD-rGO internalized in the cytoplasmic area, compared to 260 nm QD-rGO localized mainly in the cell membrane [(38), Figure 3]. However, the exact mechanism and the factors affecting the internalization of GO are yet to be elucidated.

Taking advantage of the label-free cell penetration ability of GO, several research groups attempted to apply graphene to gene or drug delivery (39–44). Bioimaging can prove the penetration of graphene-mediated delivery. For example, TAT peptide was used for nuclear target-ing to facilitate the transport of drugs into the nucleus, when TAT and PEG-linked GQD was attached with cancer chemo-drugs, confocal laser microscopic imaging and transmission electron microscopy (TEM) showed success-ful intranuclear accumulation of doxorubicin-GQD-PEG/TAT [(45), Figure 4].

Figure 1: Graphene-based immuno-biosensing system for detection of pathogen.Potential immuno-biosensor using graphene-based double antibodies sandwich method was designed for in vitro diagnosis of pathogens. Combination of rotavirus-specific antibody-immobilized GO array and AuNP-conjugated antibody clearly detected rotavirus with the fluorescence signal-off system. [Jung et al. (32), Copyright 2013.]



GO itself is able to make a contrast signal for imaging, that is to say, it emits intrinsic Raman and fluorescence signals. Prominent dispersion peaks (G band: 1580 cm − 1, 2D band: ~ 2700 cm − 1) of single-layered graphene are characteristic as a Raman spectral feature, which reflects the structure of single-layered graphene. Thus, Raman spectroscopy can be used as a primary detection techno-logy to examine graphene and a combination of GO with a chemical metal element such as gold was used to yield the surface enhanced Raman scattering (SERs) effect. Raman signals of GO/AuNP hybrid were significantly enhanced in cellular cytoplasm, compared to those of either GO or AuNP itself (46). Cellular uptake of the GO/AuNP nano-platform was an energy-dependent process of endocytosis which was inhibited at the low temperature of 4°C. Raman cellular imaging provided great spatial resolution at the

single cell level. Surface modified GO with folate could bind specifically to cancer cells and opened the possibil-ity of using GO for cancer targeting. Raman signals in the GO/AuNP/folate hybrids treatment group was prominent in folate receptor-positive HeLa cells, which was blocked by free folate and was not detectable in the folate-negative cell line (47).

As described in the previous section on in vitro micro-plate bioimaging, the high affinity of GO with single stranded nucleic acid and its capability for fluorescence quenching have an effect on the detection of intracellu-lar small RNAs in living cells. Min’s group successfully made microRNA (miRNA) sensing nanoplatform that allows multiplex visualization of different miRNAs in live cells in vitro. The graphene nanosensor was composed of fluorescence dye-labeled peptide nucleic acid (PNA)

Figure 2: Computer-based simulation trajectories showing insertion of graphene nanosheet and the extraction of lipid molecules in the outer membrane (pure POPE) and inner membrane (POPE–POPG) of E. coli.Molecular dynamics simulation showed that graphene nanosheet interacted with the outer or inner E. coli membrane through the swing mode, insertion mode and the lipid extraction mode in order within a few nanoseconds. [Tu et al. (37), Copyright 2013.]



and nanosized GO (48). Uncharged PNA was the key for this nanoplatform as this PNA minimized the unneces-sary charge repulsion from GO, which is readily detached by the complimentary miRNAs in the cytoplasm, which enabled simultaneous sensing of three different miRNAs, consistent with the standard results of flow cytometric and Northern blot analysis. It is worth noting that the sequence difference of miRNAs resulted in the differential signal-on of PNA-bound fluorophore but that only the dif-ference of quantum yield of each fluorophore should be carefully considered for multiplex imaging.

GQDs are small graphene fragments of less than 30 nm size which are often made using Hummer’s method of exfoliation from graphite as a top-down pro-cedure or the pyrolysis method of organic materials such as citric acid as bottom-up procedure (49). GQDs possess different physical and chemical properties according to the heterogeneity in size, defects and oxidation contents (49–51) and owing to its unique photoelectric proper-ties have been recognized as multifunctional nanoplat-form for bioimaging and biosensing (49, 52). GQDs have

played roles as drug delivery carriers for cancer or even neurodegenerative diseases (53–55). Recent studies dem-onstrated that amyloid beta aggregation was inhibited by non-toxic GQD (54, 55). The plausible mechanism was the inhibition of Aβ1-42 peptide assembly by GQD by electrostatic interaction of negative charged GQ with histidine residues carrying a positive net charge [(54), Figure 5]. Although they suggested that GQD passed through the blood-brain barrier (BBB) owing to its small size, there is yet no direct evidence. Bioimage-based tracing using GQD with different imaging modalities is needed to understand the mechanism of GQD action in the brain.

In vivo bioimaging of GOMany efforts to examine in vivo characteristics of GO have been undertaken in order to use GO as a drug delivery carrier with systemic administration for possible future

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Figure 3: Bioimaging of size dependent localization of QD-tagged rGO.(A) The EDC-based conjugation of folic acid (FA) to the QD-rGO. (B) Validation study for interaction of QD-rGO (260 nm) or the QD-rGO (38 nm) with folic acid-expressing MCF-7 cells by flow-cytometry assay. (C–F) Intracellular uptake of 38 nm QD-US-rGO in MCF-7 cells (C) and HeLa cells (E) displaying QD fluorescence (red color), compared to 260 nm QD-S-rGO distributed in cell membrane surface in MCF-7 cells (D) and HeLa cells (F). (G) Effective internalization of QD-US-rGO in many cytoplasmic regions by confocal microscopic images. [Hu et al. (38), Copyright 2012.]



clinical application. Large surface areas and the chemi-cal functionalization of GO made them intriguing but useful candidates as drug delivery carriers. To evaluate the applicability of GO in vivo, investigation of in vivo bioimaging should accompany therapeutic administra-tion of GO, which will disclose their location and excre-tion (56). Even though the exact excretion mechanism to find out which route the inoculated GO is cleared out is not well understood yet, several studies using a variety of imaging modalities have been conducted to elucidate the whereabouts of GO in vivo (22, 57–59). Fluorescence-based GO tracing that is readily available was most popularly

done in small animals. Although the background was a problem, NIR fluorescence dye-GO-PEG could visualize tumors in breast cancer-bearing mice at 48 h after admin-istration when the background activity was cleared (57). As GO absorbed light strongly and was a good contrast agent for photoacoustic imaging, the localization in the tumor was visualized as early as 1 h after administra-tion with GO-PEG-CySCOOH via the intravenous route. Interestingly, this ability of light absorbance in the NIR range was exploited to use GO as a therapeutic agent for photothermal ablation therapy resulting in significantly reduced tumor volume (57).

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Figure 4: Nucleus-targeted delivery of TAT-conjugated GQD for monitoring drug release process.GQD-PEG/TAT crosses the nuclear pore and doxorubicin release is monitored through FRET-based approach. Nuclear localization was seen at 4 h after treatment of GQD-PEG/TAT (B), compared to GQD-PEG treatment (A). [Chen et al. (45), Copyright 2012.]



A small fragment GO as a kind of GQD, known as car-boxylated photoluminescent graphene nanodots (cGdots) that is less than 5 nm in diameter did not require further surface fluorescence dye modification as they had intrin-sic fluorescence (58). Thus, GQD can be used as either an in vitro or an in vivo tracer for cell or drug tracking. However, compared to using visible wavelength or NIR fluorophore for small molecule drug tracing, the GQD-labeled drug of interest may cause the original drug distri-bution to be distorted due to the intrinsic drug size change or structural modification. Nevertheless, the feasibility of traceable GO (e.g. cGdots) that has the ability to generate sufficient heat energy and produce singlet oxygen by laser irradiation has been proposed to be used as appropriate photodynamic and photo thermal dual therapeutic agents.

This designed cGdots showed a theranostic effect, inhibiting growth of tumors by thermal ablation and free-radical oxygen action as well as visualization of tumor tissues in vivo. A recent study (59) adopted a new pho-tosensitizer, sinoporphyrin sodium (DVDMS) and made GO-PEG-DVDMS and could overcome the shortcomings of natural fluorescence quenching. Fluorescence inten-sity of GO-PEG-DVDMS was higher than DVDMS itself due to flexible intramolecular charge transfer between porphyrin rings, which enabled repeated fluorescence imaging and photodynamic treatment in tumors. Cancer specific release of photosensitizer is another option (60) and thus photosensitizer Ce6-bound PNA complemen-tary to miR-21 was loaded onto a dextran-coated reduced GO nanocolloid (Dex-RGON). This Ce6-PNA/Dex-RGON

complex was intratumorally injected into a mouse xeno-graft model and NIR laser irradiation yielded cancer regression (Figure 6).

Because the fluorescence imaging-based approach possesses obvious disadvantages including light absorp-tion and scattering in biological tissues with high auto-fluorescence, other imaging modalities should be developed to overcome these shortcomings. Radionuclide imaging of GO that will be easily applicable to the clinic can provide more accurate biological and clinical infor-mation through quantitative and tomographic imaging with the possibility of depth imaging (22, 61). In vivo targeted delivery using radiolabeled GO was tried earlier (62, 63). Abundant oxygen moieties on the surface of GO can easily be used to label radioisotope chelators such as 1,4,7-triazacyclononane-triacetic acid (NOTA). 125I radio-isotope having a long half-life (60 days) was labeled with PEG-GO to show long-term biodistribution and potential toxicity (62). Interestingly, activity of 125I-PEG-GO admin-istered into the mouse decreased exponentially and then gradually from the liver and spleen for up to 60 days. 125I might have been detached from 125I-PEG-GO but 125I-PEG-GO was stable in plasma up to 15 days and thyroid radi-oactivity did not rise, and the radioactivity would have demonstrated the whereabouts of the GO themselves. The exact mechanism through which route graphene sheets are cleared from the body should be thoroughly investi-gated. Cai’s group reported GO cancer targeting based on using 64Cu-labeled GO by PET imaging (63). 64Cu-labeled GO was also stable in mouse serum for 2 days, and 64Cu-GO

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Figure 5: Schematic illustration of the GQDs inhibiting the aggregation of Aβ1-42 peptides.(A) Time-dependent Aβ1-42 aggregation was measured by the thioflavin T fluorescence with or without GQD3. (B) AFM images showed that the morphology for aggregates of Aβ1-42 fibrils were disaggregated in GQD3-treated group. [Liu et al. (54), Copyright 2015.]



labeled monoclonal antibody for proliferating endothelial marker, TRC105 (64Cu-NOTA-GO-TRC105) specifically tar-geted the 4T1 breast cancer-bearing mouse.

Addition of a dual-PEGylation chain to RGO might increase circulation time, which can eventually result in a greater tumor targeting effect. Multimodal 64Cu-NOTA-RGO-iron oxide nanoparticle (IONP)-1stPEG-2ndPEG was found to show a longer half-life than PEG-RGO-IONP. The tumor-to-liver ratio was also higher. Dr. Cai’s group showed that radi-olabeled GO accumulated passively in the ischemic area using 64Cu-NOTA-RGO-iron oxide nanoparticle (IONP)-PEG. They even revealed a phenomenon of accelerated blood clearance (ABC) after the second injection of 64Cu-RGO-IONP-PEG (64, 65), and this shortening of circulation time was suggested to be due to IgM against PEG. Radionuclide imaging could contribute to understanding the localization of GO and kinetics accurately and quantitatively in small animals. Bioimaging of GO for in vivo tracing might be used

for better understanding the GO kinetics even in humans for elucidating the targeting ability and other organ distri-bution. Furthermore, the combination of GO therapeutics with therapeutic radioisotope such as 131I or 177Lu would play a synergistic role in enhancing the therapeutic effect of GO-based therapeutics in any disease of interest.

Challenges and outlookThe superiority of GO has been acknowledged in a wide range of applications of biosensing bioimaging, and drug delivery. Despite the expected versatile roles of GO in biolog-ical applications, many challenges still remain to be solved. Size controllability is one of the critical issues. The general exfoliation-based top-down method for graphene synthesis may generate irregular size distribution, resulting in larger batch-to-batch variation and difficult quality control in

Quenching of Ce6fluorescence anddeactivation of itsphotosensitizingcapability

miR-21 induced recovery of Ce6 fluorescence andactivation of its photosensitizing capability

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Figure 6: Oncogenic miRNA-responsive Ce6 photosensitizer activation for cancer cell monitoring and photodynamic therapy.Ce6-PNA-loaded Dex-RGON was accumulated into tumors overproducing oncogenic miR-21, and miR-21 dependent detachment of Ce6 pho-tosensitizer from Dex-RGON showed in vivo fluorescence recovery and significant cancer regression in tumor-bearing mouse. [Lee et al. (60), Copyright 2016.]



biosensing for developing in vitro microplate diagnostics. Biocompatibility which is a common big challenge for all of nanomedicine, is also a great challenge for the in vivo application of GO. Among them, GO’s high reactivity and non-specific adsorption of biomolecules on its surface in the bloodstream can cause undesirable responses in vivo. Also, it was reported that intratracheal instillation of 125I-GO induced the pulmonary toxicity accompanied with the accumulation of alveolar macrophage, lung edema and oxi-dative stress leading to acute lung injury (66).

Nevertheless, it was reported that surface modification such as PEGylation did not induce a noticeable long-term toxicity (20 mg/kg, ~ 3 months) by hematological and histo-logical examination (58). The establishment of an optimal administration dose is crucial to minimize side effects and the elucidation of accurate in vivo distribution using quantitative imaging tools and should provide the exact amount of GO taken up by each organ. Standardization of parameters dominating pharmacokinetics and phamaco-dynamics using bioimaging techniques is essential to move the newly introduced GO nanomaterials faster towards the clinic. In vivo bioimaging of GO nanomaterials will help to determine dose, target efficiency and body clearance rate. We expect that thanks to the bioimaging in a broad spec-trum of practicality of handling GO, graphene could have the opportunity to be harnessed in healthcare soon.

Acknowledgments: This research was supported by the Korean Health Technology R&D Project (HI13C-1299-010013) and the Ministry of Health and Welfare, Republic of Korea (HI14C1277).

Conflict of interest statement: The authors state no conflict of interest. All authors have read the journal’s Publication ethics and publication malpractice statement available at the journal’s website and hereby confirm that they comply with all its parts applicable to the present scientific work.

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BionotesDo Won HwangDepartment of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Korea; and Medical Research Center, Institute of Radiation Medicine, Seoul National University College of Medicine, Seoul, Korea

Do Won Hwang received his PhD degree in the “Program in Neuro-science” in 2009 from Seoul National University. He is currently the Brain Korea 21 plus (BK21 plus) Associate Professor in the Depart-ment of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology at Seoul National University. He received an achievement award in the field of radio-nanotechnology in 2015. His research interests focus on the biomedical application using biocompatible multifunctional nano-materials for disease theranostics, stem cell monitoring in regenera-tive medicine and image-guided exosome tracing in vivo.

Byung Hee HongDepartment of Chemistry, Seoul National University, Seoul, Korea

Byung Hee Hong received the PhD degree in Chemistry in 2002 from POSTECH in Korea. After his postdoctoral training was completed his at Columbia University, he joined the Department of Chemistry, Sungkyunkwan University (SKKU) as an Assistant Professor, in 2007. He is now an Associate Professor in the Department of Chemistry at Seoul National University and also a Visiting Associate in the Department of Physics at Harvard University. He pioneered the large-scale synthesis of graphene by CVD, which triggered chemical research studies toward the practical applications of graphene.

Dong Soo LeeDepartment of Nuclear Medicine, Seoul National University Hospital, 28 Yongon-Dong, Jongno-Gu, Seoul 110-744, Korea, Phone: +82-2-2072-2501, Fax: +82-2-2072-7690; Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Korea; and Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul, [email protected]

Dong Soo Lee is a nuclear medicine physician and Professor in the Department of Nuclear Medicine at Seoul National University (SNU) and SNU Hospital since 1990. He is also chairman of Molecular Medicine and Biopharmaceutical Sciences. He is the Director of Bio-MAX/N-Bio which is the Biotechnology Research Institute of SNU. He founded the Korean Society for Nanomedicine and was its first president in 2012 to advance nanomedicine research. His major interest is in radionanomedicine, which is the combination of nuclear medicine and nanomedicine.


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