Flash photo stimulation of human neural stem cells on graphene/TiO2 heterojunction for differentiation into neurons.

For the application of human neural stem cells (hNSCs) in neural regeneration and brain repair, it is necessary to stimulate hNSC differentiation towards neurons rather than glia. Due to the unique properties of graphene in stem cell differentiation, here we introduce reduced graphene oxide (rGO)/TiO2 heterojunction film as a biocompatible flash photo stimulator for effective differentiation of hNSCs into neurons. Using the stimulation, the number of cell nuclei on rGO/TiO2 increased by a factor of ~1.5, while on GO/TiO2 and TiO2 it increased only ~48 and 24%, respectively. Moreover, under optimum conditions of flash photo stimulation (10 mW cm(-2) flash intensity and 15.0 mM ascorbic acid in cell culture medium) not only did the number of cell nuclei and neurons differentiated on rGO/TiO2 significantly increase (by factors of ~2.5 and 3.6), but also the number of glial cells decreased (by a factor of ~0.28). This resulted in a ~23-fold increase in the neural to glial cell ratio. Such highly accelerated differentiation was assigned to electron injection from the photoexcited TiO2 into the cells on the rGO through Ti-C and Ti-O-C bonds. The role of ascorbic acid, as a scavenger of the photoexcited holes, in flash photo stimulation was studied at various concentrations and flash intensities.

[1]  O. Akhavan,et al.  Visible light photo-induced antibacterial activity of CNT–doped TiO2 thin films with various CNT contents , 2010 .

[2]  O. Akhavan,et al.  Toward single-DNA electrochemical biosensing by graphene nanowalls. , 2012, ACS nano.

[3]  Xin Wang,et al.  Graphene−Metal Particle Nanocomposites , 2008 .

[4]  Qin Song,et al.  The promotion of neurite sprouting and outgrowth of mouse hippocampal cells in culture by graphene substrates. , 2011, Biomaterials.

[5]  Kai Yang,et al.  Graphene in mice: ultrahigh in vivo tumor uptake and efficient photothermal therapy. , 2010, Nano letters.

[6]  Wanhong Ma,et al.  Preparation of titania/carbon nanotube composites using supercritical ethanol and their photocatalytic activity for phenol degradation under visible light irradiation , 2007 .

[7]  H. Emamy,et al.  Nontoxic concentrations of PEGylated graphene nanoribbons for selective cancer cell imaging and photothermal therapy , 2012 .

[8]  C. Hierold,et al.  Spatially resolved Raman spectroscopy of single- and few-layer graphene. , 2006, Nano letters.

[9]  Omid Akhavan,et al.  Graphene nanomesh promises extremely efficient in vivo photothermal therapy. , 2013, Small.

[10]  H. Dai,et al.  Ultrasmall reduced graphene oxide with high near-infrared absorbance for photothermal therapy. , 2011, Journal of the American Chemical Society.

[11]  O. Akhavan,et al.  Graphene nanogrids for selective and fast osteogenic differentiation of human mesenchymal stem cells , 2013 .

[12]  M. Mahmoudi,et al.  Graphene: promises, facts, opportunities, and challenges in nanomedicine. , 2013, Chemical reviews.

[13]  X. Duan,et al.  Graphene nanomesh , 2010, Nature nanotechnology.

[14]  Elena Cattaneo,et al.  Neural stem cell systems: physiological players or in vitro entities? , 2010, Nature Reviews Neuroscience.

[15]  Wei Zhang,et al.  Photoluminescence in anatase titanium dioxide nanocrystals , 2000 .

[16]  H. Emamy,et al.  Genotoxicity of graphene nanoribbons in human mesenchymal stem cells , 2013 .

[17]  Omid Akhavan,et al.  Escherichia coli bacteria reduce graphene oxide to bactericidal graphene in a self-limiting manner , 2012 .

[18]  J. Robertson,et al.  Interpretation of Raman spectra of disordered and amorphous carbon , 2000 .

[19]  O. Akhavan.  Graphene nanomesh by ZnO nanorod photocatalysts. , 2010, ACS nano.

[20]  Yang Xu,et al.  Cytotoxicity effects of graphene and single-wall carbon nanotubes in neural phaeochromocytoma-derived PC12 cells. , 2010, ACS nano.

[21]  Zhijun Zhang,et al.  Functional graphene oxide as a nanocarrier for controlled loading and targeted delivery of mixed anticancer drugs. , 2010, Small.

[22]  C. Fan,et al.  Protein corona-mediated mitigation of cytotoxicity of graphene oxide. , 2011, ACS nano.

[23]  Omid Akhavan,et al.  The use of a glucose-reduced graphene oxide suspension for photothermal cancer therapy , 2012 .

[24]  G. Pastorin,et al.  Graphene for controlled and accelerated osteogenic differentiation of human mesenchymal stem cells. , 2011, ACS nano.

[25]  Krista L. Niece,et al.  Selective Differentiation of Neural Progenitor Cells by High-Epitope Density Nanofibers , 2004, Science.

[26]  G. Schneider,et al.  Nano neuro knitting: peptide nanofiber scaffold for brain repair and axon regeneration with functional return of vision. , 2006, Proceedings of the National Academy of Sciences of the United States of America.

[27]  W. S. Hummers,et al.  Preparation of Graphitic Oxide , 1958 .

[28]  O. Akhavan,et al.  Lasting antibacterial activities of Ag-TiO2/Ag/a-TiO2 nanocomposite thin film photocatalysts under solar light irradiation. , 2009, Journal of colloid and interface science.

[29]  Zhuang Liu,et al.  Nano-graphene oxide for cellular imaging and drug delivery , 2008, Nano research.

[30]  J. S. Park,et al.  The effect of electrical stimulation on the differentiation of hESCs adhered onto fibronectin-coated gold nanoparticles. , 2009, Biomaterials.

[31]  Omid Akhavan,et al.  Adverse effects of graphene incorporated in TiO2 photocatalyst on minuscule animals under solar light irradiation , 2012 .

[32]  Yanli Chang,et al.  In vitro toxicity evaluation of graphene oxide on A549 cells. , 2011, Toxicology letters.

[33]  Jeffrey A. Jones,et al.  Platelet‐derived growth factor induces proliferation of hyperplastic human prostatic stromal cells , 1993, Journal of cellular biochemistry.

[34]  P. Milani,et al.  Biocompatibility of cluster-assembled nanostructured TiO2 with primary and cancer cells. , 2006, Biomaterials.

[35]  B F Sisken,et al.  Prospects on clinical applications of electrical stimulation for nerve regeneration , 1993, Journal of cellular biochemistry.

[36]  Victor Pikov,et al.  Neuronal loss due to prolonged controlled-current stimulation with chronically implanted microelectrodes in the cat cerebral cortex , 2010, Journal of neural engineering.

[37]  E. Pop,et al.  Heat conduction across monolayer and few-layer graphenes. , 2010, Nano letters.

[38]  W. Jonat,et al.  The Impact of Electrical Charge on the Viability and Physiology of Dendritic Cells , 2005, Scandinavian journal of immunology.

[39]  Andre K. Geim,et al.  The rise of graphene. , 2007, Nature materials.

[40]  J V Forrester,et al.  A small, physiological electric field orients cell division. , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[41]  A. Irajizad,et al.  Melatonin as a powerful bio-antioxidant for reduction of graphene oxide , 2011 .

[42]  J. Yao,et al.  Extended visible light response of binary TiO2-Ti2O3 photocatalyst prepared by a photo-assisted sol-gel method , 2006 .

[43]  Chwee Teck Lim,et al.  Origin of enhanced stem cell growth and differentiation on graphene and graphene oxide. , 2011, ACS nano.

[44]  Zhuang Liu,et al.  PEGylated nanographene oxide for delivery of water-insoluble cancer drugs. , 2008, Journal of the American Chemical Society.

[45]  O. Akhavan,et al.  Increasing the antioxidant activity of green tea polyphenols in the presence of iron for the reduction of graphene oxide , 2012 .

[46]  Gorka Orive,et al.  Biomaterials for promoting brain protection, repair and regeneration , 2009, Nature Reviews Neuroscience.

[47]  Moon Gyu Sung,et al.  Enhanced Differentiation of Human Neural Stem Cells into Neurons on Graphene , 2011, Advanced materials.

[48]  Omid Akhavan,et al.  Photocatalytic Reduction of Graphene Oxide Nanosheets on TiO2 Thin Film for Photoinactivation of Bacteria in Solar Light Irradiation , 2009 .

[49]  Z. Xiong,et al.  Preparation, characterization and antibacterial properties of silver-modified graphene oxide , 2011 .

[50]  H. Markram,et al.  Interfacing Neurons with Carbon Nanotubes: Electrical Signal Transfer and Synaptic Stimulation in Cultured Brain Circuits , 2007, The Journal of Neuroscience.

[51]  Omid Akhavan,et al.  Size-dependent genotoxicity of graphene nanoplatelets in human stem cells. , 2012, Biomaterials.

[52]  O. Akhavan.  The effect of heat treatment on formation of graphene thin films from graphene oxide nanosheets , 2010 .

[53]  S. Mohajerzadeh,et al.  Synthesis of titania/carbon nanotube heterojunction arrays for photoinactivation of E. coli in visible light irradiation , 2009 .

[54]  P. Nelson,et al.  Oscillating field stimulation for complete spinal cord injury in humans: a phase 1 trial. , 2005, Journal of neurosurgery. Spine.

[55]  E. Dekel,et al.  Alternating electric fields arrest cell proliferation in animal tumor models and human brain tumors , 2007, Proceedings of the National Academy of Sciences.

[56]  Omid Akhavan,et al.  Toxicity of graphene and graphene oxide nanowalls against bacteria. , 2010, ACS nano.

[57]  N. Mohanty,et al.  Graphene-based single-bacterium resolution biodevice and DNA transistor: interfacing graphene derivatives with nanoscale and microscale biocomponents. , 2008, Nano letters.

[58]  T. Seo,et al.  A Controllable Self‐Assembly Method for Large‐Scale Synthesis of Graphene Sponges and Free‐Standing Graphene Films , 2010 .

[59]  Charles M. Lieber,et al.  Nanomaterials for Neural Interfaces , 2009 .

[60]  Kai Yang,et al.  The influence of surface chemistry and size of nanoscale graphene oxide on photothermal therapy of cancer using ultra-low laser power. , 2012, Biomaterials.

[61]  Omid Akhavan,et al.  Photodegradation of Graphene Oxide Sheets by TiO2 Nanoparticles after a Photocatalytic Reduction , 2010 .

[62]  G. Wallace,et al.  Processable aqueous dispersions of graphene nanosheets. , 2008, Nature nanotechnology.

[63]  Roberto Car,et al.  Functionalized single graphene sheets derived from splitting graphite oxide. , 2006, The journal of physical chemistry. B.

[64]  B. Botterman,et al.  Carbon nanotube coating improves neuronal recordings. , 2008, Nature nanotechnology.

[65]  F. Edwards,et al.  Differential development of neuronal physiological responsiveness in two human neural stem cell lines , 2007, BMC Neuroscience.

[66]  J. Kong,et al.  Graphene substrates promote adherence of human osteoblasts and mesenchymal stromal cells , 2010 .

[67]  Kai Yang,et al.  Multimodal Imaging Guided Photothermal Therapy using Functionalized Graphene Nanosheets Anchored with Magnetic Nanoparticles , 2012, Advanced materials.

[68]  F. Gage,et al.  Mammalian neural stem cells. , 2000, Science.

[69]  Yuyan Shao,et al.  Graphene Based Electrochemical Sensors and Biosensors: A Review , 2010 .

[70]  R. Car,et al.  Single Sheet Functionalized Graphene by Oxidation and Thermal Expansion of Graphite , 2007 .

[71]  E. Cattaneo,et al.  Neural stem cell systems: physiological players or in vitro entities? , 2010, Nature Reviews Neuroscience.

[72]  O. Akhavan,et al.  Wrapping bacteria by graphene nanosheets for isolation from environment, reactivation by sonication, and inactivation by near-infrared irradiation. , 2011, The journal of physical chemistry. B.

[73]  F. Gage,et al.  Mechanisms and Functional Implications of Adult Neurogenesis , 2008, Cell.

[74]  C. Pan,et al.  TiO2/graphene composite from thermal reaction of graphene oxide and its photocatalytic activity in visible light , 2011 .

[75]  O. Akhavan.  Photocatalytic reduction of graphene oxides hybridized by ZnO nanoparticles in ethanol , 2011 .

[76]  O. Akhavan,et al.  Protein Degradation and RNA Efflux of Viruses Photocatalyzed by Graphene–Tungsten Oxide Composite Under Visible Light Irradiation , 2012 .

[77]  Chunhai Fan,et al.  Graphene-based antibacterial paper. , 2010, ACS nano.

[78]  J. Kysar,et al.  Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene , 2008, Science.

[79]  M. Suh,et al.  The control of neural cell-to-cell interactions through non-contact electrical field stimulation using graphene electrodes. , 2011, Biomaterials.

[80]  Jinbin Liu,et al.  Toward a universal "adhesive nanosheet" for the assembly of multiple nanoparticles based on a protein-induced reduction/decoration of graphene oxide. , 2010, Journal of the American Chemical Society.

[81]  Yueqin Tang,et al.  Growth of non-phototrophic microorganisms using solar energy through mineral photocatalysis , 2012, Nature Communications.

[82]  S. Stankovich,et al.  Synthesis of graphene-based nanosheets via chemical reduction of exfoliated graphite oxide , 2007 .

[83]  L. Yao,et al.  Small applied electric fields guide migration of hippocampal neurons , 2008, Journal of cellular physiology.