We present the science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems, targeting an evolution in technology, that might lead to impacts and benefits reaching into most areas of society. This roadmap was developed within the framework of the European Graphene Flagship and outlines the main targets and research areas as best understood at the start of this ambitious project. We provide an overview of the key aspects of graphene and related materials (GRMs), ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries. We also define an extensive list of acronyms in an effort to standardize the nomenclature in this emerging field.

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Science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems

https://cyberleninka.org/article/n/768408.pdf

Mechanical properties of graphene and graphene-based nanocomposites

Chemical functionalization of graphene and its applications

Owing to their unique physical and chemical properties, graphene and its derivatives such as graphene oxide (GO), reduced graphene oxide (RGO) and GO-nanocomposites have attracted tremendous interest in many different fields including biomedicine in recent years. With every atom exposed on its surface, single-layered graphene shows ultra-high surface area available for efficient molecular loading and bioconjugation, and has been widely explored as novel nano-carriers for drug and gene delivery. Utilizing the intrinsic near-infrared (NIR) optical absorbance, in vivo graphene-based photothermal therapy has been realized, achieving excellent anti-tumor therapeutic efficacy in animal experiments. A variety of inorganic nanoparticles can be grown on the surface of nano-graphene, obtaining functional graphene-based nanocomposites with interesting optical and magnetic properties useful for multi-modal imaging and imaging-guided cancer therapy. Moreover, significant efforts have also been devoted to study the behaviors and toxicology of functionalized nano-graphene in animals. It has been uncovered that both surface chemistry and sizes play key roles in controlling the biodistribution, excretion, and toxicity of nano-graphene. Biocompatibly coated nano-graphene with ultra-small sizes can be cleared out from body after systemic administration, without rendering noticeable toxicity to the treated mice. In this review article, we will summarize the latest progress in this rapidly growing field, and discuss future prospects and challenges of using graphene-based materials for theranostic applications.

Nano-graphene in biomedicine: theranostic applications

Graphene has unique mechanical, electronic, and optical properties, which researchers have used to develop novel electronic materials including transparent conductors and ultrafast transistors. Recently, the understanding of various chemical properties of graphene has facilitated its application in high-performance devices that generate and store energy. Graphene is now expanding its territory beyond electronic and chemical applications toward biomedical areas such as precise biosensing through graphene-quenched fluorescence, graphene-enhanced cell differentiation and growth, and graphene-assisted laser desorption/ionization for mass spectrometry. In this Account, we review recent efforts to apply graphene and graphene oxides (GO) to biomedical research and a few different approaches to prepare graphene materials designed for biomedical applications. Because of its excellent aqueous processability, amphiphilicity, surface functionalizability, surface enhanced Raman scattering (SERS), and fluorescence quenching ability, GO chemically exfoliated from oxidized graphite is considered a promising material for biological applications. In addition, the hydrophobicity and flexibility of large-area graphene synthesized by chemical vapor deposition (CVD) allow this material to play an important role in cell growth and differentiation. The lack of acceptable classification standards of graphene derivatives based on chemical and physical properties has hindered the biological application of graphene derivatives. The development of an efficient graphene-based biosensor requires stable biofunctionalization of graphene derivatives under physiological conditions with minimal loss of their unique properties. For the development graphene-based therapeutics, researchers will need to build on the standardization of graphene derivatives and study the biofunctionalization of graphene to clearly understand how cells respond to exposure to graphene derivatives. Although several challenging issues remain, initial promising results in these areas point toward significant potential for graphene derivatives in biomedical research.

Biomedical Applications of Graphene and Graphene Oxide

The covalent functionalization of graphene oxide (GO) with chitosan (CS) is successfully accomplished via a facile amidation process. The CS-grafted GO (GO-CS) sheets consist of about 64 wt.% CS, which imparts them with a good aqueous solubility and biocompatibility. Additionally, the physicochemical properties of GO-CS are studied. As a novel nanocarrier, GO-CS is applied to load a water-insoluble anticancer drug, camptothecin (CPT), via π-π stacking and hydrophobic interactions. It is demonstrated that GO-CS possesses a superior loading capacity for CPT, and the GO-CS-CPT complexes show remarkably high cytotoxicity in HepG2 and HeLa cell lines compared to the pure drug. At the same time, GO-CS is also able to condense plasmid DNA into stable, nanosized complexes, and the resulting GO-CS/pDNA nanoparticles exhibit reasonable transfection efficiency in HeLa cells at certain nitrogen/phosphate ratios. Therefore, the GO-CS nanocarrier is able to load and deliver both anticancer drugs and genes.

Chitosan-functionalized graphene oxide as a nanocarrier for drug and gene delivery.

Covalently functionalized graphene sheets are prepared by grafting a well-defined thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) via click chemistry. The PNIPAM-grafted graphene sheets (PNIPAM-GS) consist of about 50% polymer, which endows the sheets with a good solubility and stability in physiological solutions. The PNIPAM-GS exhibits a hydrophilic to hydrophobic phase transition at 33 °C, which is relatively lower than that of a PNIPAM homopolymer because of the interaction between graphene sheets and grafted PNIPAM. Moreover, through π–π stacking and hydrophobic interaction between PNIPAM-GS and an aromatic drug, the PNIPAM-GS is able to load a water-insoluble anticancer drug, camptothecin (CPT), with a superior loading capacity of 15.6 wt-% (0.185 g CPT per g PNIPAM-GS). The in vitro drug release behavior of the PNIPAM-GS-CPT complex is examined both in water and PBS at 37 °C. More importantly, the PNIPAM-GS does not exhibit a practical toxicity and the PNIPAM-GS-CPT complex shows a high potency of killing cancer cells in vitro. The PNIPAM-GS is demonstrated to be an effective vehicle for anticancer drug delivery.

Water‐Soluble Poly(N‐isopropylacrylamide)–Graphene Sheets Synthesized via Click Chemistry for Drug Delivery

Functionalized carbon nanomaterials as nanocarriers for loading and delivery of a poorly water-soluble anticancer drug: a comparative study

Green fabrication of chitosan films reinforced with parallel aligned graphene oxide

We present a novel approach to the fabrication of advanced polymeric nanocomposites from poly(vinyl alcohol) (PVA) by incorporation of PVA-grafted graphene oxide. In this work, we have synthesized PVA-grafted graphene oxide (PVA-g-GO) for the strong interfacial adhesion of graphene oxide (GO) to the PVA matrix. It was found that the mechanical properties of PVA were greatly improved by incorporating PVA-g-GO. For example, the tensile strength and Young’s modulus of the PVA nanocomposite films containing 1 wt % net GO in the PVA-g-GO significantly increased by 88 and 150%, respectively, as compared to unfilled PVA. The elongation at break was also increased by 22%, whereas the GO/PVA nanocomposite containing 1 wt % pristine GO was decreased by 15%. Therefore, the presence of the PVA-g-GO in the PVA matrix could make the PVA not only stronger but also tougher. The strong interfacial adhesion between PVA-g-GO and the PVA matrix was attributed to the good compatibility between PVA-g-GO and the matrix PVA as w...

Hongqian Bao

Papers

Chitosan-functionalized graphene oxide as a nanocarrier for drug and gene delivery.

Water‐Soluble Poly(N‐isopropylacrylamide)–Graphene Sheets Synthesized via Click Chemistry for Drug Delivery

Functionalized carbon nanomaterials as nanocarriers for loading and delivery of a poorly water-soluble anticancer drug: a comparative study

Green fabrication of chitosan films reinforced with parallel aligned graphene oxide

Poly(vinyl alcohol) nanocomposites filled with poly(vinyl alcohol)-grafted graphene oxide.