A simple synthetic route for the preparation of functional nanoscale graphene oxide (NGO), a novel nanocarrier for the loading and targeted delivery of anticancer drugs, is reported. The NGO is functionalized with sulfonic acid groups, which render it stable in physiological solution, followed by covalent binding of folic acid (FA) molecules to the NGO, thus allowing it to specifically target MCF-7 cells, human breast cancer cells with FA receptors. Furthermore, controlled loading of two anticancer drugs, doxorubicin (DOX) and camptothecin (CPT), onto the FA-conjugated NGO (FA-NGO) via pi-pi stacking and hydrophobic interactions is investigated. It is demonstrated that FA-NGO loaded with the two anticancer drugs shows specific targeting to MCF-7 cells, and remarkably high cytotoxicity compared to NGO loaded with either DOX or CPT only. Considering that the combined use of two or more drugs, a widely adopted clinical practice, often displays much better therapeutic efficacy than that of a single drug, the controlled loading and targeted delivery of mixed anticancer drugs using these graphene-based nanocarriers may find widespread application in biomedicine.
Neural stem cell (NSC) based therapy provides a promising approach for neural regeneration. For the success of NSC clinical application, a scaffold is required to provide three-dimensional (3D) cell growth microenvironments and appropriate synergistic cell guidance cues. Here, we report the first utilization of graphene foam, a 3D porous structure, as a novel scaffold for NSCs in vitro. It was found that three-dimensional graphene foams (3D-GFs) can not only support NSC growth, but also keep cell at an active proliferation state with upregulation of Ki67 expression than that of two-dimensional graphene films. Meanwhile, phenotypic analysis indicated that 3D-GFs can enhance the NSC differentiation towards astrocytes and especially neurons. Furthermore, a good electrical coupling of 3D-GFs with differentiated NSCs for efficient electrical stimulation was observed. Our findings implicate 3D-GFs could offer a powerful platform for NSC research, neural tissue engineering and neural prostheses.
Tremendous research efforts have been devoted to fabricating high quality quantum dots (QDs) for applications in biology and medicine. Much of this research was pursued with an ultimate goal of using QDs in clinical applications. However, a great deal of concern has been voiced about the potential hazards of QDs due to their heavy-metal content. Many studies have demonstrated toxicity of various QDs in cell culture studies. However, in a smaller number of studies using small animal models (mice and rats), no abnormal behaviour or tissue damage was noticed over periods of months after the systemic administration of QDs. Nevertheless, the correlation of these results with the potential for negative effects of QD on humans remains unclear. Many urgent questions must be answered before the QDs community moves into the clinical research phase. This review provides an overview of the toxicity assessment of QDs, ranging from cell culture studies to animal models and discusses their findings. Guidelines for using various nonhuman primate models for QD toxicity studies are highlighted. This review article is intended to promote the awareness of current developments of QD applications in biology, the potential toxicity of QDs, and approaches to minimizing toxicity.
a b s t r a c tGraphene has been demonstrated in many biomedical applications and its potentials for neural interfacing. Emerging concerns on graphene, as a biomedical material, are its biocompatibility and how biologically targeted tissue/cells respond to it. Relatively few studies attempted to address the interactions of graphene or its derivatives with the tissues/cells, while very few reports on neural system. In this study, we tried to explore how neurites, one of the key structures for neural functions, are affected by graphene during the development until maturation in a mouse hippocampal culture model. The results reveal that graphene substrates exhibited excellent biocompatibility, as cell viability and morphology were not affected. Meanwhile, neurite numbers and average neurite length on graphene were significantly enhanced during 2e7 days after cell seeding compared with tissue culture polystyrene (TCPS) substrates. Especially on Day 2 of the neural development period, graphene substrates efficiently promoted neurite sprouting and outgrowth to the maximal extent. Additionally, expression of growthassociate protein-43 (GAP-43) was examined in both graphene and TCPS groups. Western blot analysis showed that GAP-43 expression was greatly enhanced in graphene group compared to TCPS group, which might result in the boost of neurite sprouting and outgrowth. This study suggests the potential of graphene as a material for neural interfacing and provides insight into the future biomedical applications of graphene.
Novel sulfur (S) anchoring materials and the corresponding mechanisms for suppressing capacity fading are urgently needed to advance the performance of Li/S batteries. Here, we designed and synthesized a graphene-like oxygenated carbon nitride (OCN) host material that contains tens of micrometer scaled two-dimensional (2D) rippled sheets, micromesopores, and oxygen heteroatoms. N content can reach as high as 20.49 wt %. A sustainable approach of one-step self-supporting solid-state pyrolysis (OSSP) was developed for the low-cost and large-scale production of OCN. The urea in solid sources not only provides self-supporting atmospheres but also produces graphitic carbon nitride (g-C3N4) working as 2D layered templates. The S/OCN cathode can deliver a high specific capacity of 1407.6 mA h g(-1) at C/20 rate with 84% S utilization and retain improved reversible capacity during long-term cycles at high current density. The increasing micropores, graphitic N, ether, and carboxylic O at the large sized OCN sheet favor S utilization and trapping for polysulfides.
Two-dimensional materials provide extraordinary opportunities for exploring phenomena arising in atomically thin crystals. Beginning with the first isolation of graphene, mechanical exfoliation has been a key to provide high-quality two-dimensional materials, but despite improvements it is still limited in yield, lateral size and contamination. Here we introduce a contamination-free, one-step and universal Au-assisted mechanical exfoliation method and demonstrate its effectiveness by isolating 40 types of single-crystalline monolayers, including elemental two-dimensional crystals, metal-dichalcogenides, magnets and superconductors. Most of them are of millimeter-size and high-quality, as shown by transfer-free measurements of electron microscopy, photo spectroscopies and electrical transport. Large suspended two-dimensional crystals and heterojunctions were also prepared with high-yield. Enhanced adhesion between the crystals and the substrates enables such efficient exfoliation, for which we identify a gold-assisted exfoliation method that underpins a universal route for producing large-area monolayers and thus supports studies of fundamental properties and potential application of two-dimensional materials.
We develop graphene-based devices fabricated by alternating current dielectrophoresis (ac-DEP) for highly sensitive nitric oxide (NO) gas detection. The novel device comprises the sensitive channels of palladium-decorated reduced graphene oxide (Pd-RGO) and the electrodes covered with chemical vapor deposition (CVD)-grown graphene. The highly sensitive, recoverable, and reliable detection of NO gas ranging from 2 to 420 ppb with response time of several hundred seconds has been achieved at room temperature. The facile and scalable route for high performance suggests a promising application of graphene devices toward the human exhaled NO and environmental pollutant detections.
The exceptional thermal conductivity of graphene is expected to endow polymer composites with ultrahigh thermal conductivities, which can be even similar to those of some metals such as stainless steel and aluminum alloy. The thermal conductivities of composites prepared by dispersing multilayer graphene (MLG) in epoxy matrix increase only by an order of magnitude over the pure epoxy. However, the improvement has been limited since the large interfacial thermal resistance exists between graphene and the surrounding epoxy. We have reported an extraordinary increase in thermal conductivity of the MLG/epoxy composites through the fabrication of the vertically aligned and densely packed MLG in the epoxy matrix. The ultrahigh thermal conductivity of 33.54 W/(m K) has been achieved in the aligned MLG/epoxy composite (AG/E). The thermal conductivity of AG/E exhibits a positive temperature response related to the aligned structure while increasing the temperature from 40 °C to 90 °C.
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