Hong Bi

Cytotoxicity and cellular uptake of iron nanowires

The toxicity of nanostructured materials and nanoparticles are very important considerations for many nanotechnology applications. Iron nanowires (NWs), as useful magnetic nanomaterials, may be good candidates for several biomedical applications. Here Fe NWs with an average diameter of about 50 nm were prepared by electrodeposition within the nanopores of anodic aluminum oxide (AAO) templates, and characterized by using scanning electron microcopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The cytotoxicity of the Fe NWs was studied at cell level. Specifically, the influence of concentration and size on the cytotoxicity of Fe NWs to HeLa cells was evaluated by MTT assay combined with direct morphology observations by TEM and phase contrast microscopy. The results clearly showed that the presence of Fe NWs had no significant effect on the cell proliferation and cell viability, even the HeLa cells exposed to Fe NWs at the high concentration of 10,000 per cell for 72 h still showed high cell viability of about 80%. From phase contrast microscopy, confocal laser scanning microscopy (CLSM) and TEM observations, it was found that Fe NWs were indeed internalized by HeLa cells. The cellular uptake process and results of Fe NWs demonstrated that as-prepared Fe NWs had not only a good biocompatibility but also a very low cytotoxicity.

Green synthesis of nitrogen-doped carbon dots from konjac flour with “off–on” fluorescence by Fe3+ and L-lysine for bioimaging

Highly nitrogen-doped carbon dots (N-CDs) are prepared by the pyrolysis of konjac flour under mild conditions followed with a simple extraction by ethanol and water. The N-CDs exhibit excellent pH-switched photoluminescence (PL), and their PL intensity can be facilitated by either mixing with NaOH and basic amino acids or by surface passivation with non-amine-terminated polyethylene glycols of different molecular weights. Further, the fluorescence of N-CDs can be quenched with Fe3+ and recovered with l-lysine, accompanied with a red-shift of emission wavelength. In addition, the low toxicity and strongly fluorescent N-CDs are applied for cell imaging, and the quenched fluorescence by Fe3+ can be recovered inside the living cells.

Mitochondria-Targeting Nanoplatform with Fluorescent Carbon Dots for Long Time Imaging and Magnetic Field-Enhanced Cellular Uptake

In this study, a biocompatible nanoplatform has been constructed on the basis of magnetic mesoporous silica nanoparticles (Fe3O4@mSiO2) via surface modification of triphenylphospine (TPP) and then conjugation with fluorescent carbon dots (CDs). The as-prepared Fe3O4@mSiO2-TPP/CDs nanoplatform shows a very low cytotoxicity and apoptosis rate in various cell lines such as A549, CHO, HeLa, SH-SY5Y, HFF, and HMEC-1. More importantly, this nanoplatform integrates long time cell imaging, mitochondria-targeting, and magnetic field-enhanced cellular uptake functionalities into an all-in-one system. Time-dependent mitochondrial colocalization in all of the cell lines has been proved by using confocal laser scanning microscopy and flow cytometry, while the multicolored fluorescence of the Fe3O4@mSiO2-TPP/CDs could remain bright and stable after coincubation for 24 h. In addition, the cellular uptake efficiency could be enhanced in a short time as a static magnetic field of 0.30 T was applied to the coincubation system of A549 and HFF cell lines. This bionanoplatform may have potential applications in targeted drug delivery for mitochondria diseases as well as early cancer diagnosis and treatment.

Nickel nanowires induce cell cycle arrest and apoptosis by generation of reactive oxygen species in HeLa cells

Nickel nanowires (Ni NWs) have great potential to be used as a living cell manipulation tool and developed into an anticancer agent. However, their candidacy as biomedical appliances need detailed human cell studies, such as study of the interaction between Ni NWs and tumor cells. The present study investigated the cytotoxicity of Ni NWs in HeLa cells. A dose-dependent inhibition of cell growth was observed by using the MTT assay. We demonstrated that Ni NWs induced oxidative stress by generation of reactive oxygen species (ROS). Apoptosis induction was evidenced by flow cytometry, annexin V binding assay and DAPI staining. DNA flow cytometric analysis indicated that Ni NWs significantly increased the percentages of cells in S phase compared with control cells. This process was accompanied by the loss of mitochondrial membrane potential. These results revealed that Ni NWs induced apoptosis in HeLa cells via ROS generation and cell cycle arrest.

Spectra investigation on surface characteristics of graphene oxide nanosheets treated with tartaric, malic and oxalic acids.

The surface characteristics of graphene oxide nanosheets (GO) treated respectively with tartaric acid, malic acid and oxalic acid, have been investigated by mainly using optical spectroscopic methods including Fourier transform infrared spectroscopy (FT-IR), Ultraviolet-visible (UV-Vis) absorption and Raman spectroscopy. Additionally, the electrochemical property of the products has also been studied. The data revealed that oxygen-containing groups such as OH, COOH and CO on the GO surface have been almost removed and thus reduced graphene oxide nanosheets (RGN) were obtained. Interestingly, the number of sp(2) domains of RGN increases as treated by tartaric acid<malic acid<oxalic acid whereas the steric hindrance (SH) decreases and the ionization constant (IC) differs among these three acids. Furthermore, the specific capacitances (Cs) of GO have been greatly promoted from 2.4 F g(-1) to 100.8, 112.4, and 147 F g(-1) after treated with tartaric, malic and oxalic acids, respectively. This finding agrees well with the spectra result of the tendency of surface conjugated degree alteration. We claim that the difference in both SH and IC among these acids is the main reason for the diverse surface characteristics as well as the improved Cs of the RGN.

Multifunctional nanotube-like Fe3O4/PANI/CDs/Ag hybrids: An efficient SERS substrate and nanocatalyst☆

In this paper, the stable and environment-friendly Fe3O4 nanotubes with polyaniline (Fe3O4 NTs/PANI hybrids) have been prepared via mesoporous anodic alumina oxide (AAO) template, sol-gel method and in-situ polymerization. Then multifunctional Fe3O4 NTs/PANI/Ag hybrids have been obtained by decorating Ag nanoparticles by glucose reduction on surface of Fe3O4 NTs/PANI hybrids. The morphologies and structures of these hybrids were subsequently investigated by SEM, XRD, TEM and XPS measurements. The Fe3O4 NTs/PANI/Ag hybrids presented high catalytic activity due to the template-assisted presence, preventing Ag particulate agglomeration. Importantly, the Fe3O4 NTs/PANI/Ag hybrids achieve sensitive surface-enhanced Raman scattering (SERS) signals. Furthermore, the introduction of carbon dots (CDs) endows these hybrids good dispersion and stable photoluminescence (PL). Therefore, the obtained hybrids may have potential applications in waste water treatment, biomedicine, photocatalyst, and environmental analysis.

Trackable Mitochondria-Targeting Nanomicellar Loaded with Doxorubicin for Overcoming Drug Resistance

Multidrug resistance (MDR) has been recognized as a major obstacle to successful chemotherapy for cancer in the clinic. In recent years, more and more nanoscaled drug delivery systems (DDS) are constructed to modulate drug efflux protein (P-gp) and deliver chemotherapeutic drugs for overcoming MDR. Among them, d-α-tocopheryl polyethylene glycol succinate (TPGS) has been widely used as a drug carrier due to its capability of inhibiting overexpression of P-gp and good amphiphilicity favorable for improving permeation and long-circulation property of DDS. In the present work, a novel kind of mitochondria-targeting nanomicelles-based DDS is developed to integrate chemotherapeutics delivery with fluorescence imaging functionalities on a comprehensive nanoplatform. The mitochondria-targeting nanomicelles are prepared by self-assembly of triphenylphosphine (TPP)-modified TPGS and fluorescent carbon quantum dots (CQDs) in an n-hexane/H2O mixed solution, named CQDs-TPGS-TPP. Notably, although the drug loading content of doxorubicin (DOX) in the as-prepared nanomicelles is as low as 3.4%, the calculated resistant index (RI) is greatly decreased from 66.23 of free DOX to 7.16 of DOX-loaded nanomicelles while treating both parental MCF-7 cells and drug-resistant MCF-7/ADR cells. Compared with free DOX, the penetration efficiency of DOX-loaded nanomicelles in three-dimensional multicellular spheroids (MCs) of MCF-7/ADR is obviously increased. Moreover, the released DOX from the nanomicelles can cause much more damage to cells of drug-resistant MCs. These results demonstrate that our constructed mitochondria-targeting nanomicelles-based DDS have potential application in overcoming MDR of cancer cells as well as their MCs that mimic in vivo tumor tissues. The MDR-reversal mechanism of the DOX-loaded CQDs-TPGS-TPP nanomicelles is also discussed.

One pot synthesis of a highly water-dispersible hybrid glucose carbides and reduced graphene oxide material with superior electrical capacitance

In this paper, reduced graphene oxide with glucose carbides (RGO-GC) was synthesized in a simple one pot synthesis via a hydrothermal approach. Graphene oxide (GO) dispersion was dissolved together with glucose in water, and the mixture was heated to 180xa0°C in an autoclave. After hydrothermal treatment, a thin GO-like glucose carbides (GC) film grows in situ on the RGO surface. Differing from RGO, the obtained RGO-GC not only has a much better dispersion in water, but also can be used as a support and a green reductant to fabricate Ag-decorated RGO-GC. Moreover, the maximum specific capacitance of the RGO-GC reaches as high as 247xa0Fxa0g−1 at a charging/discharging current density of 0.1xa0Axa0g−1 in 1xa0M H2SO4 solution. After 1000 charging/discharging cycles, the specific capacitance still retains 95xa0% of its initial specific capacitance. The greatly improved electrochemical performance is attributed to the increased surface wettability, more effective ionic diffusion, and a higher conductivity arising from the hydrophilic GO-like GC grown on the RGO surfaces.

Room-temperature Magnetism in Carbon Dots and Enhanced Ferromagnetism in Carbon Dots-Polyaniline Nanocomposite

Room temperature magnetic ordering is reported for very small carbon dots (CDs), mat-like polyaniline nanofibers (Mat-PANI) and a composite of CDs@Mat-PANI containing 0.315u2009wt% CDs. We have found saturation magnetization (MS) of CDs, Mat-PANI and CDs@Mat-PANI at 5 (20/300) K equals to 0.0079 (0.0048/0.0019), 0.0116 (0.0065/0.0055) and 0.0349 (0.0085/0.0077) emu/g, respectively. The MS enhancement in CDs@Mat-PANI (200% and 40% at 5u2009K and 300u2009K, respectively) is attributed to electron transfer from Mat-PANI imine N-atoms to the encapsulated CDs. Changes in MS values reveal that 0.81 (0.08) electron/CD is transferred at 5 (300) K, which is supported by observation of CDs photoluminescence (PL) redshift while in CDs@Mat-PANI. Band-bending and bandgap-renormalization calculations are used to predict a redshift of 117u2009meV at 300u2009K as a result of the electron transfer, in excellent agreement with the PL data (110u2009meV). Raman, X-ray diffraction and X-ray photoelectron spectroscopy data are used to confirm the electron transfer process as well as the strong interaction of CDs with PANI within CDs@Mat-PANI, which increases the crystalline domain size of Mat-PANI from about 4.8u2009nm to 9.2u2009nm while reducing the tensile strain from about 6.2% to 1.8%.

Understanding the Capsanthin Tails in Regulating the Hydrophilic–Lipophilic Balance of Carbon Dots for a Rapid Crossing Cell Membrane

Here we use natural Chinese paprika to prepare a new kind of amphiphilic carbon dot (A-Dot) that exhibits bright, multicolored fluorescence and contains hydrophilic groups as well as lipophilic capsanthin tails on the surface. It is found that the capsanthin tails in a phospholipid-like structure can promote cell internalization of the A-Dots via crossing cell membranes rapidly in an energy-independent fashion. Compared to highly hydrophilic carbon dots (H-Dots), a control sample prepared from the microwave thermolysis of citric acid and ethylenediamine, our synthesized A-Dots can be taken up by CHO, HeLa, and HFF cells more easily. More importantly, we develop a method to calibrate the hydrophilic-lipophilic balance (HLB) values of various kinds of carbon dots (C-Dots). HLB values of A-Dots and H-Dots are determined to be 6.4 and 18.4, respectively. Moreover, we discover that the cellular uptake efficiency of C-Dots is closely related to their HLBs, and the C-Dots with an HLB value of around 6.4 cross the cell membrane easier and faster. As we regulate the HLB value of the A-Dots from 6.4 to 15.3 by removing the capsanthin tails from their surfaces via alkali refluxing, it is found that the refluxed A-Dots can hardly cross HeLa cell membranes. Our work is an essential step toward understanding the importance of regulating the HLB values as well as the surface polarity of the C-Dots for their practical use in bioimaging and also provides a simple but effective way to judge whether the C-Dots in hand are appropriate for cell imaging.