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- ItemCarbon nanotubes filled with ferromagnetic materials(Basel : MDPI, 2010) Weissker, Uhland; Hampel, Silke; Leonhardt, Albrecht; Büchner, BerndCarbon nanotubes (CNT) filled with ferromagnetic metals like iron, cobalt or nickel are new and very interesting nanostructured materials with a number of unique properties. In this paper we give an overview about different chemical vapor deposition (CVD) methods for their synthesis and discuss the influence of selected growth parameters. In addition we evaluate possible growth mechanisms involved in their formation. Moreover we show their identified structural and magnetic properties. On the basis of these properties we present different application possibilities. Some selected examples reveal the high potential of these materials in the field of medicine and nanotechnology.
- ItemFunctionalized carbon nanotubes as transporters for antisense oligodeoxynucleotides(Cambridge : Royal Society of Chemistry, 2014) Kaufmann, Anika; Kunhardt, David; Cirillo, Giuseppe; Hampel, Silke; Schwenzer, BerndThe use of DNA-based therapeutics requires efficient delivery systems to transport the DNA to their place of action within the cell. To accomplish this, we investigated multiwalled carbon nanotubes (pristine MWCNT, p-MWCNT) functionalized with hydroxyl groups via 1,3-dipolar cycloaddition. In this way, we have obtained MWCNT-f-OH with improved stability in aqueous dispersions which is an advantageous property for their use in cellular environments. Afterwards, a carrier strand oligodeoxynucleotide (CS-ODN) was adsorbed to MWCNT-f-OH followed by hybridization with a therapeutic antisense oligodeoxynucleotide (AS-ODN). The amount of adsorbed CS-ODN, as well as the complementary AS-ODN and a non-complementary oligodeoxynucleotide (NS-ODN) as reference, was directly measured by radionuclide labeling of ODNs. We show that subsequent release of AS-ODNs and NS-ODNs was possible for MWCNT-f-OH above the melting temperature of AS-ODNs at 80 °C and under physiological conditions at different pH values at 37 °C. We also show a very low influence of p-MWCNT and MWCNT-f-OH on the cell viability of the bladder carcinoma (BCa) cell line EJ28 and that both MWCNT types were internalized by EJ28. Therefore, MWCNT-f-OH represents a promising carrier able to transport and release AS-ODNs inside cells.
- ItemNitrogen-Doped Carbon Nanotube/Polypropylene Composites with Negative Seebeck Coefficient(Basel : MDPI, 2020) Krause, Beate; Konidakis, Ioannis; Arjmand, Mohammad; Sundararaj, Uttandaraman; Fuge, Robert; Liebscher, Marco; Hampel, Silke; Klaus, Maxim; Serpetzoglou, Efthymis; Stratakis, Emmanuel; Pötschke, PetraThis study describes the application of multi-walled carbon nanotubes that were nitrogen-doped during their synthesis (N-MWCNTs) in melt-mixed polypropylene (PP) composites. Different types of N-MWCNTs, synthesized using different methods, were used and compared. Four of the five MWCNT grades showed negative Seebeck coefficients (S), indicating n-type charge carrier behavior. All prepared composites (with a concentration between 2 and 7.5 wt% N-MWCNTs) also showed negative S values, which in most cases had a higher negative value than the corresponding nanotubes. The S values achieved were between 1.0 µV/K and −13.8 µV/K for the N-MWCNT buckypapers or powders and between −4.7 µV/K and −22.8 µV/K for the corresponding composites. With a higher content of N-MWCNTs, the increase in electrical conductivity led to increasing values of the power factor (PF) despite the unstable behavior of the Seebeck coefficient. The highest power factor was achieved with 4 wt% N-MWCNT, where a suitable combination of high electrical conductivity and acceptable Seebeck coefficient led to a PF value of 6.1 × 10−3 µW/(m·K2). First experiments have shown that transient absorption spectroscopy (TAS) is a useful tool to study the carrier transfer process in CNTs in composites and to correlate it with the Seebeck coefficient.
- ItemCarbon nanomaterials sensitize prostate cancer cells to docetaxel and mitomycin C via induction of apoptosis and inhibition of proliferation(Frankfurt, M. : Beilstein-Institut zur Förderung der Chemischen Wissenschaften, 2017-6-23) Erdmann, Kati; Ringel, Jessica; Hampel, Silke; Wirth, Manfred P.; Fuessel, SusanneWe have previously shown that carbon nanofibers (CNFs) and carbon nanotubes (CNTs) can sensitize prostate cancer (PCa) cells to platinum-based chemotherapeutics. In order to further verify this concept and to avoid a bias, the present study investigates the chemosensitizing potential of CNFs and CNTs to the conventional chemotherapeutics docetaxel (DTX) and mitomycin C (MMC), which have different molecular structures and mechanisms of action than platinum-based chemotherapeutics. DU-145 PCa cells were treated with DTX and MMC alone or in combination with the carbon nanomaterials. The impact of the monotreatments and the combinatory treatments on cellular function was then systematically analyzed by using different experimental approaches (viability, short-term and long-term proliferation, cell death rate). DTX and MMC alone reduced the viability of PCa cells to 94% and 68%, respectively, whereas a combined treatment with CNFs led to less than 30% remaining viable cells. Up to 17- and 7-fold higher DTX and MMC concentrations were needed in order to evoke a similar inhibition of viability as mediated by the combinatory treatments. In contrast, the dose of platinum-based chemotherapeutics could only be reduced by up to 3-fold by combination with carbon nanomaterials. Furthermore, combinatory treatments with CNFs led mostly to an additive inhibition of short- and long-term proliferation compared to the individual treatments. Also, higher cell death rates were observed in combinatory treatments than in monotreatments, e.g., a combination of MMC and CNFs more than doubled the cell death rate mediated by apoptosis. Combinations with CNTs showed a similar, but less pronounced impact on cellular functions. In summary, carbon nanomaterials in combination with DTX and MMC evoked additive to partly synergistic anti-tumor effects. CNFs and CNTs possess the ability to sensitize cancer cells to a wide range of structurally diverse chemotherapeutics and thus represent an interesting option for the development of multimodal cancer therapies. Co-administration of chemotherapeutics with carbon nanomaterials could result in a reduction of the chemotherapeutic dosage and thus limit systemic side effects.
- ItemRecent advances in the synthesis and biomedical applications of nanocomposite hydrogels(Basel : MDPI, 2015) Spizzirri, Umile Gianfranco; Curcio, Manuela; Cirillo, Giuseppe; Spataro, Tania; Vittorio, Orazio; Picci, Nevio; Hampel, Silke; Iemma, Francesca; Nicoletta, Fiore PasqualeHydrogels sensitive to electric current are usually made of polyelectrolytes and undergo erosion, swelling, de-swelling or bending in the presence of an applied electric field. The electrical conductivity of many polymeric materials used for the fabrication of biomedical devices is not high enough to achieve an effective modulation of the functional properties, and thus, the incorporation of conducting materials (e.g., carbon nanotubes and nanographene oxide) was proposed as a valuable approach to overcome this limitation. By coupling the biological and chemical features of both natural and synthetic polymers with the favourable properties of carbon nanostructures (e.g., cellular uptake, electromagnetic and magnetic behaviour), it is possible to produce highly versatile and effective nanocomposite materials. In the present review, the recent advances in the synthesis and biomedical applications of electro-responsive nanocomposite hydrogels are discussed.
- ItemMagnetic properties of individual Co2FeGa Heusler nanoparticles studied at room temperature by a highly sensitive co-resonant cantilever sensor(London : Nature Publishing Group, 2017) Körner, Julia; Reiche, Christopher F.; Ghunaim, Rasha; Fuge, Robert; Hampel, Silke; Büchner, Bernd; Mühl, ThomasThe investigation of properties of nanoparticles is an important task to pave the way for progress and new applications in many fields of research like biotechnology, medicine and magnetic storage techniques. The study of nanoparticles with ever decreasing size is a challenge for commonly employed methods and techniques. It requires increasingly complex measurement setups, often low temperatures and a size reduction of the respective sensors to achieve the necessary sensitivity and resolution. Here, we present results on how magnetic properties of individual nanoparticles can be measured at room temperature and with a conventional scanning force microscopy setup combined with a co-resonant cantilever magnetometry approach. We investigate individual Co2FeGa Heusler nanoparticles with diameters of the order of 35 nm encapsulated in carbon nanotubes. We observed, for the first time, magnetic switching of these nanoparticles in an external magnetic field by simple laser deflection detection. Furthermore, we were able to deduce magnetic properties of these nanoparticles which are in good agreement with previous results obtained with large nanoparticle ensembles in other experiments. In order to do this, we expand the analytical description of the frequency shift signal in cantilever magnetometry to a more general formulation, taking unaligned sensor oscillation directions with respect to the magnetic field into account.