Silke Hampel

Carbon nanotubes filled with a chemotherapeutic agent: a nanocarrier mediates inhibition of tumor cell growth

AIM In this paper, carbon nanotubes (CNTs) are presented as feasible carriers for carboplatin, a therapeutic agent for cancer treatment. The drug was introduced into CNTs to demonstrate that they are suited as nanocontainers and nanocarriers and can release the drug to initialize its medical virtue. METHOD The filling was accomplished by a wet-chemical approach after the CNTs were opened. The effect on cell proliferation and cytotoxicity of the carboplatin-filled CNT was investigated by using a viability assays. RESULTS Using different analysis methods such as electron energy loss spectroscopy and x-ray photoelectron spectroscopy the structure of carboplatin incorporated into the CNTs was found to be retained. In vitro studies showed that carboplatin-filled CNTs inhibited growth of bladder cancer cells whereas unfilled, opened CNTs barely affected cancer cell growth. CONCLUSION A reversible filling-emptying process could be performed successfully within this work. This highlights the potential of CNTs for applications in the field of drug delivery.

Magnetic force microscopy sensors using iron-filled carbon nanotubes

Probes for magnetic force microscopy (MFM) were prepared by pinning iron-filled multiwall carbon nanotubes to conventional scanning force microscopy probes. These nanotube MFM probes reveal a great potential for high spatial resolution of both topography and magnetic stray field. The ends of the high aspect ratio iron nanowires within the nanotubes can be considered as stationary effective magnetic monopole moments which opens the possibility of quantitative stray field measurements in a straightforward manner. The carbon shells around the iron nanowires provide wear resistance and oxidation protection.

Carbon nanotube based biomedical agents for heating, temperature sensoring and drug delivery

Due to their extraordinary physical and chemical properties carbon nanotubes reveal promising potential as biomedical agents for heating, temperature sensoring and drug delivery on the cellular level. Filling carbon nanotubes with tailored materials realises nanoscaled containers in which the active content is encapsulated by a protecting carbon shell. We describe different synthesis routes and show the structural and magnetic properties of carbon nanotubes. In particular, the filling with magnetic materials offers the potential for hyperthermia applications while the insertion of NMR active substances allows the usage as markers and sensors. The potential of carbon nanotubes for biomedical applications is highlighted by hyperthermia studies which prove their applicability for local in situ heating. In addition we have shown that a non-invasive temperature control by virtue of a carbon-wrapped nanoscaled thermometer and filling with anti-cancer drugs is possible.

Carbon Nanotubes Filled with Ferromagnetic Materials

Carbon 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.

Enhanced magnetism in Fe-filled carbon nanotubes produced by pyrolysis of ferrocene

By optimization of the synthesis of ferromagnetic-filled carbon nanotube ensembles on Si substrates (catalytic decomposition of ferrocene) and following annealing at 645°C, marked hysteresis loops can be measured by the alternating-gradient method. Unusually high coercivities and strong anisotropies with an easy magnetic axis parallel to the alignment of the nanotubes are observed from the as-grown samples, whereas an enhanced magnetic saturation moment (up to a factor of 2) and a decreased anisotropy are realized after annealing at 645°C. The increase of the magnetic saturation moment of the Fe-filled carbon nanotube ensembles is caused by the entire transformation within the tubes of the γ-Fe and Fe3C phases to ferromagnetic α-Fe and graphite. X-ray diffraction with different glancing incidence shows that the γ-Fe is predominantly at the tips of the nanotubes, while the iron carbide resides closer to the substrate. However, after the annealing process only α-Fe is found. At an annealing temperature of 6...

Stepwise current-driven release of attogram quantities of copper iodide encapsulated in carbon nanotubes.

Encapsulated nanograins of copper iodide have been sequentially discharged from individual carbon nanotubes. Using a high resolution electron microscope equipped with a two-terminal electrical measurements unit, it was possible to manipulate the filling contents with precisions of a few attograms at a time. Changes in electrical resistance and filling ratio were followed in tandem and in real-time. It is shown that the pulsed release of the halide is directly related to the overall conductance of the filled nanotube.

Graphene oxide-based drug delivery vehicles: functionalization, characterization, and cytotoxicity evaluation

Abstract As a consequence of graphene oxides (GOs) high chemical versatility, there is great interest in functionalized as a nanocarrier for in vitro and in vivo drug delivery. Within this review, the structure and properties of GO that allow covalent and non-covalent functionalization are discussed. In short, toxicity investigations show functionalized GO is biocompatible. Various works demonstrate the potential of GO derivatives as exciting nanocarriers for the loading and delivery of therapeutic drugs.

Delivery of carboplatin by carbon-based nanocontainers mediates increased cancer cell death

Since the activity of several conventional anticancer drugs is restricted by resistance mechanisms and dose-limiting side-effects, the design of nanocarriers seems to be an efficient and promising approach for drug delivery. Their chemical and mechanical stability and their possible multifunctionality render tubular nanomaterials, such as carbon nanotubes (CNTs) and carbon nanofibres (CNFs), promising delivery agents for anticancer drugs. The goal of the present study was to investigate CNTs and CNFs in order to deliver carboplatin in vitro. No significant intrinsic toxicity of unloaded materials was found, confirming their biocompatibility. Carboplatin was loaded onto CNTs and CNFs, revealing a loading yield of 0.20 mg (CNT-CP) and 0.13 mg (CNF-CP) platinum per milligram of material. The platinum release depended on the carrier material. Whereas CNF-CP marginally released the drug, CNT-CP functioned as a drug depot, constantly releasing up to 68% within 14 days. The cytotoxicity of CNT-CP and CNF-CP in urological tumour cell lines was dependent on the drug release. CNT-CP was identified to be more effective than CNF-CP concerning the impairment of proliferation and clonogenic survival of tumour cells. Moreover, carboplatin, which was delivered by CNT-CP, exhibited a higher anticancer activity than free carboplatin.

Complement activation by carbon nanotubes and its influence on the phagocytosis and cytokine response by macrophages

UNLABELLED Carbon nanotubes (CNTs) have promised a range of applications in biomedicine. Although influenced by the dispersants used, CNTs are recognized by the innate immune system, predominantly by the classical pathway of the complement system. Here, we confirm that complement activation by the CNT used continues up to C3 and C5, indicating that the entire complement system is activated including the formation of membrane-attack complexes. Using recombinant forms of the globular regions of human C1q (gC1q) as inhibitors of CNT-mediated classical pathway activation, we show that C1q, the first recognition subcomponent of the classical pathway, binds CNTs via the gC1q domain. Complement opsonisation of CNTs significantly enhances their uptake by U937 cells, with concomitant downregulation of pro-inflammatory cytokines and up-regulation of anti-inflammatory cytokines in both U937 cells and human monocytes. We propose that CNT-mediated complement activation may cause recruitment of cellular infiltration, followed by phagocytosis without inducing a pro-inflammatory immune response. FROM THE CLINICAL EDITOR This study highlights the importance of the complement system in response to carbon nanontube administration, suggesting that the ensuing complement activation may cause recruitment of cellular infiltration, followed by phagocytosis without inducing a pro-inflammatory immune response.

Antioxidant multi-walled carbon nanotubes by free radical grafting of gallic acid: new materials for biomedical applications

Objectives  To prove the possibility of covalently functionalizing multi‐walled carbon nanotubes (CNTs) by free radical grafting of gallic acid on their surface with the subsequent synthesis of materials with improved biological properties evaluated by specific in‐vitro assays.