Double-Strand DNA Breaks Induced by Paracyclophane Gold(I) Complexes.

Gold(I) complexes of ClickPhos [2.2]paracyclophane ligands were synthesized in excellent yields and fully characterized by spectroscopic methods as well as X-ray crystallography. The complexes exhibit a rigid ligand backbone and a triazolyl moiety and were systematically studied with respect to their cytotoxic properties. In combination with the ionic complex [(GemPhos)Au(tht)][ClO4 ] (tht=tetrahydrothiophene), in which the gold(I) atom exhibits a distorted trigonal coordination sphere of two phosphines and a labile tht ligand, their efficiency in cytotoxicity was investigated in HeLa, MCF7, and HCT116 cells as well as in a zebrafish model. Their cytotoxicity and their mechanisms of action are different and involve apoptosis, necrosis, and DNA damage. The compounds presented herein are potent metal-based cytostatics displaying LD50 values from 3.5-38 µm in different tumor cell lines and induce double-strand DNA breaks (DSB) as shown by H2AX phosphorylation (γH2AX) at foci of DSBs.

Novel Prodrug of Doxorubicin Modified by Stearoylspermine Encapsulated into PEG-Chitosan-Stabilized Liposomes.

Here, we report a new modification of doxorubicin based on an amphiphilic stearoylspermine anchor, enabling loading into liposomal membranes. Doxorubicin is coupled with stearoylspermine through an acid-labile hydrazone linker to ensure the release of the drug in the acidic interstitium of tumors. Using ATR-FTIR spectroscopy (Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy), the mechanism of interaction of doxorubicin with the anionic liposomal membrane was studied: incorporation of stearoyl chains leads to an increase in local microfluidity, and the amino groups of spermine interact with the phosphate groups of lipids. To stabilize liposomes against aggregation, we applied the copolymer PEG-chitosan as a coating: complex formation leads to charge neutralization, and the liposomes grow in size. According to MTT tests and confocal microscopy for cell lines A459 and Caco-2, PEG-chitosan-coated liposomes are as effective as neutral liposomes but are much more stable.

Tin Tungstate Nanoparticles: A Photosensitizer for Photodynamic Tumor Therapy.

The nanoparticulate inorganic photosensitizer ß-SnWO4 is suggested for photodynamic therapy (PDT) of near-surface tumors via reiterated 5 min blue-light LED illumination. ß-SnWO4 nanoparticles are obtained via water-based synthesis and comprise excellent colloidal stability under physiological conditions and high biocompatibility at low material complexity. Antitumor and antimetastatic effects were investigated with a spontaneously metastasizing (4T1 cells) orthotopic breast cancer BALB/c mouse model. Besides protamine-functionalized ß-SnWO4 (23 mg/kg of body weight, in PBS buffer), chemotherapeutic doxorubicin was used as positive control (2.5 mg/kg of body weight, in PBS buffer) and physiological saline (DPBS) as a negative control. After 21 days, treatment with ß-SnWO4 resulted in a clearly inhibited growth of the primary tumor (all tumor volumes below 3 cm(3)) as compared to the doxorubicin and DPBS control groups (volumes up to 6 cm(3)). Histological evaluations of lymph nodes and lungs as well as the volume of ipsilateral lymph nodes show a remarkable antimetastatic effect being similar to chemotherapeutic doxorubicin but-according to blood counts-at significantly reduced side effects. On the basis of low material complexity, high cytotoxicity under blue-light LED illumination at low dark and long-term toxicity, ß-SnWO4 can be an interesting addition to PDT and the treatment of near-surface tumors, including skin cancer, esophageal/gastric/colon tumors as well as certain types of breast cancer.

In vitro fluorescence and phototoxicity of ß-SnWO4 nanoparticles.

The nanoparticulate photocatalyst ß-SnWO4 is transfected into human liver carcinoma cells (HepG2). CLSM images and MTT assays validate a high phototoxicity under artificial daylight illumination at low systemic cytotoxicity and without long-term effects. ß-SnWO4 offers multifunctionality, including high colloidal stability and intrinsic fluorescence.

Ncam1a and Ncam1b: two carriers of polysialic acid with different functions in the developing zebrafish nervous system.

Polysialic acid (polySia) is mainly described as a glycan modification of the neural cell adhesion molecule NCAM1. PolySia-NCAM1 has multiple functions during the development of vertebrate nervous systems including axon extension and fasciculation. Phylogenetic analyses reveal the presence of two related gene clusters, NCAM1 and NCAM2, in tetrapods and fishes. Within the ncam1 cluster, teleost fishes express ncam1a (ncam) and ncam1b (pcam) as duplicated paralogs which arose from a second round of ray-finned fish-specific genome duplication. Tetrapods, in contrast, express a single NCAM1 gene. Using the zebrafish model, we identify Ncam1b as a novel major carrier of polySia in the nervous system. PolySia-Ncam1a is expressed predominantly in rostral regions of the developing nervous system, whereas polySia-Ncam1b prevails caudally. We show that ncam1a and ncam1b have different expression domains which only partially overlap. Furthermore, Ncam1a and Ncam1b and their polySia modifications serve different functions in axon guidance. Formation of the posterior commissure at the forebrain/midbrain junction requires polySia-Ncam1a on the axons for proper fasciculation, whereas Ncam1b, expressed by midbrain cell bodies, serves as an instructive guidance cue for the dorso-medially directed growth of axons. Spinal motor axons, on the other hand, depend on axonally expressed Ncam1b for correct growth toward their target region. Collectively, these findings suggest that the genome duplication in the teleost lineage has provided the basis for a functional diversification of polySia carriers in the nervous system.