Somatostatin receptor mediated targeting of acute myeloid leukemia by photodynamic metal complexes for light induced apoptosis.

Acute myeloid leukemia (AML) is characterized by relapse and treatment resistance in a major fraction of patients, underlining the need of innovative AML targeting therapies. Here we analysed the therapeutic potential of an innovative biohybrid consisting of the tumor-associated peptide somatostatin and the photosensitizer ruthenium in AML cell lines and primary AML patient samples. Selective toxicity was analyzed by using CD34 enriched cord blood cells as control. Treatment of OCI AML3, HL60 and THP1 resulted in a 92, and 99 and 97% decrease in clonogenic growth compared to the controls. Primary AML cells demonstrated a major response with a 74 to 99% reduction in clonogenicity in 5 of 6 patient samples. In contrast, treatment of CD34+ CB cells resulted in substantially less reduction in colony numbers. Subcellular localization assays of RU-SST in OCI-AML3 cells confirmed strong co-localization of RU-SST in the lysosomes compared to the other cellular organelles. Our data demonstrate that conjugation of a Ruthenium complex with somatostatin is efficiently eradicating LSC candidates of patients with AML. This indicates that receptor mediated lysosomal accumulation of photodynamic metal complexes is a highly attractive approach for targeting AML cells.

Autonomous Ultrafast Self-Healing Hydrogels by pH-Responsive Functional Nanofiber Gelators as Cell Matrices.

The synthesis of hybrid hydrogels by pH-controlled structural transition with exceptional rheological properties as cellular matrix is reported. "Depsi" peptide sequences are grafted onto a polypeptide backbone that undergo a pH-induced intramolecular O-N-acyl migration at physiological conditions affording peptide nanofibers (PNFs) as supramolecular gelators. The polypeptide-PNF hydrogels are mechanically remarkably robust. They reveal exciting thixotropic behavior with immediate in situ recovery after exposure to various high strains over long periods and self-repair of defects by instantaneous reassembly. High cytocompatibility, convenient functionalization by coassembly, and controlled enzymatic degradation but stability in 2D and 3D cell culture as demonstrated by the encapsulation of primary human umbilical vein endothelial cells and neuronal cells open many attractive opportunities for 3D tissue engineering and other biomedical applications.

Water-Dispersible Polydopamine-Coated Nanofibers for Stimulation of Neuronal Growth and Adhesion.

Hybrid nanomaterials have shown great potential in regenerative medicine due to the unique opportunities to customize materials properties for effectively controlling cellular growth. The peptide nanofiber-mediated auto-oxidative polymerization of dopamine, resulting in stable aqueous dispersions of polydopamine-coated peptide hybrid nanofibers, is demonstrated. The catechol residues of the polydopamine coating on the hybrid nanofibers are accessible and provide a platform for introducing functionalities in a pH-responsive polymer analogous reaction, which is demonstrated using a boronic acid modified fluorophore. The resulting hybrid nanofibers exhibit attractive properties in their cellular interactions: they enhance neuronal cell adhesion, nerve fiber growth, and growth cone area, thus providing great potential in regenerative medicine. Furthermore, the facile modification by pH-responsive supramolecular polymer analog reactions allows tailoring the functional properties of the hybrid nanofibers in a reversible fashion.

Synthesis, characterisation and in vitro cytotoxicity of mixed ligand Pt(ii) oxadiazoline complexes with hexamethylenetetramine and 7-nitro-1,3,5-triazaadamantane.

trans-Platinum(ii) oxadiazoline complexes with 7-nitro-1,3,5-triazaadamantane (NO2-TAA) or hexamethylenetetramine (hmta) ligands have been synthesised from trans-[PtCl2(PhCN)2] via cycloaddition of nitrones to one of the coordinated nitriles, followed by exchange of the other nitrile by NO2-TAA or hmta. Stoichiometric control allows for the selective synthesis of mono- and dinuclear complexes where 7-NO2TAA and hmta act as mono- and bidentate ligands, respectively. Precursors and the target complexes trans-[PtCl2(hmta)(oxadiazoline)], trans-[PtCl2(NO2-TAA)(oxadiazoline)] and trans-[{PtCl2(oxadiazoline)}2(hmta)] were characterised by elemental analysis, IR and multinuclear (1H, 13C, 195Pt) NMR spectroscopy. DFT (B3LYP/6-31G*/LANL08) and AIM calculations suggest a stronger bonding of hmta with the [PtCl2(oxadiazoline)] fragment, in agreement with the experimentally observed reactivity in the ligand exchange (hmta > 7-NO2TAA). Replacement of the nitrile by hmta is predicted to be more exothermic than that with 7-NO2-TAA, although the activation barriers are similar. Protonation of the non-coordinated N atoms is anticipated to weaken the Pt-N bond and lower the activation barrier for ligand exchange. This effect might help activate these compounds in a slightly acidic environment such as some tumour tissues. Ten of the new compounds were tested for their in vitro cytotoxicity in the human cancer cell lines HeLa and A549. Some of the mononuclear complexes are more potent than cisplatin, and their activity is still high in A549 where cisplatin shows little effect. The dinuclear complexes are inactive, presumably due to their lipophilicity and reduced solubility in water.

Generation and Characterization of Virus-Enhancing Peptide Nanofibrils Functionalized with Fluorescent Labels.

Retroviral gene transfer is the method of choice for the stable introduction of genetic material into the cellular genome. However, efficient gene transfer is often limited by low transduction rates of the viral vectors. We have recently described a 12-mer peptide, termed EF-C, that forms amyloid-like peptide nanofibrils (PNF), strongly increasing viral transduction efficiencies. These nanofibrils are polycationic and bind negatively charged membranes of virions and cells, thereby overcoming charge repulsions and resulting in increased rates of virion attachment and gene transfer. EF-C PNF enhance vector transduction more efficiently than other soluble additives and offer prospects for clinical applications. However, while the transduction-enhancing activity of PNF has been well-characterized, the exact mechanism and the kinetics underlying infection enhancement as well as the cellular fate of the fibrils are hardly explored. This is partially due to the fact that current labeling techniques for PNF rely on amyloid probes that cause high background staining or lose signal intensities after cellular uptake. Here, we sought to generate EF-C PNF covalently coupled with fluorescent labels. To achieve such covalent bioconjugates, the free amino groups of the EF-C peptide were coupled to the ATTO 495 or 647N NHS ester dyes. When small amounts of the labeled peptides were mixed with a 100- to 10 000-fold excess of the native peptide, PNF formed that were morphologically indistinguishable from those derived from the unlabeled peptide. The fluorescence of the fibrils could be readily detected using fluorescence spectroscopy, microscopy, and flow cytometry. In addition, labeled and nonlabeled fibrils captured viral particles and increased retroviral transduction with similar efficacy. These covalently fluorescence-labeled PNF are valuable tools with which to elucidate the mechanism(s) underlying transduction attachment and the fate of the fibrils in cells, tissues, and animal models.

Two-step synthesis of hexaammonium triptycene: an air-stable building block for condensation reactions to extended triptycene derivatives.

A simple two-step synthesis of an air-stable hexaammoniumtriptycene is introduced, which can be used for a variety of transformations by condensation reactions, e.g., to benzimidazole, benzotriazole, and quinoxaline derivatives in high yields.