Supramolecular structures from dendrons and dendrimers

This paper reviews aspects of the association of dendrons and dendrimers into a variety of supramolecular structures. There is such a wide range of primary dendron and dendrimer chemistries that it is still difficult to predict behaviour in aqueous media, and there are few studies in non-aqueous media. The aggregation of the primary units into larger and more complex forms leads to a wider range of potential carrier systems for drugs, genes and vaccines. This review deals principally with the association structures which can be formed. These include liquid crystalline structures and dendron block copolymer aggregates, surface monolayer formation, dendrimer derived nanoparticles, micellar structures and dendrisome (vesicle) formation. Of particular interest are DNA-dendrimer complexes and dendrimer-polyanion interactions. The in vivo behaviour of dendrons and dendrimers is of course crucial and is addressed. Dendrimer vesicle solubilisation by surfactants and emulsion stabilisation by dendrimers completes the survey of secondary structures. The challenge is to understand better the processes involved and to concentrate further on the design of the synthesis of dendrons and dendrimers which will associate into specific complex structures to increase the scope of dendrimer science.     

Synthesis,spectroscopic, thermal,antimicrobial and electrochemical characterization of some novel Ru(iii), Pt(iv) and Ir(iii) complexes of pipemidic acid

Three new solid complexes of pipemidic acid (Pip–H) with Ru³⁺, Pt⁴⁺ and Ir³⁺ were synthesized and characterized. Pipemidic acid acts as a uni-dentate chelator through the nitrogen atom of the –NH piperazyl ring. The spectroscopic data revealed that the general formulas of Pip–H complexes are [M(L)_n(Cl)_x]·yH₂O ((1) M = Ru³⁺, L: Pip–H, n = 3, x = 3, y = 6; (2) M = Pt⁴⁺, L: Pip–NH₄, n = 2, x = 4, y = 0 and (3) M = Ir³⁺, L: Pip–H, n = 3, x = 3, y = 6). The number of water molecules with their locations inside or outside the coordination sphere were assigned via thermal analyses (TG, DTG). The DTG curves refer to 2–3 thermal decomposition steps where the first decomposition step at a lower temperature corresponds to the loss of uncoordinated water molecules followed by the decomposition of Pip–H molecules at higher temperatures. Thermodynamic parameters (E*, ΔS*, ΔH* and ΔG*) were calculated from the TG curves using Coats–Redfern and Horowitz–Metzeger non-isothermal models. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques were carefully used to assign properly the particle sizes of the prepared Pip–H complexes. The biological enhancement of Pip–H complexes rather than free chelate were assessed in vitro against four kinds of bacteria G(+) (Staphylococcus epidermidis and Staphylococcus aureus) and G(−) (Klebsiella and Escherichia coli) as well as against the human breast cancer (MCF-7) tumor cell line.

Three new solid complexes of pipemidic acid (Pip–H) with Ru³⁺, Pt⁴⁺ and Ir³⁺ were synthesized and characterized. Pipemidic acid acts as a uni-dentate chelator through the nitrogen atom of the –NH piperazyl ring.     

An intrinsically fluorescent dendrimer as a nanoprobe of cell transport

Dendrimers, spherical or quasi-spherical synthetic polymers in the nano-size range, have found useful applications as prospective carriers in drug and gene delivery. The investigation of dendrimer uptake by cells has been previously achieved by the incorporation of a fluorescent dye to the dendrimer either by chemical conjugation or by physical interaction. Here we describe the synthesis of two intrinsically fluorescent lysine based cationic dendrimers which lack a fluorophore, but which has sufficient fluorescence intensity to be detected at low concentrations. The nomenclature used to describe our compounds results in, for example the 6th generation dendrimer being notated as Gly-Lys(63) (NH2)(64); Gly denotes that the compound has a glycine in the core coupled to 63 lysine branching units (Lys(63)) and that the surface has 64 free amino groups (NH2)(64). The use of these dendrimers in probing transport avoids the need for fluorescent tagging with its attendant problems. The uptake of Gly-Lys(63) (NH2)(64) into Caco-2 cells was followed using confocal microscopy. Being cationic, it first adsorbs to the cell surface, enters the cytoplasm and reaches the nucleus within 35-45 min. Estimates of the diffusion coefficient of the dendrimer within the cell cytoplasm leads to a value of 6.27 ( +/- 0.49) x 10(-11) cm(2) s(-1), which is up to 1000 times lower than the diffusion coefficient of the dendrimer in water. Intrinsically fluorescent dendrimers of different size and charge are useful probes of transport in cells.     

Neighbors and enemies: lessons to be learned from the Palestinian-Israeli conflict regarding cooperation in public health

We aim to demonstrate on the example of recent Palestinian-Israeli collaborative projects how sustainable cooperation can be achieved despite unfavorable political atmosphere and continuing violent disputes. Palestinian and Israeli participants of the collaborative projects declared that their attitude and belief in coexistence was positively changed as a result of their experience in cooperative work. Their main motivations were a desire to contribute to the resolution of the conflict and to improve professional skills. The experience in Israeli-Palestinian conflict showed that the collaborative projects of higher chance of success and sustainability should address issues of high priority to the concerned parties, lead to demonstrable benefits in the immediate future, and preferably be organized by non-governmental organizations. Also, to secure long-term success of collaborative projects, parity and symmetry should be maintained, as well as equal division of work and responsibility between the partners. Collaboration in public health field is first to be (re)established in conflict areas to alleviate suffering, minimize future health risks, and prevent further health deterioration. Thereby, public health can serve as a bridge to peace in areas of unrest or war.