Dielectric study of local relaxations in dendritic macromolecules

The aim of this work is to characterize the dielectric properties of amorphous dendritic macromolecules as a function of architectural complexity. By combining thermostimulated currents and dynamic dielectric spectroscopy, the dielectric permittivity has been obtained as a function of temperature, in a very broad frequency range (10−4–106 Hz). Generations g = 0 to g = 2 were investigated. The molecular origin of the quasi-Debye mode observed for g = 0 at low temperature is common to all generations: localized reorientations of aldehyde end groups. The interactions with the phosphorus/sulfur (P = S) dipoles are probably responsible for the broadening pointed out in upper generations

Biological properties of water-soluble phosphorhydrazone dendrimers

Dendrimers are hyperbranched and perfectly defined macromolecules, constituted of branches emanating from a central core in an iterative fashion. Phosphorhydrazone dendrimers constitute a special family of dendrimers, possessing one phosphorus atom at each branching point. The internal structure of these dendrimers is hydrophobic, but hydrophilic terminal groups can induce the solubility of the whole structure in water. Indeed, the properties of these compounds are mainly driven by the type of terminal groups their bear; this is especially true for the biological properties. For instance, positively charged terminal groups are efficient for transfection experiments, as drug carriers, as anti-prion agents, and as inhibitor of the aggregation of Alzheimer's peptides, whereas negatively charged dendrimers have anti-HIV properties and can influence the human immune system, leading to anti-inflammatory properties usable against rheumatoid arthritis. This review will give the most representative examples of the biological properties of water-soluble phosphorhydrazone dendrimers, organized depending on the type of terminal groups they bear.Dendrímeros são macromoléculas extremamente ramificadas e perfeitamente definidas constituídas de ramificações que partem de um foco central de uma forma iterativa. Dendrímeros de fosforidrazona constituem uma família especial de dendrímeros, que possuem um átomo de fósforo em cada ponto da ramificação. A estrutura interna destes dendrímeros é hidrofóbica, mas grupos hidrofílicos terminais podem induzir a solubilidade em água de toda estrutura. De fato, as propriedades destes compostos são principalmente orientadas pelos grupos terminais que apresentam, especialmente para as propriedades biológicas. Por exemplo, grupos terminais carregados positivamente são eficientes para experimentos de transfecção, como transportadores de fármacos, agentes antipríons e como inibidores da agregação de peptídeos do Alzheimer, enquanto que dendrímeros carregados negativamente têm propriedades anti-HIV e podem influenciar o sistema imune humano, levando propriedades antiinflamatórias úteis contra artrite reumatoide. Essa revisão dará os exemplos mais representativos das propriedades biológicas de dendrímeros de fosforidrazona solúveis em água, organizados de acordo com os grupos terminais que possuem

Stannylene and germylene as powerful dechlorinated reagents : new route to diphosphene

Dichlorophosphines RPCl2 [R=Cl ( ), Ph ( ) and 2,4,6-But3C6H2 ( ] are reduced to the corresponding phosphorus-I compounds by the stannylene Me2Si (NBut)2Sn: ( ) or by the germylene GeI2 ( ) ; in the case of the reaction of ( ) with (bis(2,4,6-tri-tert-butylphenyl)-diphosphene ( ) is obtained with a 65 % yield

Carbon coated magnetic nanoparticles as supports in microwave-assisted palladium catalyzed Suzuki-Miyaura couplings

A palladium bis-N-heterocyclic carbene complex was immobilized on polystyrene modified, magnetic carbon coated iron nanoparticles and evaluated in Suzuki-Miyaura cross-coupling reactions under conventional and microwave heating. Under the latter conditions, both aryl bromides and aryl chlorides could be employed as substrates at low loading of catalyst (0.2 mol%), which could be readily recovered by an external magnet and reused in at least four cycles. As a possible deactivation pathway of the catalyst, the formation of palladium nanoparticles in the course of the reaction that became encapsulated in the polystyrene matrix of the support is suggeste

Engineered non-invasive functionalized dendrimer/dendron-entrapped/complexed gold nanoparticles as a novel class of theranostic (radio)pharmaceuticals in cancer therapy

Nanomedicine represents a very significant contribution in current cancer treatment; in addition to surgical intervention, radiation and chemotherapeutic agents that unfortunately also kill healthy cells, inducing highly deleterious and often life-threatening side effects in the patient. Of the numerous nanoparticles used against cancer, gold nanoparticles had been developed for therapeutic applications. Inter alia, a large variety of den drimers, i.e. soft artificial macromolecules, have turned up as non-viral functional nanocarriers for entrapping drugs, imaging agents, and targeting molecules. This review will provide insights into the design, synthesis, functionalization, and development in biomedicine of engineered functionalized hybrid dendrimer-tangled gold nanoparticles in the domain of cancer theranostic. Several aspects are highlighted and discussed such as 1) dendrimer-entrapped gold(0) hybrid nanoparticles for the targeted imaging and treatment of cancer cells, 2) dendrimer encapsulating gold(0) nanoparticles (Au DENPs) for the delivery of genes, 3) Au DENPs for drug delivery applications, 4) dendrimer encapsulating gold radioactive nanoparticles for radiotherapy, and 5) dendrimer/dendron-complexed gold(III) nanoparticles as technologies to take down cancer cells.info:eu-repo/semantics/publishedVersio

Superstructured poly(amidoamine) dendrimer-based nanoconstructs as platforms for cancer nanomedicine: a concise review

Poly(amidoamine) (PAMAM) dendrimers, as a family of synthetic macromolecules with highly branched interiors, abundant surface functional groups, and well-controlled architecture, have received immense scientific and technological interests for a range of biomedical applications, in particular cancer nanome dicine. However, due to the drawbacks of single-generation dendrimers with a quite small size (e.g., gen eration 5 (G5) PAMAM dendrimer has a size of 5.4 nm) such as limited drug loading capacity, restricted tumor passive targeting based on enhanced permeability and retention effect, and lack of versatility to render them with stimuli-responsiveness, superstructured dendrimeric nanoconstructs (SDNs) have been designed to break through these obstacles in their applications in cancer nanomedicine. Here, we review the recent advances related to the creation of SDNs such as dendrimer dumbbells, core–shell tecto den drimers, dendrimer nanoclusters (NCs), dendrimer nanogels and dendrimer-templated hybrid NCs, and how these SDNs have been designed as nanoplatforms for different biomedical applications related to cancer nanomedicine including MR imaging, drug/gene delivery, combination therapy and theranostics. This review concisely describes the latest key developments in the field and also discusses the possible challenges and perspectives for translation applications.info:eu-repo/semantics/publishedVersio

Synthesis and characterization of bifunctional dendrimers: preliminary use for the coating of gold surfaces and the proliferation of human osteoblasts (HOB)

Open Access Article. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.Two different novel families of bifunctional water-soluble dendrimers are synthesized, using the specific functionalization of one function of the cyclotriphosphazene core. Dendrimers are grown from the 5 remaining functions, up to generation 2. Water-solubility is attained in the last step of the synthesis by grafting either ammonium terminal groups or carboxylate terminal groups, on generations 1 and 2 of these bifunctional dendrimers. 12 new compounds are synthesized and fully characterized, in particular by multi-nuclear NMR. The function linked to the core is thioctic acid, suitable for grafting onto gold, thus both types of water-soluble dendrimers can be used to coat gold surfaces. These macromolecular assemblies are characterized by surface plasmon resonance (SPR). In a preliminary attempt, the gold surfaces modified by either positively or negatively charged dendrimers are used for studying their interaction with cells. Exposed to human osteoblast cells (OBC), the influence of the surface coatings on the cell responses is investigated. Polycationic dendrimers provoke cell apoptosis, whereas negatively charged dendrimers support cell adhesion and proliferation

Morpholino-functionalized phosphorus dendrimers for precision regenerative medicine: osteogenic differentiation of mesenchymal stem cells

A novel bioactive macromolecule based on morpholino-functiona lized phosphorus dendrimers (generation 2, G2-Mor+ ) was devel oped for osteogenic differentiation of mesenchymal stem cells (MSCs). Interestingly, through in vitro tests, it was shown that G2- Mor+ dendrimer can strongly promote the transformation of MSCs into osteoblasts, which implies the potential application of phos phorus de medicine.info:eu-repo/semantics/publishedVersio

Influence of cationic phosphorus dendrimers on the surfactant-induced synthesis of mesostructured nanoporous silica

The concomitant use of polycationic dendrimers and cationic surfactants for the elaboration of periodic mesoporous silica of type MCM-41 is described. The hexagonal structure is preserved up to about 26% in weight of dendrimer included in the silica. The cationic surfactant can be selectively removed to liberate the pores, while preserving the non-covalently incorporated dendrimers. These dendrimers included in the mesoporous silica are fully accessible through the mesoporous volume to small molecules such as HCl and tetrahydrofuran