Synthesis and antioxidant properties of enone core based dendrimers with carbazole as surface group

Dendrimers and Derivatives as Multifunctional Nanotherapeutics for Alzheimer's Disease

Alzheimer's disease (AD) is the most prevalent form of dementia. It affects more than 30 million people worldwide and costs over US$ 1.3 trillion annually. AD is characterized by the brain accumulation of amyloid β peptide in fibrillar structures and the accumulation of hyperphosphorylated tau aggregates in neurons, both leading to toxicity and neuronal death. At present, there are only seven drugs approved for the treatment of AD, of which only two can slow down cognitive decline. Moreover, their use is only recommended for the early stages of AD, meaning that the major portion of AD patients still have no disease-modifying treatment options. Therefore, there is an urgent need to develop efficient therapies for AD. In this context, nanobiomaterials, and dendrimers in particular, offer the possibility of developing multifunctional and multitargeted therapies. Due to their intrinsic characteristics, dendrimers are first-in-class macromolecules for drug delivery. They have a globular, well-defined, and hyperbranched structure, controllable nanosize and multivalency, which allows them to act as efficient and versatile nanocarriers of different therapeutic molecules. In addition, different types of dendrimers display antioxidant, anti-inflammatory, anti-bacterial, anti-viral, anti-prion, and most importantly for the AD field, anti-amyloidogenic properties. Therefore, dendrimers can not only be excellent nanocarriers, but also be used as drugs per se. Here, the outstanding properties of dendrimers and derivatives that make them excellent AD nanotherapeutics are reviewed and critically discussed. The biological properties of several dendritic structures (dendrimers, derivatives, and dendrimer-like polymers) that enable them to be used as drugs for AD treatment will be pointed out and the chemical and structural characteristics behind those properties will be analysed. The reported use of these nanomaterials as nanocarriers in AD preclinical research is also presented. Finally, future perspectives and challenges that need to be overcome to make their use in the clinic a reality are discussed.

Synthesis and Activity of Ionic Antioxidant-Functionalized PAMAMs and PPIs Dendrimers

For this study, new dendrimers were prepared from poly(propylene imine) (PPI) and polyamidoamine (PAMAM) dendrimers using an efficient acid-base reaction with various phenolic acids. The syntheses were also optimized in both microwave and microfluidic reactors. These ionic and hydrophilic dendrimers were fully characterized and showed excellent antioxidant properties. Their cytotoxic properties have been also determined in the case of fibroblast dermal cells.

Would antioxidant-loaded nanoparticles present an effective treatment for ischemic stroke?

Ischemic stroke is a leading cause of death and disability worldwide and is in urgent need of new treatment options. The only approved treatment for stroke restores blood flow to the brain, but much of the tissue damage occurs during the subsequent reperfusion. Antioxidant therapies that directly address ischemia-reperfusion injury have shown promise in preclinical results. In this review, we discuss that reformulating antioxidant therapies as nanomedicine can potentially overcome the barriers that have kept these therapies from succeeding in the clinic. We begin by reviewing the pathophysiology of ischemic stroke with a focus on the effects of reperfusion injury. Next, we review nanotherapeutic systems designed to treat the disease with a focus on those addressing reperfusion injury. Mechanisms of passive and active transport required to traverse a blood–brain barrier are discussed. Finally, we conclude by outlining design parameters for potentially successful nanomedicines as front-line therapeutics for ischemic stroke.

Synthesis, optical properties, and antioxidant and anticancer activity of benzoheterazole dendrimers with triazole bridging unit

Benzoheterazole dendrimers with triazole bridges and bisphenol A/benzophenone core units have been successfully synthesized by click chemistry. Higher generation dendrimers exhibit better antioxidant and anticancer activities than the lower generation dendrimers.

Synthesis, Photophysical, and Antioxidant Properties of Rhodamine B Decorated Novel Dendrimers

Novel triazole bridged dendrimers with rhodamine B derivative as surface groups have been achieved using click chemistry by both divergent and convergent approaches. Rhodamine B decorated dendrimers 1, 2, and 3 were synthesised up to the second generation with spirolactam grafted at the terminal. The UV and fluorescence intensity increases with the increase in the dendritic generation. The synthesised rhodamine B decorated dendrimers show significant antioxidant behaviour compared with the standards butylated hydroxy toluene (BHT) and gallic acid when tested by 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging assay and hydroxyl radical scavenging assay methods, respectively. Rhodamine B decorated higher generation dendrimers exhibit better antioxidant activity than the lower generation dendrimers due to the presence of a greater number of triazole branching units and rhodamine B derivative surface units.

Synthesis, Optical, and Antioxidant Studies of Anthraquinone-core-based Dendrimers with N-Phenylcarbazole as Surface Group

Synthesis of hyperbranched dendrimers up to third generation with N-phenylcarbazole as surface group and anthraquinone as the core unit has been achieved. The fluorescence decay studies of the dendrimers indicate that generation growth alters the relaxation time. The highly branched third-generation dendrimer has a longer relaxation time than the zero-, first-, and second-generation dendrimers. Similarly, higher-generation dendrimers show better antioxidant behaviour with 1,1-diphenyl-2-picryl hydrazyl than the lower-generation dendrimers.

Synthesis, crystal structure and photoluminescence of phosphorescent copper (I) complexes containing hole-transporting carbazoly moiety

Two new mononuclear Cu(I) complexes based on 2-(2'-pyridyl)benzimidazolyl derivative ligand containing hole-transporting carbazole (L), [Cu(L)(DPEphos)](BF4) and [Cu(L)(PPh3)2](BF4), where L=(4-(9H-carbazol-9-yl)phenyl)methyl-2-(2'-pyridyl)benzimidazole; DPEphos=bis[2-(diphenylphosphino)phenyl]ether and PPh3=triphenylphosphine, have been synthesized and characterized on the basis of elemental analysis, (1)H NMR and FT-IR spectra. The structures of the ligand L and the Cu(I) complexes were characterized by single crystal X-ray diffraction. The results reveal that in the Cu(I) complexes the central Cu(I) ions assume the irregular distorted tetrahedral geometry and are tetra-coordinated by the two nitrogen atoms from L ligand and two phosphorus atoms from ancillary ligands. The photophysical properties of the complexes were examined by using UV-vis, photoluminescence spectroscopic analysis. The complexes exhibit weak MLCT absorption bands ranging from 360 to 480 nm, and display strong orange phosphorescence in the solid states at room temperature, which is completely quenched in solutions.