Dendrimers in Neurodegenerative Diseases

Neurodegenerative diseases (NDs), such as Parkinson’s Disease (PD), Alzheimer’s Disease (AD), Multiple Sclerosis (MS) and amyotrophic lateral sclerosis (ALS), are characterized by progressive loss of structure or function of neurons. Current therapies for NDs are only symptomatic and long-term ineffective. This challenge has promoted the development of new therapies against relevant targets in these pathologies. In this review, we will focus on the most promising therapeutic approaches based on dendrimers (DDs) specially designed for the treatment and diagnosis of NDs. DDs are well-defined polymeric structures that provide a multifunctional platform for developing different nanosystems for a myriad of applications. DDs have been proposed as interesting drug delivery systems with the ability to cross the blood–brain barrier (BBB) and increase the bioavailability of classical drugs in the brain, as well as genetic material, by reducing the synthesis of specific targets, as β-amyloid peptide. Moreover, DDs have been shown to be promising anti-amyloidogenic systems against amyloid-β peptide (Aβ) and Tau aggregation, powerful agents for blocking α-synuclein (α-syn) fibrillation, exhibit anti-inflammatory properties, promote cellular uptake to certain cell types, and are potential tools for ND diagnosis. In summary, DDs have emerged as promising alternatives to current ND therapies since they may limit the extent of damage and provide neuroprotection to the affected tissues.

NiFe2O4@B,N,F-tridoped CeO2 (NFTDNC): a mesoporous nanocatalyst in the synthesis of pyrazolopyranopyrimidine and 1H-pyrazolo[1,2-b]phthalazine-5,10-dione derivatives and as an adsorbent

Mesoporous materials, due to their unique textural and structural features and successful applications in different scientific areas, engrossed our curiosity to form a mesoporous nanostructure. A facile method for the formation of nickel ferrite immobilized over B,N,F tridoped mesoporous cerium oxide (CeO₂) nanostructures (NFTDNC) was designed and communicated in this report. It was characterized by thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction study (PXRD), scanning transmission electron microscopy (STEM), high-resolution transmission electron microscopy (HR-TEM), field emission gun-scanning electron microscopy (FE-SEM), vibrating sample magnetometry (VSM), photoluminescence (PL), Brunauer-Emmett-Teller (BET), energy dispersive X-ray analysis (EDX) and elemental mapping, UV-visible spectroscopy (UV-VIS) and Fourier transform infrared spectroscopy (FT-IR). The applications of the mesoporous nanomaterial (NFTDNC) as an adaptable heterogeneous nanocatalyst and as a phenomenal adsorbent for methyl orange (MO) dye were established. It catalyzed the formation of pyrazolopyranopyrimidine and 1H-pyrazolo[1,2-b]phthalazine-5,10-diones derivatives for the five runs. The recycled catalyst exhibited agglomeration in structural features confirmed by PXRD and HR-TEM studies. NFTDNC as an adsorbent fitted the Freundlich isotherm for the adsorption of MO dye. Moreover, it followed the linear pseudo-second-order kinetics rate equation (R² ≥ 0.98914). MO was adsorbed completely in 60 min with the NFTDNC mesoporous nanostructure.

Functionalized magnetic PAMAM dendrimer as an efficient nanocatalyst for a new synthetic strategy of xanthene pigments

A green protocol has been developed for preparation of the wide variety of colored xanthene derivatives using a new efficient magnetic solid acid catalyst bearing polyamidoamine dendrimer moiety as a nanoscopic compound. Dendrimers, highly symmetric molecules around a core and 3D spherical morphology, show interesting traits based on their functionalized groups on the branched surface. They can be designed to provide water soluble structures or pseudo-active sites of biomolecules. The catalyst was assembled via a polyamidoamine dendrimer immobilized on the surface of γ-Fe₂O₃ followed by the sulfonylation of the amine groups by chlorosulfonic acid resulting in γ-Fe₂O₃@PAMAM-SO₃H. Herein, PAMAM dendrimer with repeating amine/amide branches as catchable sites of sulfonic acid groups was introduced as transformer of homogeneous to heterogeneous acidic catalysts. The physicochemical properties of synthesized catalyst were studied using by FT-IR, FE-SEM, XRD, VSM, EDS, TGA/DTG, and TEM. Finally, the catalytic activity of γ-Fe₂O₃@PAMAM-SO₃H was evaluated for the preparation of xanthene derivatives via a one-pot, three components reaction of aromatic aldehydes with i) β-naphthol, ii) cyclic 1,3-dicarbonyl, iii) β-naphthol and cyclic 1,3-dicarbonyl compounds, iv) 2-hydroxy-1,4-naphthoquinone, leading to the eco-riendly preparation of the target compounds in good to excellent yields. The catalyst could be easily recycled for at least five consecutive runs without significant loss in its catalytic activity.

Recent development in the synthesis of heterocycles by 2-naphthol-based multicomponent reactions

2-Naphthol or β-naphthol is an important starting material that has drawn great attention in various organic transformations because of its attributes, such as low cost, easy to handle and eco-friendliness. The electron-rich aromatic framework of 2-naphthol with multiple reactive sites allows it to be utilized in several kinds of organic reactions eventuated to several organic molecules with potent biological properties. Multicomponent reaction approach has been tremendously utilized to explore the synthetic utility of 2-naphthol for the construction of diverse N/O-containing heterocyclic framework. In this review, we summarize recent data pertaining to multicomponent reactions, wherein heterocyclic compounds are synthesized utilizing 2-naphthol as one of the starting materials. It is anticipated that this review will stimulate the researchers to design new multicomponent strategies complying with the Green Chemistry principles for the further exploitation of 2-naphthol for the rapid synthesis of versatile biologically relevant heterocycles. This review provides a concise overview of the different 2-naphthol based multicomponent reactions utilized for the construction of diverse bioactive heterocyclic scaffold.

Synthesis, and molecular modeling of bis(3-(piperazine-1-yl)propyl)tungstate (BPPT) nanoparticles, and its first catalytic application for one-pot synthesis of 4H-chromene derivatives

A novel, nano-sized, bis(3-(piperazine-1-yl)propyl)tungstate (BPPT) is introduced as an efficient and reusable organometallic catalyst which is considered as a heterogeneous Bronsted-Lowry base and applied successfully for one-pot synthesis of methyl 2-amino-4-aryl substituted-4H-chromene derivatives with good to excellent yields. BPPT has been prepared via a two-step route from natrium tungstate salt. At first, the oxygens of Na₂WO₄ react with 1-bromo-3-chloropropane via nucleophilic substitution to produce bis(3-choloro propyl)tungstate. Then nucleophilic substitution of piperazine with chlorines produced bis(3-(piperazine-1-yl)propyl) tungstate. Bis(3-(piperazine-1-yl)propyl) tungstate, which was called BPPT, characterized by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), transmission electron microscopy (TEM) and scanning electron microscope (SEM). The catalyst is heterogeneous, green and recyclable. It is a thermally stable and its handling is easy. Its catalytic activity is very high and leads to the production of 4H-pyran derivatives with good to excellent yields in short reaction times. Furthermore, molecular modeling studies and ADMETox prediction revealed that not only it can inhibit acetylcholinesterase enzyme and act as an anti-Alzheimer agent but also has no variation from Lipinski's rule of five and can be a good candidate as anti-Alzheimer agents. These above-mentioned facts can be countered as advantages of the current protocol.

Multi-scale characterization of thermoresponsive dendritic elastin-like peptides

Elastin like peptides (ELPs)-polypeptides based on the protein elastin-are used widely as thermoresponsive components in biomaterials due to the presence of a sharp soluble-to-insoluble phase change at a characteristic transition temperature (T_t). While linear ELPs have been thoroughly studied, few investigations into branched ELPs have been carried out. Using lysine amino acids as branching and terminal units with 1-3 pentameric repeats between each branch, ELP dendrimers were prepared by solid-phase peptide synthesis with molecular weights as high as 14kDa. A conformation change from random coil to β-turn upon heating through the T_t, typical of ELPs, was observed by circular dichroism spectroscopy for all peptides. The high molecular weights of these peptides enabled the use of characterization techniques typically reserved for polymers. Variable-temperature small-angle X-ray scattering measurements in dilute solution revealed an increase in size and fractal dimension upon heating, even well below the T_t. These results were corroborated by cryogenic transmission electron microscopy, which confirmed the presence of aggregates below the T_t, and micro differential scanning calorimetry, which showed a broad endothermic peak below the T_t. These results collectively indicate the presence of a pre-coacervation step in the phase transition of ELP dendrimers.

Facile synthesis and investigation of 1,8-dioxooctahydroxanthene derivatives as corrosion inhibitors for mild steel in hydrochloric acid solution

For the first time, the corrosion inhibitive performance of some 1,8-dioxooctahydroxanthene derivatives is proposed.

Ultrasound promoted facile one pot synthesis of highly substituted pyran derivatives catalyzed by silica-coated magnetic NiFe2O4nanoparticle-supported H14[NaP5W30O110] under mild conditions

Application of ultrasonic method as a green source of energy to reduce the reaction times compared to conventional processes. NiFe₂O₄@SiO₂–H₁₄[NaP₅W₃₀O₁₁₀] was used as magnetically separable catalyst for synthesis of pyrans with minimum work up.

Green synthesis of tetrahydrobenzo[b]pyrans, pyrano[2,3-c]pyrazoles and spiro[indoline-3,4′-pyrano[2,3-c]pyrazoles catalyzed by nano-structured diphosphate in water

Preparation of nanostructured diphosphate Na₂CaP₂O₇. Avoiding of any acid catalysts. The prepared catalyst is reusable and eco-friendly. The method is easy and contains simple experimental procedure.

Synthesis of symmetrical N,N′-alkylidene bis-amides catalyzed by silica coated magnetic NiFe2O4 nanoparticle supported polyphosphoric acid (NiFe2O4@SiO2-PPA) and its application toward silver nanoparticle synthesis for electrochemical detection of glucose

For the first time, a new and facile Ag@PM-b-B nanocomposite electrochemical sensor was successfully developed for the detection of glucose. Also, the magnetically recoverable catalyst was easily recycled at least ten times without significant loss of catalytic activity.

Ag@TiO2 nanocomposite; synthesis, characterization and its application as a novel and recyclable catalyst for the one-pot synthesis of benzoxazole derivatives in aqueous media

A Ag@TiO₂ nanocomposite/water as a novel catalytic system is used for the synthesis of benzoxazole derivatives. A shorter reaction time along with high product yield, catalyst stability and recyclability are the merits of this novel protocol.

Silica coated magnetic NiFe2O4 nanoparticle supported phosphomolybdic acid; synthesis, preparation and its application as a heterogeneous and recyclable catalyst for the one-pot synthesis of tri- and tetra-substituted imidazoles under solvent free conditions

A novel heteropolyacid supported on silica coated nickel ferrite nanoparticles (NFS–PMA) was synthesized and used as a green catalyst for one-pot syntheses of tri/tetra-substituted imidazoles. The catalyst could be recycled and reused through application of a magnetic field.