Number Of Terminal Functional Groups Research Articles

Dendrimer Architectonics to Treat Cancer and Neurodegenerative Diseases with Implications in Theranostics and Personalized Medicine.

Integration of diagnostic and therapeutic functions in a single platform namely theranostics has become a cornerstone for personalized medicine. Theranostics platform facilitates noninvasive detection and treatment while allowing the monitoring of disease progression and therapeutic efficacy in case of chronic conditions of cancer and Alzheimer's disease (AD). Theranostic tools function by themselves or with the aid of carrier, viz. liposomes, micelles, polymers, or dendrimers. The dendrimer architectures (DA) are well-characterized molecular nanoobjects with a large number of terminal functional groups to enhance solubility and offer multivalency and multifunctional properties. Various noninvasive diagnostic tools like magnetic resonance imaging (MRI), computed tomography (CT), gamma scintigraphy, and optical techniques have been accomplished utilizing DAs for simultaneous imaging and drug delivery. Obstacles in the formulation design, drug loading, payload delivery, biocompatibility, overcoming cellular membrane and blood-brain barrier (BBB), and systemic circulation remain a bottleneck in translational efforts. This review focuses on the diagnostic, therapeutic and theranostic potential of DA-based nanocarriers in treating cancer and neurodegenerative disorders like AD and Parkinson's disease (PD), among others. In view of the inverse relationship between cancer and AD, designing suitable DA-based theranostic nanodrug with high selectivity has tremendous implications in personalized medicine to treat cancer and neurodegenerative disorders.

A critical review of membrane modification techniques for fouling and biofouling control in pressure-driven membrane processes

The demand for new water resources has been increasing worldwide due to the growing global population and industrialization. Membranes play a central role in water purification processes with continuous technology improvements, new uses and cost reductions. Phase inversion is the most commonly used technique for preparing polymeric membranes. However, most commercial membranes are prepared from hydrophobic materials, which make them more susceptible to suffer the adsorption or deposition of molecules over their surface or inside their pores. This phenomenon, commonly termed as fouling, is one of the major operational problems in membrane processes. This review covers different membranes modification techniques to enhance permeability and to reduce fouling and the accumulation of microorganisms on membrane surface. The physicochemical properties of membrane surface can be tuned by grafting or coating to introduce functionalities like hydrophilic moieties or charged groups. Blending hydrophilic additives into the casting solution is another approach to increase membrane hydrophilicity and to improve water filtration performance. This review summarises the variety of porous materials that have been used to introduce inorganic nanoparticles into the casting solution. Porous carriers are used to introduce antimicrobial metals by preserving nanoparticle stability. Additionally, organic compounds, especially dendritic structures, have attracted considerable interest due to their highly branched structure, and their large number of terminal functional groups, which can also be used to enhance membrane properties. This work reviews the modification and functionalization techniques recently proposed to improve permeability and durability of the membranes used in pressure-driven separations.

Polyethylene-block-hyperbranched polyglycerol diblock copolymers: synthesis, thermal property and compatibilization

The linear-b-hyperbranched copolymers (LHBCs) consisting of linear polyethylene (PE) block and hyperbranched polyglycerol (hbPG) segment were synthesized with a sequential method starting with V(III)-catalyzed coordination polymerization and followed by ring-opening multibranching polymerization (ROMBP). The hydroxyl groups in hbPG block are further modified to benzoyl groups to improve the solubility. Ultimately, the structures and thermal properties of LHBCs were clearly characterized by 1H/13C NMR, GPC, TGA and DSC. The SEM images show that the LHBCs are effective compatibilizers in LLDPE/PCL blends. This paper represents the first case of generation of LHBCs combining hbPG with nonpolar and crystalline polyethylene block instead of polar and/or noncrystalline linear blocks. As a result, the crystallinity of linear polyethylene can be combined with low viscosity and a large number of terminal functional groups of hbPG.

Synthesis of CpM(CO)3–DAB and –PAMAM Dendrimer Conjugates and Preliminary Evaluation of Their Biological Activity

AbstractDendrimers of different generations and core structures [diaminobutane poly(propylenimine) (DAB) G1, G2, G3; poly(amidoamine) (PAMAM) G1] were chosen as carriers for bioactive organometallic half‐sandwich complexes of the type CpM(CO)3 (Cp = cyclopentadienyl, M = Mn or Re) to study the influence of these parameters on their biological activity against cancer cells. Structure–activity relationships were determined by variation of the metal center as well as the type, molecular weight, and number of terminal functional groups of the dendrimer conjugates. All conjugates were characterized by IR and NMR spectroscopy as well as HPLC. Their biological activity was determined on MCF‐7 human breast cancer cells by the resazurin assay. Interestingly, the most‐active compounds were the first‐generation dendrimer conjugates. The Mn and Re series showed nearly the same activities. Thus, the cytotoxicity of the dendrimer conjugates does not seem to directly correlate with the type or number of terminal functional groups. Rather, it points to a mechanism of action that is different from that previously observed for peptide conjugates with similar CpM(CO)3 functional groups.

Hyperbranched polymers and dendrimers as templates for organic/inorganic hybrid nanomaterials.

This paper reviews the recent research and development of hyperbranched polymers (HPs) and dendrimers, and their use as templates for organic-inorganic hybrid nanomaterials. Hyperbranched polymers (HPs) are highly branched macromolecules with three-dimensional globular structures featuring unique properties such as low viscosity, high solubility, and a large number of terminal functional groups compared to their linear analogs. They are easily prepared by (1) condensation polymerization, (2) self-condensing vinyl copolymerization (SCVCP), and (3) ring-opening multibranch polymerization methods. Organic-inorganic hybrid nanomaterials are synthesized by a template approach using HPs/dendrimers. Monometallic, bimetallic (alloy and core/shell), semiconductor, and metal oxide nanoparticles have been prepared by this route. The dendrimer component of these composites serves not only as a template for preparing the nanoparticles but also as a stabilizer for the nanoparticles.

Hyper-Branched Dendrimers in Drug Delivery and Solubilization

periphery, which forms a closed membrane-like structure [3]. When a critical stage is reached dendrimers cannot grow because of steric hindrance. This is sometimes referred to as ‘starburst effect’. In case of PAMAM dendrimers the starburst effect can be observed after the tenth generation [4]. Number of terminal functional groups also increases exponentially with the increased branch density. These internal cavities and terminal functional groups play important role in controlling the properties of therapeutic moieties that are encapsulated or complexed with it [5].

Synthesis of hyperbranched polymers with controlled structure

Hyperbranched polymers (HBPs) are highly branched macromolecules with 3-dimensional globular structures, which have unique properties, such as low viscosity, high solubility, and a large number of terminal functional groups compared to linear analogues. They are easily prepared by the polymerization of an ABx monomer in which A and B represent two different functional groups. This facile one-pot synthesis is advantageous over the synthesis of a dendrimer which requires multi-step reactions. For the HBPs, the degree of branching (DB) is one of the most important intrinsic parameters as well as the molecular weight distribution, which has a significant influence on the physical and chemical properties of the polymeric materials. The DB is theoretically ∼50% for a polymer derived from an AB2 monomer; this value is assumed based on the equal reactivity of the two B functional groups of the AB2 monomer. Recently, several groups have successfully achieved a 100% DB, which is a characteristic property of dendrimers, by using several strategies. Moreover, HBPs with a controlled DB from 0 to 100% have been reported by changing the rate constants of the first reaction of B and the second one toward an A functional group. In addition, the molecular weight and molecular weight distribution of the HBPs can also be controlled. In this review, we focus on the recent progress in the synthesis of HBPs in order to control their structures, i.e., 100% DB, molecular weight and molecular weight distribution (≤1.1).

Recent progress in hyperbranched polymers

Hyperbranched polymers are a type of highly branched polymers with a multitude of end groups. Because of their highly branched three-dimensional and sphere-like molecular architecture, hyperbranched polymers have shown very different properties from those of their linear analogues, such as low viscosity, high solubility and a large number of terminal functional groups that can be modified. Hence, a great deal of attention has been focused on hyperbranched polymers due to their unique structure, broad application fields, relatively easy synthetic methods and low cost. This paper reviews the development and the most recent advance of hyperbranched polymers in structure (including traditional structure and novel π conjugated structure), synthetic methods, properties and applications, with an emphasis being laid on the intrinsic relationships between structure, properties and applications as novel functional materials, such as nano-materials, drug delivery agents, electroluminescent materials and sensory materials. Additionally, the perspectives and the problems should be solved in the future are provided.

Functionalization of magnetic nanoparticles with peptide dendrimers

Surface functionalization of magnetic nanoparticles (MNPs) has been an exciting area of interest for researchers in biomedicine. In this paper, we introduce a new family of peptide dendritic ligands for functionalizing MNPs of superior quality. L-Lysine- and L-glutamic acid-based dendritic ligands with dopamine located at the focal points were fully designed and synthesized before the functionalization. Then ligands of different dendritic generations (G1 to G3) were immobilized on the surface of oleic-acid-coated hydrophobic MNPsvia ligand-exchange method to realize phase transfer. The two series of modified MNPs were systematically studied viaFTIR, TGA, XRD, TEM, DLS, VSM and zeta potential measurements. The modified MNPs exhibited an adjustable number of terminal functional groups and superior stability in aqueous solutions in a broad pH range. The surface existence of water-soluble polypeptide ligands promoted monodispersity of the particles and led to an increased hydrodynamic diameter under 30 nm from G1 to G3. After the ligand exchange process, the superparamagnetic behavior was successfully retained. The two series of modified MNPs exhibited approximate magnetization in the same generation, while the saturation magnetization of the MNPs decreased with increasing surface dendritic generation. MNPs functionalized with G1L-glutamic acid dendritic ligands had the highest saturation magnetization (55 emu g−1), which was larger than for the initial MNPs. This novel functionalization strategy provides a potential platform for designing and preparing highly stable ultrafine MNPs with high magnetization for biomedicinal applications.

Chromatography at the critical condition as a method for polymer analysis

The potential of critical chromatography in investigating the macromolecule structure of synthetic polymers is considered, such as the determination of the type and number of terminal functional groups, chain topology, and character of group alternation in the chain. New possibilities arising in the combination of critical chromatography with the mass spectrometry of macromolecules were discussed.

New method for the preparation of adsorbent with high adsorption capacity

Polyamidoamine (PAMAM) is a type of macromolecule having a definite chemical structure and a large number of terminal functional groups. The synthetic approach of the adsorbent with high adsorption capacity involved arching of PAMAM onto cellulose beads by reaction with epichlorohydrin. The product thus prepared had a large number of amino groups of 2.94 mmol/g derived from 0.23 mmol/g epoxy groups on cellulose beads. This method presents an effective method for the preparation of high-loading adsorbents.