Biogenic and Synthetic Polyamines Bind Cationic Dendrimers

Biogenic polyamines are essential for cell growth and differentiation, while polyamine analogues exert antitumor activity in multiple experimental model systems, including breast and lung cancer. Dendrimers are widely used for drug delivery in vitro and in vivo. We report the bindings of biogenic polyamines, spermine (spm), and spermidine (spmd), and their synthetic analogues, 3,7,11,15-tetrazaheptadecane.4HCl (BE-333) and 3,7,11,15,19-pentazahenicosane.5HCl (BE-3333) to dendrimers of different compositions, mPEG-PAMAM (G3), mPEG-PAMAM (G4) and PAMAM (G4). FTIR and UV-visible spectroscopic methods as well as molecular modeling were used to analyze polyamine binding mode, the binding constant and the effects of polyamine complexation on dendrimer stability and conformation. Structural analysis showed that polyamines bound dendrimers through both hydrophobic and hydrophilic contacts with overall binding constants of Kspm-mPEG-G3 = 7.6×104 M−1, Kspm-mPEG-PAMAM-G4 = 4.6×104 M−1, Kspm-PAMAM-G4 = 6.6×104 M−1, Kspmd-mPEG-G3 = 1.0×105 M−1, Kspmd-mPEG-PAMAM-G4 = 5.5×104 M−1, Kspmd-PAMAM-G4 = 9.2×104 M−1, KBE-333-mPEG-G3 = 4.2×104 M−1, KBe-333-mPEG-PAMAM-G4 = 3.2×104 M−1, KBE-333-PAMAM-G4 = 3.6×104 M−1, KBE-3333-mPEG-G3 = 2.2×104 M−1, KBe-3333-mPEG-PAMAM-G4 = 2.4×104 M−1, KBE-3333-PAMAM-G4 = 2.3×104 M−1. Biogenic polyamines showed stronger affinity toward dendrimers than those of synthetic polyamines, while weaker interaction was observed as polyamine cationic charges increased. The free binding energies calculated from docking studies were: −3.2 (spermine), −3.5 (spermidine) and −3.03 (BE-3333) kcal/mol, with the following order of binding affinity: spermidine-PAMAM-G-4>spermine-PAMMAM-G4>BE-3333-PAMAM-G4 consistent with spectroscopic data. Our results suggest that dendrimers can act as carrier vehicles for delivering antitumor polyamine analogues to target tissues

In quest of a systematic framework for unifying and defining nanoscience

This article proposes a systematic framework for unifying and defining nanoscience based on historic first principles and step logic that led to a “central paradigm” (i.e., unifying framework) for traditional elemental/small-molecule chemistry. As such, a Nanomaterials classification roadmap is proposed, which divides all nanomatter into Category I: discrete, well-defined and Category II: statistical, undefined nanoparticles. We consider only Category I, well-defined nanoparticles which are >90% monodisperse as a function of Critical Nanoscale Design Parameters (CNDPs) defined according to: (a) size, (b) shape, (c) surface chemistry, (d) flexibility, and (e) elemental composition. Classified as either hard (H) (i.e., inorganic-based) or soft (S) (i.e., organic-based) categories, these nanoparticles were found to manifest pervasive atom mimicry features that included: (1) a dominance of zero-dimensional (0D) core–shell nanoarchitectures, (2) the ability to self-assemble or chemically bond as discrete, quantized nanounits, and (3) exhibited well-defined nanoscale valencies and stoichiometries reminiscent of atom-based elements. These discrete nanoparticle categories are referred to as hard or soft particle nanoelements. Many examples describing chemical bonding/assembly of these nanoelements have been reported in the literature. We refer to these hard:hard (H-n:H-n), soft:soft (S-n:S-n), or hard:soft (H-n:S-n) nanoelement combinations as nanocompounds. Due to their quantized features, many nanoelement and nanocompound categories are reported to exhibit well-defined nanoperiodic property patterns. These periodic property patterns are dependent on their quantized nanofeatures (CNDPs) and dramatically influence intrinsic physicochemical properties (i.e., melting points, reactivity/self-assembly, sterics, and nanoencapsulation), as well as important functional/performance properties (i.e., magnetic, photonic, electronic, and toxicologic properties). We propose this perspective as a modest first step toward more clearly defining synthetic nanochemistry as well as providing a systematic framework for unifying nanoscience. With further progress, one should anticipate the evolution of future nanoperiodic table(s) suitable for predicting important risk/benefit boundaries in the field of nanoscience

Synthesis of 2,2'-bipyridines : from versatile building blocks to sexy architectures and functional (nano)materials

The latest synthetic strategies to prepare 2,2-bipyridine and its mono-substituted, symmetrical and unsymmetrical 3,3-, 4,4-, 5,5-, and 6,6-disubstituted derivatives are critically discussed and evaluated. Different coupling procedures to achieve new symmetrical and unsymmetrical functionalized 2,2-bipyridines, such as Stille-type, Negishi-type, and Suzuki-type cross-coupling reactions are discussed in detail. Moreover, condensation procedures that allow further variations are presented. The application of functional group transformations for access to additional groups is examined

Poly(amidoamine) (PAMAM) dendritic nanostructures for controlled sitespecific delivery of acidic anti-inflammatory active ingredient

The purpose of the investigation was to evaluate the potential of polyamidoamine (PAMAM) dendrimer as nanoscale drug delivery units for controlled release of water insoluble and acidic anti-inflammatory drug. Flurbiprofen (FB) was selected as a model acidic anti-inflammatory drug. The aqueous solutions of 4.0 generation (G) PAMAM dendrimer in different concentrations were prepared and used further for solubilizing FB. Formation of dendrimer complex was characterized by Fourier transform infrared spectroscopy. The effect of pH on the solubility of FB in dendrimer was evaluated. Dendrimer formulations were further evaluated for in vitro release study and hemolytic toxicity. Pharmacokinetic and biodistribution were studied in male albino rats. Efficacy of dendrimer formulation was tested by carrageenan induced paw edema model. It was observed that the loaded drug displayed initial rapid release (more than 40% till 3rd hour) followed by rather slow release. Pharmacodynamic study revealed 75% inhibition at 4th hour that was maintained above 50% till 8th hour. The mean residence time (MRT) and terminal half-life (THF) of the dendritic formulation increased by 2-fold and 3-fold, respectively, compared with free drug. Hence, with dendritic system the drug is retained for longer duration in the biosystem with 5-fold greater distribution. It may be concluded that the drug-loaded dendrimers not only enhanced the solubility but also controlled the delivery of the bioactive with localized action at the site of inflammation