New Analogs of Polyamine Toxins from Spiders and Wasps: Liquid Phase Fragment Synthesis and Evaluation of Antiproliferative Activity.

Polyamine toxins (PATs) are conjugates of polyamines (PAs) with lipophilic carboxylic acids, which have been recently shown to present antiproliferative activity. Ten analogs of the spider PATs Agel 416, HO-416b, and JSTX-3 and the wasp PAT PhTX-433 were synthesized with changes in the lipophilic head group and/or the PA chain, and their antiproliferative activity was evaluated on MCF-7 and MDA-MB-231 breast cancer cells, using Agel 416 and HO-416b as reference compounds. All five analogs of PhTX-433 were of very low activity on both cell lines, whereas the two analogs of JSTX-3 were highly active only on the MCF-7 cell line with IC50 values of 2.63-2.81 µΜ. Of the remaining three Agel 416 or HO-416b analogs, only the one with the spermidine chain was highly active on both cells with IC50 values of 3.15-12.6 µM. The two most potent compounds in this series, Agel 416 and HO-416b, with IC50 values of 0.09-3.98 µΜ for both cell lines, were found to have a very weak cytotoxic effect on the MCF-12A normal breast cells. The present study points out that the structure of both the head group and the PA chain determine the strength of the antiproliferative activity of PATs and their selectivity towards different cells.

Solid-Phase Synthesis of Selectively Mono-Fluorobenz(o)ylated Polyamines as a Basis for the Development of 18F-Labeled Radiotracers.

Polyamines are highly attractive vectors for tumor targeting, particularly with regards to the development of radiolabeled probes for imaging by positron emission (PET) and single-photon emission computed tomography (SPECT). However, the synthesis of selectively functionalized derivatives remains challenging due to the presence of multiple amino groups of similar reactivity. In this work, we established a synthetic methodology for the selective mono-fluorobenz(o)ylation of various biogenic diamines and polyamines as lead compounds for the perspective development of substrate-based radiotracers for targeting polyamine-specific membrane transporters and enzymes such as transglutaminases. For this purpose, the polyamine scaffold was constructed by solid-phase synthesis of the corresponding oxopolyamines and subsequent reduction with BH3/THF. Primary and secondary amino groups were selectively protected using Dde and Boc as protecting groups, respectively, in orientation to previously reported procedures, which enabled the selective introduction of the reporter groups. For example, N1-FBz-spermidine, N4-FBz-spermidine, N8-FBz-spermidine, and N1-FBz-spermine and N4-FBz-spermine (FBz = 4-fluorobenzoyl) were obtained in good yields by this approach. The advantages and disadvantages of this synthetic approach are discussed in detail and its suitability for radiolabeling was demonstrated for the solid-phase synthesis of N1-[18F]FBz-cadaverine.

Recent Advances in the Synthesis of Polyamine Derivatives and Their Applications.

Biogenic polyamines (PAs) are involved in the growth and development of normal cells, and their intracellular concentration is stable. The concentration of PAs in cancer cells is significantly increased to promote and sustain their rapid proliferation. Over the years, synthetic PAs, which differ in their structure, have demonstrated high antitumor activity and are involved in clinical trials. The chemical synthesis of PAs and their conjugates require the correct choice of synthetic pathways-methods for constructing conjugates and the orthogonal protection of amino groups. The most common methods of synthesis of PA conjugates are acylation of regioselectively protected PAs or their alkylation under the conditions of the Fukuyama reaction. One of the most promising methods of PA synthesis is the use of a multicomponent Ugi reaction, which allows various PAs to be obtained in high yields. In this review, we describe and analyze various approaches that are used in the synthesis of polyamines and their conjugates.

Dual-Functional Dendrimer Micelles with Glycyrrhizic Acid for Anti-Inflammatory Therapy of Acute Lung Injury.

Dendrimer micelles with glycyrrhizic acid (GA) were developed for anti-inflammatory therapy of acute lung injury (ALI). Cholesterol was conjugated to histidine- and arginine-grafted polyamidoamine (PamHR) for micelle formation. The cholesterol-conjugated PamHR (PamHRchol) was mixed with amphiphilic GA to produce PamHRchol/GA mixed micelles. The GA integrated into the micelles had two functions: it acted as an anti-inflammatory drug and facilitated intracellular gene delivery. The PamHRchol/GA micelles formed stable complexes with plasmid DNA. Integrating GA into the micelles increased their transfection efficiency. Confocal microscopy and flow-cytometry studies confirmed that the PamHRchol/GA micelles improved cellular uptake compared with PamHRchol. A competition assay with free GA suggested that the enhanced transfection efficiency of the micelles might be due to the interaction between GA and its receptor. In addition, GA has a membrane-destabilizing effect, and a chloroquine pretreatment assay confirmed that GA increased endosomal escape. Furthermore, the PamHRchol/GA micelles reduced tumor necrosis factor-α in lipopolysaccharide-activated Raw264.7 cells, suggesting a mechanism for its anti-inflammatory effects. To evaluate the therapeutic potential of the PamHRchol/GA micelles, the heme oxygenase-1 (HO-1) gene was delivered into the lungs of mice with ALI. The PamHRchol/GA micelles had higher gene delivery efficiency into the lungs than polyethylenimine (25 kDa, PEI25k) and the PamHRchol micelles. The combined effects of the HO-1 gene and GA produced effective anti-inflammation response in the lungs of the ALI animals. Therefore, the dual-function PamHRchol/GA micelles, which acted as an anti-inflammatory drug and a gene carrier, could be a useful therapy for inflammatory lung diseases.

In vitro/vivo antitumor study of modified-chitosan/carboxymethyl chitosan "boosted" charge-reversal nanoformulation.

Major obstacles in the development of nanoformulations as efficient drug delivery systems are the rapid clearance from blood circulation and lysosomal entrapment. To overcome these problems, a polysaccharide-based core-shell type charge-switchable nanoformulation (CS-LA-DMMA/CMCS/PAMAM@DOX) is constructed to improve antitumor efficacy of DOX. By applying carboxymethyl chitosan (CMCS) as bridge polymer and negatively charged chitosan-derivative as outer shell, the stability and pH-sensitivity of this nanoformulation is promisingly enhanced. Furthermore, the positively charged PAMAM@DOX could escape from lysosomes via "proton sponge effect" and "cationic-anionic interaction with lysosome membranes". Admirable cellular uptake and high apoptosis/necrosis rate were detected in this study. In vitro assays demonstrate that the CS-LA-DMMA/CMCS/PAMAM@DOX was internalized into HepG2 cells predominantly via the clathrin-mediated endocytosis pathway. Excitingly, in vivo studies showed that high accumulation of CS-LA-DMMA/CMCS/PAMAM@DOX in tumor tissue led to enhanced tumor inhibition. Compared with free DOX, the tumor inhibition rate of nanoformulation was improved up to 226%.

Identifying urotropine derivatives as co-donors of formaldehyde and nitric oxide for improving antitumor therapy.

A pharmacophore integration strategy was utilized to develop the first co-donor of formaldehyde and nitric oxide (FANO), composed of urotropine derived nitramine/nitrosamine. FANO simultaneously generated formaldehyde and nitric oxide on-demand, resulting in synergistic anticancer effects. Importantly, liposomal formulation of FANO effectively inhibited tumor growth with minimal side-effects, providing a potent combined nitric oxide therapy for malignancy.

Design, Synthesis, and Biological Evaluation of Boron-Containing Macrocyclic Polyamines and Their Zinc(II) Complexes for Boron Neutron Capture Therapy.

Boron neutron capture therapy (BNCT) is a binary therapeutic method for cancer treatment based on the use of a combination of a cancer-specific drug containing boron-10 (10B) and thermal neutron irradiation. For successful BNCT, 10B-containing molecules need to accumulate specifically in cancer cells, because destructive effect of the generated heavy particles is limited basically to boron-containing cells. Herein, we report on the design and synthesis of boron compounds that are functionalized with 9-, 12-, and 15-membered macrocyclic polyamines and their Zn2+ complexes. Their cytotoxicity, intracellular uptake activity into cancer cells and normal cells, and BNCT effect are also reported. The experimental data suggest that mono- and/or diprotonated forms of metal-free [12]aneN4- and [15]aneN5-type ligands are uptaken into cancer cells, and their complexes with intracellular metals such as Zn2+ would induce cell death upon thermal neutron irradiation, possibly via interactions with DNA.

Redox-Responsive Gene Delivery from Perfluorocarbon Nanoemulsions through Cleavable Poly(2-oxazoline) Surfactants.

The clinical utility of emulsions as delivery vehicles is hindered by a dependence on passive release. Stimuli-responsive emulsions overcome this limitation but rely on external triggers or are composed of nanoparticle-stabilized droplets that preclude sizes necessary for biomedical applications. Here, we employ cleavable poly(2-oxazoline) diblock copolymer surfactants to form perfluorocarbon (PFC) nanoemulsions that release cargo upon exposure to glutathione. These surfactants allow for the first example of redox-responsive nanoemulsions in cellulo. A noncovalent fluorous tagging strategy is leveraged to solubilize a GFP plasmid inside the PFC nanoemulsions, whereupon protein expression is achieved selectively when employing a stimuli-responsive surfactant. This work contributes a methodology for non-viral gene delivery and represents a general approach to nanoemulsions that respond to endogenous stimuli.

Biotin-Containing Third Generation Glucoheptoamidated Polyamidoamine Dendrimer for 5-Aminolevulinic Acid Delivery System.

Polyamidoamine PAMAM dendrimer generation 3 (G3) was modified by attachment of biotin via amide bond and glucoheptoamidated by addition of α-D-glucoheptono-1,4-lacton to obtain a series of conjugates with a variable number of biotin residues. The composition of conjugates was determined by detailed 1-D and 2-D NMR spectroscopy to reveal the number of biotin residues, which were 1, 2, 4, 6, or 8, while the number of glucoheptoamide residues substituted most of the remaining primary amine groups of PAMAM G3. The conjugates were then used as host molecules to encapsulate the 5-aminolevulinic acid. The solubility of 5-aminolevulinic acid increased twice in the presence of the 5-mM guest in water. The interaction between host and guest was accompanied by deprotonation of the carboxylic group of 5-aminolevulinic acid and proton transfer into internal ternary nitrogen atoms of the guest as evidenced by a characteristic chemical shift of resonances in the 1H NMR spectrum of associates. The guest molecules were most likely encapsulated inside inner shell voids of the host. The number of guest molecules depended on the number of biotin residues of the host, which was 15 for non-biotin-containing glucoheptoamidated G3 down to 6 for glucoheptoamidated G3 with 8 biotin residues on the host surface. The encapsulates were not cytotoxic against Caco-2 cells up to 200-µM concentration in the dark. All encapsulates were able to deliver 5-aminolevulinic acid to cells but aqueous encapsulates were more active in this regard. Simultaneously, the reactive oxygen species were detected by staining with H2DCFDA in Caco-2 cells incubated with encapsulates. The amount of PpIX was sufficient for induction of reactive oxygen species upon 30-s illumination with a 655-nm laser beam.

A docosyl-terminated polyamine amphiphile-bonded stationary phase for multimodal separations in liquid chromatography.

A convenient synthetic approach to a linear alkyl-polyamine amphiphilic chromatographic selector was proposed. Successive immobilization of the amphiphile onto silica gel afforded a multimodal stationary phase for high-performance liquid chromatography (HPLC). The as-prepared silica material was studied comparatively with a conventional octadecyl (C18) and an amide-embedded C18 stationary phase. The new uniform docosyl-triamine tandem was featured by an enhanced shape selectivity towards geometric isomers, and a low silanol activity towards alkaline solutes. The presence of multiple amino groups rendered the new adsorbent operable in different modes, such as hydrophilic interaction and ion-exchange modes. The satisfactory performance of the said stationary phase in separating different classes of analytes, including polycyclic aromatic hydrocarbons, flavonoids, tricyclic antidepressants, calcium channel blockers, aromatic acids, inorganic anions, nucleosides and estrogens, revealed its great potential and high adaptability for multipurpose LC utility.

Nanosized T1 MRI Contrast Agent Based on a Polyamidoamine as Multidentate Gd Ligand.

A linear polyamidoamine (PAA) named BAC-EDDS, containing metal chelating repeat units composed of two tert-amines and four carboxylic groups, has been prepared by the aza-Michael polyaddition of ethylendiaminodisuccinic (EDDS) with 2,2-bis(acrylamido)acetic acid (BAC). It was characterized by size exclusion chromatography (SEC), FTIR, UV-Vis and NMR spectroscopies. The pKa values of the ionizable groups of the repeat unit were estimated by potentiometric titration, using a purposely synthesized molecular ligand (Agly-EDDS) mimicking the structure of the BAC-EDDS repeat unit. Dynamic light scattering (DLS) and ζ-potential analyses revealed the propensity of BAC-EDDS to form stable nanoaggregates with a diameter of approximately 150 nm at pH 5 and a net negative charge at physiological pH, in line with an isoelectric point <2. BAC-EDDS stably chelated Gd (III) ions with a molar ratio of 0.5:1 Gd (III)/repeat unit. The stability constant of the molecular model Gd-Agly-EDDS (log K = 17.43) was determined as well, by simulating the potentiometric titration through the use of Hyperquad software. In order to comprehend the efficiency of Gd-BAC-EDDS in contrasting magnetic resonance images, the nuclear longitudinal (r1) and transverse (r2) relaxivities as a function of the externally applied static magnetic field were investigated and compared to the ones of commercial contrast agents. Furthermore, a model derived from the Solomon-Bloembergen-Morgan theory for the field dependence of the NMR relaxivity curves was applied and allowed us to evaluate the rotational correlation time of the complex (τ = 0.66 ns). This relatively high value is due to the dimensions of Gd-BAC-EDDS, and the associated rotational motion causes a peak in the longitudinal relaxivity at ca. 75 MHz, which is close to the frequencies used in clinics. The good performances of Gd-BAC-EDDS as a contrast agent were also confirmed through in vitro magnetic resonance imaging experiments with a 0.2 T magnetic field.

The Utilization of Poly(2-ethyl-2-oxazoline)-b-Poly(ε-caprolactone) Ellipsoidal Particles for Intracellular BIKDDA Delivery to Prostate Cancer.

Prostate cancer is the most common cancer, which is about 15-20% among male cancers worldwide. As most common strategies such as radiotherapy, chemotherapy, or surgery alone can be unsuccessful in the treatment of prostate cancer, this study aims to develop a new approach to deliver newly generated proapoptotic gene, BIKDDA, to androgen independent prostate cancer cells, 22RV1, using new generation nanocarriers called ellipsoids. As far as it is known, this is the first study that assesses the ability of proapoptotic gene BIKDDA to induce apoptosis in prostate cancer cell. BIKDDA encapsulating PEtOx-b-PCL-based ellipsoids are fabricated by solvent-switch method, and their morphology, size, and BIKDDA content are characterized. Gene delivery efficiency of BIKDDA loaded PEtOx-b-PCL ellipsoids is demonstrated by analysis of BIK mRNA expression with real-time PCR. The apoptotic effect of PEtOx-b-PCL ellipsoids loaded with BIKDDA (EPs-BIKDDA) on 22RV1 is shown by Annexin V staining. The obtained results demonstrate that the treatment of 22RV1 cells with EPs-BIKDDA can significantly increase BIK mRNA levels by 4.5-fold leading to cell death. This study not only represents BIKDDA as a potential therapeutic strategy in prostate cancer but also the capacity of ellipsoids as promising in vivo gene delivery vehicles.

Total Synthesis of the Proposed Structure for Protoaculeine B, a Polycationic Marine Sponge Metabolite, with a Homogeneous Long-Chain Polyamine.

By establishing the procedures for sequential deprotections, reaction monitoring, purification, and handling, for the first time, we achieved the total synthesis of the proposed structure for protoaculeine B (2), which is a highly hydrophilic and polycationic amino acid. The NMR and mass spectra and chemical reactivity of the synthetic sample differed from those of natural protoaculeine B, which indicates the necessity for revision of the originally reported structure.

New Polyaminoisoprenyl Antibiotics Enhancers against Two Multidrug-Resistant Gram-Negative Bacteria from Enterobacter and Salmonella Species.

A series consisting of new polyaminoisoprenyl derivatives were prepared in moderate to good chemical yields varying from 32 to 64% according to two synthetic pathways: (1) using a titanium-reductive amination reaction affording a 50/50 mixture of cis and trans isomers and (2) a direct nucleophilic substitution leading to a stereoselective synthesis of the compounds of interest. These compounds were then successfully evaluated for their in vitro antibiotic enhancer properties against resistant Gram-negative bacteria of four antibiotics belonging to four different families. The mechanism of action against Enterobacter aerogenes of one of the most efficient of these chemosensitizing agents was precisely evaluated by using fluorescent dyes to measure outer-membrane permeability and to determine membrane depolarization. The weak cytotoxicity encountered led us to perform an in vivo experiment dealing with the treatment of mice infected with Salmonella typhimurium and affording preliminary promising results in terms of tolerance and efficiency of the polyaminoisoprenyl derivative 5r/doxycycline combination.

Design, synthesis, and biological characterization of a new class of symmetrical polyamine-based small molecule CXCR4 antagonists.

CXCR4, a well-studied coreceptor of human immunodeficiency virus type 1 (HIV-1) entry, recognizes its cognate ligand SDF-1α (also named CXCL12) which plays many important roles, including regulating immune cells, controlling hematopoietic stem cells, and directing cancer cells migration. These pleiotropic roles make CXCR4 an attractive target to mitigate human disorders. Here a new class of symmetrical polyamines was designed and synthesized as potential small molecule CXCR4 antagonists. Among them, a representative compound 21 (namely HF50731) showed strong CXCR4 binding affinity (mean IC50 = 19.8 nM) in the CXCR4 competitive binding assay. Furthermore, compound 21 significantly inhibited SDF-1α-induced calcium mobilization and cell migration, and blocked HIV-1 infection via antagonizing CXCR4 coreceptor function. The structure-activity relationship analysis, site-directed mutagenesis, and molecular docking were conducted to further elucidate the binding mode of compound 21, suggesting that compound 21 could primarily occupy the minor subpocket of CXCR4 and partially bind in the major subpocket by interacting with residues W94, D97, D171, and E288. Our studies provide not only new insights for the fragment-based design of small molecule CXCR4 antagonists for clinical applications, but also a new and effective molecular probe for CXCR4-targeting biological studies.

Toward a Rational Design of Polyamine-Based Zinc-Chelating Agents for Cancer Therapies.

In vitro viability assays against a representative panel of human cancer cell lines revealed that polyamines L1a and L5a displayed remarkable activity with IC50 values in the micromolar range. Preliminary research indicated that both compounds promoted G1 cell cycle arrest followed by cellular senescence and apoptosis. The induction of apoptotic cell death involved loss of mitochondrial outer membrane permeability and activation of caspases 3/7. Interestingly, L1a and L5a failed to activate cellular DNA damage response. The high intracellular zinc-chelating capacity of both compounds, deduced from the metal-specific Zinquin assay and ZnL2+ stability constant values in solution, strongly supports their cytotoxicity. These data along with quantum mechanical studies have enabled to establish a precise structure-activity relationship. Moreover, L1a and L5a showed appropriate drug-likeness by in silico methods. Based on these promising results, L1a and L5a should be considered a new class of zinc-chelating anticancer agents that deserves further development.

Amphiphilic Polymethyloxazoline-Polyethyleneimine Copolymers: Interaction with Lipid Bilayer and Antibacterial Properties.

Polycations, mimicking activity of antibacterial peptides, belong to an important class of molecules investigated as a support or as an alternative to antibiotics. In this work, studies of modified linear amphiphilic statistical polymethyloxazoline (PMOX) and polyethyleneimine copolymers (PMOX_PEI) series are presented. Variation of PEI content in the structure results in controllable changes of polymeric aggregates zeta potential. The structure with the highest positive charge shows the best antimicrobial activity, well visible in tests against model Gram-positive and Gram-negative bacteria, fungi, and mycobacterium strains. The polymer toxicity is evaluated with MTT and hemolysis assay as a reference. Quartz crystal microbalance (QCM-D) is used to investigate interaction between polycations and a model lipid membrane. Polymer activity correlates well with molecular structure, showing that amphiphilic component is altering polymer behavior in contact with the lipid bilayer.

Encapsulation of gadolinium ferrite nanoparticle in generation 4.5 poly(amidoamine) dendrimer for cancer theranostics applications using low frequency alternating magnetic field.

Iron oxide-based magnetic resonance imaging (MRI) contrast agents have negative contrast limitations in cancer diagnosis. Gadolinium (Gd)-based contrast agents show toxicity. To overcome these limitations, Gd-doped ferrite (Gd:Fe3O4 (GdIO) nanoparticles (NPs) were synthesized as T1-T2 dual-modal contrast agents for MRI-traced drug delivery. A theranostics GdIO encapsulated in a Generation 4.5 PAMAM dendrimer (G4.5-GdIO) was developed by alkaline coprecipitation. The drug-loading efficiency of the NPs was ∼24%. In the presence of a low-frequency alternating magnetic field (LFAMF), a maximum cumulative doxorubicin (DOX) release of ∼77.47% was achieved in a mildly acidic (pH = 5.0) simulated endosomal microenvironment. Relaxometric measurements indicated superior r1 (5.19 mM-1s-1) and r2 (26.13 mM-1s-1) for G4.5-GdIO relative to commercially available Gd-DTPA. Thus, G4.5-GdIO is promising as an alternative noninvasive MRI-traced cancer drug delivery system.

Mixed Carboxyl and Hydrophobic Dendrimer Surface Inhibits Amyloid-ß Fibrillation: New Insight from the Generation Number Effect.

Fibrillation of amyloid-ß peptide (Aß) is closely associated with the progression of Alzheimer's disease (AD), and so inhibition of Aß fibrillation has been considered as one of the promising strategies for AD prevention and treatment. Our group has proposed the hydrophobic binding-electrostatic repulsion (HyBER) theory on inhibiting Aß fibrillation by a surface with mixed negative charges and hydrophobic groups, which provides a new strategy for the design of potent amyloid inhibitors. Carboxyl-terminated polyamidoamine dendrimer (PAMAM) is a kind of biocompatible nanomaterial with only carboxyl groups on its surface, and its architecture and property vary with the generation number, low-generation dendrimers possessing sparse distributions of terminal groups while high-generation dendrimers having compact surface groups, which offer abundant base materials for further study of the HyBER theory. We have designed a potent amyloid inhibitor with generation 5 PAMAM. To provide new insights into the HyBER mechanism, we have herein proposed to synthesize phenyl-modified PAMAM dendrimers of generations 3 to 6 (G3-P to G6-P) and study the effect of the generation number on Aß fibrillation. Results show that phenyl derivatives of low-generation dendrimers (G3-P and G4-P) do not show any interference with Aß aggregation, whereas the phenyl derivatives of high-generation dendrimers (G5-P and G6-P) significantly inhibit Aß42 aggregation and alter the ultrastructure of Aß42 aggregates. The results indicate that the density and distribution of surface functional groups on a dendrimer is of great importance for the HyBER effect to happen. The new understanding on the HyBER mechanism would benefit in the development of potent amyloid inhibitors based on the theory.

ROS-responsive fluorinated polycations as non-viral gene vectors.

Polycation carriers hold great potential in gene therapy. However, they usually suffer from obvious cytotoxicity and unsatisfactory transfection efficiency. In this report, a series of fluorobenzene substituted and thioacetal contained polycations (TAEA-S-xF) were prepared to explore novel alternatives for safe and efficient non-viral polymeric gene vectors. The reactive oxygen species (ROS)-responsive property of thioacetal moieties together with the fluorine effect were hope to bring the vector better performance in gene delivery process. These materials could efficiently condense DNA into nanoparticles with proper size and surface potential. The structure-activity relationship of these materials was systematically investigated, and the In vitro transfection results revealed that the amount of fluorine atoms on the linkage plays important role to ensure the transfection efficiency and serum tolerance. The ROS-responsive behavior was verified by NMR, gel electrophoresis experiment and dynamic light scattering (DLS) assay. Cytotoxicity assay results also suggest that these ROS-degradable polycations show good biocompatibility in response to higher ROS level in cancer cells. Among these fluorinated polymers, the one with the most fluorine atoms showed the best transfection efficiency, which was up to 54 times higher than polyethyleneimine (PEI) 25 kDa. Mechanism studies reveal that its better performance may come from good cellular uptake and endosome escape ability.