Homologation of Polyamines in the Rapid Synthesis of Lipospermine Conjugates and Related Lipoplexes

Supramolecular Assembly of Water-Soluble Platinum(II) Complexes: From Emission Modulation to Cell Imaging in Specific Organelles

The control of self-organized metal complexes presents advantages regarding the modulation of luminescence through dynamic assembly, rendering them promising for bioimaging. Herein, we demonstrate a strategy towards a series of amphiphilic Pt(II) complexes featuring bis-cyclometalated ligands as tetradentate luminophores, which exhibit enhanced water solubility and tuneable self-assembly properties. The resulting nanostructures can be precisely controlled by adjusting concentration and solvent composition, yielding switchable luminescence from red (i. e., excimer-based) to green (i. e., monomer-centred) and reversible (dis-)assembly of the aggregates. Cytotoxicity assays confirmed the innocuous nature of these luminophores at concentrations below 10 μM, while cellular uptake studies demonstrated effective internalization in both living and fixed cells. Using photoluminescence lifetime imaging micro(spectro)scopy, we determined that the complexes localized preferentially within lysosomes of living cells, while accumulating in the nuclei of fixed cells, with differences in photophysical behavior depending on whether the species were monomeric or excimeric in nature. These new findings provide insights into the systematic design of water-soluble Pt(II)-based luminophores with photophysical properties controlled by supramolecular interactions, underlining their potential for use in cellular imaging and diagnostics.

Pulmonary siRNA Delivery with Sophisticated Amphiphilic Poly(Spermine Acrylamides) for the Treatment of Lung Fibrosis

RNA interference (RNAi) is an efficient strategy to post-transcriptionally silence gene expression. While all siRNA drugs on the market target the liver, the lung offers a variety of currently undruggable targets, which can potentially be treated with RNA therapeutics. To achieve this goal, the synthesis of poly(spermine acrylamides) (P(SpAA) is reported herein. Polymers are prepared via polymerization of N-acryloxysuccinimide (NAS) and afterward this active ester is converted into spermine-based pendant groups. Copolymerizations with decylacrylamide are employed to increase the hydrophobicity of the polymers. After deprotection, polymers show excellent siRNA encapsulation to obtain perfectly sized polyplexes at very low polymer/RNA ratios. In vitro 2D and 3D cell culture, ex vivo and in vivo experiments reveal superior properties of amphiphilic spermine-copolymers with respect to delivery of siRNA to lung cells in comparison to commonly used lipid-based transfection agents. In line with the in vitro results, siRNA delivery to human lung explants confirm more efficient gene silencing of protease-activated receptor 2 (PAR2), a G protein-coupled receptor involved in fibrosis. This study reveals the importance of the balance between efficient polyplex formation, cellular uptake, gene knockdown, and toxicity for efficient siRNA delivery in vitro, in vivo, and in fibrotic human lung tissue ex vivo.

Chemical Synthesis of a Branched Nonasaccharide Fragment from Helicobacter pylori Lipopolysaccharide

A chemical synthesis of a unique nanosaccharide fragment from Helicobacter pylori lipopolysaccharide was achieved via a convergent glycosylation method. Challenges involved in the synthesis include the highly stereoselective construction of β-3-deoxy-d-manno-oct-2-ulosonic acid (Kdo) and two 1,2-cis-glycosidic linkages, as well as the formation of a branched 2,7-disubstituted heptose subunit. Hydrogen-bond mediated aglycone delivery strategy and benzoyl-directing remote participation effect were employed, respectively, for the efficient generation of the desired β-Kdo glycoside and 1,2-cis-α-l-fucoside/d-glucoside. Moreover, the key branched framework was successfully established through a [(7 + 1) + 1] assembly approach involving the stepwise glycosylation of the heptasaccharide alcohol with two monosaccharide donors. The synthesized 1 containing a propylamine linker at the reducing end can be covalently bound to a carrier protein for further immunological studies.

Effectiveness of a novel gene nanotherapy based on putrescine for cancer treatment

Gene therapy has long been proposed for cancer treatment. However, the use of therapeutic nucleic acids presents several limitations such as enzymatic degradation, rapid clearance, and poor cellular uptake and efficiency. In this work we propose the use of putrescine, a precursor for higher polyamine biosynthesis for the preparation of cationic nanosystems for cancer gene therapy. We have formulated and characterized putrescine-sphingomyelin nanosystems (PSN) and studied their endocytic pathway and intracellular trafficking in cancer cells. After loading a plasmid DNA (pDNA) encoding the apoptotic Fas Ligand (FasL), we proved their therapeutic activity by measuring the cell death rate after treatment of MDA-MB-231 cells. We have also used xenografted zebrafish embryos as a first in vivo approach to demonstrate the efficacy of the proposed PSN-pDNA formulation in a more complex model. Finally, intratumoral and intraperitoneal administration to mice-bearing MDA-MB-231 xenografts resulted in a significant decrease in tumour cell growth, highlighting the potential of the developed gene therapy nanoformulation for the treatment of triple negative breast cancer.

Antifungal Activity of Amphiphilic Perylene Bisimides

Perylene-based compounds, either naturally occurring or synthetic, have shown interesting biological activities. In this study, we report on the broad-spectrum antifungal properties of two lead amphiphilic perylene bisimides, compounds 4 and 5, which were synthesized from perylene-3,4,9,10-tetracarboxylic dianhydride by condensation with spermine and an ammonium salt formation. The antifungal activity was evaluated using a collection of fungal strains and clinical isolates from patients with onychomycosis or sporotrichosis. Both molecules displayed an interesting antifungal profile with MIC values in the range of 2–25 μM, being as active as several reference drugs, even more potent in some particular strains. The ammonium trifluoroacetate salt 5 showed the highest activity with a MIC value of 2.1 μM for all tested Candida spp., two Cryptococcus spp., two Fusarium spp., and one Neoscytalidium spp. strain. Therefore, these amphiphilic molecules with the perylene moiety and cationic ammonium side chains represent important structural features for the development of novel antifungals.

Practical Synthesis of Antimicrobial Long Linear Polyamine Succinamides

There are many severe bacterial infections notorious for their ability to become resistant to clinically relevant antibiotics. Indeed, antibiotic resistance is a growing threat to human health, further exacerbated by the lack of new antibiotics. We now describe the practical synthesis of a series of substituted long linear polyamines that produce rapid antibacterial activity against both Gram-positive and Gram-negative bacteria, including meticillin-resistant Staphylococcus aureus. These compounds also reduce biofilm formation in Pseudomonas aeruginosa. The most potent analogues are thermine, spermine, and 1,12-diaminododecane homo- and heterodimeric polyamine succinic acid amides. They are of the order of activity of the aminoglycoside antibiotics kanamycin and tobramycin as positive controls. Their low human cell toxicity is demonstrated in ex vivo hemolytic assays where they did not produce even 5% hemolysis of human erythrocytes. These long, linear polyamines are a new class of broad-spectrum antibacterials active against drug-resistant pathogens.

Practical Synthesis of Polyamine Succinamides and Branched Polyamines

Antibiotic resistance is now a growing threat to human health, further exacerbated by the lack of new antibiotics. We describe the practical synthesis of a series of substituted polyamine succinamides and branched polyamines that are potential new antibiotics against both Gram-positive and Gram-negative bacteria, including MRSA and Pseudomonas aeruginosa. They are prepared via 1,4-Michael addition of acrylonitrile and then hydrogenation of the nitrile functional groups to primary amines. They are built upon the framework of the naturally occurring polyamines thermine (3.3.3, norspermine) and spermine (3.4.3), homo- and heterodimeric polyamine succinic amides. Linking two of the same or different polyamines together via amide bonds can be achieved by introducing a carboxylic acid group on the first polyamine, then coupling that released carboxylic acid to a free primary amine in the second polyamine. If the addition of positive charges on the amino groups along the polyamine chains are a key factor in their antimicrobial activity against Gram-negative bacteria, then increasing them will increase the antimicrobial activity. Synthesising polyamine amide dimers will increase the total net positive charge compared to their monomers. The design and practical synthesis of such homo- and hetero-dimers of linear polyamines, spermine and norspermine, are reported. Several of these compounds do not display significant antibacterial activity against Gram-positive or Gram-negative bacteria, including MRSA and Pseudomonas aeruginosa. However, the most charged analogue, a branched polyamine carrying eight positive charges at physiological pH, displays antibiofilm activity with a 50 % reduction in PAO1 at 16-32 μg mL-1 .

Antibacterial activity of novel linear polyamines against Staphylococcus aureus

New therapeutic options are urgently required for the treatment of Staphylococcus aureus infections. Accordingly, we sought to exploit the vulnerability of S. aureus to naturally occurring polyamines. We have developed and tested the anti-staphylococcal activity of three novel linear polyamines based on spermine and norspermine. Using a panel of genetically distinct and clinically relevant multidrug resistant S. aureus isolates, including the polyamine resistant USA300 strain LAC, compound AHA-1394 showed a greater than 128-fold increase in inhibition against specific S. aureus strains compared to the most active natural polyamine. Furthermore, we show that AHA-1394 has superior biofilm prevention and biofilm dispersal properties compared to natural polyamines while maintaining minimal toxicity toward human HepG2 cells. We examined the potential of S. aureus to gain resistance to AHA-1394 following in vitro serial passage. Whole genome sequencing of two stable resistant mutants identified a gain of function mutation (S337L) in the phosphatidylglycerol lysyltransferase mprF gene. Inactivation of mutant mprF confirmed the importance of this allele to AHA-1394 resistance. Importantly, AHA-1394 resistant mutants showed a marked decrease in relative fitness and increased generation time. Intriguingly, mprF::S337L contributed to altered surface charge only in the USA300 background whereas increased cell wall thickness was observed in both USA300 and SH1000. Lastly, we show that AHA-1394 displays a particular proclivity for antibiotic potentiation, restoring sensitivity of MRSA and VRSA isolates to daptomycin, oxacillin and vancomycin. Together this study shows that polyamine derivatives are impressive drug candidates that warrant further investigation.

Design and synthesis of hybrid compounds as novel drugs and medicines

The development of highly effective conjugate chemistry approaches is a way to improve the quality of drugs and of medicines. The aim of this paper is to highlight and review such hybrid compounds and the strategies underpinning their design. A variety of unique hybrid compounds provide an excellent toolkit for novel biological activity, e.g. anticancer and non-viral gene therapy (NVGT), and as templates for killing bacteria and preventing antibiotic drug resistance. First we discuss the anticancer potential of hybrid compounds, containing daunorubicin, benzyl- or tetrahydroisoquinoline-coumarin, and cytotoxic NSAID-pyrrolizidine/indolizine hybrids, then NVGT cationic lipid-based delivery agents, where steroids or long chain fatty acids as the lipid moiety are bound to polyamines as the cationic moiety. These polyamines can be linear as in spermidine or spermine, or on a polycyclic sugar template, aminoglycosides kanamycin and neomycin B, the latter substituted with six amino groups. They are highly efficient for the delivery of both fluorescent DNA and siRNA. Molecular precedents can be found for the design of hybrid compounds in the natural world, e.g., squalamine, the first representative of a previously unknown class of natural antibiotics of animal origin. These polyamine-bile acid (e.g. cholic acid type) conjugates display many exciting biological activities with the bile acids acting as a lipidic region and spermidine as the polycationic region. Analogues of squalamine can act as vectors in NVGT. Their natural role is as antibiotics. Novel antibacterial materials are urgently needed as recalcitrant bacterial infection is a worldwide problem for human health. Ribosome inhibitors founded upon dimers of tobramycin or neomycin, bound as ethers by a 1,6-hexyl linker or a more complex diether-disulfide linker, improved upon the antibiotic activity of aminoglycoside monomers by 20- to 1200-fold. Other hybrids, linked by click chemistry, conjugated ciprofloxacin to neomycin, trimethoprim, or tedizolid, which is now in clinical trials.

Polyamine-Conjugated Nitroxides Are Efficacious Inhibitors of Oxidative Reactions Catalyzed by Endothelial-Localized Myeloperoxidase

The heme enzyme myeloperoxidase (MPO) is a key mediator of endothelial dysfunction and a therapeutic target in cardiovascular disease. During inflammation, MPO released by circulating leukocytes is internalized by endothelial cells and transcytosed into the subendothelial extracellular matrix of diseased vessels. At this site, MPO mediates endothelial dysfunction by catalytically consuming nitric oxide (NO) and producing reactive oxidants, hypochlorous acid (HOCl) and the nitrogen dioxide radical (^•NO₂). Accordingly, there is interest in developing MPO inhibitors that effectively target endothelial-localized MPO. Here we studied a series of piperidine nitroxides conjugated to polyamine moieties as novel endothelial-targeted MPO inhibitors. Electron paramagnetic resonance analysis of cell lysates showed that polyamine conjugated nitroxides were efficiently internalized into endothelial cells in a heparan sulfate dependent manner. Nitroxides effectively inhibited the consumption of MPO's substrate hydrogen peroxide (H₂O₂) and formation of HOCl catalyzed by endothelial-localized MPO, with their efficacy dependent on both nitroxide and conjugated-polyamine structure. Nitroxides also differentially inhibited protein nitration catalyzed by both purified and endothelial-localized MPO, which was dependent on ^•NO₂ scavenging rather than MPO inhibition. Finally, nitroxides uniformly inhibited the catalytic consumption of NO by MPO in human plasma. These studies show for the first time that nitroxides effectively inhibit local oxidative reactions catalyzed by endothelial-localized MPO. Novel polyamine-conjugated nitroxides, ethylenediamine-TEMPO and putrescine-TEMPO, emerged as efficacious nitroxides uniquely exhibiting high endothelial cell uptake and efficient inhibition of MPO-catalyzed HOCl production, protein nitration, and NO oxidation. Polyamine-conjugated nitroxides represent a versatile class of antioxidant drugs capable of targeting endothelial-localized MPO during vascular inflammation.

Synthesis and characterization of 5-(4-carboxyphenylspermine)-10,15,20-triphenylporphyrin

We synthetized and characterized a mono spermine porphyrin derivative by NMR, UV-vis and fluorescence spectroscopy. The photophysical properties and the protonation equilibria of 5-(4-carboxyphenylspermine)-10,15,20-triphenylporphyrin have been investigated, showing that porphyrin does not aggregate in acidic solutions, differently from what occurs as soon as the core of the porphyrin is deprotonated. These aggregation processes have been detected by the rising of new fluorescence band and a significant splitting of the Soret band.

A Fluorescent Probe for Glycosaminoglycans Applied to the Detection of Dermatan Sulfate by a Mix-and-Read Assay

Glycosaminoglycans are complex biomolecules of great biological and medical importance. The quantification of glycosaminoglycans, in particular in complex matrices, is challenging due to their inherent structural heterogeneity. Heparin Red, a polycationic, fluorescent perylene diimide derivative, has recently emerged as a commercial probe for the convenient detection of heparins by a mix-and-read fluorescence assay. The probe also detects glycosaminoglycans with a lower negative charge density than heparin, although with lower sensitivity. We describe here the synthesis and characterization of a structurally related molecular probe with a higher positive charge of +10 (vs. +8 of Heparin Red). The superior performance of this probe is exemplified by the quantification of low dermatan sulfate concentrations in an aqueous matrix (quantification limit 1 ng/mL) and the detection of dermatan sulfate in blood plasma in a clinically relevant concentration range. The potential applications of this probe include monitoring the blood levels of dermatan sulfate after administration as an antithrombotic drug in the absence of heparin and other glycosaminoglycans.

Synthesis and evaluation of fatty acid amides on the N-oleoylethanolamide-like activation of peroxisome proliferator activated receptor α

A series of fatty acid amides were synthesized and their peroxisome proliferator-activated receptor α (PPAR-α) agonistic activities were evaluated in a normal rat liver cell line, clone 9. The mRNAs of the PPAR-α downstream genes, carnitine-palmitoyltransferase-1 and mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase, were determined by real-time reverse transcription-polymerase chain reaction (RT-PCR) as PPAR-α agonistic activities. We prepared nine oleic acid amides. Their PPAR-α agonistic activities were, in decreasing order, N-oleoylhistamine (OLHA), N-oleoylglycine, Oleamide, N-oleoyltyramine, N-oleoylsertonin, and Olvanil. The highest activity was found with OLHA. We prepared and evaluated nine N-acylhistamines (N-acyl-HAs). Of these, OLHA, C16:0-HA, and C18:1Δ(9)-trans-HA showed similar activity. Activity due to the different chain length of the saturated fatty acid peaked at C16:0-HA. The PPAR-α antagonist, GW6471, inhibited the induction of the PPAR-α downstream genes by OLHA and N-oleoylethanolamide (OEA). These data suggest that N-acyl-HAs could be considered new PPAR-α agonists.

Synthesis and biological evaluation of new C-10 substituted dithranol pleiotropic hybrids

Selective alkylation of the antipsoriatic drug dithranol (DTR) at C-10 with tert-butyl bromoacetate, followed by acid-mediated deprotection, produced the corresponding carboxylic acid 4 which was coupled with selectively protected polyamines (PAs), such as putrescine (PUT), spermidine (SPD) and spermine (SPM), dopamine and aliphatic amines and substituted benzylamines producing a series of DTR-PA hybrids, after acid-mediated deprotection, as well as simple amides. The compounds were tested as antioxidants and inhibitors of lipoxygenase (LOX). The amides 4,4'-dimethoxybenzhydrylamide 13 (86% and 95%), 2,4-dimethoxybenzylamide 12 (87% and 81%) and dodecylamide 9 (98% and 74%), and the hybrid DTR-SPM (7) (93% and 87%), showed the highest antioxidant activity in the DPPH and AAPH assays, whereas the most potent inhibitors of LOX were amide 13 (IC50=7 μM), the benzylamide 10 (IC50=7.9 μM) and the butylamide 8 (IC50=10 μM). Molecular binding studies showed that binding of these derivatives into the hydrophobic domain blocks approach of substrate to the active site, inhibiting soybean LOX. Amide 13 presented the highest anti-inflammatory activity (79.7%). The DTR moiety was absolutely necessary for securing high anti-inflammatory potency. Ethyl ester 3 (IC50=0.357 μM) and the amides 9 (IC50=0.022 μM) and 13 (IC50=0.56 μM) exhibited higher antiproliferative activity than DTR (IC50=0.945 μM) on HaCaT keratinocytes whereas amide 13 generally presented better cytocompatibility. Amide 13 is a very promising lead compound for further development as an anti-inflammatory and antiproliferative agent.

Helical peptide-polyamine and -polyether conjugates as synthetic ionophores

Two new synthetic ionophores in which the hydrophobic portion is represented by a short helical Aib-peptide (Aib=α-amino-isobutyric acid) and the hydrophilic one is a poly-amino (1a) or a polyether (1b) chain have been prepared. The two conjugates show a high ionophoric activity in phospholipid membranes being able to efficiently dissipate a pH gradient and, in the case of 1b, to transport Na(+) across the membrane. Bioactivity evaluation of the two conjugates shows that 1a has a moderate antimicrobial activity against a broad spectrum of microorganisms and it is able to permeabilize the inner and the outer membrane of Escherichia coli cells.

Synthesis and antimicrobial activity of chloramphenicol-polyamine conjugates

A series of chloramphenicol (CAM) amides with polyamines (PAs), suitable for structure-activity relationship studies, were synthesized either by direct attachment of the PA chain on the 2-aminopropane-1,3-diol backbone of CAM, previously oxidized selectively at its primary hydroxyl group, or from chloramphenicol base (CLB) through acylation with succinic or phthalic anhydride and finally coupling with a PA. Conjugates 4 and 5, in which the CLB moiety was attached on N4 and N1 positions, respectively, of the N(8),N(8)-dibenzylated spermidine through the succinate linker, were the most potent antibacterial agents. Both conjugates were internalized into Escherichia coli cells by using the spermidine-preferential uptake system and caused decrease in protein and polyamine content of the cells. Noteworthy, conjugate 4 displayed comparable activity to CAM in MRSA or wild-type strains of Staphylococcus aureus and Escherichia coli, but superior activity in E. coli strains possessing ribosomal mutations or expressing the CAM acetyltransferase (cat) gene. Lead compounds, and in particular conjugate 4, have been therefore discovered during the course of the present work with clinical potential.

Cell-penetrating peptoids: introduction of novel cationic side chains

During the last decade peptoid-based molecular transporters have been broadly applied. They are highly valued for their easy synthesis and their superior stability against enzymatic degradation. The special structure of peptoids generally allows introducing a variety of different side chains. Yet, the cationic side chains of cell-penetrating peptoids displayed solely lysine- or arginine-like structures. Thus this report is intended to extend the spectrum of cationic peptoid side chains. Herein, we present novel functional groups, like polyamines, aza-crown ethers, or triphenylphosphonium ions that are introduced into peptoids for the first time. In addition, the obtained peptoids were tested for their cell-penetrating properties.

Toward transmembrane anionophores based on rigid bis(choloyl) conjugates: reversal of the ion selectivity by appended polyamines

A bis(polyamine)-appending rigid linker-tethered bis(choloyl) conjugate was synthesized as a potent anionophore with high selectivity for iodide over the other monoanionic ions.

Polymerized spermine as a novel polycationic nucleic acid carrier system

Spermine, an endogenous amino-group bearing monomer that condenses DNA in sperm, was used as the basic building block to form polycationic nucleic acid carriers via condensation with one of three linker molecules - bischloroformate, succinyl chloride, and glyoxal. The three cationic polymers, polyspermine carbamate (PSP-Carb), polyspermine amide (PSP-Amide) and polyspermine imine (PSP-Imine) were examined for their degradability, cytotoxicity, ability to condense nucleic acids to nanoparticles, and ability to transfect genes or siRNA to cells. PSP-Carb and PSP-Amide exhibited a half-life of more than 2 months when incubated in aqueous buffers at 37°C, while the half-life of PSP-Imine was 11h. Relative cytotoxicity of the polymers, as measured by COS-7 and HepG2 cell viability, was in the order of PSP-Carb>PSP-Amide>PSP-Imine. Each cationic polymer condensed the luciferase plasmid to nanoparticles of 150-200 nm diameters and with a zeta potential of +15-30 mV when the mass ratio of polymer-to-DNA was over 8/1. The three polycationic carriers showed similar luciferase transfection activity in COS-7 cells, while the transfection efficiency of PSP-Carb was significantly higher than that of the other two in HepG2 cells. PSP-Amide exhibited significantly higher gene silencing activity in COS-7 cells, suggesting the linkage structures play an important role in the activity of the polyspermine-based nucleic acid carriers.

Asymmetrical N4,N9-diacyl spermines: SAR studies of nonviral lipopolyamine vectors for efficient siRNA delivery with silencing of EGFP reporter gene

Our aim is to study the effects of varying the two acyl moieties in synthesized N(4),N(9)-diacyl spermines on siRNA formulations and their delivery efficiency in cell lines. Six novel asymmetrical lipopolyamines, [N(4)-cholesteryloxy-3-carbonyl-N(9)-oleoyl-, N(4)-decanoyl-N(9)-oleoyl-, N(4)-decanoyl-N(9)-stearoyl-, N(4)-lithocholoyl-N(9)-oleoyl-, N(4)-myristoleoyl-N(9)-myristoyl-, and N(4)-oleoyl-N(9)-stearoyl]-1,12-diamino-4,9-diazadodecane, were assessed for their abilities to bind to siRNA, studied using a RiboGreen intercalation assay, and to form nanoparticles. Their siRNA delivery efficiencies were quantified in FEK4 primary skin cells and in an immortalized cancer cell line (HtTA) using a fluorescein-tagged siRNA, and compared with formulations of N(4),N(9)-dioleoyl-1,12-diamino-4,9-diazadodecane and of a leading transfecting agent, TransIT-TKO. Transfection was measured in terms of siRNA delivery and silencing of EGFP reporter gene in HeLa cells. By incorporating two different acyl moieties, changing their length and oxidation level in a controlled manner, we show efficient fluorescein-tagged siRNA formulation, delivery, and knock-down of EGFP reporter gene. N(4)-Oleoyl-N(9)-stearoyl spermine and N(4)-myristoleoyl-N(9)-myristoyl spermine are effective siRNA delivery vectors typically resulting in 89% cell delivery and gene silencing to 34% in the presence of serum, comparable with the results obtained with TransIT-TKO; adding a second lipid chain is better than incorporating a steroid moiety.

Carbon-carbon bond-forming enzymes for the synthesis of non-natural amino acids

An enzymatic methodology for the preparation of β-hydroxy-α-amino acid derivatives is described. The method consists of the stereoselective aldol addition reaction of glycine to N-Cbz-amino aldehydes furnishing 3-hydroxy-2,4-diaminobutyric derivatives.

Library of second-generation cycloruthenated compounds and evaluation of their biological properties as potential anticancer drugs: passing the nanomolar barrier

A library of 32 organoruthenium compounds has been synthesised. Known and novel C-N cyclometalated compounds as well as N-C-N and N-N-C pincer derivatives of this metal have been used in this purpose. Most of the compounds have been tested for their in vitro antitumoral behaviours, good to excellent activities have thus been found. Several of the newly synthesized compounds pass the symbolic barrier of the nanomolar range for their IC(50) indicating a critical improvement. The level of activity is tentatively correlated to physicochemical properties of the compounds such as their Ru(III/II) redox potential and their lipophilicity (log P).

99mTc-HYNIC-spermine for imaging polyamine transport system-positive tumours: preclinical evaluation

PURPOSE

F14512 exploiting the polyamine transport system (PTS) for tumour cell delivery has been described as a potent antitumour agent. The optimal use of this compound will require a probe to identify tumour cells expressing a highly active PTS that might be more sensitive to the treatment. The aim of this study was to design and characterize a scintigraphic probe to evaluate its uptake in cancer cells expressing the PTS.

METHODS

Three polyamines coupled to a hydrazinonicotinamide (HYNIC) moiety were synthesized and labelled with 99mTc. Their radiochemical purity was determined by HPLC. The plasma stability of the 99mTc-HYNIC-spermine probe and its capacity to accumulate into PTS-active cells were also evaluated. In vitro internalization was tested using murine melanoma B16/F10 cells and human lung carcinoma A549 cells. Biodistribution was determined in healthy mice and tumour uptake was studied in B16/F10 tumour-bearing mice. A HL-60-Luc human leukaemia model was used to confront single photon emission computed tomography (SPECT) images obtained with the 99mTc-labelled probe with those obtained by bioluminescence.

RESULTS

The 99mTc-HYNIC-spermine probe was selected for its capacity to accumulate into PTS-active cells and its stability in plasma. In vitro studies demonstrated that the probe was internalized in the cells via the PTS. In vivo measurements indicated a tumour to muscle scintigraphic ratio of 7.9±2.8. The combined bioluminescence and scintigraphic analyses with the leukaemia model demonstrated that the spermine conjugate accumulates into the tumour cells.

CONCLUSION

The 99mTc-HYNIC-spermine scintigraphic probe is potentially useful to characterize the PTS activity of tumours. Additional work is needed to determine if this novel conjugate may be useful to analyse the PTS status of patients with solid tumours.

Does conjugation of antioxidants improve their antioxidative/anti-inflammatory potential?

A series of symmetric and asymmetric spermine (SPM) conjugates with all-trans-retinoic acid (ATRA), acitretin (ACI), (E)-3-(trioxsalen-4'-yl)acrylic acid (TRAA) and L-DOPA, amides of ACI, l-DOPA and TRAA with 1-aminobutane, benzylamine, dopamine and 1,12-diaminobutane as well as hybrid conjugates of O,O'-dimethylcaffeic acid (DMCA) with TRAA or N-fumaroyl-indole-3-carboxanilide (FICA) and 2-(2-aminoethoxy)ethanol were synthesized and their antioxidant properties were studied. The reducing activity (RA)% of the compounds were evaluated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging assay and found to be in the range 0-92(20 min)%/96(60 min)% at 100μM, the most powerful being the conjugates L-DOPA-SPM-L-DOPA (8, RA=89%/96%) and L-DOPA-dopamine (13, RA=92%/92%). Conjugate DMCA-NH(CH₂CH₂O)₂-FICA (14) was the most powerful LOX inhibitor with IC₅₀ 33.5μM, followed by the conjugates ACI-NHCH₂Ph (10, IC₅₀ 40.5μM), ACI-SPM-TRAA (7, IC₅₀ 41.5μM), DMCA-NH(CH₂CH₂O)₂-TRAA (15, IC₅₀ 65μM), 13 (IC₅₀ 81.5μM) and ACI-dopamine (11, IC₅₀ 87μM). The most potent inhibitors of lipid peroxidation at 100μM were the conjugates 15 (98%) and ACI-SPM-ACI (4, 97%) whereas all other compounds showed activities comparable or lower than trolox. The most interesting compounds, namely ATRA-SPM-ATRA (3), 4, 10, 11 and 15, as well as unconjugated compounds such as ATRA and dopamine, were studied for their anti-inflammatory activity in vivo on rat paw oedema induced by Carrageenan and found to exhibit, for doses of 0.01 mmol/mL of conjugates per Kg of rat body weight, weaker anti-inflammatory activities (3.6-40%) than indomethacin (47%) with conjugate 3 being the most potent (40%) in this series of compounds. The cytocompatibility of selected compounds was evaluated by the viability of RAMEC cells in the presence of different concentrations (0.5-50μM) of the compounds. Conjugates 3 (IC₅₀ 2.6μM) and 4 (IC₅₀ 4.7μM) were more cytotoxic than the corresponding unconjugated retinoids ATRA (IC₅₀ 18.3μM) and ACI (IC₅₀ 14.6μM), whereas conjugate 15 (IC₅₀ 12.9μM) was less cytotoxic than either DCSP (IC₅₀ 11.3μM) or the tert-butyl ester of TRAA (IC₅₀ 2.9μM).

Very long chain N4, N9 -diacyl spermines: non-viral lipopolyamine vectors for efficient plasmid DNA and siRNA delivery

PURPOSE

To study the effect of increasing the chain length over C-18 and varying the oxidation level in synthesized N4, N9-diacyl spermines on DNA and siRNA formulation, and then to compare their transfection efficiency in cell lines

METHODS

The five novel very long chain N4, N9-diacyl polyamines: N4, N9-[diarachidoyl, diarachidonoyl, dieicosenoyl, dierucoyl and dinervonoyl]-1,12-diamino-4,9-diazadodecane were synthesized. The abilities of these novel compounds to condense DNA and to form nanoparticles were studied using ethidium bromide fluorescence quenching and nanoparticle characterization techniques. Transfection efficiency was studied in FEK4 primary skin cells and in an immortalized cancer cell line (HtTA), and compared with the non-liposomal transfection formulation Lipogen, N4, N9-dioleoyl-1,12-diamino-4,9-diazadodecane. Also, the abilities of these compounds to condense siRNA and to form nanoparticles were studied using a RiboGreen intercalation assay and their abilities to deliver siRNA into cells were studied in FEK4 and HtTA cells using fluorescein-labelled Label IT(R) RNAi Delivery Control, a sequenced 21-mer from Mirus.

RESULTS

We show efficient pEGFP and siRNA formulation and delivery to primary skin and cancer cell lines.

CONCLUSIONS

Adding two C20 or C22 chains, both mono-cis-unsaturated, N4, N9-dieicosenoyl spermine and N4, N9-dierucoyl spermine, gave efficient siRNA delivery vectors, even in the presence of serum, comparable to TransIT-TKO and with excellent cell viability.

Oligonucleotide-polyamine conjugates: influence of length and position of 2'-attached polyamines on duplex stability and antisense effect

Tethering cationic ligands to oligonucleotides results in zwitterionic molecules with often improved target affinity and better cell membrane permeation. Due to the ideal distance between cationic groups, polyamines are perfect counter ions for oligonucleotides. Using an easy and versatile procedure for attaching ligands to the 2'-position, polyamines were conjugated to distinct terminal and internal positions of oligonucleotides. With polyamines attached to terminal nucleosides, the affinity to complementary DNA or RNA strands increased with growing number of cationic amines. Tethering polyamines to an internal nucleoside of wild type DNA oligonucleotides resulted in a considerable decrease in duplex stability, but in phosphorothioates, no significant decrease was detected. Conjugates exhibited progressively higher target downregulation ability with increasing polyamine chain length in a human melanoma cell culture assay.