Anionic Dendrimers Research Articles

Phosphorus dendrimers and photodynamic therapy. Spectroscopic studies on two dendrimer-photosensitizer complexes: Cationic phosphorus dendrimer with rose bengal and anionic phosphorus dendrimer with methylene blue

Dendrimers due to their unique architecture may play an important role in drug delivery systems including chemotherapy, gene therapy and recently, photodynamic therapy as well. We investigated two dendrimer-photosensitizer systems in context of potential use of these systems in photodynamic therapy. The mixtures of an anionic phosphorus dendrimer of the second generation and methylene blue were studied by UV–vis spectroscopy while that of a cationic phosphorus dendrimer (third generation) and rose bengal were investigated by spectrofluorimetric methods. Spectroscopic analysis of these two systems revealed the formation of dendrimer-photosensitizer complexes via electrostatic interactions as well as π stacking. The stoichiometry of the rose bengal-cationic dendrimer complex was estimated to be 7:1 and 9:1 for the methylene blue-anionic dendrimer complex. The results suggest that these polyanionic or polycationic phosphorus dendrimers can be promising candidates as carriers in photodynamic therapy.

In Vitro Evaluation of Gd(3+)-Anionic Linear Globular Dendrimer-Monoclonal Antibody: Potential Magnetic Resonance Imaging Contrast Agents for Prostate Cancer Cell Imaging.

Early stage prostate cancer diagnosis is of high global interest. Magnetic resonance imaging (MRI) is a non-invasive modality for early cancer diagnosis, in particular for prostate cancer detection. The research aim is to synthesize a nanodendrimer and its conjugate with C595 monoclonal antibody (mAb C595), against prostate cancer, followed by its chelating with Gd(3+). Anti-MUC-1 mAb C595 was conjugated to an anionic linear globular dendrimer (ALGDG2). The polyethylene glycol core and citric acid shell were synthesized followed by loading with Gd(3+) to make novel contrast agents for functional MRI. The in vitro behavior and MRI parameters of the nanoconjugate were investigated performing several studies such as cell toxicity and TNF-alpha evaluations. The investigation of magnetic resonance imaging parameters indicated how well nanoconjugate performs in (1)H-NMR and (17)O-NMR in vitro. Results showed a potential specific MRI activity by improving the swelling responses cell binding. The MTT (2-(4,5-dimethyl-2-thiazolyl)-3,5-diphenyl-2H-tetrazolium bromide) assay demonstrated that this contrast agent had significant cytotoxicity on prostate cancer cells. These results showed that Gd(3+)-ALGDG2-C595 is a potential prostate molecular imaging agent and could be considered as an ideal functional nanoprobe. Additionally, further investigations by clinical trials are in the pipeline.

Nanosilver based anionic linear globular dendrimer with a special significant antiretroviral activity.

HIV is commonly caused to a very complicated disease which has not any recognized vaccine, so designing and development of novel antiretroviral agents with specific application of nanomedicine is a globally interested research subject worldwide. In the current study, a novel structure of silver complexes with anionic linear globular dendrimer was synthesized, characterized and then assessed against HIV replication pathway in vitro as well. The results showed a very good yield of synthesis (up to 70%) for the nano-complex as well as a very potent significant (P < 0.05) antiretroviral activity with non-severe toxic effects in comparison with the Nevirapine as standard drug in positive control group. According to the present data, silver anionic linear globular dendrimers complex may have a promising future to inhibit replication of HIV viruse in clinical practice.

Influence of Anionic Surface Charged Biocompatible Dendrimer With a Photosensitizer, Protoporphyrin IX, on Human Red Blood Cells: A Spectroscopic Investigation

A biocompatible anionic dendrimer with carboxylic acid and phenolic hydroxyl functional groups at the surface of every half and full generations was designed by condensing phloroglucinol and succinic acid and its hemolytic effect on red blood cells was studied. The study reveals that the anionic surface charged dendrimer exhibits hemocompatibility and satisfies the reduction of dark toxicity of photosensitizer when loaded inside the nanocarrier, one of the prime requirements for a drug delivery system in photodynamic therapy applications.

Transcorneal iontophoresis of dendrimers: PAMAM corneal penetration and dexamethasone delivery

Iontophoresis of nanocarriers in the eye has been proposed to sustain drug delivery and maintain therapeutic concentrations. Fourth generation polyamidoamine (PAMAM) dendrimers are semi-rigid nanoparticles with surface groups that are easily modified. These dendrimers are known to modulate tight junctions, increase paracellular transport of small molecules and be translocated across epithelial barriers, exhibiting high uptake by different cell lines. The first aim of this study was to investigate the effect of iontophoresis on PAMAM penetration and distribution into the cornea. The second aim was to evaluate, ex vivo and in vivo, the effect of these dendrimers in dexamethasone (Dex) transcorneal iontophoresis. Anionic (PAMAM G3.5) and cationic (PAMAM G4) dendrimers were labeled with fluorescein isothiocyanate (FITC), and their distribution in the cornea was investigated using confocal microscopy after ex vivo anodal and cathodal iontophoresis for various application times. The particle size distribution and zeta potential of the dendrimers in an isosmotic solution were determined using dynamic light scattering and Nanoparticle Tracking Analysis (NTA), where the movement of small particles and the formation of large aggregates, from 5 to 100nm, could be observed. Transcorneal iontophoresis increased the intensity and depth of PAMAM-FITC fluorescence in the cornea, suggesting improved transport of the dendrimers across the epithelium toward the stroma. PAMAM complexes with Dex were characterized by 13C-NMR, 1H-NMR and DOSY. PAMAM G3.5 and PAMAM G4 increased the aqueous solubility of Dex by 10.3 and 3.9-fold, respectively; however, the particle size distribution and zeta potential remained unchanged. PAMAM G3.5 decreased the Dex diffusion coefficient 48-fold compared with PAMAM G4. The ex vivo studies showed that iontophoresis increased the amount of Dex that penetrated into the cornea by 2.9, 5.6 and 3.0-fold for Dex, Dex-PAMAM G4 and Dex-PAMAM G3.5, respectively. In vivo experiments, however, revealed that iontophoresis of Dex-PAMAM-G3.5 increased Dex concentration in the aqueous humor by 6.6-fold, while iontophoresis of Dex-PAMAM G4 and Dex increased it 2.5 and 2-fold, respectively. Therefore, iontophoresis targeted PAMAM to the cornea but it is the sustained delivery of the Dex from PAMAM that prevents its rapid elimination from the aqueous humor. In conclusion, iontophoresis of PAMAM complexes represents a promising strategy for targeted and sustained topical drug delivery to the eye.

Broad-spectrum Anti-HIV-1 Activity of Anionic Carbosilane Dendrimers and Synergy in Combination with Maraviroc and Tenofovir as Topical Microbicide

Broad-spectrum Anti-HIV-1 Activity of Anionic Carbosilane Dendrimers and Synergy in Combination with Maraviroc and Tenofovir as Topical Microbicide

Enhanced activity of carbosilane dendrimers against HIV when combined with reverse transcriptase inhibitor drugs: searching for more potent microbicides.

Self-administered topical microbicides or oral preexposure prophylaxis could be very helpful tools for all risk groups to decrease the human immunodeficiency virus (HIV)-1 infection rates. Up until now, antiretrovirals (ARVs) have been the most advanced microbicide candidates. Nevertheless, the majority of clinical trials has failed in HIV-1 patients. Nanotechnology offers suitable approaches to develop novel antiviral agents. Thereby, new nanosystems, such as carbosilane dendrimers, have been shown to be safe and effective compounds against HIV with great potential as topical microbicides. In addition, because most of the attempts to develop effective topical microbicides were unsuccessful, combinatorial strategies could be a valid approach when designing new microbicides. We evaluated various combinations of anionic carbosilane dendrimers with sulfated (G3-S16) and naphthyl sulfonated (G2-NF16) ended groups with different ARVs against HIV-1 infection. The G3-S16 and G2-NF16 dendrimers showed a synergistic or additive activity profile with zidovudine, efavirenz, and tenofovir in the majority of the combinations tested against the X4 and R5 tropic HIV-1 in cell lines, as well as in human primary cells. Therefore, the combination of ARVs and polyanionic carbosilane dendrimers enhances the antiviral potency of the individual compounds, and our findings support further clinical research on combinational approaches as potential microbicides to block the sexual transmission of HIV-1.

Anionic Linear Globular Dendrimer-G2-Ciprofloxacin Nano-Conjugate: Novel Agent against Wilson Disease Cell Model

Inherited defect of the gene ATP7B causes malexcretion of copper in the bile and leads to several complications that need treatment to deplete it from organs. Current therapy of Wilson disease, D-penicillamine has very serious side effects and drug with optimum therapeutic effects and minimum side effects is of importance. In the present study ciprofloxacin was conjugated with an anionic globular dendrimer to lower the intracellular copper concentration. The results showed its efficacy and safety to certain levels. Based on the results, ciprofloxacin-anionic linear globular dendrimer conjugate can be a useful option to reduce intracellular copper concentration and an investigational therapeutic agent in Wilson disease. Keywords: Copper, Dendrimer-ciprofloxacin nano-particle, Fluoroquinolone, Metal ions, Wilson disease.

Inhibition of PI3K contributes to nanoparticle-mediated exaggeration of endotoxin-induced leukocyte procoagulant activity (INC6P.340)

Abstract Nanoparticles are increasingly used in biomedical applications due to their ability to change biodistribution, increase safety and improve efficacy of drugs. However, application of engineered nanomaterials in medicine is often halted by safety concerns. Endotoxin contamination is very common in nanomaterials and there is an increasing number of studies reporting that certain nanoparticles can exaggerate endotoxin-mediated inflammation. We studied the relationship between physicochemical properties of polyamidoamine (PAMAM) dendrimers and their ability to exaggerate LPS-induced procoagulant activity (PCA) of human leukocytes in vitro. The PCA is phospholipid-protein complex composed of tissue factor (TF) and phosphotidylserine (PS). We found that cationic but not anionic or neutral PAMAM dendrimers, increase LPS-induced leukocyte PCA. Cationic PAMAM dendrimers enhanced both LPS-induced TF expression and PS exposure on the cell surface. The mechanism of LPS-induced PCA exaggeration by PAMAM dendrimers is not mediated by the electrostatic interaction between cationic dendrimers and anionic LPS, calcium influx and secondary messengers released by dendrimer activated platelets. We hypothesize that dendrimers exaggerate LPS-mediated PCA through the inhibition of negative regulation of inflammation. Specifically, we demonstrate that cationic PAMAM dendrimers inhibit phosphoinositol-3-kinase (PI3K), a negative regulator of TF expression in response to endotoxin.

DEVELOPMENT AND VALIDATION OF A RAPID AND SIMPLE HPLC-UV METHOD FOR THE ANALYSIS OF SORAFENIB IN THE PRESENCE OF POLYAMIDOAMINE (PAMAM) DENDRIMERS

A rapid and simple liquid chromatography-UV spectrometric assay was developed for the quantitative determination of sorafenib in the presence of cationic and anionic PAMAM dendrimers. PAMAM dendrimer:sorafenib (SFB) admixture was prepared by Higuchi rotating bottle method for different generations (G4, G4.5, G5). Separation was achieved on a C18 column (Knauer Eurospher 150 mm × 4.6 mm with precolumn) at room temperature using an isocratic elution method with acetonitrile/K-phosphate buffer 25 mM pH 7.4: 55/45 (v/v) at a flow rate of 1.5 ml/min. The SFB peak was separated well from PAMAM dendrimers peak. Calibration curves were linear in the concentration range of 0.097–100 mcg/mL with R2 > 0.9988. The accuracy [Bias (%)] and precision [RSD (%)] values, calculated from three different sets of quality control samples analyzed in triplicate on four different days, ranged from −3.6–16 and 2.1–14.5, respectively. The limit of quantitation was 97 ng/mL.

Synthesis of anionic carbosilane dendrimers via “click chemistry” and their antiviral properties against HIV

ABSTRACTThe synthesis and characterization of four families of anionic carbosilane dendrimers bearing carboxylate, phosphonate, naphthylsulfonate, and sulfate terminal groups prepared by cycloaddition of azide–alkyne catalyzed by copper (CuAAC) are presented here. For the preparation of these anionic carbosilane dendrimers, two strategies starting from azide‐terminated carbosilane dendrimers were followed: (i) click coupling of neutral alkynes followed by derivatization into anionic moieties or (ii) click coupling of anionic alkynes. Both strategies require different reaction conditions in order to accommodate the different substrate polarities. These anionic dendrimers, in general, do not present cell toxicity in vitro until concentration up to 20 µM. Therefore, they can be used in inhibition experiments in concentrations below this limit. We have observed that dendrimers bearing phosphonate groups possess poor anti‐HIV capabilities in vitro in PBMCs, while carboxylate dendrimers can reduce HIV infection levels moderately. On the other hand, sulfate and naphthylsulfonate dendrimers are powerful anti‐HIV agents and their antiviral activity is generation and concentration dependent. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1099–1112

Synthesis of new anionic carbosilane dendrimers via thiol-ene chemistry and their antiviral behaviour.

A synthetic strategy has been developed for the preparation of anionic carbosilane dendrimers bearing sulfonate or carboxylate groups at their periphery by means of thiol-ene chemistry. It offers significant advantages, such as milder reaction conditions, shorter reaction times and more facile purification methods, when compared with other synthetic protocols used previously, e.g. hydrosilylation followed by a Michael-type addition or azide-alkyne coupling reactions. Molecular dynamics simulations of the second generation anionic dendrimers addressing shape and size effects of the terminal groups and conformational variability indicated that the core eccentricity and flexibility might need to be taken into account for toxicity and interaction with viral and/or cellular receptors, respectively. The biocompatibility of anionic carbosilane dendrimers has been explored showing differences between silicon-cored and polyphenoxo-cored dendrimers. In addition, silicon-cored dendrimers achieved 85-90% of HIV inhibition without inducing inflammation or vaginal irritation in mice, which makes them likely candidates for readily available, good and safe topical vaginal microbicides against HIV.

Controlling the number of dendrimers in dendrimicelle nanoconjugates from 1 to more than 100

Herein, we present a facile strategy to controllably build up dendrimicelles by self-assembly of anionic PAMAM dendrimers with cationic-neutral diblock copolymers. We present a systematic study incorporating a full decade (0-9) of dendrimer generations, tracing the gradual variation from aggregates (G0 and G1) to self-assembled micelles (G2-G8), and an unidendrimer micelle structure (G9) by different scattering techniques (light and X-ray). The formed micelles (G2-G9) are spherical in shape with a hydrodynamic radius of about 25 nm. Interestingly, the micellar size, structure and number of incorporated block copolymers are independent of the dendrimer generation (for G2 to G9), while the aggregation number of the dendrimers decreases from 108 to 1, and the stability of the micelles increases upon an increase in the dendrimer generation. Moreover, the micelles with lower generation dendrimers transform from spherical into worm-like structures upon an increase in the positive charge fraction (excess polymers) or ionic strength, while micelles with higher generation dendrimers do not show such a transition. This differential behavior is in-line with a change from a flexible configuration into rigid globular nanoparticles with increasing dendrimer generation. The reported systematic investigation of dendrimicelles comprising a full decade of dendrimer generations provides the basis for versatile strategies focused on building up new (multi)functional materials, e.g. by packing multiple types of dendrimers with different functional groups or encapsulated cargos controllably within one micelle.

Synergistic activity profile of carbosilane dendrimer G2-STE16 in combination with other dendrimers and antiretrovirals as topical anti-HIV-1 microbicide

Polyanionic carbosilane dendrimers represent opportunities to develop new anti-HIV microbicides. Dendrimers and antiretrovirals (ARVs) acting at different stages of HIV replication have been proposed as compounds to decrease new HIV infections. Thus, we determined the potential use of our G2-STE16 carbosilane dendrimer in combination with other carbosilane dendrimers and ARVs for the use as topical microbicide against HIV-1. We showed that these combinations obtained 100% inhibition and displayed a synergistic profile against different HIV-1 isolates in our model of TZM.bl cells. Our results also showed their potent activity in the presence of an acidic vaginal or seminal fluid environment and did not activate an inflammatory response. This study is the first step toward exploring the use of different anionic carbosilane dendrimers in combination and toward making a safe microbicide. Therefore, our results support further studies on dendrimer/dendrimer or dendrimer/ARV combinations as topical anti-HIV-1 microbicide. From the Clinical EditorThis paper describes the first steps toward the use of anionic carbosilane dendrimers in combination with antivirals to address HIV-1, paving the way to further studies on dendrimer/dendrimer or dendrimer/ARV combinations as topical anti-HIV-1 microbicides.

Poly(amido amine) dendrimers as absorption enhancers for oral delivery of camptothecin

Oral delivery of camptothecin has a treatment advantage but is limited by low bioavailability and gastrointestinal toxicity. Poly(amido amine) or PAMAM dendrimers have shown promise as intestinal penetration enhancers, drug solubilizers and drug carriers for oral delivery in vitro and in situ. There have been very limited studies in vivo to evaluate PAMAM dendrimers for oral drug delivery. In this study, camptothecin (5 mg/kg) was formulated and co-delivered with cationic, amine-terminated PAMAM dendrimer generation 4.0 (G4.0) (100 and 300 mg/kg) and anionic, carboxylate-terminated PAMAM generation 3.5 (G3.5) (300 and 1000 mg/kg) in CD-1 mice. Camptothecin associated to a higher extent with G4.0 than G3.5 in the formulation, attributed to an electrostatic interaction on the surface of G4.0. Both PAMAM G4.0 and G3.5 increased camptothecin solubilization in simulated gastric fluid and caused a 2-3 fold increase in oral absorption of camptothecin when delivered at 2 h. PAMAM G4.0 and G3.5 did not increase mannitol transport suggesting that the oral absorption of camptothecin was not due to tight junction modulation. Histologic observations of the epithelial layer of small intestinal segments of the gastrointestinal tract (GIT) at 4 h post dosing supported no evidence of toxicity at the evaluated doses of PAMAM dendrimers. This study demonstrates that both cationic (G.4) and anionic (G3.5) PAMAM dendrimers were effective in enhancing the oral absorption of camptothecin. Results suggest that drug inclusion in PAMAM interior controlled solubilization in simulated gastric and intestinal fluids, and increased oral bioavailability.

Cytotoxicity and in vitro characterization studies of synthesized Jeffamine-cored PAMAM dendrimers

The objective of this study is to make comprehensive cytotoxicity evaluation and in vitro characterization of Jeffamine-cored polyamidoamine (PAMAM) dendrimers on L929 cell lines for oral drug delivery purposes. Ester-, amine- and carboxylic acid-terminated PAMAMs were investigated for their cytotoxicity on L929 cells at different generations and concentrations. Cationic surface charge caused highest cytotoxicity on L929 cells, while ester-terminated PAMAMs showed generation- and concentration-dependent toxicity. Anionic dendrimers were determined as the lowest cytotoxic group, and highest generation number presented lowest cellular toxicity. Encapsulation studies were performed with anionic PAMAMs at 2.5, 3.5 and 4.5 generations and different concentrations. Increasing generation number provides greater loaded naproxen amounts and larger particle size. Moreover, formulations provide controlled release at simulated terminal ileum conditions. Consequently, Jeffamine-cored carboxylic acid-terminated PAMAMs can be a promising option for oral drug delivery of poorly water-soluble drugs.

Paramagnetic NMR Investigation of Dendrimer-Based Host-Guest Interactions

In this study, the host-guest behavior of poly(amidoamine) (PAMAM) dendrimers bearing amine, hydroxyl, or carboxylate surface functionalities were investigated by paramagnetic NMR studies. 2,2,6,6-Tetramethylpiperidinyloxy (TEMPO) derivatives were used as paramagnetic guest molecules. The results showed that TEMPO-COOH significantly broaden the 1H NMR peaks of amine- and hydroxyl-terminated PAMAM dendrimers. In comparison, no paramagnetic relaxation enhancement (PRE) was observed between TEMPO-NH2, TEMPO-OH and the three types of PAMAM dendrimers. The PRE phenomenon observed is correlated with the encapsulation of TEMPO-COOH within dendrimer pockets. Protonation of the tertiary amine groups within PAMAM dendrimers plays an important role during this process. Interestingly, the absence of TEMPO-COOH encapsulation within carboxylate-terminated PAMAM dendrimer is observed due to the repulsion of TEMPO-COO- anion and anionic dendrimer surface. The combination of paramagnetic probes and 1H NMR linewidth analysis can be used as a powerful tool in the analysis of dendrimer-based host-guest systems.

Synthesis and Development of Gd&amp;lt;sup&amp;gt;3+&amp;lt;/sup&amp;gt;-ALGDG&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;-C595 as MR Imaging Contrast Agent

Magnetic Resonance imaging (MR imaging) as a powerful non-invasive modality is of high global interest for early cancer detection. The aim of this study was the synthesis of nanodendrimer and its conjugate with monoclonal antibody C595 against breast cancer cell, followed by its chelating with gadolinium for its magnetic property. First, anti-MUC-1 monoclonal antibody C595 was coupled to a biodegradable biocompatible Anionic Linear Globular Dendrimer G2 (having polyethylene glycol core and citric acid shell). Then prepared nanocomplex loaded by gadolinium to make novel agent of functional MR imaging. Anticancer effects and MR imaging parameters of the prepared nanoconjugate was investigated under in vitro conditions doing performing several studies such as evaluation of monoclonal antibody C595 binding to mucine-1 (MUC-1) cell, its purification, size of nanoconjugate and relaxivity measurements. The obtained data showed a powerful relaxations as well as selective MUC-1 antigen binding to the cell. Based on the findings from the present research Gd3+-ALGDG2-C595 nano-probe may be a potential breast molecular imaging and therapeutic agent. However, further investigations by in vivo studies and clinical trials are in the pipeline.

Gd3+-Anionic Linear Globular Dendrimer-G2-C595 A Dual Novel Nanoprobe for MR Imaging and Therapeutic Agent: An In Vitro Study

Early cancer detection using MR imaging is of high global interest as a powerful non-invasive modality. The aim of this study was to synthesize a nano-dendrimer and its conjugate with C595 mab against breast cancer cell, followed by its chelating with Gd3+. At the end, its ability as a nanosized probe for detection of breast cancer cells was investigated. For this reason, anti-MUC-1 mab C595 was coupled to a biocompatible anionic linear globular dendrimer G2 (ALGDG2) (Poly Ethylene Glycol PEG core and citric acid shell) followed by loading with Gd3+. MR imaging parameters of the prepared nanoconjugate was investigated in vitro performing several studies such as 1H-NMR and 17O-NMR, MUC-1 antigen. The obtained data showed a powerful relaxations as well as selective MUC-1 antigen and cell binding. Findings of this study showed that Gd3+-ALGDG2-C595 nano-probe is potentially, a selective breast molecular imaging agent.

A Comparative Study of Two Novel Nanosized Radiolabeled Analogues of Methionine for SPECT Tumor Imaging

It has been reported that most tumor cells show an increased uptake of variety of amino acids specially methionine when compared with normal cells and amino acid transport is generally increased in malignant transformation. Based on the evidences, two novel nanosized analogues of methionine (Anionic Linear Globular Dendrimer G(2), a biodigredabale anionic linear globular-Methionin, and DTPA-Methionine(1) conjugates) were synthesized and labeled with (99m)Tc and used in tumor imaging/ therapy in vitro and in vivo. The results showed marked tumor SPECT molecular imaging liabilities for both compounds but with a better performance by administration of (99m)Tc-Dendrimer G(2)-Methionin. The results also showed a good anticancer activity for 99mTc-DTPA-Methionine. Based on the present study (99m)Tc-Dendrimer G(2)-Methionin or 99mTc-DTPA-(Methionine)(1) have potentials to be used in tumor molecular imaging as well as cancer therapy in future.