G4 Dendrimer Research Articles

MALDI-MS Imaging Analysis of Noninflammatory Type III Rotaxane Dendrimers.

Rotaxane dendrimers with hyperbranched macromolecular interlocked structures and size modulation capacity demonstrate drug binding and release ability upon external stimuli. Mass spectrometry imaging (MSI) can offer the high-throughput screening of endogenous/exogenous compounds. Herein, we reported a novel method to display the in situ spatial distribution of label-free monodispersed type III rotaxane dendrimers (RDs) G1 (first generation, size ∼1.5 nm) and G2 (second generation, size ∼5 nm) that were explored as potential drug vehicles in spleen tissue by using matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-MSI). Experimental results indicated that the trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB) matrix exhibited the best performance for monodispersed type III RDs G1 and G2. The optimized method was successfully applied to map the in vivo spatial distribution of type III RDs G1 and G2 in the spleen from intraperitoneally injected mice. The MALDI-MSI images revealed that RDs G1 and G2 were relatively stable in the spleen within 24 h after administration. It was found that the identified type III RDs G1 and G2 penetrated through the tunica serosa and were predominantly localized in red pulp regions of spleens. They were also mapped in a marginal zone of spleens simultaneously. There was almost no toxicity of type III RDs G1 and G2 to mice spleens from the H&E results. Furthermore, the type III RDs did not induce the expression of inflammatory cytokines from peripheral blood mononuclear cells (PBMCs) or THP-1 monocytes. The MSI analysis not only demonstrated its ability to image select rotaxane dendrimers in a rapid and efficient manner but also provided tremendous assistance on the applications of the further treatment of cancerous tissue as safe drug carriers. Furthermore, the new strategy demonstrated in this study could be applied on other label-free mechanically interlocked molecules, molecular machines, and macromolecules, which opened a new path to evaluate the toxicological and pharmacokinetic characteristics of these novel materials at the suborgan level.

Celecoxib substituted biotinylated poly(amidoamine) G3 dendrimer as potential treatment for temozolomide resistant glioma therapy and anti-nematode agent

Glioblastoma multiforme (GBM) is a one of the most widely diagnosed and difficult to treat type of central nervous system tumors. Resection combined with radiotherapy and temozolomide (TMZ) chemotherapy prolongs patients' survival only for 12 - 15 months after diagnosis. Moreover, many patients develop TMZ resistance, thus important is search for a new therapy regimes including targeted drug delivery. Most types of GBM reveal increased expression of cyclooxygenase-2 (COX-2) and production of prostaglandin E2 (PGE2), that are considered as valuable therapeutic target. In these studies, the anti-tumor properties of the selective COX-2 inhibitor celecoxib (CXB) and biotinylated third generation of the poly(amidoamine) dendrimer substituted with 31 CXB residues (G3BC31) on TMZ –resistantU-118 MG glioma cell line were examined and compared with the effect of TMZ alone including viability, proliferation, migration and apoptosis, as well as the cellular expression of COX-2, ATP level, and PGE2 production. Confocal microscopy analysis with the fluorescently labeled G3BC31 analogue has shown that the compound was effectively accumulated in U-118 MG cells in time–dependent manner and its localization was confirmed in lysosomes but not nuclei. G3BC31 reveal much higher cytotoxicity for U-118 MG cells at relatively low concentrations in the range of 2–4 µM with compared to CBX alone, active at 50–100 µM. This was due to induction of apoptosis and inhibition of proliferation and migration. Observed effects were concomitant with reduction of PGE2 production but independent of COX-2 expression. We suggest that investigated conjugate may be a promising candidate for therapy of TMZ-resistant glioblastoma multiforme, although applicable in local treatment, since our previous study of G3BC31 did not demonstrate selectivity against glioma cells compared to normal human fibroblasts.However, it has to be pointed that in our in vivo studies conducted with model organism, Caenorhabditis elegans indicated high anti-nematode activity of G3BC31 in comparison with CXB alone that confirms of usefulness of that organism for estimation of anti-cancer drug toxicity.

The in-vitro and In-vivo histopathology and toxicity of Gd(III)-anionic linear globular dendrimer second-generation G2-C595 nanoprobe

Objective(s): Toxico-histopathological studies are used to assess the toxic impacts of nanoparticles in organism exposure. The present study aimed to evaluate the prospective nano-cytotoxicity impacts of Gd(III)-anionic linear globular dendrimer second-generation G2-C595 (Gd[III] dendrimer G2-C595) contrast nanoprobe in terms of the exposure of many nude mice organs and organisms. In addition, we assessed the potential of the Gd(III)-dendrimer G2-C595 nanoprobe as a novel magnetic resonance imaging (MRI) nano-contrast agent for the human breast cancer cell line (MCF-7) and human embryonic kidney cell line (HEK-293).Materials and Methods: Gadolinium (Gd[III]) was loaded with dendrimer G2 and conjugated with the C595 monoclonal antibody to generate the Gd(III)-dendrimer G2-C595 to determine the impact on MUC1 beneficial cancer tumors. The cytotoxic effects of the Gd(III)-dendrimer G2-C595 nanoprobe on the HEK-293 cells were also investigated in-vitro and in-vivo. In addition, the Gd(III)-dendrimer G2-C595 nanoprobe was used on nude mice bearing the MCF-7 tumors to explore its specific activity against the in-vivo model of cancer.Results: The Gd(III)-dendrimer G2-C595 contrast nanoprobes affected the cytotoxicity of MCF-7, and no in-vivo toxicity was induced in the HEK-293 cells, kidneys, heart, lungs, brain, liver tissues, and other organs.Conclusion: According to the results, the Gd(III)-dendrimer G2 and Gd(III)-dendrimer G2-C595 induced no toxicity in the HEK-293 cells and heart, liver, and brain tissues of mice. In addition, the Gd(III)-dendrimer G2-C595 showed specific anti-action against the in-vivo tumor model. Therefore, the Gd(III)-dendrimer G2-C595 nanoprobe is highly recommended as a novel and effective MR contrast agent and antitumor carrier agent. Furthermore, the Gd(III)-dendrimer G2-C595 nano-sized probes demonstrated excellent biocompatibility and safety with no impact on normal organ functioning.

Spectroscopic, electrochemical and calorimetric studies on the interactions of poly(propyleneimine) G4 dendrimer with 5-fluorouracil in aqueous solutions

Results of zeta potential measurements and of spectroscopic (increased solubility, equilibrium dialysis, 1H NMR titration) and calorimetric measurements (isothermal ITC titration) indicate that fourth generation poly(propyleneimine) dendrimer (PPI G4) spontaneously binds (∆G < 0) 5-fluorouracil (FU) molecules in aqueous environments. The poly(propyleneimine) G4 dendrimer binds approximately n = 42 ± 3 drug molecules with an equilibrium constant of K = 220 ± 30. The process of saturation of dendrimer active centres with drug molecules is exothermic (∆H < 0) and accompanied by increased ordering of reagents (∆S < 0). Results of equilibrium dialysis indicate that poly(propyleneimine) G4 dendrimer has two sets of active centres comprising: n1 = 5 ± 1 sites with higher binding constant towards 5-fluorouracil and n2 = 39 ± 3 sites with lower binding constant towards this particular drug. The obtained results of a study on binding of 5-fluorouracil by the poly(propyleneimine) G4 dendrimer were compared with results for binding of this drug by poly (amidoamine) (PAMAM) G4 dendrimer macromolecules with the same number of surface, primary amine groups.

Duplex of Polyamidoamine Dendrimer/Custom-Designed Nuclear-Localization Sequence Peptide for Enhanced Gene Delivery.

Background: Dendrimers are an attractive alternative to viral vectors due to the low cost of production, larger genetic insert-carrying capacity, and added control over immune- and genotoxic complications through versatile functionalization. However, their transfection rates pale in comparison to their viral counterparts, resulting in widespread research efforts in the attempt to improve transfection efficiency. Materials and Methods: In this work, we designed a synthetic diblock nuclear-localization sequence peptide (NLS) (DDDDDDVKRKKKP) and complexed it with polyamidoamine (PAMAM) dendrimer G4 to form a duplex for gene delivery. We conducted transmission electron microscopy, gel mobility shift assay, and intracellular trafficking studies. We also assessed its transfection efficiency for the delivery of a green fluorescent protein-encoding plasmid (pGFP) to NIH3T3 cells. Results: PAMAM dendrimer G4, NLS, and plasmid DNA can form a stable three-part polyplex and gain enhanced entry into the nucleus. We found transfection efficiency, in large part, depends on the ratio of G4:NLS:plasmid. The triplex prepared at the ratio of 1:60:1 for G4:NLS:pGFP has been shown to be more significantly efficient in transfecting cells than the control group (G4/pGFP, 0.5:1). Conclusions: This new diblock NLS peptide can facilely complex with dendrimers to improve dendrimer-based gene transfection. It can also complex with other polycationic polymers to produce more potent nonviral duplex gene delivery vehicles.

Synthesis of imidazolium-terminated carbosilane dendrimers and dendrons and study of their interactions with a cell membrane model

A new family of imidazolium-terminated carbosilane dendrimers and dendrons was synthesized and characterized as a nanotechnological alternative to current therapies. The aim of this research was the study of the interacting process of nano-structures with a cell membrane model (lecithin liposomes), with the final ambitious purpose to use these nano-structures for biomedical applications, e.g. as anticancer drug. The interactions occurring over time between the dendrimers, at different generations (from G1 to G3) and different concentrations (1 mM, 10 mM and 20 mM), and cell membrane models were investigated using a computer-aided analysis of the electron paramagnetic resonance (EPR) spectra of selected spin probes, able to enter the liposome membrane, mimicking the phospholipid behavior. The EPR analysis provided structural and dynamical information on the systems indicating that the increase in generation and concentration produced an increased perturbation of the liposome structure. The dendrons and G1 dendrimers poorly interacted and this interaction was almost independent on dendrimer concentration and decreased over time. Conversely, G3 dendrimers showed a significant variation of the interacting process in respect of concentration. A fast kinetics of internalization was proposed at low dendrimer concentration, while accumulation of dendrimers at the liposome surface slowed down the internalization process. The cytotoxic effect of the dendrimers and the dendrons was verified by an in vitro screening in a selection of tumor cell lines, in parallel with the EPR results.

Revisiting Cationic Phosphorus Dendrimers as a Nonviral Vector for Optimized Gene Delivery Toward Cancer Therapy Applications.

Gene delivery, one important cancer-therapy mode, still remains to be challenging because of the shortage of highly efficient and safe nonviral vectors. Here, we revisit the development of cationic phosphorus dendrimers by synthesizing them with different generations (G1-3) and surface ligands (1-(2-aminoethyl) pyrrolidine, 1-(3-aminopropyl) piperidine, or 1-(2-aminoethyl) piperidine) for optimized gene delivery toward cancer-gene-therapy applications. First, the synthesized dendrimer derivatives were employed to condense plasmid DNA (pDNA) encoding enhanced green fluorescent protein (EGFP) to optimize their gene-delivery efficiency by varying the dendrimer generations and surface polycationic ligands. We show that all dendrimer/pDNA polyplexes display good cytocompatibility, and the 1-(2-aminoethyl) pyrrolidine-modified protonated G1 dendrimers (1-G1) display the best gene-delivery efficiency to HeLa cells under the same conditions through flow cytometry and fluorescence microscopic imaging analyses. Hence, 1-G1 dendrimers were then used as a vector to transfect pDNA encoding both EGFP and p53 protein for cancer-gene-therapy applications. Our results reveal that under the optimized conditions, the transfection of pDNA induces the significant p53 protein expression as verified through the resulted cell cycle arrest (regulation of p21 and Cdk4/Cyclin-D1 expression) and Western blotting. The cancer-gene-therapy potential of the polyplexes was finally validated through therapy of a xenografted tumor model after intratumoral injection without systemic toxicity. The developed cationic 1-G1 dendrimers may be adopted as a powerful vector system for gene therapy of cancer, as well as for highly effective gene therapy of other diseases.

Breast Tumor Targeting with PAMAM-PEG-5FU-99mTc As a New Therapeutic Nanocomplex: In In-vitro and In-vivo studies

Dendrimer-based targeted drug delivery, as an innovative polymeric drug-delivery system, is promising for cancer therapy. Folate receptors (FR) are overexpressed in many types of tumor cells, such as breast cell carcinomas, which allow folate-targeted delivery. Therefor polyethylene glycol (PEG) modified-PAMAM G4 dendrimers were functionalized with folic acid (FA), as targeting agent. Then, 5-FU (5-fluorouracil) and 99mTc (technetium-99m) as therapeutic agents were respectively loaded and conjugated to previous nano-complex (PEG-PAMAM G4-FA-5FU-99mTc). The value of drug loading was calculated by TGA analysis (16.97%). Drug release profiles of PEG-PAMAM G4-FA-5FU-99mTc and PEG-PAMAM G4-FA-5FU were evaluated. The radiochemical purity of PEG-PAMAM G4-FA-5FU-99mTc and PEG-PAMAM G4-FA-99mTc was obtained at >95% with excellent in-vitro and in-vivo stabilities. PEG-PAMAM G4-FA-5FU-99mTc was synthesized and the stability studies were carried out by the ITLC methods in serum (86.67% and 83.75%) and PBS. Combinational therapy effects of 5-FU and 99mTc containing nano-complexes were evaluated on 4T1 (mouse breast cancer) and MDA-MB-231 (human breast adenocarcinoma) cancer cell lines. Excellent uptake values were obtained for FA-decorated nano-complexes on 4T1 and MDA-MB-231 cell lines. Subsequently, tumor inhibition effects of PEG-PAMAM G4-FA-5FU-99mTc and PEG-PAMAM G4-FA-5FU were evaluated using the breast tumor-bearing BALB/C mice. Graphical abstract Breast Tumor Targeting with PAMAM-PEG-5FU- 99mTc As a New Therapeutic Nanocomplex: in In-vitro and In-vivo Studies was presented. This targeted drug delivery system can significantly increase the efficiency of cancer therapy, and reduce the treatment cost and time.

Dendrimer size effects on the selective brain tumor targeting in orthotopic tumor models upon systemic administration.

Malignant gliomas are the most common and aggressive form of primary brain tumors, with a median survival of 15–20 months for patients receiving maximal interventions. Advances in nanomedicine have provided tumor‐specific delivery of chemotherapeutics to potentially overcome their off‐target toxicities. Recent advances in dendrimer‐based nanomedicines have established that hydroxyl‐terminated poly(amidoamine) dendrimers can intrinsically target neuroinflammation and brain tumors from systemic administration without the need for targeting moieties. The size of nanocarriers is a critical parameter that determines their tumor‐targeting efficiency, intratumor distribution, and clearance mechanism. In this study, we explore the dendrimer size effects on brain tumor targeting capability in two clinically relevant orthotopic brain tumor models, the 9L rat and GL261 mouse models, which capture differing aspects of gliomas. We show that increasing dendrimers from Generation 4 to Generation 6 significantly enhances their tumor accumulation (~10‐fold greater at 24 hr), tumor specificity (~2–3 fold higher), and tumor retention. The superior tumor targeting effect of G6 dendrimers is associated with its reduced renal clearance rate, resulting in longer circulation time compared to G4 dendrimers. Additionally, the increase in dendrimer generation does not compromise its homogeneous tumor distribution and intrinsic targeting of tumor‐associated macrophages. These results validate the potential for these dendrimers as an effective, clinically translatable platform for effectively targeting tumor‐associated macrophages in malignant gliomas.

Synergistic cellular toxicity and uptake effects of iodixanol conjugated to anionic linear globular dendrimer G2

Objective(s): Early diagnosis of cancer using noninvasive imaging techniques has been discussed in several recent studies. The present study aimed to assess the synergistic effects of iodixanol-conjugated polyethylene glycol (PEG)-citrate (anionic linear globular) dendrimer G2 on MCF-7 breast cancer cells and human embryonic kidney 293 (HEK293) cells. Materials and Methods: PEG-citrate dendrimer G2 was synthesized and purified. The product was characterized using atomic force microscopy (AFM), electron energy loss spectroscopy (EELS), dynamic light scattering (DLS). At the next stage, the product was conjugated to iodixanol, purified and lyophilized. The cytotoxic effects of the iodixanol, plain PEG-citrate dendrimer G2, and iodixanol-PEG-citrate dendrimer G2 complex were evaluated using methylthiazole-tetrazolium (MTT) assay on the MCF-7 and HEK293 cells. Inductively coupled plasma mass spectrometry (ICP MS) is a mass spectrometry technique, which applies inductively coupled plasma to ionize samples.Results: According to the obtained results, the uptake of PEG-citrate dendrimer G2 iodixanol increased significantly compared to iodixanol alone (P<0.05), indicating the importance of lack of significant in-vitro toxicity. Moreover, in the particle size and higher negative zeta potential confirmed the loading of iodixanol in dendrimer G2. Increase, the loading of iodixanol in dendrimer was confirmed by the chemical shifts in HNMR. Conclusion: Therefore, it was concluded that the addition of anionic linear globular dendrimer G2 to iodixanol affected the cellular uptake of the drug with no significant toxicity. Recent findings also confirmed that this novel complex could be applied as an effective cancer imaging agent for molecular biology and molecular imaging applications.

Synthesis of structurally enhanced magnetite cored poly(propyleneimine) dendrimer nanohybrid material and evaluation of its functionality in sustainable catalysis of condensation reactions

The conventional method of dendrimer synthesis especially poly(propyleneimine) dendrimer (PPI) involves complicated reaction workup and tedious separation strategies. Since it has greater number of nitrogen atom in their structure, its applications are innumerable in different fields. But the PPI dendrimer is used once, it cannot be recycled for subsequent utility. In order to overcome these issues, for the first time divergent synthesis of poly(propyleneimine) dendrimer G3 on silica coated magnetite has been achieved with structurally enhanced PPI dendrimer on core-shell type magnetic silica nanostructure. This nanohybrid material was characterized by using HRTEM, FTIR, XRD, TGA, XPS and VSM studies. Further, nitrogen concentration of PPI dendrimer was quantified by conductometric titration and Prussian blue complex methods. The probing of catalytic efficacy of structurally enhanced magnetite cored poly(propyleneimine) dendrimer G3 as magnetically recyclable heterogeneous organic base catalyst was employed for representative reactions such as Knoevenagel condensation, Knoevenagel-Michael cyclocondensation and Henry reaction at ambient conditions. The catalyst was reused for minimum of eight cycles without significant loss of its catalytic activity.

Cellular internalization of targeted and non-targeted delivery systems for contrast agents based on polyamidoamine dendrimers

New high-molecular-weight contrast agents based on polyamidoamine (PAMAM) dendrimers for targeted imaging of malignant tumors characterized by overexpression of human epidermal growth factor receptor (EGFR) and human alpha-fetoprotein receptor (RECAF) were designed. Conjugates of second (G2) and third (G3) generation polyamidoamine dendrimers with 1,4,7,10-tetraazocyclodecane-1,4,7,10-tetraacetic acid (DOTA) were obtained. The quantitative composition of the conjugates was determined by 1HNMR spectroscopy. It was shown that four out of the 16 terminal NH2 groups in G2-DOTA and nine out of the 32 groups in G3-DOTA were modified with DOTA. The morphology, size, and charge of the synthesized macromolecules were characterized by dynamic light scattering and electrophoresis. Gadolinium(III) was loaded into the conjugates and the Gd content was determined by atomic emission spectroscopy. For increasing the selectivity of accumulation in the tumor cells, two recombinant proteins able to bind selectively to EGFR and RECAF, namely, human recombinant epidermal growth factor (rEGF) and human recombinant 3rd domain of alpha-fetoprotein (3dAFPpG), were conjugated with G2 and G3 dendrimers. The conjugates containing vector molecules were mainly accumulated via clathrin-dependent endocytosis, whereas G2-DOTA and G3-DOTA were absorbed via caveolin-dependent endocytosis and macropinocytosis. The dendrimer conjugates with vector molecules were intensely accumulated in A549 cells characterized by high expression of EGFR (Herl) and RECAF, whereas the accumulation of conjugates in the control K562 cells (with low expression of Her1) and in the CD14− population of human unstimulated mononuclear white blood cells was insignificant. The 3dAFPpG-conjugated dendrimers were partly recycled. All synthesized conjugates had a rather low toxicity in the range of 350–450 µmol L−1 (IC50).

Effective Elimination of Charge-associated Toxicity of Low Generation Polyamidoamine Dendrimer Eases Drug Delivery of Oxaliplatin

Polyamidoamine (PAMAM) dendrimer is emerging as an effective nanocarrier for delivering anticancer drugs. Still, unmodified PAMAM dendrimer is hardly used in vivo because of unsatisfied drug release, high tendency of interfering with cellular membranes, and rapid clearance by reticuloendothelial system. In this study, low generation polyamidoamine (PAMAM) dendrimer G3.0 is developed and surface modified with methoxypolyethylene glycol (PAMAM G3.0-mPEG) to overcome its limitations. Specifically, PAMAM G3.0 conjugated with mPEG at different ratios are investigated to effectively eliminate its charge-associated toxicity, in which PAMAM G3.0-mPEG- 8 is chosen for oxaliplatin (OX) loading. Results reveal that OX-loaded PAMAM G3.0-mPEG-8 has desirable size, good entrapment efficiency, and sustained release with minimum drug leakage. In addition, Resazurin assay indicates that the toxicity of loaded OX is reduced as compared to free drug but still maintain substantially anticancer activity on HeLa cells, suggesting the potential application of PAMAM G3.0-mPEG-8 for OX delivery in cancer therapy.

Structural changes in lipid mesophases due to intercalation of dendritic polymer nanoparticles: Swollen lamellae, suppressed curvature, and augmented structural disorder

Understanding interactions between nanoparticles and model membranes is relevant to functional nano-composites and the fundamentals of nanotoxicity. In this study, the effect of polyamidoamine (PAMAM) dendrimers as model nanoparticles (NP) on the mesophase behaviour of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) has been investigated using high-pressure small-angle X-ray scattering (HP-SAXS). The pressure-temperature (p−T) diagrams for POPE mesophases in excess water were obtained in the absence and presence of G2 and G4 polyamidoamine (PAMAM) dendrimers (29 Å and 45 Å in diameter, respectively) at varying NP-lipid number ratio (ν = 0.0002–0.02) over the pressure range p = 1–3000 bar and temperature range T = 20–80 °C. The p−T phase diagram of POPE exhibited the Lβ, Lα and HII phases. Complete analysis of the phase diagrams, including the relative area pervaded by different phases, phase transition temperatures (Tt) and pressures (pt), the lattice parameters (d-spacing), the pressure-dependence of d-spacing (Δd/Δp), and the structural ordering in the mesophase as gauged by the Scherrer coherence length (L) permitted insights into the size- and concentration-dependent interactions between the dendrimers and the model membrane system. The addition of dendrimers changed the phase transition pressure and temperature and resulted in the emergence of highly swollen lamellar phases, dubbed Lβ-den and Lα-den. G4 PAMAM dendrimers at the highest concentration ν = 0.02 suppressed the formation of the HII phase within the temperature range studied, whereas the addition of G2 PAMAM dendrimers at the same concentration promoted an extended mixed lamellar region in which Lα and Lβ phases coexisted. Statement of SignificanceUsing high pressure small angle X-ray scattering in the pressure range 1–3000 bar and temperature range 20–60 °C, we have studied interactions between PAMAM dendrimers (as model nanoparticles) and POPE lipid mesophases (as model membranes). We report the pressure-temperature phase diagrams for the dendrimer-lipid mesophases for the first time. We find that the dendrimers alter the phase transition temperatures (Tt) and pressures (pt), the lattice parameters (d-spacing), and the structural order in the mesophase. We interpret these unprecedented results in terms of the fluidity of the lipid membranes and the interactions between the dendrimers and the membranes. Our findings are of fundamental relevance to the field of nanotoxicity and functional nanomaterials that integrate nanoparticles and organized lipid structures.

Synthesis of Melamine Core Starburst Polyamide G1 Dendrimer and its Antibacterial and Antioxidant Activities

A novel polyamide first-generation dendrimer 7 was synthesized from new methodology under mild reaction conditions. The AB2 adduct, ethyl 2-[N-[2,2-bis(hydroxymethyl)propionyl]amino]ethylate (3), was prepared from 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) and glycine as a linker. Further, G1 dendrimer 7 was synthesized by coupling melamine (5) with monomer 3. The structural elucidations of all the compounds were confirmed by FTIR, 1H &amp; 13C NMR and HRMS. The G1 dendrimer was found to exhibit significant antibacterial activity against S. aureus and E. cloacae and antioxidant activity by DPPH scavenging method when compared to the standard, ascorbic acid.

Dendrimeric calcium-sensitive MRI probes: the first low-field relaxometric study.

Different classes of small- or nano-sized calcium-sensitive probes for magnetic resonance imaging (MRI) have been proposed in the last two decades. These compounds have been developed mainly for functional MRI purposes and tested in vivo in different animal models. Most of them are paramagnetic systems that change their relaxivity in the presence of the divalent ion calcium, resulting in increased T1 or T2 contrast. In this work, we report the investigation of their relaxometric behavior at low magnetic fields, specifically the comparison of the monomeric Ca-sensitive probe and the corresponding dendrimer conjugates of generations 0, 1 and 2 (G0, G1 and G2, respectively). As a result, a relaxivity hump between 10 and 100 MHz of the Larmor frequency progressively appeared with an increase in the size of the investigated contrast agent, indicative of a restricted rotational motion of the complexes as long as the size of the molecule increases. The same trend with a more pronounced effect was detectable in the presence of calcium. The relaxivity enhancement for the Ca2+ adducts, primarily caused by an increase of the hydration state of Gd3+, went from ca. 130% for the monomeric probe to ca. 310% for the G2 dendrimer conjugate at 0.5 T and 25 °C. T1 weighted magnetic resonance images acquired at 1 T displayed the strong ability of these systems to change their contrast according to the presence of calcium at this field, thus laying the basis for promising future in vivo applications.

Efficient modification of PAMAM G1 dendrimer surface with β-cyclodextrin units by CuAAC: impact on the water solubility and cytotoxicity.

The toxicity of the poly(amidoamine) dendrimers (PAMAM) caused by the peripheral amino groups has been a limitation for their use as drug carriers in clinical applications. In this work, we completely modified the periphery of PAMAM dendrimer generation 1 (PAMAM G1) with β-cyclodextrin (β-CD) units through the Cu(i)-catalyzed azide–alkyne cycloaddition (CuAAC) to obtain the PAMAM G1-β-CD dendrimer with high yield. The PAMAM G1-β-CD was characterized by 1H- and 13C-NMR and mass spectrometry studies. Moreover, the PAMAM G1-β-CD dendrimer showed remarkably higher water solubility than native β-CD. Finally, we studied the toxicity of PAMAM G1-β-CD dendrimer in four different cell lines, human breast cancer cells (MCF-7 and MDA-MB-231), human cervical adenocarcinoma cancer cells (HeLa) and pig kidney epithelial cells (LLC-PK1). The PAMAM G1-β-CD dendrimer did not present any cytotoxicity in cell lines tested which shows the potentiality of this new class of dendrimers.

Glucoheptoamidated polyamidoamine PAMAM G3 dendrimer as a vehicle for succinate linked doxorubicin; enhanced toxicity of DOX against grade IV glioblastoma U-118 MG cells

Glioblastoma multiforme (GBM), known as astrocytoma grade IV, is the most common primary malignant brain tumor and one of the most lethal forms of cancer with a median survival rate of approximately 15 months after standard treatment. Currently, the chance of increasing the survival rate is found in therapy with doxorubicin (DOX) delivered to the central nervous system by polymeric carriers.In this study, we synthesized and characterized by NMR spectroscopy, a vehicle for DOX based on glucoheptoamidated poly (amidoamine) dendrimers of third generation (G3gh) and its derivative substituted with 4 residues of DOX attached via succinate linkers (G3gh4DOX). The pH dependent DOX release profile from the well soluble G3gh4DOX indicates a slow release that is significantly higher in an acidic environment due to hydrolytic cleavage of an amide bond between DOX and the succinate linker, not the ester bond between succinate linker and the glucoheptoamide substituent. Biological studies demonstrate efficient grade IV human U-118 MG glioma cells damage by G3gh4DOX conjugates at very low concentrations, with IC50 < 1 μM after 24–72 h of incubation. The conjugate studied was about 2.7–4.5 fold more toxic than DOX alone. G3gh4DOX killed glioma cells through a more desirable apoptosis pathway and inhibited their proliferation with cell cycle-arrest at the G2/M phase. The effect of G3gh4DOX was probably the result of action of the entire conjugate, but not DOX alone. Therefore, G3gh4DOX seems to be a promising candidate for local glioma therapy.

Ribbon Phase of Dendrimer–Surfactant Complexes

The cylindrical micelles formed by amphiphilic surfactants in aqueous media generally organize in two-dimensional (2D) hexagonal lattice because of their largely circular cross section. Here we demonstrate that the packing habit of the cylindrical micelles of anionic sodium dodecyl sulfate (SDS) was perturbed by the electrostatic binding with a positively charged poly(amidoamine) (PAMAM) G4 dendrimer via cooperative deformation for charge matching, leading to the ribbon phase with nonhexagonal 2D lattices. The cylindrical micelles with elliptic cross section packed in the centered rectangular lattice with orthorhombic cmm symmetry over a broad range of surfactant-to-dendrimer amine group molar ratio. The packing structure transformed to the oblique lattice with monoclinic p2 symmetry at the stoichiometric composition. Detailed analysis of the geometry of the dendrimers accommodated in the interstitial tunnels surrounded by the SDS cylinders revealed that the dendrimer molecules were elongated into prolate...

Radical dendrimers: Synthesis, anti-tumor activity and enhanced cytoprotective performance of TEMPO free radical functionalized polyurethane dendrimers

Polyurethane dendrimers up to fourth generation, functionalized with stable 4-hydroxy-2, 2, 6, 6-tetramethylpiperidin-1-yloxyl (4-hydroxy TEMPO), were prepared via a single-step urethane interchange reaction and their structures were confirmed by NMR, FT-IR, MALDI-TOF MS and SEC-MALLS techniques. The terminal TEMPO radicals of the dendrimers exhibited a triplet with nitrogen hyperfine splitting constant of 14.4 G, at g = 2.0026 in the EPR spectrum and their paramagnetic nature were confirmed by vibrating sample magnetometer. The MTT assay results revealed that the G4 dendrimer had significant anti-tumor activity in A549 lung adenocarcinoma cells and this dendrimer was found not induced any cell death in normal L132 lung cells. Further, antioxidant effect of G4 dendrimer was evaluated in normal L132 lung cells; the in-vitro studies include cell morphological studies, measurement of total intracellular reactive oxygen species (ROS) using H2DCF dye and analysis of SOD, CAT, GSH and GPx. This study demonstrated the efficacy of the dendrimers through decrease in free radicals and confirmed their enhanced cytoprotective performance over N-acetyl cysteine standard used.