G3 Polyamidoamine Dendrimer Research Articles

Cytotoxicity and heating efficiency of dendrimer functionalized graphene oxide modified nickel ferrite nanoparticles

Magnetic nanoparticles have garnered significant interest, offering a promising avenue for magnetic hyperthermia. In this study, nickel ferrite nanoparticles were successfully synthesized using green-mediated sol–gel approach and subsequently modified with graphene oxide and functionalized using G3 Polyamidoamine dendrimer. Saturation magnetization values obtained from VSM analysis were found to be 51.8 emu/g and 11.2 emu/g for bare and functionalized nickel ferrite nanoparticles, respectively. The functionalized nanostructure exhibited potential for hyperthermia applications, with a specific absorption rate of 16 W/g. The in-vitro cytotoxicity of the functionalized nickel ferrite nanoparticles shows cell viability of 94.55 %, underscoring the non-toxic nature of the functionalized material.

The Effect of Absorption-Enhancement and the Mechanism of the PAMAM Dendrimer on Poorly Absorbable Drugs.

The polyamidoamine (PAMAM) dendrimer is a highly efficient absorption promoter. In the present study, we studied the absorption-enhancing effects and the mechanism of PAMAM dendrimers with generation 0 to generation 3 (G0–G3) and concentrations (0.1–1.0%) on the pulmonary absorption of macromolecules. The absorption-enhancing mechanisms were elucidated by microarray, western blotting analysis, and PCR. Fluorescein isothiocyanate-labeled dextrans (FDs) with various molecular weights were used as model drugs of poorly absorbable drugs. The absorption-enhancing effects of PAMAM dendrimers on the pulmonary absorption of FDs were in a generation- and concentration-dependent manner. The G3 PAMAM dendrimer with high effectiveness was considered to the best absorption enhancer for improving the pulmonary absorption of FDs. G3 PAMAM dendrimers at three different concentrations were non-toxic to Calu-3 cells. Based on the consideration between efficacy and cost, the 0.1% G3 PAMAM dendrimer was selected for subsequent studies. The results showed that treatment with a 0.1% G3 PAMAM dendrimer could increase the secretion of organic cation transporters (OCTs), OCT1, OCT2, and OCT3, which might be related to the absorption-enhancing mechanisms of the pulmonary absorption of FDs. These findings suggested that PAMAM dendrimers might be potentially safe absorption enhancers for improving absorption of FDs by increasing the secretion of OCT1, OCT2, and OCT3.

The antibacterial effect of G3-poly-amidoamine dendrimer on gram negative and gram positive bacteria in aqueous solutions

Dendrimers are symmetric, round and ramose macromolecules made up of monomers which have a certain structural order. The aim of this study was to evaluate the antibacterial effects of different concentrations of G3-poly-amidoamine dendrimer (G3-PAD) on 7 species of gram-negative and gram-positive bacteria in aqueous solutions. Different concentrations of G3-PAD were prepared and from each bacterial species, a suspension with a different pH was prepared according to the McFarland 0.5 standard. Bacteria were left in a 37 degrees C incubator and shaker from 0 to 60 min, and were cultivated on a Mueller-Hinton Agar plate. The bacteria that grew on each plate were counted and analyzed. The results showed that the antibacterial effect of G3-PAD in aqueous solutions was directly related to dendrimer concentration, contact time and pH. The strongest effect on Salmonella and Bacillus Subtilis was at pH = 6.5 and 7.5 and contact time 45 min, and in pH = 9, contact time 30 min; for Enterococcus faecalis in all three pH, it was 60 min; for Staphylococcus Aureus in pH = 6.5 and 7.5, 60 min and in pH = 9, 30 min; for E. coli in pH = 6.5 and 7.5, 60 min and in pH = 9, 45 min. G3-PAD showed its strongest effect on Shigella bacteria in pH = 6.5, contact time 60 min. In pH = 7.5 there was no optimum condition and in pH = 9, the optimum contact time was 60 min. The strongest effect of G3-PAD on all species was seen in 2000 ppm concentration. These results show a new strategy to improve bacteria elimination from aqueous solutions. However, safely using dendrimers for disinfecting drinking water still needs more research.

In Vitro Evaluation of Third Generation PAMAM Dendrimer Conjugates.

The present study compares the use of high generation G3 and low generation G0 Polyamidoamine (PAMAM) dendrimers as drug carriers of naproxen (NAP), a poorly water soluble drug. Naproxen was conjugated to G3 in different ratios and to G0 in a 1:1 ratio via a diethylene glycol linker. A lauroyl chain (L), a lipophilic permeability enhancer, was attached to G3 and G0 prodrugs. The G3 and G0 conjugates were more hydrophilic than naproxen as evaluated by the measurement of partitioning between 1-octanol and a phosphate buffer at pH 7.4 and pH 1.2. The unmodified surface PAMAM-NAP conjugates showed significant solubility enhancements of NAP at pH 1.2; however, with the number of NAP conjugated to G3, this was limited to 10 molecules. The lactate dehydrogenase (LDH) assay indicated that the G3 dendrimer conjugates had a concentration dependent toxicity towards Caco-2 cells. Attaching naproxen to the surface of the dendrimer increased the IC50 of the resulting prodrugs towards Caco-2 cells. The lauroyl G3 conjugates showed the highest toxicity amongst the PAMAM dendrimer conjugates investigated and were significantly more toxic than the lauroyl-G0-naproxen conjugates. The permeability of naproxen across monolayers of Caco-2 cells was significantly increased by its conjugation to either G3 or G0 PAMAM dendrimers. Lauroyl-G0 conjugates displayed considerably lower cytotoxicity than G3 conjugates and may be preferable for use as a drug carrier for low soluble drugs such as naproxen.

Different patterns of nuclear and mitochondrial penetration by the G3 PAMAM dendrimer and its biotin-pyridoxal bioconjugate BC-PAMAM in normal and cancer cells in vitro.

The intracellular localization and colocalization of a fluorescently labeled G3 amine-terminated cationic polyamidoamine (PAMAM) dendrimer and its biotin–pyridoxal (BC-PAMAM) bioconjugate were investigated in a concentration-dependent manner in normal human fibroblast (BJ) and squamous epithelial carcinoma (SCC-15) cell lines. After 24 hours treatment, both cell lines revealed different patterns of intracellular dendrimer accumulation depending on their cytotoxic effects. Cancer cells exhibited much higher (20-fold) tolerance for native PAMAM treatment than fibroblasts, whereas BC-PAMAM was significantly toxic only for fibroblasts at 50 µM concentration. Fibroblasts accumulated the native and bioconjugated dendrimers in a concentration-dependent manner at nontoxic range of concentration, with significantly lower bioconjugate loading. After reaching the cytotoxicity level, fluorescein isothiocyanate-PAMAM accumulation remains at high, comparable level. In cancer cells, native PAMAM loading at higher, but not cytotoxic concentrations, was kept at constant level with a sharp increase at toxic concentration. Mander’s coefficient calculated for fibroblasts and cancer cells confirmed more efficient native PAMAM penetration as compared to BC-PAMAM. Significant differences in nuclear dendrimer penetration were observed for both cell lines. In cancer cells, PAMAM signals amounted to ~25%–35% of the total nuclei area at all investigated concentrations, with lower level (15%–25%) observed for BC-PAMAM. In fibroblasts, the dendrimer nuclear signal amounted to 15% at nontoxic and up to 70% at toxic concentrations, whereas BC-PAMAM remained at a lower concentration-dependent level (0.3%–20%). Mitochondrial localization of PAMAM and BC-PAMAM revealed similar patterns in both cell lines, depending on the extracellular dendrimer concentration, and presented significantly lower signals from BC-PAMAM, which correlated well with the cytotoxicity.

Bioconjugates of PAMAM dendrimers with trans-retinal, pyridoxal, and pyridoxal phosphate

BackgroundBioconjugates of a polyamidoamine (PAMAM) G3 dendrimer and an aldehyde were synthesized as carriers for vitamins A and B6, and the bioavailability of these vitamins for skin nutrition was investigated.MethodsNuclear magnetic resonance (NMR) and ultraviolet-visible methods were used to characterize the structure of the bioconjugates and for monitoring release of pyridoxal (Pyr) and pyridoxal phosphate (PLP) from these bioconjugates in vitro. A skin model permeation of bioconjugates was also studied in a Franz chamber.ResultsA transdermal G3 PAMAM dendrimer was used to synthesize bioconjugates with trans-retinal (Ret), pyridoxal (Pyr), or PLP. These nanomolecules, containing up to four covalently linked Ret, Pyr, or PLP (G34Ret, G34Pyr, and G34PLP), were able to permeate the skin, as demonstrated in vitro using a model skin membrane. PLP and Pyr bound to a macromolecular vehicle were active cofactors for glutamic pyruvic transaminase, as shown by 1H NMR spectral monitoring of the progress of the L-alanine + α-ketoglutarate → glutamic acid + pyruvic acid reaction.ConclusionPAMAM-PLP, PAMAM-Pyr, and PAMAM-Ret bioconjugates are able to permeate the skin. PLP and Pyr are available as cofactors for glutamic pyruvic transaminase.

Molecular dynamics simulations of the interactions of charge-neutral PAMAM dendrimers with pulmonary surfactant

We have performed coarse grained molecular dynamics simulations (CGMD) to investigate the interactions of generation 7, 5 and 3 (G7, G5 and G3) charge-neutral polyamidoamine (PAMAM) dendrimers with a DPPC (dipalmitoylphosphatidylcholine) monolayer at the air–water interface (model pulmonary surfactant) during the end-expiration process. Our results show that different generations of PAMAM dendrimers have different influences on the DPPC monolayer. Generally, G3 PAMAM dendrimers show little influence on the DPPC monolayer's structure and relative properties. While G7 and G5 PAMAM dendrimers tend to induce the formation of largely deformed structures of the DPPC monolayer and inhibit or even reverse the normal phase transition of the interfacial DPPC molecules during the process of compression. Besides, we find that the formation processes of these disrupted structures are energy-favorable based on analyzing van der Waals interaction energy between PAMAM dendrimers and the whole system.

Surface Modification of PAMAM Dendrimers Modulates the Mechanism of Cellular Internalization

The aim of this study was to investigate the influence of dendrimer surface properties on cellular internalization and intracellular trafficking in the human colon adenocarcinoma HT-29 cell line. Third-generation (G3) polyamidoamine (PAMAM) dendrimers were modified to contain either two lauroyl chains (G3L2), two propranolol molecules (G3P2), or two lauroyl and two propranolol molecules (G3L2P2) at the dendrimer surface. Surface-modified and unmodified dendrimers were labeled with fluorescein isothiocyanate (FITC) at an average molar ratio of 1:1. The mechanisms of cellular internalization and intracellular trafficking of dendrimers were analyzed by confocal laser scanning microscopy and flow cytometry. The internalization of G3 and G3P2 dendrimers involved both caveolae-dependent endocytosis and macropinocytosis pathways; internalization of G3L2P2 dendrimer appeared to involve caveolae-dependent, and possibly clathrin-dependent, endocytosis pathways; and internalization of G3L2 dendrimer occurred via caveolae-dependent, clathrin-dependent, and macropinocytosis pathways. Subcellular colocalization data indicated that unmodified and all surface-modified G3 PAMAM dendrimers were internalized and trafficked to endosomes and lysosomes. It is therefore apparent that the initial mode of dendrimer internalization into HT-29 cells is influenced by the surface properties of G3 PAMAM dendrimer.

Systematic Investigation of Polyamidoamine Dendrimers Surface-Modified with Poly(ethylene glycol) for Drug Delivery Applications: Synthesis, Characterization, and Evaluation of Cytotoxicity

Surface modification of amine-terminated polyamidoamine (PAMAM) dendrimers by poly(ethylene glycol) (PEG) groups generally enhances water-solubility and biocompatibility for drug delivery applications. In order to provide guidelines for designing appropriate dendritic scaffolds, a series of G3 PAMAM-PEG dendrimer conjugates was synthesized by varying the number of PEG attachments and chain length (shorter PEG 550 and PEG 750 and longer PEG 2000). Each conjugate was purified by size exclusion chromatography (SEC) and the molecular weight (MW) was determined by (1)H NMR integration and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). NOESY experiments performed in D 2O on selected structures suggested no penetration of PEG chains to the central PAMAM domain, regardless of chain length and degree of substitution. CHO cell cultures exposed to PAMAM-PEG derivatives (< or =1 microM) showed a relatively high cell viability. Generally, increasing the degree of PEG substitution reduced cytotoxicity. Moreover, compared to G3 PAMAM dendrimers that were N-acetylated to varying degrees, a lower degree of surface substitution with PEG was needed for a similar cell viability. Interestingly, when longer PEG 2000 was fully incorporated on the surface, cell viability was reduced at higher concentrations (32 muM), suggesting increased toxicity potentially by forming intermolecular aggregates. A similar observation was made for anionic carboxylate G5.5 PAMAM dendrimer at the same dendrimer concentration. Our findings suggest that a lower degree of peripheral substitution with shorter PEG chains may suffice for these PAMAM-PEG conjugates to serve as efficient universal scaffolds for drug delivery, particularly valuable in relation to targeting or other ligand-receptor interactions.

PAMAM dendrimers for the delivery of the antibacterial Triclosan

Many oral care products incorporate an antibacterial compound to prevent the formation of dental plaque which predisposes teeth to dental caries or periodontal disease []. Triclosan (TCN) is a commonly used antiplaque agent in toothpastes []. Strategies to increase the delivery efficiency of antibacterials using formulation aids such as polyamidoamine (PAMAM) dendrimers are of interest.Solubilisation studies over the pH range 5-12 demonstrated an increase in the level of TCN solubilised with increasing dendrimer concentration (1 mM–5 mM). However, the dendrimer was unable to enhance TCN solubility at lower pH values and the solubilising effect observed was attributed to the ionization of TCN (pKa 8.14) resulting from dendrimer induced pH changes.End group modification of G3 PAMAM dendrimer with phenylalanine in order to promote solubility through π–π stacking between TCN and the amino acid has been carried out. Phenylalanine:G3 PAMAM conjugates of different ratios (32:1, 21:1, 16:1) were synthesized. The fully conjugated dendrimer (32:1) had poor aqueous solubility, whereas the 21:1 and 16:1 dendrimer conjugates were water soluble. The 21:1 conjugate was tested for its ability to solubilise TCN, however, again there was no increase over control buffer solutions of the same pH. An alternative approach under investigation is to directly conjugate TCN to PAMAM dendrimers via a hydrolysable linkage.

Dendrimers as a Carrier for Pulmonary Delivery of Enoxaparin, a Low-Molecular Weight Heparin

This study was designed to test the hypothesis that positively charged dendrimers form a complex with enoxaparin, a low-molecular weight heparin (LMWH), and that the resulting drug-dendrimer complex is effective in preventing deep vein thrombosis after pulmonary administration. Fourier Transform Infrared (FTIR) spectroscopy and the azure A assay were used to evaluate interactions between dendrimers and enoxaparin. The efficacy of polyamidoamine (PAMAM) dendrimers in enhancing pulmonary absorption of enoxaparin was studied by administering enoxaparin-dendrimer formulations into the lungs of anesthetized rats and monitoring drug absorption by measuring plasma anti-factor Xa activity. The optimized formulations were evaluated for their efficacy in preventing deep vein thrombosis in a rodent model. The safety of the formulations was tested by studying their effects on mucociliary transport rate (MTR) in a frog palate model and by measuring injury markers in rat bronchoalveolar fluid. The FTIR data and azure A assay revealed ionic interactions between the amino groups of cationic dendrimers and the carboxylic and sulfate groups of enoxaparin. Positively charged dendrimers increased the relative bioavailability of enoxaparin by 40%, while a negatively charged dendrimer had no effect. Formulations containing 1% G2 or 0.5% G3 PAMAM dendrimer plus enoxaparin were as efficacious in preventing deep vein thrombosis in a rat model as subcutaneously administered enoxaparin. The formulations did not adversely affect the MTR or produce extensive damage to the lungs. Positively charged dendrimers are a suitable carrier for pulmonary delivery of enoxaparin. They enhance pulmonary absorption of LMWH probably by reducing negative surface charge density of the drug molecule.

Evaluation of polyamidoamine (PAMAM) dendrimers as drug carriers of anti-bacterial drugs using sulfamethoxazole (SMZ) as a model drug

Sulfamethoxazole (SMZ), a sulfonamide with well-known anti-bacterial properties, is not freely soluble in water and causes problems in its clinical applications. In the present study we investigated the potential of ethylenediamine (EDA) core polyamidoamine (PAMAM) dendrimers as drug carriers of SMZ by aqueous solubility, in vitro release as well as anti-bacterial activity studies. Results showed that the aqueous solubility of SMZ was approximately proportional to dendrimer concentration (a 40-fold increase in solubility in 10 mg/ml G3 PAMAM dendrimer solutions compared with that in double-distilled water at 37 °C). The in vitro release of SMZ in the presence of PAMAM dendrimers was significantly slower compared to pure SMZ dissolved in ethanol. Microbiology studies showed that PAMAM dendrimers could increase the anti-bacterial activity of SMZ (a 4- or 8-fold increase in the anti-bacterial activity of SMZ in dendrimer solution compared to pure SMZ dissolved in dimethylsulfoxide (DMSO) or 0.01 M NaOH solution). The in vitro release behavior and anti-bacterial activity studies indicated that PAMAM dendrimers might be considered as potential drug carriers of sulfonamides with a sustained release behavior under suitable conditions.