The influence of PAMAM dendrimers surface groups on their interaction with porcine pepsin.

In this study the ability of three polyamidoamine (PAMAM) dendrimers with different surface charge (positive, neutral and negative) to interact with a negatively charged protein (porcine pepsin) was examined. It was shown that the dendrimer with a positively charged surface (G4 PAMAM-NH2), as well as the dendrimer with a neutral surface (G4 PAMAM-OH), were able to inhibit enzymatic activity of pepsin. It was also found that these dendrimers act as mixed partially non-competitive pepsin inhibitors. The negatively charged dendrimer (G3.5 PAMAM-COOH) was not able to inhibit the enzymatic activity of pepsin, probably due to the electrostatic repulsion between this dendrimer and the protein. No correlation between changes in enzymatic activity of pepsin and alterations in CD spectrum of the protein was observed. It indicates that the interactions between dendrimers and porcine pepsin are complex, multidirectional and not dependent only on disturbances of the secondary structure.

Modified PAMAM dendrimer with 4-carbomethoxypyrrolidone surface groups reveals negligible toxicity against three rodent cell-lines.

Modification of the surface groups of dendrimers is one of the methods to improve their biocompatibility. This article presents results of experiments related to the toxicity of a modified polyamidoamine (PAMAM) dendrimer of the fourth generation with 4-carbomethoxypyrrolidone surface groups (PAMAM-pyrrolidone dendrimer). The cytotoxic activity of the dendrimer was tested on Chinese hamster fibroblasts (B14), embryonic mouse hippocampal cells (mHippoE-18) and rat liver derived cells (BRL-3A). The same cell lines were used to investigate the influence of pyrrolidone dendrimer on the mitochondrial membrane potential, intracellular ROS level and its ability to induce apoptosis or necrosis. The analyzed dendrimer showed only minor toxicity and no ability to induce apoptosis. The most important finding is the lack of influence of the PAMAM-pyrrolidone dendrimer on intracellular ROS level and mitochondrial membrane potential. FROM THE CLINICAL EDITOR: The authors demonstrate that pyrrolidone-functionalized PAMAM dendrimers have very low toxicity in the tested cell lines, as evidenced by no alteration of mitochondrial membrane potential and no increase of ROS production.

The influence of PAMAM-OH dendrimers on the activity of human erythrocytes ATPases.

Dendrimers are a relatively new and still not fully examined group of polybranched polymers. In this study polyamidoamine dendrimers with hydroxyl surface groups (PAMAM-OH) of third, fourth and fifth generation (G3, G4 and G5) were examined for their ability to influence the activity of human erythrocyte plasma membrane adenosinetriphosphatases (ATPases). Plasma membrane ATPases are a group of enzymes related, among others, to the maintenance of ionic balance inside the cell. An inhibition of their activity may result in a disturbance of cell functioning. Two of examined dendrimers (G4 and G5) were found to inhibit the activity of Na(+)/K(+) ATPase and Ca(2+) ATPase by 20-30%. The observed effect was diminished when higher concentrations of dendrimers were used. The experiment with the use of pyrene as fluorescent probe sensitive to the changes in microenvironment's polarity revealed that it was an effect of dendrimers' self-aggregation. Additional studies showed that PAMAM-OH dendrimers were able to decrease the fluidity of human erythrocytes plasma membrane. Obtained results suggest that change in plasma membrane fluidity was not caused by the dendrimer-lipid interaction, but dendrimer-protein interaction. Different pattern of influence of dendrimers on ATPases activity and erythrocyte membrane fluidity suggests that observed change in ATPases activity is not a result of dendrimer-lipid interaction, but may be related to direct interaction between dendrimers and ATPases.

Surface modification of PAMAM dendrimer improves its biocompatibility.

Modification of dendrimer surface groups is one of the methods available to obtain compounds characterized by reduced toxicity. This article reports results of preliminary biocompatibility studies of a modified polyamidoamine dendrimer of the fourth generation. Reaction with dimethyl itaconate resulted in transformation of surface amine groups into pyrrolidone derivatives. Interaction of the modified dendrimer with human serum albumin (HSA) was analyzed. The influence of the dendrimer on mouse neuroblastoma cell line viability and its hemolytic properties were also investigated. The binding constant between analyzed dendrimer and HSA was found to be equal to 1.2 × 10(5) ± 0.2 × 10(5) M(-1). Small changes in HSA secondary structure were observed. The analyzed dendrimer revealed minor toxic activity, as diminishment in cell viability was observed only for dendrimer concentrations higher than 2 mg/mL. Moreover, under the applied experimental conditions, no hemolytic activity was observed. Those observations point to the potential of the analyzed compound for further studies toward its applicability in nanomedicine.

Tautomeric forms study of 1H-(2'-pyridyl)-3-methyl-5-hydroxypyrazole and 1H-(2'-pyridyl)-3-phenyl-5-hydroxypyrazole. Synthesis, structure, and cytotoxic activity of their complexes with palladium(II) ions.

In this article the synthesis of new 1H-(2'-pyridyl)-3-methyl-5-hydroxypyrazole and 1H-(2'-pyridyl)-3-phenyl-5-hydroxypyrazole complexes with palladium(II) ions is reported. The structures of obtained compounds have been characterized by X-ray crystallography and DFT (density functional theory) calculations. The cytotoxicity of complexes and ligands has been examined for two human leukemia cell lines (HL-60 and NALM-6) and one human melanoma cell line (WM-115). The palladium(II) complex with 1H-(2'-pyridyl)-3-phenyl-5-hydroxypyrazole has been shown to possess greater activity than carboplatin against the WM-115 melanoma cell line. Additionally, the ligands' tautomeric forms existence in different solvents (chloroform, methanol, DMSO) has been characterized by (1)H nuclear magnetic resonance (NMR) analysis and DFT calculations. The obtained results have been compared with those from other studies of similar compounds.

2-Meth-oxy-3-[(3,4,5-trimethoxy-anilino)methyl-idene]-3,4-dihydro-2H-1-benzopyran-4-one.

The title mol-ecule, C(20)H(21)NO(6), adopts a keto-amine tautomeric form. An intra-molecular N-H⋯O hydrogen bond, classified as a resonanse-assisted hydrogen bond, influences the mol-ecular conformation; the two benzene rings form a dihedral angle of 24.6 (1)°. In the crystal structure, weak inter-molecular C-H⋯O hydrogen bonds link mol-ecules into chains propagating along [001].

Synthesis, physico-chemical properties and biological analysis of newly obtained copper(II) complexes with pyrazole derivatives.

Three new copper(II) complexes containing two different pyrazole bound ligands (1, 2) have been synthesized and characterized by IR, LSI-MS (liquid secondary ion mass spectrometry) and elemental analysis. (1)H NMR spectra of the organic ligands have been recorded. We describe the influence of these complexes on particular cancer cell lines and DNA structure by MTT-assay [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide], APA (acid phosphatase activity)-assay or CD-spectroscopy and agarose gel electrophoresis methods, together with their physico-chemical properties such as lipophilicity and stability in aqueous solution. The cytotoxic effect on HUVEC (endothelial cells) for the most active complex 4 has been also investigated. Moreover, the ability of these complexes to induce apoptosis in cancer cells has been assessed by using fluorescence microscopy. Our results indicate that dichloridobis{1-[amino(thioxo)methyl]-5-hydroxy-3-phenyl-1H-pyrazole-κN2}copper(II) is the most potent complex among the tested complexes.

The influence of maltose modified poly(propylene imine) dendrimers on hen egg white lysozyme structure and thermal stability.

In this study the influence of dendrimers' surface modification upon the strength of interaction with proteins was examined. Unmodified, cationic poly(propylene imine) dendrimer of the fourth generation (PPI G4), two PPI G4 dendrimers, partially and fully coated with maltose residues, and anionic polyamidoamine dendrimer of the third and a half generation (PAMAM G3.5 dendrimer), were used in the study. Hen egg white lysozyme, which possesses a cationic net charge under physiological conditions, was chosen as a model protein. The influence of dendrimers on the thermal stability of lysozyme was studied using differential scanning calorimetry (DSC) and circular dichroism (CD) methods. Additionally, the effect of dendrimers on the availability of lysozyme tryptophan residues to fluorescence quenchers was examined. It was shown that modification of dendrimer surface with maltose reduced its influence on lysozyme properties. However, even full surface modification, resulting in a neutral surface charge, did not deprive dendrimer of the ability to interact with the protein. It was probably caused by the introduction of a large number of hydroxyl groups from maltose residues on the surface of the dendrimer. In the study a comparable strength of influence exerted on lysozyme by cationic PPI dendrimer and anionic PAMAM G3.5 dendrimer was observed. The possible explanation of this fact is the presence of both positively and negatively charged areas on the surface of lysozyme. Such areas allow dendrimers possessing opposite surface charges to interact with lysozyme.