Anna Janaszewska

In vivo toxicity of poly(propyleneimine) dendrimers

Dendrimers are highly branched macromolecules with the potential to be used for biomedical applications. Several dendrimers are toxic owing to their positively charged surfaces. However, this toxicity can be reduced by coating these peripheral cationic groups with carbohydrate residues. In this study, the toxicity of three types of 4th generation poly (propyleneimine) dendrimers were investigated in vivo; uncoated (PPI-g4) dendrimers, and dendrimers in which 25% or 100% of surface amino groups were coated with maltotriose (PPI-g4-25%m or PPI-g4-100%m), were administered to Wistar rats. Body weight, food and water consumption, and urine excretion were monitored daily. Blood was collected to investigate biochemical and hematological parameters, and the general condition and behavior of the animals were analyzed. Unmodified PPI dendrimers caused changes in the behavior of rats, a decrease in food and water consumption, and lower body weight gain. In the case of PPI-g4 and PPI-g4-25%m dendrimers, disturbances in urine and hematological and biochemical profiles returned to normal during the recovery period. PPI-g4-100%m was harmless to rats. The PPI dendrimers demonstrated dose- and sugar-modification-degree dependent toxicity. A higher dose of uncoated PPI dendrimers caused toxicity, but surface modification almost completely abolished this toxic effect.

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.

Cytotoxicity of PAMAM, PPI and maltose modified PPI dendrimers in Chinese hamster ovary (CHO) and human ovarian carcinoma (SKOV3) cells

Characterization of dendrimers as potential therapeutics or drug carriers is complete only when toxicity is assessed. There are numerous studies on the influence of surface modification of PAMAM and PPI dendrimers on their cytotoxic properties but without proposing a mechanism for their toxic effect. In this study cytotoxicity profiles of acid-terminated PAMAM G3.5 and amino-terminated PAMAM G4 in comparison to unmodified amino-terminated PPI-G4 and maltotriose modified PPI-G4 dendrimers were checked. Also the mechanism of cell death in Chinese hamster ovary (CHO) and human ovarian carcinoma (SKOV3) cell lines was investigated. The anionic PAMAM G3.5 dendrimers seem to be the most suitable dendrimers for therapeutic applications, because of their high biocompatibility and low cytotoxicity. Cationic PPI-G4 and PAMAM G4 were the most harmful for both CHO and SKOV3 cell lines, especially in high doses. Maltotriose modification has significantly reduced toxicity within the series of PPI-G4 dendrimers. The moderately doxorubicin and cisplatin resistant human ovarian carcinoma SKOV3 cell line was more vulnerable to modified PPI dendrimers than Chinese hamster ovary CHO cell line which does not show resistance to majority of anticancer agents. This unique property makes these dendrimers potentially interesting for an anticancer therapy.

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

UNLABELLED 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.

Anticancer siRNA cocktails as a novel tool to treat cancer cells. Part (B). Efficiency of pharmacological action

This paper examines a perspective to use newly engineered nanomaterials as effective and safe carriers for gene therapy of cancer. Three different groups of cationic dendrimers (PAMAM, phosphorus, and carbosilane) were complexed with anticancer siRNA and the biophysical properties of the dendriplexes created were analyzed. The potential of the dendrimers as nanocarriers for anticancer Bcl-xl, Bcl-2, Mcl-1 siRNAs and additionally a scrambled sequence siRNA has been explored. Dendrimer/siRNA complexes were characterised by various methods including fluorescence, zeta potential, dynamic light scattering, circular dichroism, gel electrophoresis and transmission electron microscopy. In this part of study, the transfection of complexes in HeLa and HL-60 cells was analyzed using both single apoptotic siRNAs and a mixture (cocktail) of them. Cocktails were more effective than single siRNAs, allowing one to decrease siRNAs concentration in treating cells. The dendrimers were compared as siRNA carriers, the most effective being the phosphorus-based ones. However, they were also the most cytotoxic on their own, so that in this regard the application of all dendrimers in anticancer therapy will be discussed.

The biodistribution of maltotriose modified poly(propylene imine) (PPI) dendrimers conjugated with fluorescein—proofs of crossing blood–brain–barrier

Oligosaccharide-modified poly(propylene imine) dendrimers are promising candidates as drug carriers and as anti-prion agents. Here, we report the biodistribution of maltotriose-modified 4th generation poly(propylene imine) (PPI) dendrimers and their ability to cross the blood–brain–barrier that is important if these glycodendrimers are considered as potential therapeutic agents in the central nervous system (CNS).

Antimicrobial activity of poly(propylene imine) dendrimers

Poly(propylene imine) dendrimers have been investigated for their biological applications but their antibacterial activity has not been extensively explored. Thus, the fourth generation of poly(propylene imine) dendrimers (PPI-G4) and PPI dendrimers with a surface modified by attaching maltose in 25% and 100% (PPI-25%mG4 and PPI-100%mG4, respectively) was evaluated for the antibacterial activity against Gram-positive bacteria: Staphylococcus aureus ATCC 6538, Staphylococcus epidermidis ATCC 12228, Gram-negative bacteria: Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 15442 and yeast Candida albicans ATCC 10231. Cytotoxicity of all tested dendrimers was checked on a Chinese hamster fibroblast cell line (B14), human liver hepatocellular carcinoma cell line (HepG2), mouse neuroblastoma cell line (N2a) and rat liver cell line (BRL-3A). The obtained results indicate that studied nano-sized macromolecules possess the greatest antimicrobial activity against S. aureus. PPI G4 dendrimers modified with 25% of maltose display antibacterial activity and a striking selectivity toward S. aureus, at the concentrations, which are at the same time harmless for the eukaryotic cell lines. Moreover, at the higher concentrations of unmodified dendrimers efficient growth inhibition of S. epidermidis and C. albicans has been observed.

Promising Low-Toxicity of Viologen-Phosphorus Dendrimers against Embryonic Mouse Hippocampal Cells

A new class of viologen-phosphorus dendrimers (VPDs) has been recently shown to possess the ability to inhibit neurodegenerative processes in vitro. Nevertheless, in the Central Nervous Systems domain, there is little information on their impact on cell functions, especially on neuronal cells. In this work, we examined the influence of two VPD (VPD1 and VPD3) of zero generation (G0) on murine hippocampal cell line (named mHippoE-18). Extended analyses of cell responses to these nanomolecules comprised cytotoxicity test, reactive oxygen species (ROS) generation studies, mitochondrial membrane potential (ΔΨm) assay, cell death detection, cell morphology assessment, cell cycle studies, as well as measurements of catalase (CAT) activity and glutathione (GSH) level. The results indicate that VPD1 is more toxic than VPD3. However, these two tested dendrimers did not cause a strong cellular response, and induced a low level of apoptosis. Interestingly, VPD1 and VPD3 treatment led to a small decline in ROS level compared to untreated cells, which correlated with slightly increased catalase activity. This result indicates that the VPDs can indirectly lower the level of ROS in cells. Summarising, low-cytotoxicity on mHippoE-18 cells together with their ability to quench ROS, make the VPDs very promising nanodevices for future applications in the biomedical field as nanocarriers and/or drugs per se.

PAMAM dendrimer with 4-carbomethoxypyrrolidone—In vitro assessment of neurotoxicity

Cytotoxicity of cationic amino-terminated PAMAM dendrimer and modified PAMAM-pyrrolidone dendrimer was compared. LDH assay and cell visualization technique were employed. Mouse embryonic hippocampal cells (mHippoE-18) were used. The experiments were performed in FBS-deprived medium. Pyrrolidone-modification significantly diminished toxicity of PAMAM dendrimer. The absence of FBS did not reveal significant impact on the toxic effect. Results from LDH assay and MTT test were in good consistency. Low cytotoxicity of PAMAM-pyrrolidone dendrimer increases reliability of the results showing a small impact of this dendrimer on cell viability.

The antibacterial effect of the co-administration of poly(propylene imine) dendrimers and ciprofloxacin

Fluoroquinolones, including ciprofloxacin, are often used to treat bacterial diseases. Due to the spread of drug resistance among microorganisms, alternative treatments are being sought. We report here on the antimicrobial activity of generation 4 (G4) PPI dendrimers in the presence of ciprofloxacin against the reference strains of Gram-positive bacterium Staphylococcus aureus ATCC 6538 and Gram-negative bacterium Escherichia coli ATCC 25922. Cytotoxicity of these compounds was investigated in the eukaryotic B14 Chinese hamster fibroblast cell line, HepG2 human liver hepatocellular carcinoma cell line, mouse neuroblastoma N2a cell line and BRL-3A rat liver cell line. For both strains, the administration of PPI dendrimers along with ciprofloxacin significantly improved its antibacterial effect compared to the cultures given the drug alone. The simultaneous application of dendrimers and ciprofloxacin shows the opportunity of using it at lower doses. Ciprofloxacin and PPI dendrimers are harmful to bacterial strains at the concentrations non-toxic to the eukaryotic cells.