Influence Of Dendrimers Research Articles

Synthesis and biophysical evaluation of carbosilane dendrimers as therapeutic siRNA carriers

Gene therapy presents an innovative approach to the treatment of previously incurable diseases. The advancement of research in the field of nanotechnology has the potential to overcome the current limitations and challenges of conventional therapy methods, and therefore to unlocking the full potential of dendrimers for use in the gene therapy of neurodegenerative disorders. The blood–brain barrier (BBB) poses a significant challenge when delivering therapeutic agents to the central nervous system. In this study, we investigated the biophysical properties of dendrimers and their complexes with siRNA directed against the apolipoprotein E (APOE) gene to identify an appropriate nanocarrier capable of safely delivering the cargo across the BBB. Our study yielded valuable insights into the complexation process, stability over time, the mechanisms of interaction, the influence of dendrimers on the oligonucleotide's spatial structure, and the potential cytotoxic effects on human cerebral microvascular endothelium cells. Based on our findings, we identified that the dendrimer G3Si PEG6000 was an optimal candidate for further research, potentially serving as a nanocarrier capable of safely delivering therapeutic agents across the BBB for the treatment of neurodegenerative disorders.

Design, Synthesis and Activity of New N1-Alkyl Tryptophan Functionalized Dendrimeric Peptides against Glioblastoma

Background: Due to resistance to conventional therapy, a blood–brain barrier that results in poor drug delivery, and a high potential for metastasis, glioblastoma (GBM) presents a great medical challenge. Since the repertoire of the possible therapies is very limited, novel therapeutic strategies require new drugs as well as new approaches. The multiple roles played by L-tryptophan (Trp) in tumorigenesis of GBM and the previously found antiproliferative properties of Trp-bearing dendrimers against this malignancy prompted us to design novel polyfunctional peptide-based dendrimers covalently attached to N1-alkyl tryptophan (Trp) residues. Their antiproliferative properties against GBM and normal human astrocytes (NHA) and their antioxidant potential were tested. Methods: Two groups of amphiphilic peptide dendrimers terminated with N1-butyl and N1-aminopentane tryptophan were designed. The influence of dendrimers on viability of NHA and human GBM cell lines, displaying different genetic backgrounds and tumorigenic potentials, was determined by the MTT test. The influence of compounds on the clonogenic potential of GBM cells was assessed by colony-formation assay. Dendrimers were tested for radical scavenging potency as well as redox capability (DPPH, ABTS, and FRAP models). Results: Several peptide dendrimers functionalized with N1-alkyl-tryptophan at 5 µM concentration exhibited high selectivity towards GBM cells retaining 85–95% viable NHA cells while killing cancer cells. In both the MTT and colony-formation assays, compounds 21 (functionalized with N1-butyl-Trp and (+)8 charged) and 25 (functionalized with N1-aminopentane-Trp and (+)12 charged) showed the most promise for their development into anticancer drugs. According to ABTS, DPPH, and FRAP antioxidant tests, dendrimers functionalized with N1-alkylated Trp expressed higher ROS-scavenging capacity (ABTS and DPPH) than those with unsubstituted Trp. Conclusions: Peptide dendrimers functionalized with N1-alkyl-tryptophan showed varying toxicity to NHA, while all were toxic to GBM cells. Based on their activity towards inhibition of GBM viability and relatively mild effect on NHA cells the most advantageous were derivatives 21 and 25 with the respective di-dodecyl and dodecyl residue located at the C-terminus. As expected, peptide dendrimers functionalized with N1-alkyl-tryptophan expressed higher scavenging potency against ROS than dendrimers with unsubstituted tryptophan.

Peptide Dendrimers with Non-Symmetric Bola Structure Exert Long Term Effect on Glioblastoma and Neuroblastoma Cell Lines.

Background: Glioblastoma (GBM) is the most common malignant tumor of the central nervous system (CNS). Neuroblastoma (NB) is one of the most common cancers of childhood derived from the neural crest cells. The survival rate for patients with GBM and high-risk NB is poor; therefore, novel therapeutic approaches are needed. Increasing evidence suggests a dual role of redox-active compounds in both tumorigenesis and cancer treatment. Therefore, in this study, polyfunctional peptide-based dendrimeric molecules of the bola structure carrying residues with antiproliferative potential on one side and the antioxidant residues on the other side were designed. Methods: We synthesized non-symmetric bola dendrimers and assessed their radical scavenging potency as well as redox capability. The influence of dendrimers on viability of rat primary cerebellar neurons (CGC) and normal human astrocytes (NHA) was determined by propidium iodide staining and cell counting. Cytotoxicity against human GBM cell lines, T98G and LN229, and NB cell line SH-SY5Y was assessed by cell counting and colony forming assay. Results: Testing of CGC and NHA viability allowed to establish a range of optimal dendrimers structure and concentration for further evaluation of their impact on two human GBM and one human NB cell lines. According to ABTS, DPPH, FRAP, and CUPRAC antioxidant tests, the most toxic for normal cells were dendrimers with high charge and an excess of antioxidant residues (Trp and PABA) on both sides of the bola structure. At 5 μM concentration, most of the tested dendrimers neither reduced rat CGC viability below 50–40%, nor harmed human neurons (NHA). The same dose of compounds 16 or 22, after 30 min treatment decreased the number of SH-SY5Y and LN229 cells, but did not affect the number of T98G cells 48 h post treatment. However, either compound significantly reduced the number of colonies formed by SH-SY5Y, LN229, and T98G cells measured 14 days after treatment. Conclusions: Peptide dendrimers with non-symmetric bola structure are excellent scaffolds for design of molecules with pro/antioxidant functionality. Design of molecules with an excess of positive charges and antioxidant residues rendered molecules with high neurotoxicity. Single, 30 min exposition of the GBM and NB cell lines to the selected bola dendrimers significantly suppressed their clonogenic potential

The influence of different charged poly (amido amine) dendrimer on the transport and deposition of bacteria in porous media

The influence of dendrimer on the bacterial transport and deposition behaviors in saturated porous media (quartz sand) was investigated in both NaCl (10 and 25 mM) and CaCl2 solutions (1.2 and 5 mM). 3.5G and 4G poly (amido amine) (PAMAM) dendrimer was employed as negatively and positively charged dendrimer, respectively. Three dendrimer concentrations (10 μg/L, 1 and 10 mg/L) were considered in present study. We found that regardless of the solution chemistry (ionic strength and ion types) and dendrimer concentrations, the presence of negatively charged PAMAM 3.5G in suspensions enhanced bacterial transport and inhibited their deposition in quartz sand; while the presence of positive charged PAMAM 4G yet induced the opposite effects (decreased bacterial transport and increased their deposition in quartz sand). The increased repulsive force between cell and quartz sand due to the adsorption of PAMAM 3.5G onto both cell and sand surfaces, the competition deposition sites as well as the steric repulsion via the suspended PAMAM 3.5G drove to the increased bacterial transport with PAMAM 3.5G copresent in suspensions in quartz sand. While the reduced repulsive force between cell and quartz sand induced by the chemical heterogeneity on both cell and sand surfaces (due to the adsorption of positive charged PAMAM 4G) increased bacterial retention in quartz sand with copresence of PAMAM 4G (10 μg/L and 1 mg/L) in suspensions. Steric repulsion due to the presence of great amount of suspended PAMAM 4G yet lead to the enhanced bacterial transport with furthering increasing PAMAM 4G to 10 mg/L relative to the lower PAMAM 4G concentration.

Dendrimer-based nanoparticles for potential personalized therapy in chronic lymphocytic leukemia: Targeting the BCR-signaling pathway

Chronic lymphocytic leukemia (CLL) is one of the most prevalent forms of leukemia in western society. Although classic chemoimmune therapy is still the gold standard of care for leukemic patients, effective therapy of CLL is yet to be achieved. The present study examines the influence of poly(propylene)imine (PPI) dendrimers with primary amino surface groups modified with maltotriose residues in approximately 90% (PPI-G4-DS-Mal-III) or 30% (PPI-G4-OS-Mal-III) of cases on CLL cells (MEC-1 cell line with del(17p)), and confirms that the main trigger in this interaction is the induction of the apoptotic mechanism. The efficacy of each dendrimer was compared using fludarabine (FA). Gene expression profiling (GEP) by microarray identified a group of genes in the BCR signaling pathway characterized by different levels of expression directly associated with the tested agent and type of interaction. Network analysis revealed the potential patterns involved in potential personalized therapy of CLL. The expression of most BCR genes decreased under the influence of dendrimers, which might translate into decreased maturation and proliferation of CLL lymphocytes. Moreover, PPI-G4-OS/DS-Mal-III dendrimers affected gene expression and CLL cells in a different way to FA. Thanks to unique properties, dendrimers may be specifically targeted, thus improving the effectiveness of CLL therapy.

Blockage of Wnt/B-Catenin Signaling By Nanoparticles Reduces Survival and Proliferation of CLL Cells in Vitro

The Wnt pathway is critical for the proliferation and cell fate determination of many cell types, including B cells of chronic lymphocytic leukemia (CLL). Wnt proteins act on target cells by binding to the Frizzled (Fz)/low-density lipoprotein (LRP) complex at the cell membrane. In the hematopoietic system, Wnt/β-catenin signaling pathway has been shown to be important in the control of the survival, proliferation and differentiation of hematopoietic cells.Nanotechnology, a new and promising field, may be of use in medicine and the pharmaceutical industry. Dendrimers are nanoparticles of dendritic architecture. We have already proved the influence of PPI-G4-OS-M3 dendrimers in cultures in vitro on CLL cells apoptosis. CLL lymphocytes are characterized by the failure in the apoptosis pathway, but it is also proved that they manifest increased proliferation.Herein, the objective was to evaluate how MEC-1 cells survival and proliferation in vitro is affected by blockage of Wnt pathway by PPI-G4-OS-M3 dendrimer comparing to FA.Material and methodsDendrimer, in which approximately 35% of peripheral amino groups, was coated with maltotriose have been defined as PPI-G4-OS-M3 and was used in concentration of 8 mg/ml (the IC50 value for this dendrimer). 'OS' abbreviation stands for the open shell structure of carbohydrate-modified dendrimers. The molar mass of this PPI dendrimer was 31000 g/mol.Fludarabine (FA, Genzyme) in concentration of 1.6 µ M, based on previous studies, was used.MEC-1 (DSMZ no. ACC 497) was used as a homogenous cell line with del(17p)(11q).In cultures the percentage of apoptotic cells was verified using AnnV and PI by means of flow cytometer. Cells predominated in the early stage of apoptosis.A microarray gene expression (Agilent SurePrint Technologies) was performed. Samples were hybridized to a whole human genome microarray 8x60K. Arrays were scanned on Agilent DNA Microarray Scanner. Data were deposited at Gene Expression Omnibus (GEO) (accession number GSE68094).Analysis of differential expression of genes was done with the limma method (Smyth, G. K., 2004) as implemented in R/Bioconductor software. We used the FDR multiple testing adjustment. We declared as differentially expressed the genes with FDR-adjusted p-value <0.1, which means that 10% of genes declared as DE are expected to be false positives.ResultsPPI-G4-OS-M3 dendrimer depicts the ability to inhibit the proliferation increases with the rise in dendrimer concentration (MethoCultTM Assay, Stemcell Technology).Microarray data analysis pointed 7 out of 100 members of Wnt genes whose expression was significantly important. Details concerning genes description and expression are collected in the table 1.Table 1Wnt genes expression in MEC-1 cells under influence of dendrimers and FA in 4-hour-cultures.PPI-G4-OS-M3FAProbe setGene symbolGene full namelogFCadj P valuelogFCadj P valueP102117WNT10AWingless-type MMTV integration site family, member 10A-0.590.04-0.560.03P81103SFRP2Secreted frizzled-related protein 20.960.04-0.590.07P65518DACT1Dishevelled-binding antagonist of beta-catenin 10.660.050.810.03P206359CDH1Cadherin 1 type 1-0.710.05-0.990.03P119916WNT6Wingless-type MMTV integration site family, member 6-1.930.1-0.230.8 (NS)P1505LRP5Low density lipoprotein receptor-related protein 50.390.1-0.280.1P117029LDLRLow density lipoprotein receptor0.210.1-0.490.03Conclusion: Our results show significant changes and differences in some of Wnt/β-catenin pathway genes expression in CLL influenced by glycodendrimer and FA treatment. The downregulation in WNT10A, WNT6, SFRP2 expression results in β-catenin less phosphorylation and is subjected to proteosomal degradation. LRP5 and LDLR genes expression is also weak thus a reaction cascade is blocked and transcription process is suppressed. The loss of Wnt signals by dendrimers and FA treatment induces a reduction in the proliferation and survival of treatment resistant cell line MEC-1.To summarize, the PPI-G4-OS-M3 dendrimer demonstrated inhibition of proliferation beside higher cytotoxicity towards CLL cells. Its potency is similar to FA widely used in CLL therapy. Thus, dendrimers are a potential tool for CLL treatment.The study was partially supported by Grant No. DEC-2011/01/B/NZ5/01371from the National Science Centre, Poland DisclosuresRobak:Novartis: Consultancy, Honoraria, Research Funding; GlaxoSmithKline: Research Funding.

Viologen-Phosphorus Dendrimers Inhibit α-Synuclein Fibrillation

Inhibition of α-synuclein (ASN) fibril formation is a potential therapeutic strategy in Parkinson's disease and other synucleinopathies. The aim of this study was to examine the role of viologen-phosphorus dendrimers in the α-synuclein fibrillation process and to assess the structural changes in α-synuclein under the influence of dendrimers. ASN interactions with phosphonate and pegylated surface-reactive viologen-phosphorus dendrimers were examined by measuring the zeta potential, which allowed determining the number of dendrimer molecules that bind to the ASN molecule. The fibrillation kinetics and the structural changes were examined using ThT fluorescence and CD spectroscopy. Depending on the concentration of the used dendrimer and the nature of the reactive groups located on the surface, ASN fibrillation kinetics can be significantly reduced, and even, in the specific case of phosphonate dendrimers, the fibrillation can be totally inhibited at low concentrations. The presented results indicate that viologen-phosphorus dendrimers are able to inhibit ASN fibril formation and may be used as fibrillar regulating agents in neurodegenerative disorders.

Interaction between viologen-phosphorus dendrimers and α-synuclein

In this study the interaction between viologen-phosphorus dendrimers and α-synuclein (ASN) was examined. Polycationic viologen-phosphorus dendrimers (two positive charges per viologen unit) are novel compounds with relatively unknown properties. The influence of these viologen dendrimers on ASN was tested using fluorimetric and circular dichroism methods. ASN contains four tyrosine residues; therefore, the influence of dendrimers on protein molecular conformation by measuring the changes in the ASN fluorescence in the presence of dendrimers was evaluated. The interaction of dendrimers with free l-tyrosine was also monitored. Results show that viologen-phosphorus dendrimers interact with ASN; they quenched the fluorescence of ASN as well as free tyrosine by dynamic and static ways. However, the quenching was not accompanied by modifications in the ASN secondary structure.

Influence of dendrimer’s structure on its activity against amyloid fibril formation

Inhibition of fibril assembly is a potential therapeutic strategy in neurodegenerative disorders such as prion and Alzheimer’s diseases. Highly branched, globular polymers—dendrimers—are novel promising inhibitors of fibril formation. In this study, the effect of polyamidoamine (PAMAM) dendrimers (generations 3rd, 4th, and 5th) on amyloid aggregation of the prion peptide PrP 185–208 and the Alzheimer’s peptide Aβ 1–28 was examined. Amyloid fibrils were produced in vitro and their formation was monitored using the dye thioflavin T (ThT). Fluorescence studies were complemented with electron microscopy. The results show that the higher the dendrimer generation, the larger the degree of inhibition of the amyloid aggregation process and the more effective are dendrimers in disrupting the already existing fibrils. A hypothesis on dendrimer–peptide interaction mechanism is presented based on the dendrimers’ molecular structure.