Biodistribution and toxicity assessment of methoxyphenyl phosphonium carbosilane dendrimers in 2D and 3D cell cultures of human cancer cells and zebrafish embryos.

The consideration of human and environmental exposure to dendrimers, including cytotoxicity, acute toxicity, and cell and tissue accumulation, is essential due to their significant potential for various biomedical applications. This study aimed to evaluate the biodistribution and toxicity of a novel methoxyphenyl phosphonium carbosilane dendrimer, a potential mitochondria-targeting vector for cancer therapeutics, in 2D and 3D cancer cell cultures and zebrafish embryos. We assessed its cytotoxicity (via MTT, ATP, and Spheroid growth inhibition assays) and cellular biodistribution. The dendrimer cytotoxicity was higher in cancer cells, likely due to its specific targeting to the mitochondrial compartment. In vivo studies using zebrafish demonstrated dendrimer distribution within the vascular and gastrointestinal systems, indicating a biodistribution profile that may be beneficial for systemic therapeutic delivery strategies. The methoxyphenyl phosphonium carbosilane dendrimer shows promise for applications in cancer cell delivery, but additional studies are required to confirm these findings using alternative labelling methods and more physiologically relevant models. Our results contribute to the growing body of evidence supporting the potential of carbosilane dendrimers as vectors for cancer therapeutics.

Neurotoxicity of poly(propylene imine) glycodendrimers.

Published results of studies on poly(propylene imine) (PPI) dendrimers indicate their potential use in the treatment of brain cancer or neurodegenerative diseases due to their ability to cross the blood-brain barrier. However, depending on dose, neurotoxicity may occur. Here, we discuss the impact of maltotriose modified PPI dendrimers on rat's nervous system. Wistar rats were treated intravenously for 14 consecutive days with densely (dense-shell; DS) and partly (open-shell; OS) modified PPI dendrimers at doses established as safe in the previous experiment following a single DS or OS administration. The examination included an estimation of the motility and the clinical symptoms of the respiratory, nervous, and cardiovascular systems. Both DS and OS glycodendrimers (GDs) induced adverse effects at the doses tested. Multiple administrations of PPI-OS had a detrimental influence on rats' survival. These findings suggest that the dendrimers adversely influence the nervous system and their toxic effects accumulate over time. In PPI-DS treated animals, the harmful effects were less severe but still present. However, with each treatment day, the clinical symptoms in both groups were less severe as if the animals developed tolerance to GDs. We hypothesize that the neurotoxicity of tested dendrimers is related to nanoparticles-induced autophagy.

Plasma Corona Protects Human Immune Cells from Structurally Nanoengineered Antimicrobial Peptide Polymers.

Safe and effective antimicrobials are needed to combat emerging antibiotic-resistant bacteria. Structurally nanoengineered antimicrobial peptide polymers (termed SNAPPs) interact with bacterial cell membranes to potently kill bacteria but may also interact at some level with human cell membranes. We studied the association of four different SNAPPs with six different white blood cells within fresh whole human blood by flow cytometry. In whole human blood, SNAPPs had detectable association with phagocytic cells and B cells, but not natural killer and T cells. However, without plasma proteins and therefore no protein corona on the SNAPPs, a greater marked association of SNAPPs with all white blood cell types was detected, resulting in cytotoxicity against most blood cell components. Thus, the formation of a protein corona around the SNAPPs reduced the association and prevented human blood cell cytotoxicity of the SNAPPs. Understanding the bio-nano interactions of these SNAPPs will be crucial to ensuring that the design of next-generation SNAPPs and other promising antimicrobial nanomaterials continues to display high efficacy toward antibiotic-resistant bacteria while maintaining a low toxicity to primary human cells.

Applications and Limitations of Dendrimers in Biomedicine.

Biomedicine represents one of the main study areas for dendrimers, which have proven to be valuable both in diagnostics and therapy, due to their capacity for improving solubility, absorption, bioavailability and targeted distribution. Molecular cytotoxicity constitutes a limiting characteristic, especially for cationic and higher-generation dendrimers. Antineoplastic research of dendrimers has been widely developed, and several types of poly(amidoamine) and poly(propylene imine) dendrimer complexes with doxorubicin, paclitaxel, imatinib, sunitinib, cisplatin, melphalan and methotrexate have shown an improvement in comparison with the drug molecule alone. The anti-inflammatory therapy focused on dendrimer complexes of ibuprofen, indomethacin, piroxicam, ketoprofen and diflunisal. In the context of the development of antibiotic-resistant bacterial strains, dendrimer complexes of fluoroquinolones, macrolides, beta-lactamines and aminoglycosides have shown promising effects. Regarding antiviral therapy, studies have been performed to develop dendrimer conjugates with tenofovir, maraviroc, zidovudine, oseltamivir and acyclovir, among others. Furthermore, cardiovascular therapy has strongly addressed dendrimers. Employed in imaging diagnostics, dendrimers reduce the dosage required to obtain images, thus improving the efficiency of radioisotopes. Dendrimers are macromolecular structures with multiple advantages that can suffer modifications depending on the chemical nature of the drug that has to be transported. The results obtained so far encourage the pursuit of new studies.

Fine-Tuning the Interaction and Therapeutic Effect of Cu(II) Carbosilane Metallodendrimers in Cancer Cells: An In Vitro Electron Paramagnetic Resonance Study.

Copper(II) carbosilane metallodendrimers are promising nanosized anticancer metallodrugs. The precise control on their design enables an accurate structure-to-activity study. We hypothesized that different structural features, such as the dendrimer generation and metal counterion, modulate the interaction with tumor cells, and subsequently, the effectivity and selectivity of the therapy. A computer-aided analysis of the electron paramagnetic resonance (EPR) spectra allowed us to obtain dynamical and structural details on the interactions over time between the dendrimers and the cells, the myeloid U937 tumor cells and peripheral blood mononuclear cells (PBMC). The intracellular fate of the metallodendrimers was studied through a complete in vitro evaluation, including cytotoxicity, cytostaticity, and sublethal effects regarding mitochondria function, lysosomal compartments, and autophagic organelle involvement. EPR results confirmed a higher membrane stabilization for chloride dendrimers and low generation complexes, which ultimately influence the metallodrug uptake and intracellular fate. The in vitro evaluation revealed that Cu(II) metallodendrimers are cytostatic and moderate cytotoxic agents for U937 tumor cells, inducing death processes through the mitochondria-lysosome axis as well as autophagic vacuole formation, while barely affecting healthy monocytes. The study provided valuable insight into the mechanism of action of these nanosized metallodrugs and relevant structural parameters affecting the activity.

Combination of G2-S16 dendrimer/dapivirine antiretroviral as a new HIV-1 microbicide.

Aim: To research the synergistic activity of G2-S16 dendrimer and dapivirine (DPV) antiretroviral as microbicide candidate to prevent HIV-1 infection. Materials & methods: We assess the toxicity of DPV on cell lines by MTT assay, the anti-HIV-1 activity of G2-S16 and DPV alone or combined at several fixed ratios. Finally, their ability to inhibit the bacterial growth in vitro was assayed. The analysis of combinatorial effects and the effective concentrations were performed with CalcuSyn software. Conclusion: Our results represent the first proof-of-concept study of G2-S16/DPV combination to develop a safe microbicide.

Lactoferrin Coupled Lower Generation PAMAM Dendrimers for Brain Targeted Delivery of Memantine in Aluminum-Chloride-Induced Alzheimer's Disease in Mice.

Lower generation PAMAM dendrimers have an immense potential for drug delivery with lower toxicity, but these dendrimers yet need certain basic ameliorations. In this study, the brain delivery potential of the synthesized PAMAM-Lf (lower generation PAMAM and lactoferrin conjugate) loaded with memantine (MEM) was explored and evaluated in vitro and in vivo in the disease-induced mouse model. The developed nanoscaffolds were characterized for size, zeta potential and in vitro release. Increase in the average size from 11.54 ± 0.91 to 131.72 ± 4.73 nm, respectively, was observed for drug-loaded PAMAM (i.e., PAMAM-MEM) and PAMAM-Lf (i.e., MEM-PAMAM-Lf).  Release profile of MEM from MEM-PAMAM-Lf was slow and sustained up to 48 h. In vivo biodistribution in the Sprague-Dawley rat model revealed that the brain uptake of MEM-PAMAM-Lf was significantly higher than that of MEM alone. The behavioral response study in the healthy rats did not result in any significant changes. The in vivo study in an AlCl3-induced Alzheimer's (AD) mice model showed a significant improvement in behavioral responses. Optical density, which reflects the acetylcholinesterase (AChE) activity, was highest in the AL group 0.16 ± 0.01 (higher than the CON group, 0.09 ± 0.02; p < 0.05). No significant suppression of AChE activity was recorded in all the other treated groups. Similarly, the DOPAmine and 3,4 dihydroxyphenylacetic acid (DOPAC) levels were unaffected by the developed formulations. The study reported improved brain bioavailability of MEM in AlCl3-induced Alzheimer's mice leading to improved memory, with the resultant mechanism behind in a descriptive manner. This study is among the preliminary studies reporting the memory improvement aspect of PAMAM-Lf conjugates for MEM in AlCl3-AD induced mice. The formulation developed was beneficial in AD-induced mice and had a significant impact on the memory aspects.

Cytotoxicity of Dendrimers.

Drug delivery systems are molecular platforms in which an active compound is packed into or loaded on a biocompatible nanoparticle. Such a solution improves the activity of the applied drug or decreases its side effects. Dendrimers are promising molecular platforms for drug delivery due to their unique properties. These macromolecules are known for their defined size, shape, and molecular weight, as well as their monodispersity, the presence of the void space, tailorable structure, internalization by cells, selectivity toward cells and intracellular components, protection of guest molecules, and controllable release of the cargo. Dendrimers were tested as carriers of various molecules and, simultaneously, their toxicity was examined using different cell lines. It was discovered that, in general, dendrimer cytotoxicity depended on the generation, the number of surface groups, and the nature of terminal moieties (anionic, neutral, or cationic). Higher cytotoxicity occurred for higher-generation dendrimers and for dendrimers with positive charges on the surface. In order to decrease the cytotoxicity of dendrimers, scientists started to introduce different chemical modifications on the periphery of the nanomolecule. Dendrimers grafted with polyethylene glycol (PEG), acetyl groups, carbohydrates, and other moieties did not affect cell viability, or did so only slightly, while still maintaining other advantageous properties. Dendrimers clearly have great potential for wide utilization as drug and gene carriers. Moreover, some dendrimers have biological properties per se, being anti-fungal, anti-bacterial, or toxic to cancer cells without affecting normal cells. Therefore, intrinsic cytotoxicity is a comprehensive problem and should be considered individually depending on the potential destination of the nanoparticle.

Partial Surface Modification of Low Generation Polyamidoamine Dendrimers: Gaining Insight into their Potential for Improved Carboplatin Delivery.

Carboplatin (CAR) is a second generation platinum-based compound emerging as one of the most widely used anticancer drugs to treat a variety of tumors. In an attempt to address its dose-limiting toxicity and fast renal clearance, several delivery systems (DDSs) have been developed for CAR. However, unsuitable size range and low loading capacity may limit their potential applications. In this study, PAMAM G3.0 dendrimer was prepared and partially surface modified with methoxypolyethylene glycol (mPEG) for the delivery of CAR. The CAR/PAMAM G3.0@mPEG was successfully obtained with a desirable size range and high entrapment efficiency, improving the limitations of previous CAR-loaded DDSs. Cytocompatibility of PAMAM G3.0@mPEG was also examined, indicating that the system could be safely used. Notably, an in vitro release test and cell viability assays against HeLa, A549, and MCF7 cell lines indicated that CAR/PAMAM G3.0@mPEG could provide a sustained release of CAR while fully retaining its bioactivity to suppress the proliferation of cancer cells. These obtained results provide insights into the potential of PAMAM G3.0@mPEG dendrimer as an efficient delivery system for the delivery of a drug that has strong side effects and fast renal clearance like CAR, which could be a promising approach for cancer treatment.

Ultrafast in situ forming poly(ethylene glycol)-poly(amido amine) hydrogels with tunable drug release properties via controllable degradation rates.

Fast in situ forming, chemically crosslinked hydrogels were prepared by the amidation reaction between N-succinimidyl ester end groups of multi-armed poly(ethylene glycol) (PEG) and amino surface groups of poly(amido amine) (PAMAM) dendrimer generation 2.0. To control the properties of the PEG/PAMAM hydrogels, PEGs were used with different arm numbers (4 or 8) as well as different linkers (amide or ester) between the PEG arms and their terminal N-succinimidyl ester groups. Oscillatory rheology measurements showed that the hydrogels form within seconds after mixing the PEG and PAMAM precursor solutions. The storage moduli increased with crosslink density and reached values up to 2.3 kPa for hydrogels based on 4-armed PEG. Gravimetrical degradation experiments demonstrated that hydrogels with ester linkages between PEG and PAMAM degrade within 2 days, whereas amide-linked hydrogels were stable for several months. The release of two different model drugs (fluorescein isothiocyanate-dextran with molecular weights of 4·103 and 2·106 g/mol, FITC-DEX4K and FITC-DEX2000K, respectively) from amide-linked hydrogels was characterized by an initial burst followed by diffusion-controlled release, of which the rate depended on the size of the drug. In contrast, the release of FITC-DEX2000K from ester-containing hydrogels was governed mainly by degradation of the hydrogels and could be modulated via the ratio between ester and amide linkages. In vitro cytotoxicity experiments indicated that the PEG/PAMAM hydrogels are non-toxic to mouse fibroblasts. These in situ forming PEG/PAMAM hydrogels can be tuned with a broad range of mechanical, degradation and release properties and therefore hold promise as a platform for the delivery of therapeutic agents.

In Vitro Anticancer Properties of Copper Metallodendrimers.

Newly synthesized carbosilane copper dendrimers (CCD) with chloride and nitrate surface groups seem to be good candidates to be used as gene and drug carriers in anti-cancer therapy, due to their properties such as size and surface charge. Copper attached to the nanoparticles is an important element of many biological processes and recently their anti-cancer properties have been widely examined. Zeta size and potential, transmission electron microscopy (TEM), circular dichroism (CD), analysis of haemolytic activity, and fluorescence anisotropy techniques were used to characterize copper dendrimers. Additionally, their cytotoxic properties toward normal (PBMC) and cancer (1301; HL-60) cells were examined. All tested dendrimers were more cytotoxic against cancer cells in comparison with normal cells.

Set of Highly Stable Amine- and Carboxylate-Terminated Dendronized Au Nanoparticles with Dense Coating and Nontoxic Mixed-Dendronized Form.

The synthesis of a novel poly(propyleneimine) (PPI) dendron in gram scale as well as its use in the formation of a highly stable, dendronized gold nanoparticle (AuNP)-based drug delivery platform is described herein. The AuNP-based platform is composed of three complementary parts: (i) a 15 nm AuNP core, (ii) a heterofunctional thioctic acid-terminated tetraethylene glycol spacer, and (iii) a third-generation PPI dendron with a unique protonation profile and diverse end-group functionalization that allows for further derivatization. The prepared dendronized AuNPs are able to withstand several rounds of lyophilization cycles with no sign of aggregation, are stable in phosphate-buffered saline and Hanks' buffer as well as in serum, and are resistant to degradation by glutathione exchange reactions. This nanocarrier platform displays a dense coating, with >1400 dendrons/AuNPs, which will enable very high payload. Furthermore, while amine-terminated AuNPs expectedly showed cytotoxicity against the MCF-7 breast cancer cell line from a NP concentration of 1 nM, the mixed monolayer AuNPs (coated with 40/60 amine/carboxylate dendrons) interestingly did not exhibit any sign of toxicity at concentrations as high as 15 nM, similar to the carboxylate-terminated AuNPs. The described dendronized AuNPs address the current practical need for a stable NP-based drug delivery platform which is scalable and easily conjugable, has long-term stability in solution, and can be conveniently formulated as a powder and redispersed in desired buffer or serum.

ROS-Response-Induced Zwitterionic Dendrimer for Gene Delivery.

As one of the most promising therapeutic methods, gene therapy has been playing a more and more important role in treating disease due to its ultra-high therapy efficiency. Even if nonviral gene vectors represented by polycation, liposomal, dendrimers, and zwitterionic materials have made great progress in gene complexation, low immunogenicity, and biocompatibility, intracellular gene release with low toxicity is effectively still a bottleneck restricting the clinical application of gene therapy. We designed and synthesized a reactive oxygen species (ROS)-responsive dendrimer poly(amido amine)- N-(4-boronobenzyl)- N, N-diethyl-2-(propionyloxy)ethan-1-aminium (PAMAM-(B-DEAEP)16) as a gene vector whose potential can vary from positive to negative under the elevated ROS (H2O2) in cancerous cells. Dynamic light scattering results showed that the zeta potential of PAMAM-(B-DEAEP)16 decreased from +12.3 to -5 mV under 80 mM H2O2 in PBS buffer. The 1H NMR results demonstrated that the intermediate status of PAMAM-(B-DEAEP)16 was zwitterionic in ∼6 h because it consisted of the positive quaternary ammonium and negative carboxylic acid simultaneously before the ester bond was completely hydrolyzed. Gel retardation assay showed that PAMAM-(B-DEAEP)16 can condense DNA at above N/P = 1; then, PAMAM-(B-DEAEP)16 transfers to zwitterionic, which begins to continuously release DNA with the decrease in the positive charges and increase in the negative charges, and finally to negatively charged poly(amido amine)-propionic acid (PAMAM-PAc16) in the 80 mM H2O2. Fluorescence-labeled Cy-5 DNA indicated that PAMAM-(B-DEAEP)16 can enter into the cell completely in ∼4 h. The results showed that this compound we designed exhibited higher gene transfection efficiency and lower cytotoxicity than commercial PEI. This is the first time that the positively charged dendrimer was transferred to zwitterionic dendrimer under the stimuli of H2O2 and was successfully applied to gene delivery. Unlike all of the previous reports, we did not seek a compromise between the high gene transfection and low toxicity but find a new avenue to make the gene carrier not only have higher gene transfection efficiency but also exhibit lower toxicity by introducing stimuli-sensitive groups into the positively charged dendrimer to make it capable of adjusting the charge property according to the microenvironment. This study not only provides a good method to design materials for gene delivery but also opens a new perspective to understand the process of gene delivery.

Dendrimer Heparan Sulfate Glycomimetics: Potent Heparanase Inhibitors for Anticancer Therapy.

Heparanase is a mammalian endoglycosidase that cleaves heparan sulfate (HS) polysaccharides and contributes to remodelling of the extracellular matrix and regulation of HS-binding protein bioavailabilities. Heparanase is upregulated in malignant cancers and inflammation, aiding cell migration and the release of signaling molecules. It is established as a highly druggable extracellular target for anticancer therapy, but current compounds have limitations, because of cost, production complexity, or off-target effects. Here, we report the synthesis of a novel, targeted library of single-entity glycomimetic clusters capped with simple sulfated saccharides. Several dendrimer HS glycomimetics display low nM IC50 potency for heparanase inhibition equivalent to comparator compounds in clinical development, and potently inhibit metastasis and growth of human myeloma tumor cells in a mouse xenograft model. Importantly, they lack anticoagulant activity and cytotoxicity, and also inhibit angiogenesis. They provide a new candidate class for anticancer and wider therapeutic applications, which could benefit from targeted heparanase inhibition.

Evaluation of Amino-Functional Polyester Dendrimers Based on Bis-MPA as Nonviral Vectors for siRNA Delivery.

Herein, we present the first evaluation of cationic dendrimers based on 2,2-bis(methylol)propionic acid (bis-MPA) as nonviral vectors for transfection of short interfering RNA (siRNA) in cell cultures. The study encompassed dendrimers of generation one to four (G1⁻G4), modified to bear 6⁻48 amino end-groups, where the G2⁻G4 proved to be capable of siRNA complexation and protection against RNase-mediated degradation. The dendrimers were nontoxic to astrocytes, glioma (C6), and glioblastoma (U87), while G3 and G4 exhibited concentration dependent toxicity towards primary neurons. The G2 showed no toxicity to primary neurons at any of the tested concentrations. Fluorescence microscopy experiments suggested that the dendrimers are highly efficient at endo-lysosomal escape since fluorescently labeled dendrimers were localized specifically in mitochondria, and diffuse cytosolic distribution of fluorescent siRNA complexed by dendrimers was observed. This is a desired feature for intracellular drug delivery, since the endocytic pathway otherwise transfers the drugs into lysosomes where they can be degraded without reaching their intended target. siRNA-transfection was successful in C6 and U87 cell lines using the G3 and G4 dendrimers followed by a decrease of approximately 20% of target protein p42-MAPK expression.

In vivo drug tracking with 19F MRI at therapeutic dose.

Tracking drugs with 19F MRI would be beneficial for developing theranostics and optimizing drug therapy. To this end, a fluorinated dendritic amphiphile with high 19F MRI sensitivity and biocompatibility has been developed for 19F MRI tracking of doxorubicin (DOX)-loaded liposomes in mice, which may provide an effective platform to in vivo trace various drugs with 19F MRI.

Toxicological assessment of nanomaterials: the role of in vitro Raman microspectroscopic analysis.

The acceleration of nanomaterials research has brought about increased demands for rapid analysis of their bioactivity, in a multi-parametric fashion, to minimize the gap between potential applications and knowledge of their toxicological properties. The potential of Raman microspectroscopy for the analysis of biological systems with the aid of multivariate analysis techniques has been demonstrated. In this study, an overview of recent efforts towards establishing a 'label-free high content nanotoxicological assessment technique' using Raman microspectroscopy is presented. The current state of the art for cellular toxicity assessment and the potential of Raman microspectroscopy are discussed, and the spectral markers of the cellular toxic responses upon exposure to nanoparticles, changes on the identified spectral markers upon exposure to different nanoparticles, cell death mechanisms, and the effects of nanoparticles on different cell lines are summarized. Moreover, 3D toxicity plots of spectral markers, as a function of time and dose, are introduced as new methodology for toxicological analysis based on the intrinsic properties of the biomolecular changes, such as cytoplasmic RNA aberrations, protein and lipid damage associated with the toxic response. The 3D evolution of the spectral markers are correlated with the results obtained by commonly used cytotoxicity assays, and significant similarities are observed between band intensity and percentage viability obtained by the Alamar Blue assay, as an example. Therefore, the developed 3D plots can be used to identify toxicological properties of a nanomaterial and can potentially be used to predict toxicity, which can provide rapid advances in nanomedicine. Graphical Abstract Spectral markers of cytotoxicity as a function of time and dose.

Designing Dendron-Polymer Conjugate Based Targeted Drug Delivery Platforms with a "Mix-and-Match" Modularity.

Polymeric micellar systems are emerging as a very important class of nanopharmaceuticals due to their ability to improve pharmacokinetics and biodistribution of chemotherapy drugs, as well as to reduce related systemic toxicities. While these nanosized delivery systems inherently benefit from passive targeting through the enhanced permeation and retention effect leading to increased accumulation in the tumor, additional active targeting can be achieved through surface modification of micelles with targeting groups specific for overexpressed receptors of tumor cells. In this project, nontoxic, biodegradable, and modularly tunable micellar delivery systems were generated using two types of dendron-polymer conjugates. Either an AB type dendron-polymer construct with 2K PEG or an ABA type dendron-polymer-dendron conjugate with 6K PEG based middle block was used as primary construct; along with an AB type dendron-polymer containing a cRGDfK targeting group to actively target cancer cells overexpressing αυß3/αυß5 integrins. A set of micelles encapsulating docetaxel, a widely employed chemotherapy drug, were prepared with varying feed ratios of primary construct and targeting group containing secondary construct. Critical micelle concentrations of all micellar systems were in the range of 10-6 M. DLS measurements indicated hydrodynamic size distributions varying between 170 to 200 nm. An increase in docetaxel release at acidic pH was observed for all micelles. Enhanced cellular internalization of Nile red doped micelles by MDA-MB-231 human breast cancer cells suggested that the most efficient uptake was observed with targeted micelles. In vitro cytotoxicity experiments on MDA-MB-231 breast cancer and A549 lung carcinoma cell lines showed improved toxicity for RGD containing micelles. For A549 cell line EC50 values of drug loaded micellar sets were in the range of 10-9 M whereas EC50 value of free docetaxel was around 10-10 M. For MDA-MB-231 cell line EC50 value of free docetaxel was 6 × 10-8 M similar to EC50 of nontargeted AB type docetaxel doped micellar constructs whereas the EC50 value of its targeted counterpart decreased to 5.5 × 10-9 M. Overall, in this comparative study, the targeting group containing micellar construct fabricated with a 2 kDa PEG based diblock dendron-polymer conjugate emerges as an attractive drug delivery vehicle due to the ease of synthesis, high stability of the micelles, and efficient targeting.

Controlling Cellular Uptake and Toxicity of Polyphenylene Dendrimers by Chemical Functionalization.

Polyphenylene dendrimers (PPDs) represent a unique class of macromolecules based on their monodisperse and shape-persistent nature. These characteristics have enabled the synthesis of a new genre of "patched" surface dendrimers, where their exterior can be functionalized with a variety of polar and nonpolar substituents to yield lipophilic binding sites in a site-specific way. Although such materials are capable of complexing biologically relevant molecules, show high cellular uptake in various cell lines, and low to no toxicity, there is minimal understanding of the driving forces to these characteristics. We investigated whether it is the specific chemical functionalities, relative quantities of each moiety, or the "patched" surface patterning on the dendrimers that more significantly influences their behavior in biological media.

A transgenic rat hepatocyte - Kupffer cell co-culture model for evaluation of direct and macrophage-related effect of poly(amidoamine) dendrimers.

Increasing number of papers demonstrate that Kupffer cells (KCs) play a role in the development of drug induced liver injury (DILI). Furthermore, elevated intracellular Ca2+ level of hepatocytes is considered as a common marker of DILI. Here we applied an in vitro model based on hepatocyte mono- and hepatocyte/KC co-cultures (H/KC) isolated from transgenic rats stably expressing the GCaMP2 fluorescent Ca2+ sensor protein to investigate the effects of polycationic (G5), polyanionic (G4.5) and polyethylene-glycol coated neutral (G5 Peg) dendrimers known to accumulate in the liver, primarily in KCs. Following dendrimer exposure, hepatocyte homeostasis was measured by MTT cytotoxicity assay and by Ca2+ imaging, while hepatocyte functions were studied by CYP2B1/2 inducibility, and bilirubin and taurocholate transport. G5 was significantly more cytotoxic than G4.5 for hepatocytes and induced Ca2+ oscillation and sustained Ca2+ signals at 1µM and10 µM, respectively both in hepatocytes and KCs. Dendrimer-induced Ca2+ signals in hepatocytes were attenuated by macrophages. Activation of KCs by lipopolysaccharide and G5 decreased the inducibility of CYP2B1/2, which was restored by depleting the KCs with gadolinium-chloride and pentoxyphylline, suggesting a role of macrophages in the hindrance of CYP2B1/2 induction by G5 and lipopolysaccharide. In the H/KC, but not in the hepatocyte mono-culture, G5 reduced the canalicular efflux of bilirubin and stimulated the uptake and canalicular efflux of taurocholate. In conclusion, H/KC provides a good model for the prediction of hepatotoxic potential of drugs, especially of nanomaterials known to be trapped by macrophages, activation of which presumably contributes to DILI.