Dual-Responsive Alginate Hydrogel Constructed by Sulfhdryl Dendrimer as an Intelligent System for Drug Delivery

Intelligent stimulus-triggered release and high drug-loading capacity are crucial requirements for drug delivery systems in cancer treatment. Based on the excessive intracellular GSH expression and pH conditions in tumor cells, a novel glutathione (GSH) and pH dual-responsive hydrogel was designed and synthesized by conjugates of glutamic acid-cysteine dendrimer with alginate (Glu-Cys-SA) through click reaction, and then cross-linked with polyethylene glycol (PEG) through hydrogen bonds to form a 3D-net structure. The hydrogel, self-assembled by the inner disulfide bonds of the dendrimer, is designed to respond to the GSH heterogeneity in tumors, with a remarkably high drug loading capacity. The Dox-loaded Glu-Cys-SA hydrogel showed controlled drug release behavior, significantly with a release rate of over 76% in response to GSH. The cytotoxicity investigation indicated that the prepared DOX-loaded hydrogel exhibited comparable anti-tumor activity against HepG-2 cells with positive control. These biocompatible hydrogels are expected to be well-designed GSH and pH dual-sensitive conjugates or polymers for efficient anticancer drug delivery.

Linear-Dendritic Polymer-Platinum Complexes Forming Well-Defined Nanocapsules for Acid-Responsive Drug Delivery

Polymeric nanocapsules hold considerable applications in cancer drug delivery, but the synthesis of well-defined nanocapsules with a tunable drug release property remains a significant challenge in fabrication. Herein, we demonstrate a supramolecular complexation strategy to assemble small molecular platinum (Pt) compounds into well-defined nanocapsules with high drug loading, acidity-sensitivity, and tunable Pt releasing profile. The design utilizes poly(ethylene glycol)-dendritic polylysine-G4/amides to complex with Pt compounds, forming stable nanocapsules with diameters approximately ∼20 nm and membrane thickness around several nanometers. The stability, drug content, and release profiles are tunable by tailoring the dendritic structure. The designated polymer-Pt nanocapsules, PEG-G4/MSA-Pt, showed sustained blood retention, preferential tumor accumulation, enhanced cellular uptake, lysosomal drug release, and nuclear delivery capability. PEG-G4/MSA-Pt showed enhanced antitumor efficacy compared to free cisplatin and other nanocapsules, which stopped the progression of both A549 cell xenografts and patient-derived xenografts (PDXs) of hepatocellular carcinoma on a mice tumor model. Thus, we believe this strategy is promising for developing Pt-based nanomedicine for cancer drug delivery.

Novel G-CSF conjugated anionic globular dendrimer: Preparation and biological activity assessment

The most crucial role of granulocyte colony-stimulating factor (G-CSF) in the body is to increase the strength of immune system. In recent years, research on the use of nanoparticles in pharmaceuticals has been considered, most of which have been for drug-loading purposes. In this study, a novel G-CSF conjugated dendrimer was synthesized and characterized using different techniques. In vitro cytotoxicity was assessed on A549 and L929 cells, while abnormal toxicity was studied in mice. In vitro and in vivo biological activities were assessed in NFS60 cells and rats, respectively. In addition, in vivo distribution, plasma half-life, and histopathological effect were studied in rat. The characterization tests confirmed the successful conjugation. There was no difference between G-CSF cytotoxicity before and after conjugation, and no difference with the control group. No mice showed abnormal toxicity. Although in vitro biological activity revealed both conjugated and free G-CSF promote proliferation cells, biological activity decreased significantly after conjugation about one-third of the unconjugated form. Nonetheless, in vivo biological activity of conjugated G-CSF increased by more than 2.5-fold relative to the unconjugated form, totally. Fortunately, no histopathologic adverse effect was observed in vital rat tissues. Also, in vivo distribution of the conjugate was similar to the native protein with an enhanced terminal half-life. Our data revealed that G-CSF conjugated dendrimer could be considered as a candidate to improve the in vivo biological activity of G-CSF. Moreover, multivalent capability of the dendrimer may be used for other new potentials of G-CSF in future perspectives.

Mechanism of Anticancer Action of Novel Imidazole Platinum(II) Complex Conjugated with G2 PAMAM-OH Dendrimer in Breast Cancer Cells

Transition metal coordination compounds play an important role in the treatment of neoplastic diseases. However, due to their low selectivity and bioavailability, as well as the frequently occurring phenomenon of drug resistance, new chemical compounds that could overcome these phenomena are still being sought. The solution seems to be the synthesis of new metal complexes conjugated with drug carriers, e.g., dendrimers. Numerous literature data have shown that dendrimers improve the bioavailability of the obtained metal complexes, solving the problem of their poor solubility and stability in an aqueous environment and also breaking down inborn and acquired drug resistance. Therefore, the aim of this study was to synthesize a novel imidazole platinum(II) complex conjugated with and without the second-generation PAMAM dendrimer (PtMet2–PAMAM and PtMet2, respectively) and to evaluate its antitumor activity. Cell viability studies indicated that PtMet2–PAMAM exhibited higher cytotoxic activity than PtMet2 in MCF-7 and MDA-MB-231 breast cancer cells at relatively low concentrations. Moreover, our results indicated that PtMet2–PAMAM exerted antiproliferative effects in a zebrafish embryo model. Treatment with PtMet2–PAMAM substantially increased apoptosis in a dose-dependent manner via caspase-9 (intrinsic pathway) and caspase-8 (extrinsic pathway) activation along with pro-apoptotic protein expression modulation. Additionally, we showed that apoptosis can be induced by activating POX, which induces ROS production. Furthermore, our results also clearly showed that the tested compounds trigger autophagy through p38 pathway activation and increase Beclin-1, LC3, AMPK, and mTOR inhibition. The high pro-apoptotic activity and the ability to activate autophagy by the imidazole platinum(II) complex conjugated with a dendrimer may be due to its demonstrated ability to reverse multidrug resistance (MDR) and thereby increase cellular accumulation in breast cancer cells.

Chemical characterization (LC-MS-ESI), cytotoxic activity and intracellular localization of PAMAM G4 in leukemia cells

Generation 4 of polyamidoamine dendrimer (G4-PAMAM) has several biological effects due to its tridimensional globular structure, repetitive branched amides, tertiary amines, and amino-terminal subunit groups liked to a common core. G4-PAMAM is cytotoxic due to its positive charges. However, its cytotoxicity could increase in cancer cells due to the excessive intracellular negative charges in these cells. Furthermore, this work reports G4-PAMAM chemical structural characterization using UHPLC-QTOF-MS/MS (LC-MS) by electrospray ionization to measure its population according to its positive charges. Additionally, the antiproliferative effects and intracellular localization were explored in the HMC-1 and K-562 cell lines by confocal microscopy. The LC-MS results show that G4-PAMAM generated multivalent mass spectrum values, and its protonated terminal amino groups produced numerous positive charges, which allowed us to determine its exact mass despite having a high molecular weight. Additionally, G4-PAMAM showed antiproliferative activity in the HMC-1 tumor cell line after 24 h (IC50 = 16.97 µM), 48 h (IC50 = 7.02 µM) and 72 h (IC50 = 5.98 µM) and in the K-562 cell line after 24 h (IC50 = 15.14 µM), 48 h (IC50 = 14.18 µM) and 72 h (IC50 = 9.91 µM). Finally, our results showed that the G4-PAMAM dendrimers were located in the cytoplasm and nucleus in both tumor cell lines studied.

Genetically Encoded and Biologically Produced All-DNA Nanomedicine Based on One-Pot Assembly of DNA Dendrimers for Targeted Gene Regulation

All-DNA nanomedicines have emerged as potential anti-tumor drugs. DNA nanotechnology provides all-DNA nanomedicines with unlimited possibilities in controlling the diversification of size, shape, and loads of the therapeutic motifs. As DNA is a biological polymer, it is possible to genetically encode and produce the all-DNA nanomedicines in living bacteria. Herein, DNA-dendrimer-based nanomedicines are designed to adapt to the biological production, which is constructed by the flexible 3-arm building blocks to enable a highly efficient one-pot DNA assembly. For the first time, a DNA nanomedicine, D4-3-As-DzSur, is successfully genetically encoded, biotechnologically produced, and directly self-assembled. The performance of the biologically produced D4-3-As-DzSur in targeted gene regulation has been confirmed by in vitro and in vivo studies. The biological production capability will fulfill the low-cost and large-scale production of all-DNA nanomedicines and promote clinical applications.

A Radiolabeled Self-assembled Nanoparticle Probe for Diagnosis of Lung-Metastatic Melanoma

Melanoma is a highly malignant skin cancer that frequently metastasizes to the lung, bone, and brain at an early phase. Therefore, noninvasive detection of metastasized melanoma could be beneficial to determine suitable therapeutic strategies. We previously reported a biocompatible ternary anionic complex composed of plasmid DNA (pDNA), polyethyleneimine (PEI), and γ-polyglutamic acid (γ-PGA) based on an electrostatic interaction, which was highly taken up by melanoma cells (B16-F10), even if it was negatively charged. Here, we developed a radiolabeled γ-PGA complex by using indium-111 (111In)-labeled polyamidoamine dendrimer (4th generation; G4) instead of pDNA and iodine-125 (125I)-labeled PEI instead of native PEI, and evaluated its effectiveness as a melanoma-targeted imaging probe. This ternary complex was synthesized at a theoretical charge ratio; carboxyl groups of 111In-diethylenetriaminepentaacetic acid (DTPA)-G4 : amino groups of 125I-PEI : carboxyl groups of γ-PGA was 1 : 8 : 16, and the size and zeta potential were approximately 29 nm and -33 mV, respectively. This complex was taken up by B16-F10 cells with time. Furthermore, a biodistribution study, using normal mice, demonstrated its accumulation in the liver, spleen, and lung, where macrophage cells are abundant. Almost the same level of radioactivity derived from both 111In and 125I was observed in these organs at an early phase after probe injection. Compared with the normal mice, significantly higher lung-to-blood ratios of radioactivity were observed in the B16-F10-lung metastatic cancer model. In conclusion, the radiolabeled γ-PGA complex would hold potentialities for nuclear medical imaging of lung metastatic melanoma.

MALDI-MS Imaging Analysis of Noninflammatory Type III Rotaxane Dendrimers

Rotaxane dendrimers with hyperbranched macromolecular interlocked structures and size modulation capacity demonstrate drug binding and release ability upon external stimuli. Mass spectrometry imaging (MSI) can offer the high-throughput screening of endogenous/exogenous compounds. Herein, we reported a novel method to display the in situ spatial distribution of label-free monodispersed type III rotaxane dendrimers (RDs) G1 (first generation, size ∼1.5 nm) and G2 (second generation, size ∼5 nm) that were explored as potential drug vehicles in spleen tissue by using matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-MSI). Experimental results indicated that the trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB) matrix exhibited the best performance for monodispersed type III RDs G1 and G2. The optimized method was successfully applied to map the in vivo spatial distribution of type III RDs G1 and G2 in the spleen from intraperitoneally injected mice. The MALDI-MSI images revealed that RDs G1 and G2 were relatively stable in the spleen within 24 h after administration. It was found that the identified type III RDs G1 and G2 penetrated through the tunica serosa and were predominantly localized in red pulp regions of spleens. They were also mapped in a marginal zone of spleens simultaneously. There was almost no toxicity of type III RDs G1 and G2 to mice spleens from the H&E results. Furthermore, the type III RDs did not induce the expression of inflammatory cytokines from peripheral blood mononuclear cells (PBMCs) or THP-1 monocytes. The MSI analysis not only demonstrated its ability to image select rotaxane dendrimers in a rapid and efficient manner but also provided tremendous assistance on the applications of the further treatment of cancerous tissue as safe drug carriers. Furthermore, the new strategy demonstrated in this study could be applied on other label-free mechanically interlocked molecules, molecular machines, and macromolecules, which opened a new path to evaluate the toxicological and pharmacokinetic characteristics of these novel materials at the suborgan level.

Sorafenib-Loaded Nanoparticles Based on Biodegradable Dendritic Polymers for Enhanced Therapy of Hepatocellular Carcinoma

PURPOSE

In spite of its enhanced efficacy and reduced side effects in clinical hepatocellular carcinoma (HCC) therapy, the therapeutic efficacy of antitumor angiogenesis inhibitor sorafenib (SFB) is still restricted due to short in vivo half-life and drug resistance. Here, a novel SFB-loaded dendritic polymeric nanoparticle (NP-TPGS-SFB) was developed for enhanced therapy of HCC.

METHODS

NP-TPGS-SFB was fabricated by encapsulating SFB with biodegradable dendritic polymers poly(amidoamine)-poly(γ-benzyl-L-Glutamate)-b-D-α-tocopheryl polyethylene glycol 1000 succinate (PAM-PBLG-b-TPGS).

RESULTS

NP-TPGS-SFB exhibited excellent stability and achieved acid-responsive release of SFB. It also exhibited much higher cellular uptake efficiency in HepG2 human liver cells than PEG-conjugated NP (NP-PEG-SFB). Furthermore, MTT assay confirmed that NP-TPGS-SFB induced higher cytotoxicity than NP-PEG-SFB and free SFB, respectively. Lastly, NP-TPGS-SFB significantly inhibited tumor growth in mice bearing HepG2 xenografts, with negligible side effects.

CONCLUSION

Our result suggests that NP-TPGS-SFB may be a novel approach for enhanced therapy of HCC with promising potential.

Intratumor Performance and Therapeutic Efficacy of PAMAM Dendrimers Carried by Clustered Nanoparticles

In recent years, small nanoparticles (NPs) with a diameter of less than 10 nm have aroused considerable interest in biomedical applications. However, their intratumor performance, as well as the antitumor efficacy, has not been well understood due to their size-dependent pharmacokinetics, which presents a formidable challenge for delivering a comparable amount of different small NPs to tumor tissues. Utilizing the multistage delivery strategy, we construct G3-, G5-, and G7-iCluster delivery systems by using poly(amidoamine) (PAMAM) dendrimers of different generations (G3-, G5-, and G7-PAMAM) as building blocks. The iCluster nanoparticles showed comparable pharmacokinetics and similar initial tumor deposition due to their similarity in size and surface chemistry. After accumulating at a tumor site, individual small dendrimers were released, and thus, their intratumor performance was comparatively investigated. Our results indicated that a subtle change in generation markedly affects their intratumor activities. G5-iCluster outperformed G3-iCluster and G7-iCluster in the treatment efficacy in an orthotopic pancreatic tumor model. The mechanistic study revealed that G3-PAMAM showed reduced particle retention in tumor tissue due to its small size and weak cell internalization, while G7-PAMAM was much less penetrative because of its relatively large size and strong particle-cell interaction. In contrast, G5-PAMAM exhibited balanced tumor penetration, cell internalization, and tumor retention. Our finding highlights the huge influence of the subtle difference of small NPs in their intratumor performance.

Transformable nanoparticles triggered by cancer-associated fibroblasts for improving drug permeability and efficacy in desmoplastic tumors

Cancer-associated fibroblasts (CAFs) are important barriers for nanoparticles (NPs) to deeply penetrate into tumors and severely limit the antitumor efficacy of nanomedicines. Herein, we proposed a CAF-triggered transformable drug delivery system based on a cleavable peptide responsive to fibroblast activation protein-α (FAP-α) specifically overexpressed on the surface of CAFs. The NPs were composed of cationic poly(amidoamine) (PAMAM) dendrimers cross-linked by our designed peptide, a chemotherapeutical drug was incorporated onto PAMAM using disulfide bonds and finally, hyaluronic acid (HA) was conjugated to improve the tumor targetability as well as biocompatibility through electrostatic interactions. These NPs had an initial size of ∼200 nm and negative zeta potential favorable for stable blood circulation; however, after docking with CAFs, they dissociated into smaller NPs and exposed the relative positive surface charge to facilitate penetration and enter the tumor cells together with CAFs. An interesting finding was that this system intracellularly released different levels of drugs in these two kinds of cells, which was beneficial for the disruption of the stromal barrier and increasing the local drug accumulation. Our investigation confirmed that the constructed system could alleviate the biological barriers and hold promising therapeutic efficiency for desmoplastic solid tumors.

Biodistribution and Biosafety of a Poly(Phosphorhydrazone) Dendrimer, an Anti-Inflammatory Drug-Candidate

Dendrimers are nanosized, arborescent polymers of which size and structure are perfectly controlled. This is one reason why they are widely used for biomedical purposes. Previously, we showed that a phosphorus-based dendrimer capped with anionic azabisphosphonate groups (so-called ABP dendrimer) has immuno-modulatory and anti-inflammatory properties towards human immune cells in vitro. Thereafter, we have shown that the ABP dendrimer has a promising therapeutic efficacy to treat models of chronic inflammatory disorders. On the way to clinical translation, the biodistribution and the safety of this drug-candidate has to be thoroughly assessed. In this article, we present preliminary non-clinical data regarding biodistribution, hematological safety, genotoxicity, maximal tolerated doses, and early cardiac safety of the ABP dendrimer. One of the genotoxicity assays reveals a potential mutagen effect of the item at a concentration above 200 µM, i.e., up to 100 times the active dose in vitro on human immune cells. However, as the results obtained for all the other assays show that the ABP dendrimer has promising biodistribution and safety profiles, there is no red flag raised to hamper the regulatory pre-clinical development of the ABP dendrimer.

Dendrimer mediated targeting of siRNA against polo-like kinase for the treatment of triple negative breast cancer

Irresponsiveness of triple negative breast cancer (TNBC) toward conventional therapies has drawn attention toward siRNA therapeutics. In gene delivery, dendrimers are gaining significant attention due to their characteristic features and polo-like kinase (PLK1) is reported as a potential target for TNBC. In this work, phosphorus and polyamidoamine dendrimer (generation 3 and 4 of each type) are explored to address delivery challenges of PLK1 siRNA (siPLK1). Dendriplexes were formed and complexation was found at 3:1 N/P ratio for all dendrimers by gel electrophoresis. Complexation was also supported by zeta potential, circular dichroism and intercalation assay. Dendriplexes were found to be stable in presence of ribonuclease and serum. Dendriplexes resulted in enhanced cell uptake of siPLK1 compared to siPLK1 solution in MDA-MB-231 and MCF-7 cells. Dendriplexes caused increased cell arrest in sub-G1 phase compared to solution. These observations suggested phosphorus and polyamidoamine dendrimers as potential carriers for siPLK1 delivery to treat TNBC.

AIE Supramolecular Assembly with FRET Effect for Visualizing Drug Delivery

Here, we constructed a nanostructured pH/redox dual-responsive supramolecular drug carrier with both aggregation-induced emission (AIE) and Forster resonance energy transfer (FRET) effects, which enabled selective drug release and monitoring drug delivery and release processes. Taking the hyperbranched polyamide amine (H-PAMAM) with intrinsic AIE effects as the core, poly(ethylene glycol) (PEG) was bridged on its periphery by dithiodipropionic acid. Then, through the host-guest interaction of PEG and α-cyclodextrin, the supramolecular nanoparticles with AIE effects were constructed to load the anticancer drug doxorubicin (DOX). The supramolecular assembly has sufficiently large DOX loading due to the abundant cavities formed by branched structures. The hyperbranched core H-PAMAM has strong fluorescence, and the dynamic track of drug carriers and the dynamic drug release process can be monitored by the AIE and FRET effects between H-PAMAM and DOX, respectively. Furthermore, the introduction of disulfide bonds and the pH sensitivity of H-PAMAM enable the achievement of rapid selective release of loaded DOX at the tumor while remaining stable under normal physiological conditions. In vitro cytotoxicity indicates that the drug-loaded supramolecular assembly has a good therapeutic effect on cancer. In addition, the H-PAMAM core is different from the traditional AIE functional group, which has no conjugated structure, such as a benzene ring, thereby providing better biocompatibility. This technology will have broad applications as a new drug delivery system.

Exploration of biomedical dendrimer space based on in-vivo physicochemical parameters: Key factor analysis (Part 2)

In nanomedicine, the widespread concern of nanoparticles in general, and dendrimers, in particular, is the analysis of key in-vivo physicochemical parameters to ensure the preclinical and clinical development of 'safe' bioactive nanomaterials. It is clear that for biomedical applications, biocompatible dendrimers, used as nanocarriers or active per se, should be devoid of toxicity and immunogenicity, and have adequate PK/PD behaviors (adequate exposure) in order to diffuse in different tissues. Functionalization of dendrimers has a dramatic effect on in-vivo physicochemical parameters. In this review, we highlighted key in-vivo physicochemical properties, based on data from biochemical, cellular and animal models, to provide biocompatible dendrimers. Up-to-date, only scarce studies have been described on this topic.

68Ga tagged dendrimers for molecular tumor imaging in animals

Dear Editor, Angiogenesis is an essential physiological process that involves formation of new blood vessels from the pre-existing ones and is one of the fundamental processes required for normal growth and development. The ability to non-invasively evaluate angiogenesis might provide new insights into cancer biology pathway. This approach might lead to opportunities to more appropriately select patients likely to respond to anti-angiogenic drugs. Polyamidoamine dendrimers are a member of a versatile, new class of dendritic polymers and are the most well characterized and widely used polymers. In the present study we have utilized them for imaging of a crucial process of angiogenesis in a cancer model of mice. Amongst, several PET radionuclides, there has been a renewed interest in ⁶⁸Ga for many reasons. Gallium-68 is well suited for use as a radiolabel for PET because of its comparatively shorter half-life of 68min. The emission of two divergent photons per decay allows the construction of three-dimensional images. Furthermore, the advances in generator technology for ⁶⁸Ga production and its favorable chemistry for radiocomplexation have paved the way for emerging applications of ⁶⁸Ga radiopharmaceuticals. A recent study reported the blood pharmacokinetics of different generations of PAMAM dendrimers (generations 3-6) derivatized with large chelating ligands to facilitate complexation of gadolinium ions for imaging applications. It was observed that the resulted PAMAM gadolinium complexes cleared from the blood circulation in a biphasic manner (fast component-10min; slow component-1h). The rapid clearance of the dendrimers from blood observed in our study was in accordance with previous observations. The biodistribution studies of ⁶⁸Ga-DOTA-G4 PAMAM showed the major uptake at an early time interval of 15min in the kidneys. This confirmed that kidneys are the major excretory organs for DOTA conjugated G4 PAMAM dendrimers. The radioactivity in kidneys, as compared with other organs was higher initially and declined with time. A study in the recent past also reported a high uptake of indium-111 (¹¹¹In)-DOTA analog-PAMAM dendrimer in rats' kidneys, immediately after administration of radioactivity. A considerable amount of radioactivity was also recovered from lungs which were higher in case of ⁶⁸Ga-DOTA-G4 PAMAM conjugate. Lung is an important component of the reticulo-endothelial system (RES) and thus is involved in the clearance of macromolecules. Additionally, due to its rich vasculature, lungs are likely targets for the location of intravenously injected dendrimer nanoparticles. The animal biodistribution data in tumor bearing mice demonstrated that the tumor uptake (at 1h) of ⁶⁸Ga-DOTA-G4 PAMAM dendrimer was 0.33%. It has been reported that using higher generation PAMAM dendrimers, magnetic resonance imaging (MRI) agents affect the biodistribution patterns in animal tumor models. Animal PET imaging data showed that maximum tumor to background ratio was obtained at 1h post injection of ⁶⁸Ga DOTA-G4 PAMAM dendrimer suggesting that the designed nanoprobes could efficiently target tumor tissues and be retained there due to their enhanced permeability and retention (EPR) effect. Dendrimers can achieve passive EPR mediated targeting to a tumor by controlling their size and physicochemical properties. Further, an earlier study reported that branched PAMAM dendrimer showed significantly higher accumulation in ovarian tumor bearing mice than the conventional linear N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer of comparable molecular weight. The use of radiolabeled dendrimers due to their topology, functionality and dimensions has been described as a promising approach for the molecular visualization of tumor angiogenesis. So, the successful radiolabeling of ⁶⁸Ga-DOTA-G4 PAMAM dendrimers is encouraging as it showed good localization of both the radiolabeled by ⁶⁸Ga and ¹¹¹In products in the tumor.

Redox-sensitive, cholesterol-bearing PEGylated poly(propylene imine)-based dendrimersomes for drug and gene delivery to cancer cells

Stimuli-responsive nanocarriers have attracted increased attention as materials that can facilitate drug and gene delivery in cancer therapy. The present study reports the development of redox-sensitive dendrimersomes comprising disulfide-linked cholesterol-bearing PEGylated dendrimers, which can be used as drug and gene delivery systems. Two disulfide-linked cholesterol-bearing PEGylated generation 3 diaminobutyric polypropylenimine dendrimers have been successfully synthesized via an in situ two-step reaction. They were able to spontaneously self-assemble into stable, cationic, nanosized vesicles (or dendrimersomes) with lower critical aggregation concentration values for high-cholesterol-bearing vesicles. These dendrimersomes were able to entrap both hydrophilic and hydrophobic dyes, and they also showed a redox-responsive sustained release of the entrapped guests in the presence of a glutathione concentration similar to that of a cytosolic reducing environment. The high-cholesterol-bearing dendrimersomes were found to have a higher melting enthalpy, increased adsorption tendency on mica surface, entrapping ability for a larger amount of hydrophobic drugs, and increased resistance to redox-responsive environments in comparison with their low-cholesterol counterpart. In addition, both dendrimersomes were able to condense more than 85% of the DNA at all the tested ratios for the low-cholesterol vesicles, and at dendrimer : DNA weight ratios of 1 : 1 and higher for the high-cholesterol vesicles. These vesicles resulted in an enhanced cellular uptake of DNA, by up to 15-fold when compared with naked DNA with low-cholesterol vesicles. As a result, they increased the gene transfection on the PC-3 prostate cancer cell line, with the highest transfection being obtained with low-cholesterol vesicle complexes at a dendrimer : DNA weight ratio of 5 : 1 and high-cholesterol vesicle complexes at a dendrimer : DNA weight ratio of 10 : 1. These transfection levels were about 5-fold higher than those observed when treated with naked DNA. These cholesterol-bearing PEGylated dendrimer-based vesicles are, therefore, promising as redox-sensitive drugs and gene delivery systems for potential applications in combination cancer therapies.

PAMAM dendrimers: blood-brain barrier transport and neuronal uptake after focal brain ischemia

Drug delivery to the central nervous system is restricted by the blood-brain barrier (BBB). However, with the onset of stroke, the BBB becomes leaky, providing a window of opportunity to passively target the brain. Here, cationic poly(amido amine) (PAMAM) dendrimers of different generations were functionalized with poly(ethylene glycol) (PEG) to reduce cytotoxicity and prolong blood circulation half-life, aiming for a safe in vivo drug delivery system in a stroke scenario. Rhodamine B isothiocyanate (RITC) was covalently tethered to the dendrimer backbone and used as a small surrogate drug as well as for tracking purposes. The biocompatibility of PAMAM was markedly increased by PEGylation as a function of dendrimer generation and degree of functionalization. The PEGylated RITC-modified dendrimers did not affect the integrity of an in vitro BBB model. Additionally, the functionalized dendrimers remained safe when in contact with the bEnd.3 cells and rat primary astrocytes composing the in vitro BBB model after hypoxia induced by oxygen-glucose deprivation. Modification with PEG also decreased the interaction and uptake by endothelial cells of PAMAM, indicating that the transport across a leaky BBB due to focal brain ischemia would be facilitated. Next, the functionalized dendrimers were tested in contact with red blood cells showing no haemolysis for the PEGylated PAMAM, in contrast to the unmodified dendrimer. Interestingly, the PEG-modified dendrimers reduced blood clotting, which may be an added beneficial function in the context of stroke. The optimized PAMAM formulation was intravenously administered in mice after inducing permanent focal brain ischemia. Twenty-four hours after administration, dendrimers could be detected in the brain, including in neurons of the ischemic cortex. Our results suggest that the proposed formulation has the potential for becoming a successful delivery vector for therapeutic application to the injured brain after stroke reaching the ischemic neurons.

Biologically-derived nanomaterials for targeted therapeutic delivery to the brain

Delivery of imaging agents and pharmaceutical payloads to the central nervous system (CNS) is essential for efficient diagnosis and treatment of brain diseases. However, therapeutic delivery is often restricted by the blood-brain barrier (BBB), which prevents transport of clinical compounds to their region of interest. This review discusses the methods that have been used to avoid or overcome this barrier, presenting the use of biologically-derived nanomaterial systems as an efficient strategy for the diagnosis and treatment of CNS diseases. Biological nanomaterials have many advantages over synthetic systems, including being biodegradable, biocompatible, easily surface functionalised for conjugation of targeting moieties, and are often able to self-assemble. These abilities are discussed in relation to various systems, including liposomes, dendrimers, and viral nanoparticles.

Effect of mannose targeting of hydroxyl PAMAM dendrimers on cellular and organ biodistribution in a neonatal brain injury model

Neurotherapeutics for the treatment of central nervous system (CNS) disorders must overcome challenges relating to the blood-brain barrier (BBB), brain tissue penetration, and the targeting of specific cells. Neuroinflammation mediated by activated microglia is a major hallmark of several neurological disorders, making these cells a desirable therapeutic target. Building on the promise of hydroxyl-terminated generation four polyamidoamine (PAMAM) dendrimers (D4-OH) for penetrating the injured BBB and targeting activated glia, we explored if conjugation of targeting ligands would enhance and modify brain and organ uptake. Since mannose receptors [cluster of differentiation (CD) 206] are typically over-expressed on injured microglia, we conjugated mannose to the surface of multifunctional D4-OH using highly efficient, atom-economical, and orthogonal Cu(I)-catalyzed alkyne-azide cycloaddition (CuAAC) click chemistry and evaluated the effect of mannose conjugation on the specific cell uptake of targeted and non-targeted dendrimers both in vitro and in vivo. In vitro results indicate that the conjugation of mannose as a targeting ligand significantly changes the mechanism of dendrimer internalization, giving mannosylated dendrimer a preference for mannose receptor-mediated endocytosis as opposed to non-specific fluid phase endocytosis. We further investigated the brain uptake and biodistribution of targeted and non-targeted fluorescently labeled dendrimers in a maternal intrauterine inflammation-induced cerebral palsy (CP) rabbit model using quantification methods based on fluorescence spectroscopy and confocal microscopy. We found that the conjugation of mannose modified the distribution of D4-OH throughout the body in this neonatal rabbit CP model without lowering the amount of dendrimer delivered to injured glia in the brain, even though significantly higher glial uptake was not observed in this model. Mannose conjugation to the dendrimer modifies the dendrimer's interaction with cells, but does not minimize its inherent inflammation-targeting abilities.

AS1411 Aptamer-Anionic Linear Globular Dendrimer G2-Iohexol Selective Nano-Theranostics

Molecular theranostics is of the utmost interest for diagnosis as well as treatment of different malignancies. In the present study, anionic linear globular dendrimer G2 is employed as a suitable carrier for delivery and AS1411 aptamer is exploited as the targeting agent to carry Iohexol specifically to the human breast cancer cells (MCF-7). Dendrimer G2 was prepared and conjugation of dendrimer and aptamer was carried out thereafter. Based on the data yielded by AFM, morphology of smooth and spherical non-targeted dendrimer changed to the rough aspherical shape when it conjugated. Then, conjugation was confirmed using DLS, ELS and SLS methods. Toxicity on nucleolin positive MCF-7 cells and nucleolin negative HEK-293 cells was assessed by XTT and apoptosis/necrosis assays. In vitro uptake was determined using DAPI-FITC staining and ICP-MS methods. In vivo studies including in vivo CT imaging, pathology and blood tests were done to confirm the imaging ability, bio-safety and targeted nature of the Nano-Theranostics in vivo. In a nutshell, the prepared construction showed promising effects upon decreasing the toxicity of Iohexol on normal cells and accumulation of it in the cancer tumors as well as reducing the number of cancer cells.

RGD Conjugated Dendritic Polylysine for Cellular Delivery of Antisense Oligonucleotide

Dendritic polylysines (DPL) are highly branched nano-sized spherical polymer with positively charged primary amino groups on surface. This structural feature is useful for a delivery of antisense oligonucleotide or siRNA. In this study, we modified the surface of DPL with cyclic RGD (and iRGD) peptide by conjugation reaction generating RGD (and iRGD) peptide conjugated dendritic poly-lysines, RGD-DPL or iRGD-DPL. The prepared conjugates were evaluated for integrin receptor-mediated cellular delivery of antisense oligonucleotide. The conjugation of RGD or iRGD peptide on DPL was monitored by measuring the retention time in capillary zone electrophoresis and the absorbance at UV-Vis spectroscopy. Cellular delivery by DPL-RGD (or -iRGD)/antisense oligonucleotide complex was examined by antisense splicing correction assay on integrin alpha v/beta 3 positive A375B3-Luc cells, which were stably transfected with plasmid pLuc/705. DPL-RGD (or -iRGD)/antisense oligonucleotide complexes exhibited integrin receptor mediated uptake on A375B3 cells without inducing cellular toxicity. In addition, the delivery of antisense oligonucleotide was integrin receptor-dependent with moderate efficiency.

Selective Localization of a Novel Dendrimer Nanoparticle in Myocardial Ischemia-Reperfusion Injury

BACKGROUND

Dendrimer nanoparticle therapies represent promising new approaches to drug delivery, particularly in diseases associated with inflammatory injury. However, their application has not been fully explored in models of acute myocardial ischemia (MI) and reperfusion injury.

METHODS

White male New Zealand rabbits underwent left thoracotomy with 30-minute temporary left anterior descending artery occlusion and MI confirmed by electrocardiography and histology (MI rabbits, n = 9), or left thoracotomy and pericardial opening for 30 minutes but no left anterior descending artery occlusion (control [C] rabbits, n = 9) rabbits. Following the 30-minute period, a dendrimer (generation 6 dendrimer conjugated to cyanine-5 fluorescent dye [G6-Cy5], 6.7 nm diameter) was administered intravenously and the chest closed in layers. Animals were sacrificed at 3 hours (3 MI, 3 C), 24 hours (3 MI, 3 C), or 48 hours (3 MI, 3 C) postsurgery.

RESULTS

As compared to controls, MI rabbits had twofold G6-Cy5 uptake in the myocardial anterior wall as compared to the same region in nonischemic control rabbits at 24 hours postsurgery (6.01 ± 0.57 μg/g versus 2.85 ± 0.85 μg/g; p = 0.04). This trend was also present at 48 hours (6.38 ± 1.53 μg/g versus 3.95 ± 0.60 μg/g, p = 0.21) and was qualitatively evident on confocal microscopy. G6-Cy5 half-life in serum was approximately 12 hours, with 22% of the injected G6-Cy5 dose remaining at 48 hours.

CONCLUSIONS

This study demonstrates for the first time that dendrimer nanodevices selectively localize in ischemic as compared to healthy myocardium. This indicates that dendrimer nanodevices are promising agents to deliver drugs specifically to the ischemic myocardium to attenuate the injury. Subsequent studies will assess the efficacy of a dendrimer-drug conjugate in ameliorating reperfusion injury following MI.

Cellular uptake of glucoheptoamidated poly(amidoamine) PAMAM G3 dendrimer with amide-conjugated biotin, a potential carrier of anticancer drugs

In search for soluble derivatives of PAMAM dendrimers as potential carriers for hydrophobic drugs, the conjugates of PAMAM G3 with biotin, further converted into glycodendrimer with d-glucoheptono-1,4-lactone, were prepared. Polyamidoamine dendrimer (PAMAM) of third generation, G3 was functionalized with four biotin equivalents covalently attached to terminal amine nitrogens via amide bond G3^4B. The remaining 28 amine groups were blocked by glucoheptoamide substituents (gh) to give G3^4B28gh or with one fluorescein equivalent (attached by reaction of G3^4B with fluorescein isothiocyanate, FITC) via thiourea bond as FITC followed by exhaustive glucoheptoamidation to get G3^4B27gh1F. As a control the G3 substituted totally with 32 glucoheptoamide residues, G3^gh and its fluorescein labeled analogue G3^31gh1F were synthesized. The glucoheptoamidation of PAMAM G0 dendrimer with glucoheptono-1,4-lactone was performed in order to fully characterize the ¹H NMR spectra of glucoheptoamidated PAMAM dendrimers and to control the derivatization of G3 with glucoheptono-1,4-lactone. Another two derivatives of G3, namely G3^4B28gh1F' and G3^32ghF', with ester bonded fluorescein were also obtained. Biological properties of obtained dendrimer conjugates were estimated in vitro with human cell lines: normal fibroblast (BJ) and two cancer glioblastoma (U-118 MG) and squamous carcinoma (SCC-15), including cytotoxicity by reduction of XTT and neutral red (NR) assays. Cellular uptake of dendrimer conjugates was evaluated with confocal microscopy. Obtained results confirmed, that biotinylated bioconjugates have always lower cytotoxicity and 3-4 times higher cellular uptake than non-biotinylated dendrimer conjugates in all cell lines. Comparison of various cell lines revealed different dose-dependent cell responses and the lower cytotoxicity of examined dendrimer conjugates for normal fibroblasts and squamous carcinoma, as compared with much higher cytotoxic effects seen in glioblastoma cell line. Synthetized multi-functional conjugate (G3^4B27gh1F) is a promising candidate as biocompatible vehicle for hydrophobic molecules used in anticancer therapy.

Development of Dendrimer Encapsulated Radio-Ytterbium and Biodistributionin Tumor Bearing Mice

The aim of this study is preparation of dendrimer encapsulated ytterbium-175 radio-nanoparticles and investigation of the compound chemical characteristic before and after the neutron irradiation and also study the in vivo biodistribution for targeted radiopharmaceutical dose delivery to solid tumors. For preparation of dendrimer-metal nanocomposite, a dendrimer compound containing an average of 55 Yb⁺³ ions per dendrimer was prepared. The synthesized encapsulated ytterbium irradiated by neutron for 2 h at 3×10¹¹ n.cm [Formula: see text] neutron flux. The resulting mixture was injected into 2 separate groups of tumor bearing mice. One group were injected intravenously and the other group were injected directly in tumor and were excised, weighed and counted at certain times to study the biodistribution and to compare the tumor treatment and the leakage of the radiopharmaceutical to non-target organs. The formation of dendrimer-Yb³⁺complex was confirmed by UV-vis spectrometer. High-resolution transmission electron microscopy (HRTEM) and Dynamic Light Scattering (DLS) results showed a particle size of less than 10 nm. The specific activity and radio-ytterbium purity of the irradiated nano-composite were as follows: 7 MBq/mg and >95%. The measured radiochemical purity by Instant Thin Layer Chromatography (ITLC) was more than 99%. In intravenous injection the complex showed rapid up take in liver, spleen, and lung, while accumulation in other organs was insignificant. In tumor direct injection the average size of the tumor mass in mice was reduced by 30%.

In Vivo Biodistribution of Dendrimers and Dendrimer Nanocomposites — Implications for Cancer Imaging and Therapy

Our results indicate that the surface chemistry, composition, and 3-D structure of nanoparticles are critical in determining their in vivo biodistribution, and therefore the efficacy of nanodevice imaging and therapies. We demonstrate that gold/dendrimer nanocomposites in vivo, present biodistribution characteristics different from PAMAM dendrimers in a B16 mouse tumor model system.

We review important chemical and biologic uses of these nanodevices and discuss the potential of nanocomposite devices to greatly improve cancer imaging and therapy, in particular radiation therapy. We also discuss major issues confronting the use of nanoparticles in the near future, with consideration of toxicity analysis and whether biodegradable devices are needed or even desirable.

Dendrimers Target the Ischemic Lesion in Rodent and Primate Models of Nonarteritic Anterior Ischemic Optic Neuropathy

Introduction

Polyamidoamine dendrimer nanoparticles (~ 4 nanometers) are inert polymers that can be linked to biologically active compounds. These dendrimers selectively target and accumulate in inflammatory cells upon systemic administration. Dendrimer-linked compounds enable sustained release of therapeutic compounds directly at the site of damage. The purpose of this study was to determine if dendrimers can be used to target the optic nerve (ON) ischemic lesion in our rodent and nonhuman primate models of nonarteritic anterior ischemic optic neuropathy (NAION), a disease affecting >10,000 individuals in the US annually, and for which there currently is no effective treatment.

Methods

NAION was induced in male Long-Evans rats (rNAION) and in one adult male rhesus monkey (pNAION) using previously described procedures. Dendrimers were covalently linked to near-infrared cyanine-5 fluorescent dye (D-Cy5) and injected both intravitreally and systemically (in the rats) or just systemically (in the monkey) to evaluate D-Cy5 tissue accumulation in the eye and optic nerve following induction of NAION.

Results

Following NAION induction, Cy-5 dendrimers selectively accumulated in astrocytes and circulating macrophages. Systemic dendrimer administration provided the best penetration of the ON lesion site when injected shortly after induction. Systemic administration 1 day post-induction in the pNAION model gave localization similar to that seen in the rats.

Conclusions

Dendrimers selectively target the ischemic ON lesion after induction of both rNAION and pNAION. Systemic nanoparticle-linked therapeutics thus may provide a powerful, targeted and safe approach to NAION treatment by providing sustained and focused treatment of the cells directly affected by ischemia.

Low generation polyamine dendrimers bearing flexible tetraethylene glycol as nanocarriers for plasmids and siRNA

Low G1 generation polyamine dendrimers built around programmable, flexible, and short tetraethyleneglycol branches were readily prepared in a divergent manner using a combination of orthogonal AB3 or AB5 units and highly efficient chemical transformations based on Cu(i) catalyzed alkyne-azide cycloaddition (CUAAC) and thiol-ene click reactions. The constructs showed that the G1 polyamines with only twelve and eighteen amine surface groups can successfully deliver siRNA in human cells, with transfection efficiency comparable to that of Lipofectamine 2000®. Measurements of cell viability following transfection of plasmid DNA and siRNA showed that the dendritic polyamines are less cytotoxic than Lipofectamine 2000® and are thus preferable for biological applications.

Dendrimer technologies for brain tumor

Despite low prevalence, brain tumors are one of the most lethal forms of cancer. Unfortunately the blood-brain barrier (BBB), a highly regulated, well coordinated and efficient barrier, checks the permeation of most of the drugs across it. Hence, crossing this barrier is one of the most significant challenges in the development of efficient central nervous system therapeutics. Surface-engineered dendrimers improve biocompatibility, drug-release kinetics and aptitude to target the BBB and/or tumors and facilitate transportation of anticancer bioactives across the BBB. This review sheds light on different aspects of brain tumors and dendrimers based on different approaches for treatment including recent research, opportunities and challenges encountered in development of novel and efficient dendrimer-based therapeutics for the treatment of brain tumors.

Synthesis and Characterization of a Poly(amido amine) Modified Magnetic Nanocarrier for Controlled Delivery of Doxorubicin

We prepared a magnetic poly(amido amine) (G2.5)-hydrazine hydrate nanocarrier, denoted by MNPs@PAMAM-H. PAMAM dendrimer was conjugated onto the surface of magnetic nanoparticles (MNPs) to increase the biocompatibility of the nanocarrier and provided a large number of reactive sites for coupling of drug molecules. DOX was covalently attached to the nanocarrier via a pH-sensitive linker, hydrazone bond, which hydrolyzes in the acidic lysosomal environment to allow pH-sensitive release of DOX. DOX was successfully loaded into the nanocarrier with a high drug loading (27.53%) and entrapment efficiency (86.44%). Nearly 88% DOX was released within 60 h at pH 5.0, compared with only 30% at pH 7.4. The in vitro MTT assay in HeLa cells demonstrated that MNPs@PAMAM-DOX exhibited high anti-tumor activity, while the MNPs@PAMAM-H were practically non-toxic. These results revealed that MNPs@ PAMAM-H were biocompatible. The Synthesized nanocarrier had the potential to be used as MR probe and guide DOX to enter target sites in cancer therapy by an outer magnet.

[Accumulation of doxorubicin conjugates with dendritic polymer and vector protein in normal and tumor cells in vitro]

Accumulation of doxorubicin (Dox), its conjugates with the second generation dendritic polymer (G2-Dox) and vector pro- tein (recombinant third domain of alpha-fetoprotein - 3D-G2- Dox) in normal and tumor cells was studied in vitro within the framework of the development of selective transport system of anticancer drugs to the target cells. The objects of the study were cells of peripheral blood mononuclear fraction of healthy donors and cells of breast adenocarcinoma lines MCF-7 and MCF-7/MDR1, differing in chemosensitivity. G2-Dox and 3D-G2-Dox accumulated in tumor cells of the both lines better than free Dox (p<0,05). However removal of these drugs out of cells MCF-7 and MCF-7/MDR1 was significantly different: in the latter case all free Dox was excluded from the cells for 24 hours while Dox, accumulated in composition with dendrimers, still remained in the cells. It was important that 3D-G2-Dox (unlike the G2-Dox) accumulated in normal cells worse than free Dox (p<0.01). Thus, the results indicate that the use of 3D-G2-Dox is the most promising because it accumulates in tumor cells better and in normal cells worse than free Dox. Furthermore it can be assumed that the use of 3D-G2-Dox would be especially useful in cases of multi-drug resistance associated with the high expression of P-glycoprotein.

Systemic dendrimer-drug treatment of ischemia-induced neonatal white matter injury

Extreme prematurity is a major risk factor for perinatal and neonatal brain injury, and can lead to white matter injury that is a precursor for a number of neurological diseases, including cerebral palsy (CP) and autism. Neuroinflammation, mediated by activated microglia and astrocytes, is implicated in the pathogenesis of neonatal brain injury. Therefore, targeted drug delivery to attenuate neuroinflammation may greatly improve therapeutic outcomes in models of perinatal white matter injury. In this work, we use a mouse model of ischemia-induced neonatal white matter injury to study the biodistribution of generation 4, hydroxyl-functionalized polyamidoamine dendrimers. Following systemic administration of the Cy5-labeled dendrimer (D-Cy5), we demonstrate dendrimer uptake in cells involved in ischemic injury, and in ongoing inflammation, leading to secondary injury. The sub-acute response to injury is driven by astrocytes. Within five days of injury, microglial proliferation and migration occurs, along with limited differentiation of oligodendrocytes and oligodendrocyte death. From one day to five days after injury, a shift in dendrimer co-localization occurred. Initially, dendrimer predominantly co-localized with astrocytes, with a subsequent shift towards microglia. Co-localization with oligodendrocytes reduced over the same time period, demonstrating a region-specific uptake based on the progression of the injury. We further show that systemic administration of a single dose of dendrimer-N-acetyl cysteine conjugate (D-NAC) at either sub-acute or delayed time points after injury results in sustained attenuation of the 'detrimental' pro-inflammatory response up to 9days after injury, while not impacting the 'favorable' anti-inflammatory response. The D-NAC therapy also led to improvement in myelination, suggesting reduced white matter injury. Demonstration of treatment efficacy at later time points in the postnatal period provides a greater understanding of how microglial activation and chronic inflammation can be targeted to treat neonatal brain injury. Importantly, it may also provide a longer therapeutic window.

Novel stable dendrimersome formulation for safe bioimaging applications

Dendrimersomes are nanosized vesicles constituted by amphiphilic Janus dendrimers (JDs), which have been recently proposed as innovative nanocarriers for biomedical applications. Recently, we have demonstrated that dendrimersomes self-assembled from (3,5)12G1-PE-BMPA-G2-(OH)8 dendrimers can be successfully loaded with hydrophilic and amphiphilic imaging contrast agents. Here, we present two newly synthesized low generation isomeric JDs: JDG0G1(3,5) and JDG0G1(3,4). Though less branched than the above-cited dendrimers, they retain the ability to form self-assembled, almost monodisperse vesicular nanoparticles. This contribution reports on the characterization of such nanovesicles loaded with the clinically approved MRI probe Gadoteridol and the comparison with the related nanoparticles assembled from more branched dendrimers. Special emphasis was given to the in vitro stability test of the systems in biologically relevant media, complemented by preliminary in vivo data about blood circulation lifetime collected from healthy mice. The results point to very promising safety and stability profiles of the nanovesicles, in particular for those made of JDG0G1(3,5), whose spontaneous self-organization in water gives rise to a homogeneous suspension. Importantly, the blood lifetimes of these systems are comparable to those of standard liposomes. By virtue of the reported results, the herein presented nanovesicles augur well for future use in a variety of biomedical applications.

Partially Acetylated Dendrimer-Entrapped Gold Nanoparticles with Reduced Cytotoxicity for Gene Delivery Applications

Gene therapy has been concerned to be one of the most promising strategies to treat many diseases such as genetic disorders and cancer. However, design of safe and highly efficient gene delivery vectors still remains a great challenge. In this work, we report the use of partially acetylated dendrimer-entrapped gold nanoparticles (Au DENPs) for gene delivery applications. First, partially acetylated generation 5 poly(amidoamine) dendrimers with different acetylation degrees were used as templates to synthesize Au DENPs. The formed Au DENPs were characterized via different techniques and were used to complex two different pDNAs encoding luciferase (Luc) and enhanced green fluorescent protein (EGFP), respectively for gene transfection studies. The Au DENPs/pDNA polyplexes with different N/P ratios were characterized by gel retardation assay, dynamic light scattering, and zeta potential measurements, and the gene transfection efficiency was evaluated by Luc assay and fluorescence microscopic imaging of the EGFP expression, respectively. We show that despite the partial acetylation (5, 10, 20, and 30 acetyl groups per G5 dendrimer according to the molar feeding ratio), all acetylated Au DENPs are able to effectively compact the pDNA and transfect genes to the model cell line with high efficiency comparable to the Au DENPs without acetylation. With the proven less cytotoxicity of the partially acetylated Au DENPs than that of non-acetylated Au DENPs by cell viability assay, the developed partially acetylated Au DENPs may serve as promising vectors for safe gene delivery applications with non-compromised gene transfection efficiency.

Hexameric Mn(II) dendrimer as MRI contrast agent

A Mn(II) chelating dendrimer was prepared as a contrast agent for MRI applications. The dendrimer comprises six tyrosine-derived [Mn(EDTA)(H2 O)](2-) moieties coupled to a cyclotriphosphazene core. Variable temperature (17) O NMR spectroscopy revealed a single water co-ligand per Mn(II) that undergoes fast water exchange (kex =(3.0±0.1)×10(8)  s(-1) at 37 °C). The 37 °C per Mn(II) relaxivity ranged from 8.2 to 3.8 mM(-1)  s(-1) from 0.47 to 11.7 T, and is sixfold higher on a per molecule basis. From this field dependence a rotational correlation time was estimated as 0.45(±0.02) ns. The imaging and pharmacokinetic properties of the dendrimer were compared to clinically used [Gd(DTPA)(H2 O)](2-) in mice at 4.7 T. On first pass, the higher per ion relaxivity of the dendrimer resulted in twofold greater blood signal than for [Gd(DTPA)(H2 O)](2-) . Blood clearance was fast and elimination occurred through both the renal and hepatobiliary routes. This Mn(II) containing dendrimer represents a potential alternative to Gd-based contrast agents, especially in patients with chronic kidney disease where the use of current Gd-based agents may be contraindicated.

Synthesis, biodistribution, and imaging of PEGylated-acetylated polyamidoamine dendrimers

Polyamidoamine (PAMAM) dendrimers have been widely used as drug carriers, non-viral gene vectors and imaging agents. However, the use of dendrimers in biological system is constrained because of inherent toxicity and organ accumulation. In this study, the strategy of acetylation and PEGylation-acetylation was used to minimize PAMAM dendrimers toxicities and to improve their biodistribution and pharmacokinetics for medical application. PEGylated-acetylated PAMAM (G4-Ac-PEG) dendrimers were synthesized by PEGylation of acetylated PAMAM dendrimer of generation 4 (G4) with acetic anhydride and polyethylene glycol (PEG) 3.4 k. To investigate the cytotoxicity and in vivo biodistribution of the conjugates, in vitro cell viability analysis, Iodine-125 (125I) imaging, tissue distribution and hematoxylin-eosin (HE) staining were performed. We find that acetylation and PEGylation-acetylation essentially eliminates the inherent dendrimer cytotoxicity in vitro. Planar gamma (gamma) camera imaging revealed that all the conjugates were slowly eliminated from the body, and higher abdominal accumulation of acetylation PAMAM dendrimer was observed. Tissue distribution analysis showed that PEGylated-acetylated dendrimers have longer blood retention and lower accumulation in organs such as the kidney and liver than the non-PEGylated-acetylated dendrimers, but acetylation only can significantly increase the accumulation of G4 in the kidney and decrease the concentration in blood. Histology results reveal that no obvious damage was observed in all groups after high dose administration. This study indicates that PEGylation-acetylation could improve the blood retention, decrease organ accumulation, and improve pharmacokinetic profile, which suggests that PEGylation-acetylation provides an alternative method for PAMAM dendrimers modification.

Efficient delivery of p53 and cytochrome c by supramolecular assembly of a dendritic multi-domain delivery system

Versatile nanocarrier systems facilitating uptake of exogenous proteins are highly alluring in evaluating these proteins for therapeutic applications. The self-assembly of an efficient nano-sized protein transporter consisting of three different entities is presented: A streptavidin protein core functioning as an adapter, second generation polyamidoamine dendrons for facilitating cell uptake as well as two different therapeutic proteins (tumor suppressor p53 or pro-apoptotic cytochrome c as cargo). Well-defined dendrons containing a biotin core are prepared and display no cytotoxic behavior upon conjugation to streptavidin. The integration of biotinylated human recombinant p53 (B-p53) into the three component system allows excellent internalization into HeLa, A549 and SaOS osteosarcoma cells monitored via confocal microscopy, immunoblot analysis and co-localization studies. In addition, the conjugation of B-p53 to dendronized streptavidin preserves its specific DNA-binding in vitro, and its delivery into SaOS cells impairs cell viability with concomitant activation of caspases 3 and 7. The versatility of this system is further exhibited by the significant enhancement of the pro-apoptotic effects of internalized cytochrome c which is analyzed by flow cytometry and cell viability assays. These results demonstrate that the "bio-click" self-assembly of biotinylated dendrons and proteins on a streptavidin adapter yields a stable supramolecular complex. This efficient bionanotransporter provides an attractive platform for mediating the delivery of functional proteins of interest into living mammalian cells in a facile and rapid way.

Targeting hepatic cancer cells with pegylated dendrimers displaying N-acetylgalactosamine and SP94 peptide ligands

Poly(amidoamine) (PAMAM) dendrimers are branched water-soluble polymers defined by consecutive generation numbers (Gn) indicating a parallel increase in size, molecular weight, and number of surface groups available for conjugation of bioactive agents. In this article, we compare the biodistribution of N-acetylgalactosamine (NAcGal)-targeted [(14) C]1 -G5-(NH2 )5 -(Ac)108 -(NAcGal)14 particles to non-targeted [(14) C]1 -G5-(NH2 )127 and PEGylated [(14) C]1 -G5-(NH2 )44 -(Ac)73 -(PEG)10 particles in a mouse hepatic cancer model. Results show that both NAcGal-targeted and non-targeted particles are rapidly cleared from the systemic circulation with high distribution to the liver. However, NAcGal-targeted particles exhibited 2.5-fold higher accumulation in tumor tissue compared to non-targeted ones. In comparison, PEGylated particles showed a 16-fold increase in plasma residence time and a 5-fold reduction in liver accumulation. These results motivated us to engineer new PEGylated G5 particles with PEG chains anchored to the G5 surface via acid-labile cis-aconityl linkages where the free PEG tips are functionalized with NAcGal or SP94 peptide to investigate their potential as targeting ligands for hepatic cancer cells as a function of sugar conformation (α versus β), ligand concentration (100-4000 nM), and incubation time (2 and 24 hours) compared to fluorescently (Fl)-labeled and non-targeted G5-(Fl)6 -(NH2 )122 and G5-(Fl)6 -(Ac)107 -(cPEG)15 particles. Results show G5-(Fl)6 -(Ac)107 -(cPEG[NAcGalβ ])14 particles achieve faster uptake and higher intracellular concentrations in HepG2 cancer cells compared to other G5 particles while escaping the non-specific adsorption of serum protein and phagocytosis by Kupffer cells, which make these particles the ideal carrier for selective drug delivery into hepatic cancer cells.

Analysis of biotinylated generation 4 poly(amidoamine) (PAMAM) dendrimer distribution in the rat brain and toxicity in a cellular model of the blood-brain barrier

Dendrimers are highly customizable nanopolymers with qualities that make them ideal for drug delivery. The high binding affinity of biotin/avidin provides a useful approach to fluorescently label synthesized dendrimer-conjugates in cells and tissues. In addition, biotin may facilitate delivery of dendrimers through the blood-brain barrier (BBB) via carrier-mediated endocytosis. The purpose of this research was to: (1) measure toxicity using lactate dehydrogenase (LDH) assays of generation (G)4 biotinylated and non-biotinylated poly(amidoamine) (PAMAM) dendrimers in a co-culture model of the BBB, (2) determine distribution of dendrimers in the rat brain, kidney, and liver following systemic administration of dendrimers, and (3) conduct atomic force microscopy (AFM) on rat brain sections following systemic administration of dendrimers. LDH measurements showed that biotinylated dendrimers were toxic to cell co-culture after 48 h of treatment. Distribution studies showed evidence of biotinylated and non-biotinylated PAMAM dendrimers in brain. AFM studies showed evidence of dendrimers only in brain tissue of treated rats. These results indicate that biotinylation does not decrease toxicity associated with PAMAM dendrimers and that biotinylated PAMAM dendrimers distribute in the brain. Furthermore, this article provides evidence of nanoparticles in brain tissue following systemic administration of nanoparticles supported by both fluorescence microscopy and AFM.

Multifunctional dendrimer-based nanoparticles for in vivo MR/CT dual-modal molecular imaging of breast cancer

Development of dual-mode or multi-mode imaging contrast agents is important for accurate and self-confirmatory diagnosis of cancer. We report a new multifunctional, dendrimer-based gold nanoparticle (AuNP) as a dual-modality contrast agent for magnetic resonance (MR)/computed tomography (CT) imaging of breast cancer cells in vitro and in vivo. In this study, amine-terminated generation 5 poly(amidoamine) dendrimers modified with gadolinium chelate (DOTA-NHS) and polyethylene glycol monomethyl ether were used as templates to synthesize AuNPs, followed by Gd(III) chelation and acetylation of the remaining dendrimer terminal amine groups; multifunctional dendrimer-entrapped AuNPs (Gd-Au DENPs) were formed. The formed Gd-Au DENPs were used for both in vitro and in vivo MR/CT imaging of human MCF-7 cancer cells. Both MR and CT images demonstrate that MCF-7 cells and the xenograft tumor model can be effectively imaged. The Gd-Au DENPs uptake, mainly in the cell cytoplasm, was confirmed by transmission electron microscopy. The cell cytotoxicity assay, cell morphology observation, and flow cytometry show that the developed Gd-Au DENPs have good biocompatibility in the given concentration range. Our results clearly suggest that the synthetic Gd-Au DENPs are amenable for dual-modality MR/CT imaging of breast cancer cells.

Molecular properties of lysine dendrimers and their interactions with Aβ-peptides and neuronal cells

Prevention of amyloidosis by chemical compounds is a potential therapeutic strategy in Alzheimer's, prion and other neurodegenerative diseases. Regularly branched dendrimers and less regular hyperbranched polymers have been suggested as promising inhibitors of amyloid aggregation. As demonstrated in our previous studies, some widely used dendrimers (PAMAM, PPI) could not only inhibit amyloid aggregation in solution but also dissolve mature fibrils. In this study we have performed computer simulation of polylysine dendrimers of 3rd and 5th generations (D3 and D5) and analysed the effect of these dendrimers and some hyperbranched polymers on a lysine base (HpbK) on aggregation of amyloid peptide in solution. The effects of dendrimers on cell viability and their protective action against Aβ-induced cytotoxicity and alteration of K+channels was also analysed using human neuroblastoma SH-SY5Y cells. In addition, using fluorescence microscopy, we analysed uptake of FITC-conjugated D3 by SH-SY5Y cells and its distribution in the brain after intraventricular injections to rats. Our results demonstrated that dendrimers D3 and D5 inhibited amyloid aggregation in solution while HpbK enhanced amyloid aggregation. Cell viability and patch-clamp studies have shown that D3 can protect cells against Aβ-induced cytotoxicity and K+channel modulation. In contrast, HpbK had no protective effect against Aβ. Fluorescence microscopy studies demonstrated that FITC-D3 accumulates in the vacuolar compartments of the cells and can be detected in various brain structures and populations of cells after injections to the brain. As such, polylysine dendrimers D3 and D5 can be proposed as compounds for developing antiamyloidogenic drugs.

Enhanced bioactivity of internally functionalized cationic dendrimers with PEG cores

Hybrid dendritic-linear block copolymers based on a 4-arm poly(ethylene glycol) (PEG) core were synthesized using an accelerated AB2/CD2 dendritic growth approach through orthogonal amine/epoxy and thiol-yne chemistries. The biological activity of these 4-arm and the corresponding 2-arm hybrid dendrimers revealed an enhanced, dendritic effect with an exponential increase in cell internalization concomitant with increasing amine end groups and low cytotoxicity. Furthermore, the ability of these hybrid dendrimers to induce endosomal escape combined with their facile and efficient synthesis makes them attractive platforms for gene transfection. The 4-arm-based dendrimer showed significantly improved DNA binding and gene transfection capabilities in comparison with the 2-arm derivative. These results combined with the MD simulation indicate a significant effect of both the topology of the PEG core and the multivalency of these hybrid macromolecules on their DNA binding and delivery capablities.

Cellular imaging using biocompatible dendrimer-functionalized graphene oxide-based fluorescent probe anchored with magnetic nanoparticles

We describe a novel multicomponent graphene nanostructured system that is biocompatible, and has strong NIR optical absorbance and superparamagnetic properties. The fabrication of the multicomponent nanostructure system involves the covalent attachment of 3 components; Fe(3)O(4)(Fe) nanoparticles, PAMAM-G4-NH(2) (G4) dendrimer and Cy5 (Cy) on a graphene oxide (GO) surface to synthesize a biologically relevant multifunctional system. The resultant GO-G4-Fe-Cy nanosystem exhibits high dispersion in an aqueous medium, and is magnetically responsive and fluorescent. In vitro experiments provide a clear indication of successful uptake of the GO-G4-Fe-Cy nanosystem by MCF-7 breast cancer cells, and it is seen to behave as a bright and stable fluorescent marker. The study also reveals varied cellular distribution kinetics profile for the GO nanostructured system compared to free Cy. Furthermore, the newly developed GO nanostructured system is observed to be non-toxic to MDA-MB-231 cell growth, in striking contrast to free G4 dendrimer and GO-G4 conjugate. The GO-G4-Fe-Cy nanostructured system characterized by multifunctionality suggests the merits of graphene for cellular bioimaging and the delivery of bioactives.

Uptake and intracellular traffic of siRNA dendriplexes in glioblastoma cells and macrophages

BACKGROUND

Gene silencing using small interfering RNA (siRNA) is a promising new therapeutic approach for glioblastoma. The endocytic uptake and delivery of siRNA to intracellular compartments could be enhanced by complexation with polyamidoamine dendrimers. In the present work, the uptake mechanisms and intracellular traffic of siRNA/generation 7 dendrimer complexes (siRNA dendriplexes) were screened in T98G glioblastoma and J774 macrophages.

METHODS

The effect of a set of chemical inhibitors of endocytosis on the uptake and silencing capacity of dendriplexes was determined by flow cytometry. Colocalization of fluorescent dendriplexes with endocytic markers and occurrence of intracellular dissociation were assessed by confocal laser scanning microscopy.

RESULTS

Uptake of siRNA dendriplexes by T98G cells was reduced by methyl-β-cyclodextrin, and genistein, and cytochalasine D, silencing activity was reduced by genistein; dendriplexes colocalized with cholera toxin subunit B. Therefore, caveolin-dependent endocytosis was involved both in the uptake and silencing activity of siRNA dendriplexes. On the other hand, uptake of siRNA dendriplexes by J774 cells was reduced by methyl-β-cyclodextrin, genistein, chlorpromazine, chloroquine, cytochalasine D, and nocodazole, the silencing activity was not affected by chlorpromazine, genistein or chloroquine, and dendriplexes colocalized with transferrin and cholera toxin subunit B. Thus, both clathrin-dependent and caveolin-dependent endocytosis mediated the uptake and silencing activity of the siRNA dendriplexes. SiRNA dendriplexes were internalized at higher rates by T98G but induced lower silencing than in J774 cells. SiRNA dendriplexes showed relatively slow dissociation kinetics, and their escape towards the cytosol was not mediated by acidification independently of the uptake pathway.

CONCLUSION

The extent of cellular uptake of siRNA dendriplexes was inversely related to their silencing activity. The higher silencing activity of siRNA dendriplexes in J774 cells could be ascribed to the contribution of clathrin-dependent and caveolin-dependent endocytosis vs only caveolin-dependent endocytosis in T98G cells.

Determination of puerarin in rabbit aqueous humor by liquid chromatography tandem mass spectrometry using microdialysis sampling after topical administration of puerarin PAMAM dendrimer complex

To study pharmacokinetic properties of puerarin poly(amido amine) (PAMAM) dendrimer complex, a sensitive liquid chromatography tandem mass spectrometry method (LC-MS/MS) was developed and validated to determine puerarin in rabbit aqueous humor using microdialysis sampling. Astilbin was used as the internal standard. The linear range for puerarin was from 2 to 1000ng/mL (r=0.9986) based on 20μL of aqueous humor. The coefficients of variations for intra-day and inter-day precisions were less than 10.0%, and the relative error of accuracy was within ±6.3%. The mean extraction recovery of puerarin varied from 80.4% to 85.5%. Microdialysis provides a complete concentration versus time profile. A significant difference was observed in main pharmacokinetic parameters of C(max), AUC and t(1/2) between puerarin solution and puerarin PAMAM dendrimer complex. Complex formation resulted in an obvious increase in bioavailability of puerarin after topical administration to rabbit according to the above LC-MS/MS assay method.

Enhanced pulmonary absorption of a macromolecule through coupling to a sequence-specific phage display-derived peptide

With the aim of identifying a peptide sequence that promotes pulmonary epithelial transport of macromolecule cargo we used a stringent peptide-phage display library screening protocol against rat lung alveolar epithelial primary cell cultures. We identified a peptide-phage clone (LTP-1) displaying the disulphide-constrained 7-mer peptide sequence, C-TSGTHPR-C, that showed significant pulmonary epithelial translocation across highly restrictive polarised cell monolayers. Cell biological data supported a differential alveolar epithelial cell interaction of the LTP-1 peptide-phage clone and the corresponding free synthetic LTP-1 peptide. Delivering select phage-clones to the intact pulmonary barrier of an isolated perfused rat lung (IPRL) resulted in 8.7% of lung deposited LTP-1 peptide-phage clone transported from the IPRL airways to the vasculature compared (p<0.05) to the cumulative transport of less than 0.004% for control phage-clone groups. To characterise phage-independent activity of LTP-1 peptide, the LTP-1 peptide was conjugated to a 53kDa anionic PAMAM dendrimer. Compared to respective peptide-dendrimer control conjugates, the LTP-1-PAMAM conjugate displayed a two-fold (bioavailability up to 31%) greater extent of absorption in the IPRL. The LTP-1 peptide-mediated enhancement of transport, when LTP-1 was either attached to the phage clone or conjugated to dendrimer, was sequence-dependent and could be competitively inhibited by co-instillation of excess synthetic free LTP-1 peptide. The specific nature of the target receptor or mechanism involved in LTP-1 lung transport remains unclear although the enhanced transport is enabled through a mechanism that is non-disruptive with respect to the pulmonary transport of hydrophilic permeability probes. This study shows proof-of principle that array technologies can be effectively exploited to identify peptides mediating enhanced transmucosal delivery of macromolecule therapeutics across an intact organ.

[Impact of polyamidoamine dendrimer liposome on the cellular uptake and cytotoxicity of colonic cancer cells]

OBJECTIVE

To evaluate the effects of polyamidoamine dendrimer (PAMAM) liposome as gene carriers on the cellular uptake and its cytotoxicity in colonic cancer cell.

METHODS

The liposome modified PAMAM was synthesized with liposome and polyamidoamine dendrimer. Plasmid PEGFP-N1 was mixed with the liposome-modified PAMAM or unmodified PAMAM to form nanoparticle complexes. The shape and size of the nanoparticle complexes were observed by transmission electron microscope and the zeta potential was measured by analytical tool. The encapsulating efficiency was determined by ultraviolet spectrophotometer in centrifuging method. After the cell lines SW620 (colonic cancer cell), MCF-7 (breast cancer cell), ECV304 (vascular endothelial cell) were transfected by the two kinds of PAMAM nanoparticle complexes, the flow cytometry was used to determine the uptake of enhanced green fluorescent protein (EGFP) gene. The cytotoxicity of PAMAM liposome nanoparticles and PAMAM nanoparticles was evaluated by MTT assay.

RESULTS

The diameter of liposome modified PAMAM complex was (192 ± 16) nm, and that of PAMAM complex was (189 ± 19) nm (P > 0.05); and the zeta potential of liposome modified PAMAM complex was higher than that of PAMAM complex [(42 ± 7) mV vs. (32 ± 7) mV, P < 0.05]. There was no significant difference in envelopment rate between the two groups [(82 ± 7)% vs. (84 ± 6)%, P > 0.05]. After the colonic cancer cell line SW620 was transfected with the two kinds of PAMAM nanoparticle complexes, the cellular uptake of the cells with the liposome-modified PAMAM complex was significantly higher than that of the cell with PAMAM complex (P < 0.05). The cellular survival rate of the cell lines with liposome-modified PAMAM complex was significantly higher than that of cell lines with PAMAM complex (P < 0.05).

CONCLUSION

The liposome modified PAMAM can improve gene transfection efficiency and suppress its cytotoxicity.

Comparison of MRI properties between derivatized DTPA and DOTA gadolinium-dendrimer conjugates

In this report we directly compare the in vivo and in vitro MRI properties of gadolinium-dendrimer conjugates of derivatized acyclic diethylenetriamine-N,N',N',N'',N''-pentaacetic acid (1B4M-DTPA) and macrocyclic 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (C-DOTA). The metal-ligand chelates were pre-formed in alcohol prior to conjugation to the generation 4 PAMAM dendrimer (G4D), and the dendrimer-based agents were purified by Sephadex(R) G-25 column. The analysis and SE-HPLC data indicated chelate to dendrimer ratios of 30:1 and 28:1, respectively. Molar relaxivity measured at pH 7.4, 22 degrees C, and 3T are comparable (29.5 vs 26.9 mM(-1)s(-1)), and both conjugates are equally viable as MRI contrast agents based on the images obtained. The macrocyclic agent however exhibits a faster rate of clearance in vivo (t(1/2)=16 vs 29 min). Our conclusion is that the macrocyclic-based agent is the more suitable agent for in vivo use for these reasons combined with kinetic inertness associated with the Gd(III) DOTA complex stability properties.

Arginine-glycine-aspartic acid-conjugated dendrimer-modified quantum dots for targeting and imaging melanoma

Angiogenesis is essential for the development of malignant tumors and provides important targets for tumor diagnosis and therapy. Quantum dots have been broadly investigated for their potential application in cancer molecular imaging. In present work, CdSe quantum dots were synthesized, polyamidoamine dendrimers were used to modify surface of quantum dots and improve their solubility in water solution. Then, dendrimer-modified CdSe quantum dots were conjugated with arginine-glycine-aspartic acid (RGD) peptides. These prepared nanoprobes were injected into nude mice loaded with melanoma (A375) tumor xenografts via tail vessels, IVIS imaging system was used to image the targeting and bio-distribution of as-prepared nanoprobes. The dendrimer-modified quantum dots exhibit water-soluble, high quantum yield, and good biocompatibility. RGD-conjugated quantum dots can specifically target human umbilical vein endothelial cells (HUVEC) and A375 melanoma cells, as well as nude mice loaded with A735 melanoma cells. High-performance RGD-conjugated dendrimers modified quantum dot-based nanoprobes have great potential in application such as tumor diagnosis and therapy.

PAMAM dendrimers as solubilizers and hosts for 8-methoxypsoralene enabling transdermal diffusion of the guest

PAMAM dendrimers form host-guest complexes with 8-methoxypsoralene (8-MOP) - the photosensitizer for PUVA therapy. The stoichiometry of complexes was studied by (1)H NMR spectroscopy in solution and by differential scanning calorimetry in neat mixtures containing 8-MOP and dendrimers of generations G2.5, G3, G3.5, and G4. The dendrimers showed solubilization effect for 8-MOP resulting in increase of 8-MOP concentration in methanol up to 15 molecules of 8-MOP per G2.5 and G3 and 30 molecules of 8-MOP per G3.5, and G4. Isolation of oily host-guest complexes containing 3 or 7 molecules of 8-MOP per G3 and G4, respectively corroborate well with DSC results; glass transition temperature of neat host-guest complexes increases with number of host molecules in comparison with G3 or G4, until the capacity of host is exceeded. The oily host-guest complexes of stoichiometry 3:1 and 7:1 of 8-MOP to G3 and G4, respectively are well soluble in water. The 3:1 host-guest complexes diffused slowly through polyvinyldifluoride and pig ear skin membranes, when released from o/w emulsion. The host-guest complex 8-MOP-G3 was proposed as convenient formulation for psoralene skin administration in PUVA therapy.