Starburst Polyamidoamine Dendrimers Research Articles

Synthesis and Characterization of Inclusion Complex of Carbamide with Extremely Branched, Globular, Mono-Disperse, Nanometric Starburst PAMAM Dendrimer

All Dendrimers are the emerging polymeric architectures known for their defined structure, low polydispersity, nanometric size and high functionality. These nanostructure macromolecules have shown their potential abilities in entrapping and conjugating the high molecular weight hydrophobic or hydrophilic entities by host-guest interaction and covalent bonding respectively. Dendrimer is the irresistible candidature for the formation of inclusion complexes capable of accomplishing the various applications. This is due to the presence of various terminal groups with varied functionalities. PAMAM Dendrimer has been growing interest because of their unique characteristics like globular, nanoscale, macromolecule with different functionalities at periphery. PAMAM is comparatively novel group of these distinctive materials that is grown from the core side and each half or complete generation needs some repeating reactions. Also it has potential applicability in a wide range of areas makes it the promising candidate for lots of applications.Herein, we have synthesized Polyamidoamine (PAMAM) dendrimer of various generations and characterized by Fourier transform infrared (FTIR) spectroscopy and Mass spectrometry. The -0.5G PAMAM has differential functionality and special characteristics which allows the formation of inclusion complexes with various molecules. At this place, the inclusion complexes formed with carbamide molecules, which implant more functionality through host-guest interaction compared to the host molecules

A reactive oxygen species-responsive dendrimer with low cytotoxicity for efficient and targeted gene delivery

Nonviral vectors have been attracting more attention for several advantages in gene delivery and the development of nonviral gene carriers with high delivery efficiency and low cytotoxicity has long been a key project. Starburst polyamidoamine dendrimers are a class of synthetic polymers with unique structural and physical characteristics. However, when they are used as gene carrier, the gene transfection efficiency is not satisfactory. Herein, a novel thioketal-core polyamidoamine dendrimer (i.e., ROS-PAMAM) was synthesized and characterized. Compared to ethylenediamine-core dendrimers or widely used cationic polymers of polyetherimide, ROS-PAMAM showed lower cytotoxicity. Moreover, ROS-PAMAM demonstrated reactive oxygen species responsive characteristics, which can facilitate the release of siRNA in the tumor microenvironment. In vitro gene transfection experiments based on A549 cells confirmed that siRNA/ROS-PAMAM exhibits high gene transfection efficiency. It is concluded that ROS-PAMAM shows great potential as a generalizable vehicle for gene therapy applications.

Polyamidoamine starburst dendrimer-activated chromatography paper-based assay for sensitive detection of telomerase activity

Telomerase is extensively expressed in various cancer cells and recognized as a target for cancer drug discovery. In the present study, a simple and amplification-free fluorescence assay based on polyamidoamine starburst dendrimer (PAMAM dendrimer)-activated paper device is proposed for sensitive detection of telomerase activity through hybridization of Cy5 modified single strand DNA probes with telomerase extension products. The paper substrate is fabricated by hand drawing according to a template, which is low cost, instrument free and easy operation. PAMAM is rich in amino groups on its surface and employed to immobilize the telomerase substrate (TS) primer. Highly sensitive detection of telomerase activity in HeLa cell lysate of 10 cells is achieved since the PAMAM dendrimer-activated paper surface can provide high density of binding sites for immobilization of TS primer. The experimental results also demonstrate that the assay can be employed to evaluate telomerase activity levels of various cell lines and screen telomerase inhibitors.

Preparation and evaluation of polyamidoamine dendrimer conjugate with glucuronylglucosyl-β-cyclodextrin (G3) as a novel carrier for siRNA

In this study, we newly synthesized the polyamidoamine STARBURST dendrimer (dendrimer, generation 3: G3) conjugates with 6-O-α-(4-O-α-d-glucuronyl)-d-glucosyl-β-cyclodextrin [GUG-β-CDE (G3)] having the various degrees of substitution (DS) of GUG-β-cyclodextrin of 1.6, 3.0, 3.7, 5.0 and 8.6, and evaluated them as a siRNA transfer carrier. GUG-β-CDEs (G3) formed the positively charged and nano-order complexes with siRNA. Of the siRNA complexes with five GUG-β-CDEs (G3), the complex with GUG-β-CDE (G3, DS 3.7) showed the highest RNAi effect and cellular uptake with negligible cytotoxicity in KB cells at a charge ratio of 20. In addition, the RNAi effect and cellular uptake of the complex with GUG-β-CDE (G3, DS 3.7) were higher than those of α-CDE (G3, DS 2.4) and comparable to those of Lipofectamine™ 2000. Furthermore, the complex with GUG-β-CDE (G3, DS 3.7) possessed the endosomal escaping ability, the releasing property of siRNA in the cytoplasm and serum resistance. These results suggest that GUG-β-CDE (G3, DS 3.7) has the potential as a novel siRNA carrier.

Design and evaluation of polyamidoamine dendrimer conjugate with PEG, α-cyclodextrin and lactose as a novel hepatocyte-selective gene carrier in vitro and in vivo

To develop a novel hepatocyte-selective gene carrier, we prepared polyamidoamine starburst dendrimer (generation 3, G3) conjugates with three functional molecules, i.e. α-cyclodextrin, polyethylene glycol (PEG, molecular weight = 2170) and lactose (PEG-LαCs), and evaluated gene delivery efficiency of these conjugates in vitro and in vivo. PEG-LαC (G3, degrees of substitution of the PEG moiety (DSP) 2.1) showed higher gene transfer activity than other PEG-LαCs (G3, DSP4.0, 6.2) in HepG2 cells, expressing asialoglycoprotein receptor, and the activity decreased in HeLa cells, non-expressing the receptor and in the presence of asialofetuin. High gene transfer activity of PEG-LαC (G3, DSP2.1) was retained even in the presence of 50% serum, although the activity of α-cyclodextrin/lactosylated dendrimer (G3) conjugate (Lac-α-CDE (G3)), which is lacking a PEG moiety, was severely decreased in the presence of 20% serum. PEG-LαC (G3, DSP2.1) provided negligible cytotoxicity up to a charge ratio of 50 (carrier/pDNA) in HepG2 cells and less acute organ toxicity. PEG-LαC (G3, DSP2.1) showed selective gene transfer activity to hepatic parenchymal cells rather than hepatic non-parenchymal cells. These results suggest that PEG-LαC (G3, DSP2.1) is useful as a hepatocyte-selective gene carrier in vitro and in vivo.

Folate-PEG-Appended Dendrimer Conjugate with α-Cyclodextrin as a Novel Cancer Cell-Selective siRNA Delivery Carrier

We previously reported that of the various polyamidoamine (PAMAM) STARBURST dendrimer (generation 3, G3) (dendrimer) conjugates with cyclodextrins (CyDs), the dendrimer (G3) conjugate with α-CyD having an average degree of substitution of 2.4 (α-CDE (G3)) has the greatest potential for a novel carrier for siRNA in vitro and in vivo. To improve the siRNA transfer activity and the lack of target specificity of α-CDE (G3), we prepared folate-polyethylene glycol (PEG)-appended α-CDEs (G3) (Fol-PαCs) with various degrees of substitution of folate (DSF) and evaluated their siRNA transfer activity to folate receptor (FR)-overexpressing cancer cells in vitro and in vivo. Of the three Fol-PαCs (G3, DSF 2, 4 and 7), Fol-PαC (G3, DSF 4) had the highest siRNA transfer activity in KB cells (FR-positive). Fol-PαC (G3, DSF 4) was endocytosed into KB cells through FR. No cytotoxicity of the siRNA complex with Fol-PαC (G3, DSF 4) was observed in KB cells (FR-positive) or A549 cells (FR-negative) up to the charge ratio of 100/1 (carrier/siRNA). In addition, the siRNA complex with Fol-PαC (G3, DSF 4) showed neither interferon response nor inflammatory response. Importantly, the siRNA complex with Fol-PαC (G3, DSF 4) tended to show the in vivo RNAi effects after intratumoral injection and intravenous injection in tumor cells-bearing mice. The FITC-labeled siRNA and TRITC-labeled Fol-PαC (G3, DSF 4) were actually accumulated in tumor tissues after intravenous injection in the mice. In conclusion, the present results suggest that Fol-PαC (G3, DSF 4) could potentially be used as a FR-overexpressing cancer cell-selective siRNA delivery carrier in vitro and in vivo.

Molecular dynamics and neutron scattering study of the dependence of polyelectrolyte dendrimer conformation on counterion behavior

Atomistic molecular dynamics (MD) simulations and contrast variation small angle neutron scattering (SANS) have been combined to investigate the Generation-5 polyelectrolyte polyamidoamine starburst dendrimer. This work reveals the dendrimer conformational dependence on counterion association at different levels of molecular charge. The accuracy of the simulations is verified through satisfactory comparison between modeled results, such as excess intra-dendrimer scattering length density distribution and hydration level, and their experimental counterparts. While the counterion distributions are not directly measureable with SANS, the spatial distribution of the counterions and their dendrimer association are extracted from the validated MD equilibrium trajectories. It is found that the conformation of the charged dendrimer is strongly dependent on the counterion association. Sensitivity of the distribution of counterions around charged amines to the counterion valency is qualitatively explained by adopting Langmuir adsorption theory. Moreover, via extending the concept of electrical double layer for compact charged colloids, we define an effective radius of a charged dendrimer including the spatial distribution of counterions in its vicinity. Within the same framework, the correlation between the strength of intra-dendrimer electrostatic repulsion and the counterion valency and dynamics is also addressed.

Structured water in polyelectrolyte dendrimers: Understanding small angle neutron scattering results through atomistic simulation

Based on atomistic molecular dynamics (MD) simulations, the small angle neutron scattering (SANS) intensity behavior of a single generation-4 polyelectrolyte polyamidoamine starburst dendrimer is investigated at different levels of molecular protonation. The SANS form factor, P(Q), and Debye autocorrelation function, γ(r), are calculated from the equilibrium MD trajectory based on a mathematical approach proposed in this work. The consistency found in comparison against previously published experimental findings (W.-R. Chen, L. Porcar, Y. Liu, P. D. Butler, and L. J. Magid, Macromolecules 40, 5887 (2007)) leads to a link between the neutron scattering experiment and MD computation, and fresh perspectives. The simulations enable scattering calculations of not only the hydrocarbons but also the contribution from the scattering length density fluctuations caused by structured, confined water within the dendrimer. Based on our computational results, we explore the validity of using radius of gyration R(G) for microstructure characterization of a polyelectrolyte dendrimer from the scattering perspective.

Potential use of folate-polyethylene glycol (PEG)-appended dendrimer (G3) conjugate with α-cyclodextrin as DNA carriers to tumor cells

We previously reported that polyamidoamine STARBURST dendrimer (generation 3, G3) (dendrimer) conjugate with α-cyclodextrin (α-CyD) having an average degree of substitution of 2.4 of α-CyD (α-CDE) provided remarkable aspects as novel carriers for DNA and small-interfering RNA. To develop novel α-CDE derivatives with tumor cell specificity, we prepared folate-appended α-CDEs (Fol-α-CDEs) and folate-polyethylene glycol (PEG)-appended α-CDEs (Fol-PαCs) with the various degrees of substitution of folate (DSF), and evaluated in vitro and in vivo gene transfer activity, cytotoxicity, cellular association and physicochemical properties. In vitro gene transfer activity of Fol-α-CDEs (G3, DSF 2, 5 or 7) was lower than that of α-CDE (G3) in KB cells, folate receptor (FR)-overexpressing cancer cells. Of the three Fol-PαCs (G3, DSF 2, 5 or 7), Fol-PαC (G3, DSF 5) had the highest gene transfer activity in KB cells. The activity of Fol-PαC (G3, DSF 5) was significantly higher than that of α-CDE (G3) in KB cells, but not in A549 cells, FR-negative cells. Negligible cytotoxicity of the plasmid DNA (pDNA) complex with Fol-PαC (G3, DSF 5) was observed in KB cells or A549 cells up to a charge ratio of 100/1 (carrier/pDNA). The cellular association of the pDNA complex with Fol-PαC (G3, DSF 5) could be mediated by FR on KB cells, resulting in its efficient cellular uptake. Fol-PαC (G3, DSF 5) had a higher binding affinity with folate-binding protein than α-CDE (G3), although the physicochemical properties of pDNA complex with Fol-PαC (G3, DSF 5) were almost comparable to that with α-CDE (G3), although the onset charge ratio and the compaction ability of Fol-PαC (G3, DSF 5) were slightly different. Fol-PαC (G3, DSF 5) tended to show a higher gene transfer activity than α-CDE (G3) 12 h after intratumoral administration in mice. These results suggest that Fol-PαC (G3, DSF 5), not Fol-α-CDEs, could be potentially used as a FR-overexpressing cancer cell-selective DNA carrier.

Possible enhancing mechanisms for gene transfer activity of glucuronylglucosyl-β-cyclodextrin/dendrimer conjugate

We previously reported that glucuronylglucosyl-β-cyclodextrin (GUG-β-CyD) conjugate with polyamidoamine starburst dendrimer (GUG-β-CDE conjugate) with the average degree of substitution (DS) of cyclodextrin (CyD) of 1.8 (GUG-β-CDE conjugate (DS 1.8)), showed remarkably higher gene transfer activity than α-CyD/dendrimer conjugate (α-CDE conjugate (DS 1.2)) and β-CyD/dendrimer conjugate (β-CDE conjugate (DS 1.3)) in vitro and in vivo. In this study, to clarify the enhancing mechanism for high gene transfer activity of GUG-β-CDE conjugate (DS 1.8), we investigated the physicochemical properties, cellular uptake, endosomal escape and nuclear translocation of the plasmid DNA (pDNA) complexes as well as pDNA release from the complexes. The particle size, ζ-potential and cellular uptake of GUG-β-CDE conjugate (DS 1.8)/pDNA complex were mostly comparable to those of α-CDE conjugate (DS 1.2) and β-CDE conjugate (DS 1.3). Meanwhile, GUG-β-CDE conjugate (DS 1.8)/pDNA complex was likely to have high endosomal escaping ability and nuclear localization ability in A549 and RAW264.7 cells. In addition, the pDNA condensation and decondensation abilities of GUG-β-CDE conjugate (DS 1.8) were lower and higher than that of α-CDE conjugate (DS 1.2) or β-CDE conjugate (DS 1.3), respectively. These results suggest that high gene transfer activity of GUG-β-CDE conjugate (DS 1.8) could be, at least in part, attributed to high endosomal escaping ability, nuclear localization ability and suitable pDNA release from its complex.

Potential Use of Polyamidoamine Dendrimer Conjugates with Cyclodextrins as Novel Carriers for siRNA

Cyclodextrin (CyD)-based nanoparticles and polyamidoamine (PAMAM) starburst dendrimers (dendrimers) are used as novel carriers for DNA and RNA. Recently, small interfering RNA (siRNA) complex with β-CyD-containing polycations (CDP) having adamantine-PEG or adamantine-PEG-transferrin underwent a phase I study for treatment of solid tumors. Multifunctional dendrimers can be used for a wide range of biomedical applications, including the interaction and intracellular delivery of DNA and RNA. The present review will address the latest developments in dendrimer conjugates with cyclodextrins for siRNA delivery including the novel sustained release system.

Potential use of glucuronylglucosyl-β-cyclodextrin/dendrimer conjugate (G2) as a DNA carrier in vitro and in vivo

In this study, we evaluated the polyamidoamine starburst dendrimer (dendrimer, generation 2: G2) conjugate with 6-O-α-(4-O-α-D-glucuronyl)-D-glucosyl-β-cyclodextrin (GUG-β-CDE (G2)) as a gene transfer carrier. The in vitro gene transfer activity of GUG-β-CDE (G2, degree of substitution (DS) of cyclodextrin (CyD) 1.8) was remarkably higher than that of dendrimer (G2) conjugate with α-CyD (α-CDE (G2, DS 1.2)) and that with β-CyD(β-CDE (G2, DS 1.3)) in A549 and RAW264.7 cells. The particle size, ζ-potential, DNase I-catalyzed degradation, and cellular association of plasmid DNA (pDNA) complex with GUG-β-CDE (G2, DS 1.8) were almost the same as those of the other CDEs. Fluorescent-labeled GUG-β-CDE (G2, DS 1.8) localized in the nucleus 6 h after transfection of its pDNA complex in A549 cells, suggesting that nuclear localization of pDNA complex with GUG-β-CDE (G2, DS 1.8), at least in part, contributes to its high gene transfer activity. GUG-β-CDE (G2, DS 1.8) provided higher gene transfer activity than α-CDE (G2, DS 1.2) and β-CDE (G2, DS 1.3) in kidney with negligible changes in blood chemistry values 12 h after intravenous injection of pDNA complexes with GUG-β-CDE (G2, DS 1.8) in mice. In conclusion, the present findings suggest that GUG-β-CDE (G2, DS 1.8) has the potential for a novel polymeric pDNA carrier in vitro and in vivo.

Potential Use of Folate-polyethylene glycol (PEG)-Appended Dendrimer (G3) Conjugate with alpha-Cyclodextrin as DNA Carriers to Tumor Cells

AbstractWe previously reported that polyamidoamine STARBURST dendrimer (generation 3, G3) (dendrimer) conjugate with alpha-cyclodextrin (alpha-CyD) having an average degree of substitution of 2.4 of alpha-CyD (alpha-CDE) provided remarkable aspects as novel carriers for DNA and siRNA. To develop novel alpha-CDE derivatives with tumor cell specificity, we prepared folate-appended alpha-CDEs (Fol-alpha-CDEs) and folate-polyethylene glycol (PEG)-appended alpha-CDEs (Fol-PalphaCs) with the various degrees of substitution of folate (DSF), and evaluated in vitro and in vivo gene transfer activity, cytotoxicity, cellular association and physicochemical properties. In vitro gene transfer activity of Fol-alpha-CDEs (G3, DSF 2, 5 or 7) was lower than that of &x03B1;-CDE (G3) in KB cells, folate receptor (FR)-overexpressing cancer cells. Of the three Fol-PalphaCs (G3, DSF 2, 5 or 7), Fol-PalphaC (G3, DSF 5) had the highest gene transfer activity in KB cells. The activity of Fol-PalphaC (G3, DSF 5) was significantly higher than that of alpha-CDE (G3) in KB cells, but not in A549 cells, FR-negative cells. Negligible cytotoxicity of the pDNA complex with Fol-PalphaC (G3, DSF 5) was observed in KB cells or A549 cells up to a charge ratio of 100/1 (carrier/pDNA). The cellular association of the pDNA complex with Fol-PalphaC (G3, DSF 5) could be mediated by FR on KB cells, resulting in its efficient cellular uptake. Fol-PalphaC (G3, DSF 5) had higher binding affinity with folate binding protein (FBP) than alpha-CDE (G3), although the physicochemical properties of pDNA complex with Fol-PalphaC (G3, DSF 5) were almost comparable to that with alpha-CDE (G3), although the onset charge ratio and the compaction ability of Fol-PalphaC (G3, DSF 5) were slightly different. Fol-PalphaC (G3, DSF 5) tended to show higher gene transfer activity than alpha-CDE (G3) 12 h after intratumoral administration in mice. These results suggest that Fol-PalphaC (G3, DSF 5), not Fol-alpha-CDEs, could be potentially used as a FR-overexpressing cancer cell-selective DNA carrier.

Polyamines and Polyamine Amides as Potent Selective Receptor Probes, Novel Therapeutic Lead Compounds and Synthetic Vectors in Gene Therapy

The family of polyamines and polyamine amides, especially unsymmetrical synthetic members, is critically assessed with respect to chemical structure and pharmacological activity. Naturally occurring polyamines (and diamines) and mono- (and di-) acylated polyamines (polyamine amides) are blockers of cation channels that are receptor- or voltage-gated. Such compounds are leads for the design of novel therapeutic agents. Furthermore, polyamines and polyamine amides are templates for the design of synthetic vectors with potential application in gene therapy. Natural di- and polyamines, spider and wasp venom polyamine amide toxins and their analogues, and totally synthetic polyamines, are potent cation-channel blockers with uses as selective receptor probes for nicotinic acetylcholine and glutamate (NMDA and non-NMDA) receptors, sodium and calcium channels. Therefore, as receptor probes, they may help us to understand the molecular mechanisms of neurodegeneration, and ultimately to design drugs for the treatment of neurodegenerative diseases, especially stroke. Polyamine conjugates are also novel therapeutic lead compounds for possible treatments of cancer, diarrhoea, malaria and haemochromatosis (β-thalassaemia). The metal chelating properties of (poly-) ethylenediamines have led to their incorporation in ion chelators which are synthetic RNase and DNase enzymes. Synthetic polyamines and polyamine amides have potential as novel vectors in gene delivery. Such compounds can condense DNA to form toroidal particles which may be incorporated in a non-viral gene delivery system. The applications of polylysine, polyethylenimine, Starburst polyamidoamine dendrimers, Transfectam (DOGS), cholic acid, and cholesterol conjugates to gene therapy are compared as a function of structure and pKa. This assessment of polyamines and polyamine amides stresses the basicity of the amine functional groups. The pKa's of these functionalities are a major determinant in their binding to biological macromolecules. Selectivity of pharmacological action also encompasses contributions from solution conformation and lipophilicity as well as amine pKa. The use of these compounds as leads for the design of novel therapeutics or gene medicines is demonstrated to be practical as well as theoretically possible.

Preparation and evaluation of polyamidoamine dendrimer (G2)/branched-β-cyclodextrin conjugate as a novel gene transfer carrier

The purpose of this study is to evaluate the potential use of polyamidoamine (PAMAM) starburst dendrimer (generation 2, G2) conjugates with 6-O-α-(4-O-α-d-glucuronyl)-d-glucosyl-β-cyclodextrin (GUG-β-CDE (G2)) having glucose as a spacer between dendrimer and cyclodextrin (CyD) as a novel gene transfer carrier. GUG-β-CDE (G2) was found to have lower hemolytic activity than dendrimer (G2), suggesting that GUG-β-CDE (G2) had lower local irritation than dendrimer (G2). Of GUG-β-CDEs (G2) having the various average degree of substitution (DS) of a glucuronylglycoside group, GUG-β-CDE (G2, DS 1.8) possessed much higher gene transfer activity than α-CDE (G2, DS 1.2) and β-CDE (G2, DS 1.3) in A549 and RAW264.7 cells, suggesting the crucial role of a spacer between dendrimer and CyD for high gene transfer activity of GUG-β-CDE (G2, DS 1.8). In sharp contrast to linear polyethyleneimine (10 kDa, PEI), GUG-β-CDE (G2, DS 1.8) had negligible cytotoxicity. These results suggest that GUG-β-CDE (G2, DS 1.8) could have the potential for a novel gene transfer carrier, compared to α-CDE (G2, DS 1.2), β-CDE (G2, DS 1.3) and PEI.

In vitro gene delivery mediated by lactosylated dendrimer (generation 3, G3)/α-cyclodextrin conjugates into hepatocytes

The purpose of this study is to evaluate in vitro gene delivery efficiency of polyamidoamine (PAMAM) starburst dendrimer (generation 3, G3) conjugates with α-cyclodextrin (α-CDE (G3)) bearing lactose (Lac-α-CDE) with various degrees of substitution of the lactose moiety (DSL) as a novel hepatocyte-selective carrier. Lac-α-CDE (G3, DSL 1.2) was found to have much higher gene transfer activity than α-CDE (G3), Lac-α-CDE (G2, DSL 2.6) and Lac-α-CDEs (G3, DSL 2.6, 4.1 and 6.1) in HepG2 cells, which are dependent on the expression of cell-surface asialoglycoprotein receptor (ASGP-R). Lac-α-CDE (G3, DSL 1.2) provided negligible cytotoxicity up to a charge ratio of 100 (carrier/pDNA) in HepG2 cells. These results suggest the potential use of Lac-α-CDE (G3, DSL 1.2) as a non-viral vector for gene delivery toward hepatocytes.

In Vitro and In Vivo gene delivery mediated by Lactosylated Dendrimer/α-Cyclodextrin Conjugates (G2) into Hepatocytes

The purpose of this study is to evaluate in vitro and in vivo gene delivery efficiency of polyamidoamine (PAMAM) starburst dendrimer (generation 2, G2) conjugates with α-cyclodextrin (α-CDE (G2)) bearing lactose (Lac-α-CDE) with various degrees of substitution of the lactose moiety (DSL) as a novel hepatocyte-selective carrier in hepatocytes. Lac-α-CDE (DSL 2.6) was found to have much higher gene transfer activity than dendrimer, α-CDE, Lac-α-CDE (DSL 1.2, 4.6, 6.2 and 10.2) and lactosylated dendrimer (Lac-dendrimer, DSL 2.4) in HepG2 cells, which are dependent on the expression of cell-surface asialoglycoprotein receptor (ASGP-R), reflecting the cellular association of the plasmid DNA (pDNA) complexes. The physicochemical properties of pDNA complex with Lac-α-CDE (DSL 2.6) were almost comparable to that with α-CDE. Lac-α-CDE (DSL 2.6) provided negligible cytotoxicity up to a charge ratio of 150 in HepG2 cells. Lac-α-CDE (DSL 2.6) provided gene transfer activity higher than jetPEI TM-Hepatocyte to hepatocytes with much less changes of blood chemistry values 12 h after intravenous administration in mice. These results suggest the potential use of Lac-α-CDE (DSL 2.6) as a non-viral vector for gene delivery toward hepatocytes.

PAMAM Nanoparticles Promote Acute Lung Injury by Inducing Autophagic Cell Death through the Akt-TSC2-mTOR Signaling Pathway

Nanotechnology is an important and emerging industry with a projected annual market of around one trillion US dollars by 2011-2015. Concerns about the toxicity of nanomaterials in humans, however, have recently been raised. Although studies of nanoparticle toxicity have focused on lung disease the molecular link between nanoparticle exposure and lung injury remained unclear. In this report, we show that cationic Starburst polyamidoamine dendrimer (PAMAM), a class of nanomaterials that are being widely developed for clinical applications can induce acute lung injury in vivo. PAMAM triggers autophagic cell death by deregulating the Akt-TSC2-mTOR signaling pathway. The autophagy inhibitor 3-methyladenine rescued PAMAM dendrimer-induced cell death and ameliorated acute lung injury caused by PAMAM in mice. Our data provide a molecular explanation for nanoparticle-induced lung injury, and suggest potential remedies to address the growing concerns of nanotechnology safety.

Counterion Association and Structural Conformation Change of Charged PAMAM Dendrimer in Aqueous Solutions Revealed by Small Angle Neutron Scattering

AbstractOur previous study of the structure change of poly(amidoamine) starburst dendrimers (PAMAM) dendrimer of generation 5 (G5) have demonstrated that although the overall molecular size is practically unaffected by increasing DCl concentration, a configurational transformation, from a diffusive density profile to a more uniform density distribution, is clearly observed. In the current paper, the focus is placed on understanding the effect of counterion identity on the inter‐molecular structure and the conformational properties by studying the effect due to DBr using small angle neutron scattering (SANS) and integral equation theory. While the overall molecular size is found to be essentially unaffected by the change in the pD of solutions, it is surprising that the intra‐molecular configurational transformation is not observed when DBr is used. The overall effective charge of a dendrimer is nearly the same for α < 1, independent of the type of acids. However, when α > 1, the effect of counterion identity becomes significant, the effective charge carried by a charged G5 PAPAM protonated by DBr becomes smaller than that of solutions with DCl. As a consequence, a counterion identity dependence of counterion association is revealed: Under the same level of molecular protonation, the specific counterion association, which is defined as the ratio of bound chloride anions to positively charged amines per molecule, is larger for the G5 PAMAM dendrimer charged by DBr than the one by DCl.

Structural Investigation of PAMAM Dendrimers in Aqueous Solutions Using Small-Angle Neutron Scattering: Effect of Generation

We investigate a series of poly(amidoamine) starburst dendrimers (PAMAM) of different generations in acidic, aqueous solutions using small-angle neutron scattering (SANS). While the overall molecular size is found to be practically unaffected by a pD change, a strong generational dependence of counterion association is revealed. Upon increasing the dendrimer generation, the effective charge obtained from our SANS experiments only shows a small increase in contrast to the nearly exponential increase predicted by a recent atomic simulation. We also find that with the same degree of molecular protonation the specific counterion association, which is defined as the ratio of bound chloride anions to positively charged amines in solutions, is larger for higher-generation PAMAM dendrimer. The associated counterion density also increases upon increasing generation number.