The role of ganglioside GM1 in cellular internalization mechanisms of poly(amidoamine) dendrimers

Biogenically synthesized gold nanocarrier ameliorated antiproliferative and apoptotic efficacy of doxorubicin against lung cancer

Introduction

Conventional chemotherapy treatment is commonly linked to significant side effects due to high therapeutic doses. In this regard, nanoformulations with chemotherapeutic medications hold promise in enhancing drug effectiveness through the reduction of therapeutic dosages, thereby mitigating the potential for adverse side effects. Because of numerous applications in the biomedical arena, there has been a rising interest in developing an environmentally acceptable, long-lasting, and affordable technique for the production of gold nanoparticles. In this particular context, the incorporation of plant extracts in the production of metallic nanoparticles has garnered the interest of numerous scholars. Here, we report the synthesis of gold particles by the green method using Cannabis sativa L. leaf extract and their conjugation with doxorubicin.

Methods

The gold nanoparticles were synthesized by using Cannabis sativa extract and were characterized with various biophysical techniques. Subsequently, gold nanoparticles were conjugated with doxorubicin and their efficacy was tested on A549 cells.

Results and Discussion

The biogenic synthesis of gold nanoparticles was ascertained through an absorption peak at a wavelength of 524 nm, and it was shifted to 527 nm when conjugated with doxorubicin. Nanoparticles were found to be stable exhibiting a zeta potential value of -20.1 mV, and it changed to -12.7 mV when loaded with doxorubicin. The hydrodynamic diameter of nanoparticles was determined to be 45.64 nm and it was increased to 58.95 nm when conjugated with the drug. The average size of nanoparticles analyzed by TEM was found to be approximately 17.2 nm, while it was 23.5 nm in the case of drug-nanoconjugate. Moreover, there was a significant amelioration in the antiproliferative potential of doxorubicin against lung cancer A549 cells when delivered with gold nanocarrier, which was evident by the lower IC50 and IC75 values of drug-nanoconjugates in comparison to drug alone. Furthermore, the inhibitory effect of drug-nanoconjugates and drug alone was characterized by alteration in the cell morphology, nuclear condensation, increased production of reactive oxygen species, abrogation of mitochondrial membrane potential, and enhanced caspase activities in A549 cells. In sum, our results suggested enhanced efficacy of doxorubicin-gold nanoconjugates, indicating effective delivery of doxorubicin inside the cell by gold nanoparticles.

Survivin-targeted nanomedicine for increased potency of abiraterone and enzalutamide against prostate cancer

Prostate cancer is the leading and most aggressive cancer around the world, several therapeutic approaches have emerged but none have achieved the satisfactory result. However, these therapeutic approaches face many challenges related to their delivery to target cells, including their in vivo decay, the limited uptake by target cells, the requirements for nuclear penetration (in some cases), and the damage caused to healthy cells. These barriers can be avoided by effective, targeted, combinatorial approaches, with minimal side effects, which are being investigated for the treatment of cancer. Here, we developed a combinatorial nanomedicine comprising abiraterone and enzalutamide bioconjugated survivin-encapsulated gold nanoparticles (AbEzSvGNPs) for targeted therapy of prostate cancer. AbEzSvGNPs were characterized by different biophysical techniques such as UV visible spectroscopy, dynamic light scattering, zeta potential, transmission electron microscope, and Fourier transform infrared spectroscopy. Interestingly, the effect of abiraterone, enzalutamide and surviving encapsulated gold nanoparticles was found to be synergistic in nature in AbEzSvGNPs against DU 145 (IC50 = 4.21 µM) and PC-3 (IC50 = 5.58 µM) cells and their potential was observed to be greatly enhanced as compared with the combined effect of the drugs (abiraterone and enzalutamide) in their free form. Furthermore, AbEzSvGNPs were found to be highly safe and did not exhibit significant cytotoxicity against normal rat kidney cells. The observed effects of AbEzSvGNPs involved the modulation of different signaling pathways in prostate cancer cells. This delivery system employed non-androgen receptor-dependent delivery of abiraterone and enzalutamide. The anionic AbEzSvGNPs delivered abiraterone and enzalutamide unaltered into the nucleus through caveolae mediated internalization to act nonspecifically on DNA; internalization of the anionic nanoparticles into the cytoplasm was also observed via other routes. AbEzSvGNPs synthesized and evaluated in this study are promising candidates for prostate cancer therapy.

Developments in Treatment Methodologies Using Dendrimers for Infectious Diseases

Dendrimers comprise a specific group of macromolecules, which combine structural properties of both single molecules and long expanded polymers. The three-dimensional form of dendrimers and the extensive possibilities for use of additional substrates for their construction creates a multivalent potential and a wide possibility for medical, diagnostic and environmental purposes. Depending on their composition and structure, dendrimers have been of interest in many fields of science, ranging from chemistry, biotechnology to biochemical applications. These compounds have found wide application from the production of catalysts for their use as antibacterial, antifungal and antiviral agents. Of particular interest are peptide dendrimers as a medium for transport of therapeutic substances: synthetic vaccines against parasites, bacteria and viruses, contrast agents used in MRI, antibodies and genetic material. This review focuses on the description of the current classes of dendrimers, the methodology for their synthesis and briefly drawbacks of their properties and their use as potential therapies against infectious diseases.

Dendronized vesicles: formation, self-organization of dendron-grafted amphiphiles and stability

Fundamental bacterial functions like quorum sensing can be targeted to replace conventional antibiotic therapies. Nanoparticles or vesicles that bind interfacially to charged biomolecules could be used to block quorum sensing pathways in bacteria. Towards this goal, dendronized vesicles (DVs) encompassing polyamidoamine dendron-grafted amphiphiles (PDAs) and dipalmitoyl-sn-glycero-3-phosphocholine lipids are investigated using the molecular dynamics simulation technique in conjunction with an explicit solvent coarse-grained force field. The key physical factors determining the stability of DVs as a function of the dendron generation and relative concentration are identified. The threshold concentration of each dendron generation that yields stable DVs is determined. Dendrons with lower generations rupture the DVs at high relative concentrations due to the electrostatic repulsions between the terminally protonated amines. Whereas, dendrons with intermediate generations demonstrate a mushroom-to-brush transition. Conformational changes in the dendrons expand the outer DV surface, resulting in instability in the DV bilayer. DVs encompassing dendrons with higher generations incur stresses on the bilayer due to their high charge density and spontaneous curvature. The self-organization of PDAs on the DV surface are examined to understand how the asymmetric stresses are minimized across the bilayer. A set of conditions are determined to be conducive for the formation of a single cluster of PDAs that decorates the DV surface like a mesh. Results from this study can potentially guide the design and synthesis of nanoparticles which target quorum sensing pathways in bacteria towards the prevention and treatment of bacterial infections. Furthermore, these nanoparticles can be used in diverse applications in biomedicine, energy or electronics that require synthetic dendronized cells or the adsorption and transport of charged species.

Nanoapproaches to Modifying Epigenetics of Epithelial Mesenchymal Transition for Treatment of Pulmonary Fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is a chronically progressive interstitial lung that affects over 3 M people worldwide and rising in incidence. With a median survival of 2-3 years, IPF is consequently associated with high morbidity, mortality, and healthcare burden. Although two antifibrotic therapies, pirfenidone and nintedanib, are approved for human use, these agents reduce the rate of decline of pulmonary function but are not curative and do not reverse established fibrosis. In this review, we discuss the prevailing epithelial injury hypothesis, wherein pathogenic airway epithelial cell-state changes known as Epithelial Mesenchymal Transition (EMT) promotes the expansion of myofibroblast populations. Myofibroblasts are principal components of extracellular matrix production that result in airspace loss and mortality. We review the epigenetic transition driving EMT, a process produced by changes in histone acetylation regulating mesenchymal gene expression programs. This mechanistic work has focused on the central role of bromodomain-containing protein 4 in mediating EMT and myofibroblast transition and initial preclinical work has provided evidence of efficacy. As nanomedicine presents a promising approach to enhancing the efficacy of such anti-IPF agents, we then focus on the state of nanomedicine formulations for inhalable delivery in the treatment of pulmonary diseases, including liposomes, polymeric nanoparticles (NPs), inorganic NPs, and exosomes. These nanoscale agents potentially provide unique properties to existing pulmonary therapeutics, including controlled release, reduced systemic toxicity, and combination delivery. NP-based approaches for pulmonary delivery thus offer substantial promise to modify epigenetic regulators of EMT and advance treatments for IPF.

Dendrimer Conjugation Enhances Tumor Penetration and Efficacy of Doxorubicin in Extracellular Matrix-Expressing 3D Lung Cancer Models

Doxorubicin (DOX) is a chemotherapeutic agent broadly used in the treatment of a range of solid tumors. In spite of its high potency, as is the case for many other chemotherapeutic drugs, there are many challenges associated with the use of DOX in clinical oncology. This is particularly true for DOX in the treatment of lung cancer, where in vitro potency is shown to be very high, but low lung distribution and off-target toxicity (particularly cardiotoxicity) restrict its use. Nanocarrier-based drug delivery systems (nanoDDS) have been shown to help alter biodistribution and alleviate off-target toxicity associated with DOX. While significant understanding exists regarding the design parameters to achieve those clinical benefits, much less is known regarding the design of nanoDDS capable of enhancing tumor penetration of DOX (and other drugs), which is another major factor leading to DOX's reduced efficacy. The purpose of this study was to design a dendrimer-based nanoDDS capable of enhancing the penetration of DOX as measured in an in vitro 3D lung tumor model and to correlate those results with its efficacy. Spheroids formed with the A549 human lung adenocarcinoma cells/murine fibroblast cell line (NIH/3T3 cell line) are shown to produce the essential components of the extracellular matrix (ECM), which is known as a physical barrier that hinders the transport of DOX. DOX was conjugated to generation 4 succinamic acid-terminated poly(amido-amine) (PAMAM) dendrimers (G4SA) through an enzyme-liable tetrapeptide (G4SA-GFLG-DOX), resulting in a nanoDDS with ∼5.5 DOX, -17 mV surface (ζ) potential, and a 10 nm hydrodynamic diameter (HD). The penetration of DOX to the core of the spheroid in terms of DOX fluorescence was determined to be 3.1-fold greater compared to free DOX, which positively correlated with enhanced efficacy as measured by the Caspase 3/7 assay. This improved penetration happens as the interactions between the G4SA-GFLG-DOX and the highly negatively charged ECM are minimized by shielding the protonatable amine of DOX upon conjugation, and the HD of the conjugate is kept smaller than the estimated mesh size of the ECM. Interestingly, the conjugate provided more specificity for DOX to tumor cells compared to fibroblasts, while free DOX is equally distributed in both tumor and fibroblasts as assessed in the coculture spheroids. Growth inhibition studies show that the released DOX maintains its activity and leads to tumor reduction to the same extent as free DOX. The results obtained here are of relevance for the design of dendrimer-based nanoDDS and for the treatment of solid tumors as they provide critical information regarding desirable surface characteristics and sizes for efficient tumor penetration.

Dendrimer-Based Drug Delivery Systems for Brain Targeting

Human neuroscience has made remarkable progress in understanding basic aspects of functional organization; it is a renowned fact that the blood-brain barrier (BBB) impedes the permeation and access of most drugs to central nervous system (CNS) and that many neurological diseases remain undertreated. Therefore, a number of nanocarriers have been designed over the past few decades to deliver drugs to the brain. Among these nanomaterials, dendrimers have procured an enormous attention from scholars because of their nanoscale uniform size, ease of multi-functionalization, and available internal cavities. As hyper-branched 3D macromolecules, dendrimers can be maneuvered to transport diverse therapeutic agents, incorporating small molecules, peptides, and genes; diminishing their cytotoxicity; and improving their efficacy. Herein, the present review will give exhaustive details of extensive researches in the field of dendrimer-based vehicles to deliver drugs through the BBB in a secure and effectual manner. It is also a souvenir in commemorating Donald A. Tomalia on his 80th birthday.

Hydrogels composed of hyaluronic acid and dendritic ELPs: hierarchical structure and physical properties

Hydrogels that mimic the native extracellular matrix were prepared from hyaluronic acid (HA) and amine-terminated dendritic elastin-like peptides (denELPs) of generations 1, 2, and 3 (G1, 2, and 3) as crosslinking units. The physical properties of the hydrogels were investigated by rheology, scanning electron microscopy, swelling tests, small-angle X-ray scattering (SAXS), and model drug loading and release assays. Hydrogel properties depended on the generation number of the denELP, which contained structural segments based on the repeating GLPGL pentamer. Hydrogels with higher generation denELPs (G2 and 3) showed similar properties, but those prepared from G1 denELPs were rheologically weaker, had a larger mesh size, absorbed less model drug, and released the drug more quickly. Interestingly, most of the HA_denELP hydrogels studied here remained transparent upon gelation, but after lyophilization and addition of water retained opaque, "solid-like" regions for up to 4 d during rehydration. This rehydration process was carefully evaluated through time-course SAXS studies, and the phenomenon was attributed to the formation of pre-coacervates in the gel-forming step, which slowly swelled in water during rehydration. These findings provide important insights into the behavior of ELP-based hydrogels, in which physical crosslinking of the ELP domains can be controlled to tune mechanical properties, highlighting the potential of HA_denELP hydrogels as biomaterials.

Efficient siRNA delivery and gene silencing using a lipopolypeptide hybrid vector mediated by a caveolae-mediated and temperature-dependent endocytic pathway

Background

We developed a non-viral vector, a combination of HIV-1 Tat peptide modified with histidine and cysteine (mTat) and polyethylenimine, jetPEI (PEI), displaying the high efficiency of plasmid DNA transfection with little toxicity. Since the highest efficiency of INTERFERin (INT), a cationic amphiphilic lipid-based reagent, for small interfering RNA (siRNA) transfection among six commercial reagents was shown, we hypothesized that combining mTat/PEI with INT would improve transfection efficiency of siRNA delivery. To elucidate the efficacy of the hybrid vector for siRNA silencing, β-actin expression was measured after siRNA β-actin was transfected with mTat/PEI/INT or other vectors in HSC-3 human oral squamous carcinoma cells.

Results

mTat/PEI/INT/siRNA produced significant improvement in transfection efficiency with little cytotoxicity compared to other vectors and achieved ≈ 100% knockdown of β-actin expression compared to non-treated cells. The electric charge of mTat/PEI/INT/siRNA was significantly higher than INT/siRNA. The particle size of mTat/PEI/INT/siRNA was significantly smaller than INT/siRNA. Filipin III and β-cyclodextrin, an inhibitor of caveolae-mediated endocytosis, significantly inhibited mTat/PEI/INT/siRNA transfection, while chlorpromazine, an inhibitor of clathrin-mediated endocytosis, did not inhibit mTat/PEI/INT/siRNA transfection. Furthermore, the transfection efficiency of mTat/PEI/INT at 4 °C was significantly lower than 37 °C.

Conclusions

These findings demonstrated the feasibility of using mTat/PEI/INT as a potentially attractive non-viral vector for siRNA delivery.

Size-dependent uptake of electrically neutral amphipathic polymeric nanoparticles by cell-sized liposomes and an insight into their internalization mechanism in living cells

The size-dependent uptake of amphipathic uncharged-nanoparticles in cell-sized liposomes is emerging as a new insight into their internalization mechanism in living cells.

Gold nanoconjugates reinforce the potency of conjugated cisplatin and doxorubicin

Osteosarcoma or osteogenic sarcoma is the most common and prevalent cancerous tumor of bone and occurs especially in children and teens. Recent treatment strategy includes a combination of both chemotherapy and surgeries. Although, the use of single drug-based chemotherapy treatment remains unsatisfactory. Therefore, combinatorial therapy has emerged as a potential strategy for treatment with limited side- effects. Here, we evaluated the combinatorial anticancerous effect of cisplatin (CIS) and doxorubicin (DOX) bioconjugated bromelain encapsulated gold nanoparticles (B-AuNPs conjugated CIS and DOX) in the treatment of osteosarcoma. The synthesized B-AuNPs conjugated CIS and DOX were characterized by various characterization techniques like UV-vis spectroscopy, TEM, DLS and zeta potential to ensure the synthesis, size, shape, size distribution and stability. Drug loading efficiency bioconjugation of CIS and DOX was ensured by UV-vis spectroscopy. Bioconjugation of CIS and DOX was further confirmed using UV-vis spectroscopy, TEM, DLS, Zeta potential and FT-IR analysis. The combinatorial effect of CIS and DOX in B-AuNPs conjugated CIS and DOX showed highly improved potency against MG-63 and Saos-2 cells at a very low concentration where primary osteoblasts didn't show any cytotoxic effect. The apoptotic effect of B-AuNPs conjugated CIS and DOX on osteosarcoma and primary osteoblasts cells were analyzed by increased permeability of the cell membrane, condensed chromatin and deep blue fluorescent condensed nucleus. The results clearly showed that B-AuNPs conjugated CIS and DOX significantly improved the potency of both the chemotherapeutic drugs by delivering them specifically into the nucleus of cancer cells through caveolae-dependent endocytosis. Thus, the greater inhibitory effect of combinatorial drugs (B-AuNPs conjugated CIS and DOX) over single drug based chemotherapy would be of great advantage during osteosarcoma treatment.

Nanoparticle-macrophage interactions: A balance between clearance and cell-specific targeting

The surface properties of nanoparticles (NPs) are a major factor that influences how these nanomaterials interact with biological systems. Interactions between NPs and macrophages of the reticuloendothelial system (RES) can reduce the efficacy of NP diagnostics and therapeutics. Traditionally, to limit NP clearance by the RES system, the NP surface is neutralized with molecules like poly(ethylene glycol) (PEG) which are known to resist protein adsorption and RES clearance. Unfortunately, PEG modification is not without drawbacks including difficulties with the synthesis and associations with immune reactions. To overcome some of these obstacles, we neutralized the NP surface by acetylation and compared this modification to PEGylation for RES clearance and tumor-specific targeting. We found that acetylation was comparable to PEGylation in reducing RES clearance. Additionally, we found that dendrimer acetylation did not impact folic acid (FA)-mediated targeting of tumor cells whereas PEG surface modification reduced the targeting ability of the NP. These results clarify the impact of different NP surface modifications on RES clearance and cell-specific targeting and provide insights into the design of more effective NPs.

Nonviral cancer gene therapy: Delivery cascade and vector nanoproperty integration

Gene therapy represents a promising cancer treatment featuring high efficacy and limited side effects, but it is stymied by a lack of safe and efficient gene-delivery vectors. Cationic polymers and lipid-based nonviral gene vectors have many advantages and have been extensively explored for cancer gene delivery, but their low gene-expression efficiencies relative to viral vectors limit their clinical translations. Great efforts have thus been devoted to developing new carrier materials and fabricating functional vectors aimed at improving gene expression, but the overall efficiencies are still more or less at the same level. This review analyzes the cancer gene-delivery cascade and the barriers, the needed nanoproperties and the current strategies for overcoming these barriers, and outlines PEGylation, surface-charge, size, and stability dilemmas in vector nanoproperties to efficiently accomplish the cancer gene-delivery cascade. Stability, surface, and size transitions (3S Transitions) are proposed to resolve those dilemmas and strategies to realize these transitions are comprehensively summarized. The review concludes with a discussion of the future research directions to design high-performance nonviral gene vectors.

Nano-biomimetic carriers are implicated in mechanistic evaluation of intracellular gene delivery

Several tissue specific non-viral carriers have been developed for gene delivery purposes. However, the inability to escape endosomes, undermines the efficacy of these carriers. Researchers inspired by HIV and influenza virus, have randomly used Gp41 and H5WYG fusogenic peptides in several gene delivery systems without any rational preference. Here for the first time, we have genetically engineered two Nano-biomimetic carriers composed of either HWYG (HNH) or Gp41 (GNH) that precisely provide identical conditions for the study and evaluation of these fusogenic peptides. The luciferase assay demonstrated a two-fold higher transfection efficiency of HNH compared to GNH. These nanocarriers also displayed equivalent properties in terms of DNA binding ability and DNA protection against serum nucleases and formed similar nanoparticles in terms of surface charge and size. Interestingly, hemolysis and cellular analysis demonstrated both of nanoparticles internalized into cells in similar rate and escaped from endosome with different efficiency. Furthermore, the structural analysis revealed the mechanisms responsible for the superior endosomal escaping capability of H5WYG. In conclusion, this study describes the rationale for using H5WYG peptide to deliver nucleic acids and suggests that using nano-biomimetic carriers to screen different endosomal release peptides, improves gene delivery significantly.

Role of Cell Membrane-Vector Interactions in Successful Gene Delivery

Cationic polymers have been investigated as nonviral vectors for gene delivery due to their favorable safety profile when compared to viral vectors. However, nonviral vectors are limited by poor efficacy in inducing gene expression. The physicochemical properties of cationic polymers enabling successful gene expression have been investigated in order to improve expression efficiency and safety. Studies over the past several years have focused on five possible rate-limiting processes to explain the differences in gene expression: (1) endosomal release, (2) transport within specific intracellular pathways, (3) protection of DNA from nucleases, (4) transport into the nucleus, and (5) DNA release from vectors. However, determining the relative importance of these processes and the vector properties necessary for optimization remain a challenge to the field. In this Account, we describe over a decade of studies focused on understanding the interaction of cationic polymer and cationic polymer/oligonucleotide (polyplex) interactions with model lipid membranes, cell membranes, and cells in culture. In particular, we have been interested in how the interaction between cationic polymers and the membrane influences the intracellular transport of intact DNA to the nucleus. Recent advances in microfluidic patch clamp techniques enabled us to quantify polyplex cell membrane interactions at the cellular level with precise control over material concentrations and exposure times. In attempting to relate these findings to subsequent intracellular transport of DNA and expression of protein, we needed to develop an approach that could distinguish DNA that was intact and potentially functional for gene expression from the much larger pool of degraded, nonfunctional DNA within the cell. We addressed this need by developing a FRET oligonucleotide molecular beacon (OMB) to monitor intact DNA transport. The research highlighted in this Account builds to the conclusion that polyplex transported DNA is released from endosomes by free cationic polymer intercalated into the endosomal membrane. This cationic polymer initially interacts with the cell plasma membrane and appears to reach the endosome by lipid cycling mechanisms. The fraction of cells displaying release of intact DNA from endosomes quantitatively predicts the fraction of cells displaying gene expression for both linear poly(ethylenimine) (L-PEI; an effective vector) and generation five poly(amidoamine) dendrimer (G5 PAMAM; an ineffective vector). Moreover, intact OMB delivered with G5 PAMAM, which normally is confined to endosomes, was released by the subsequent addition of L-PEI with a corresponding 10-fold increase in transgene expression. These observations are consistent with experiments demonstrating that cationic polymer/membrane partition coefficients, not polyplex/membrane partition coefficients, predict successful gene expression. Interestingly, a similar partitioning of cationic polymers into the mitochondrial membranes has been proposed to explain the cytotoxicity of these materials. Thus, the proposed model indicates the same physicochemical property (partitioning into lipid bilayers) is linked to release from endosomes, giving protein expression, and to cytotoxicity.

Eradication of Acute Myeloid Leukemia with FLT3 Ligand-Targeted miR-150 Nanoparticles

Acute myeloid leukemia (AML) is a common and fatal form of hematopoietic malignancy. Overexpression and/or mutations of FLT3 have been shown to occur in the majority of cases of AML. Our analysis of a large-scale AML patient cohort (N = 562) indicates that FLT3 is particularly highly expressed in some subtypes of AML, such as AML with t(11q23)/MLL-rearrangements or FLT3-ITD. Such AML subtypes are known to be associated with unfavorable prognosis. To treat FLT3-overexpressing AML, we developed a novel targeted nanoparticle system: FLT3 ligand (FLT3L)-conjugated G7 poly(amidoamine) (PAMAM) nanosized dendriplex encapsulating miR-150, a pivotal tumor suppressor and negative regulator of FLT3 We show that the FLT3L-guided miR-150 nanoparticles selectively and efficiently target FLT3-overexpressing AML cells and significantly inhibit viability/growth and promote apoptosis of the AML cells. Our proof-of-concept animal model studies demonstrate that the FLT3L-guided miR-150 nanoparticles tend to concentrate in bone marrow, and significantly inhibit progression of FLT3-overexpressing AML in vivo, while exhibiting no obvious side effects on normal hematopoiesis. Collectively, we have developed a novel targeted therapeutic strategy, using FLT3L-guided miR-150-based nanoparticles, to treat FLT3-overexpressing AML with high efficacy and minimal side effects. Cancer Res; 76(15); 4470-80. ©2016 AACR.

How do the full-generation poly(amido)amine (PAMAM) dendrimers activate blood platelets? Activation of circulating platelets and formation of "fibrinogen aggregates" in the presence of polycations

Direct use of poly(amido)amine (PAMAM) dendrimers as drugs may be limited, due to uncertain (cyto)toxicity. Peripheral blood components, which constitute the first line of a contact with administered pharmaceuticals, may become vastly affected by PAMAM dendrimers. The aim of this study was to explore how PAMAMs' polycationicity might affect blood platelet activation and reactivity, and thus trigger various haemostatic events. We monitored blood platelet reactivity in rats with experimental diabetes upon a long-term administration of the unmodified PAMAM dendrimers. In parallel, the effects on blood flow in a systemic circulation was recorded intravitally in mice administered with PAMAM G2, G3 or G4. Compounding was the in vitro approach to monitor the impact of PAMAM dendrimers on blood platelet activation and reactivity and on selected haemostatic and protein conformation parameters. We demonstrated the activating effects of polycations on blood platelets. Some diversity of the revealed outcomes considerably depended on the used approach and the particular technique employed to monitor blood platelet function. We discovered undesirable impact of plain PAMAM dendrimers on primary haemostasis and their prothrombotic influence. We emphasize the need of a more profound verifying of all the promising findings collected for PAMAMs with the use of well-designed in vivo preclinical studies.

Recent advances in targeted drug delivery approaches using dendritic polymers

Since they were first synthesized over 30 years ago, dendrimers have seen rapid translation into various biomedical applications. A number of reports have not only demonstrated their clinical utility, but also revealed novel design approaches and strategies based on the elucidation of underlying mechanisms governing their biological interactions. This review focuses on presenting the latest advances in dendrimer design, discussing the current mechanistic understandings, and highlighting recent developments and targeted approaches using dendrimers in drug/gene delivery.

Multifunctional Poly(methyl vinyl ether-co-maleic anhydride)-graft-hydroxypropyl-β-cyclodextrin Amphiphilic Copolymer as an Oral High-Performance Delivery Carrier of Tacrolimus

In order to improve oral bioavailability of tacrolimus (FK506), a novel poly(methyl vinyl ether-co-maleic anhydride)-graft-hydroxypropyl-β-cyclodextrin amphiphilic copolymer (CD-PVM/MA) is developed, combining the bioadhesiveness of PVM/MA, P-glycoprotein (P-gp), and cytochrome P450-inhibitory effect of CD into one. The FK506-loaded nanoparticles (CD-PVM/MA-NPs) were obtained by solvent evaporation method. The physiochemical properties and intestinal absorption mechanism of FK506-loaded CD-PVM/MA-NPs were characterized, and the pharmacokinetic behavior was investigated in rats. FK506-loaded CD-PVM/MA-NPs exhibited nanometer-sized particles of 273.7 nm, with encapsulation efficiency as high as 73.3%. FK506-loaded CD-PVM/MA-NPs maintained structural stability in the simulated gastric fluid, and about 80% FK506 was released within 24 h in the simulated intestinal fluid. The permeability of FK506 was improved dramatically by CD-PVM/MA-NPs compared to its solution, probably due to the synergistic inhibition effect of P-gp and cytochrome P450 3A (CYP3A). The intestinal biodistribution of fluorescence-labeled CD-PVM/MA-NPs confirmed its good bioadhesion to the rat intestinal wall. Two endocytosis pathways, clathrin- and caveolae-mediated endocytosis, were involved in the cellular uptake of CD-PVM/MA-NPs. The important role of lymphatic transport in nanoparticles' access to the systemic circulation, about half of the contribution to oral bioavailability, was observed in mesenteric lymph duct ligated rats. The AUC0-24 of FK506 loaded in nanoparticles was enhanced up to 20-fold compared to FK506 solutions after oral administration. The present study suggested that the novel multifunctional CD-PVM/MA is a promising efficient oral delivery carrier for FK506, due to its ability in solubilization, inhibitory effects on both P-gp and CYP 3A, high bioadhesion, and sustained release capability.

Quantification of cytosolic plasmid DNA degradation using high-throughput sequencing: implications for gene delivery

BACKGROUND

Although cytosolic DNA degradation plays an important role in decreasing transgene expression, the plasmid degradation pattern remains largely unexplored.

METHODS

Illumina dye sequencing was employed to provide degradation site information for S1 and cytosolic nucleases. S1 nuclease provided a positive control for a comparison between the agarose gel method and sequencing approaches.

RESULTS

The poly(A) region between the β-lactamase gene and the cytomegalovirus (CMV) promoter was identified as the most likely cut site for polyplex-treated cytosol. The second most likely site, at the 5' end of the β-lactamase gene, was identified by gel electrophoresis and sequencing. Additional sites were detected in the OriC region, the SV40/poly(A) region, the luciferase gene and the CMV promoter. Sequence analysis of plasmid treated with cytosol from control cells showed the greatest cut activity in the OriC region, the β-lactamase gene and the poly(A) region following the luciferase gene. Additional regions of cut activity include the SV40 promoter and the β-lactamase poly(A) termination sequence. Both cytosolic nucleases and the S1 nuclease showed substantial activity at the bacterial origin of replication (OriC).

CONCLUSIONS

High-throughput plasmid sequencing revealed regions of the luciferase plasmid DNA sequence that are sensitive to cytosolic nuclease degradation. This provides new targets for improving plasmid and/or polymer design to optimize the likelihood of protein expression.

Elucidation of the interaction mechanism with liposomes of gH625-peptide functionalized dendrimers

We have demonstrated that amide-based dendrimers functionalized with the membrane-interacting peptide gH625 derived from the herpes simplex virus type 1 (HSV-1) envelope glycoprotein H enter cells mainly through a non-active translocation mechanism. Herein, we investigate the interaction between the peptide-functionalized dendrimer and liposomes composed of PC/Chol using fluorescence spectroscopy, isothermal titration calorimetry, and surface plasmon resonance to get insights into the mechanism of internalization. The affinity for the membrane bilayer is very high and the interaction between the peptide-dendrimer and liposomes took place without evidence of pore formation. These results suggest that the presented peptidodendrimeric scaffold may be a promising material for efficient drug delivery.

Poly(ethylene glycol) Corona Chain Length Controls End-Group-Dependent Cell Interactions of Dendron Micelles

To systematically investigate the relationship among surface charge, PEG chain length, and nano-bio interactions of dendron-based micelles (DMs), a series of PEGylated DMs with various end groups (-NH2, -Ac, and -COOH) and PEG chain lengths (600 and 2000 g/mol) are prepared and tested in vitro. The DMs with longer PEG chains (DM2K) do not interact with cells despite their positively charged surfaces. In sharp contrast, the DMs with shorter PEG chains (DM600) exhibit charge-dependent cellular interactions, as observed in both in vitro and molecular dynamics (MD) simulation results. Furthermore, all DMs with different charges display enhanced stability for hydrophobic dye encapsulation compared to conventional linear-block copolymer-based micelles, by allowing only a minimal leakage of the dye in vitro. Our results demonstrate the critical roles of the PEG chain length and polymeric architecture on the terminal charge effect and the stability of micelles, which provides an important design cue for polymeric micelles.

Epithelial-mesenchymal transition enhances nanoscale actin filament dynamics of ovarian cancer cells

Epithelial ovarian cancer cells enhance their ability to migrate and invade through the epithelial-mesenchymal transition (EMT), resulting in cell seeding and metastasis in the peritoneal cavity and onto adjacent organ surfaces. It has been speculated that cytoskeletal dynamics, such as those of the actin filament, play a role in enhanced cell motility; however, direct evidence has not been provided. Herein, we have directly measured pico- to nanonewton-scale mechanical forces generated by actin dynamics of ovarian cancer SKOV-3 cells upon binding of integrin α5β1 to fibronectin (FN), i.e., formation of a focal adhesion, using real-time atomic force microscopy (AFM) in a force spectroscopy mode. The dendrimer surface chemistry through which FN was immobilized on the AFM probe surfaces further enhanced the sensitivity of the force measurement by 1.5-fold. Post-EMT SKOV-3 cells, induced by transforming growth factor-β, generated larger focal adhesion mechanical forces (17 and 41 nN before and after EMT, respectively) with migration faster than that of pre-EMT cells. Importantly, 22% of the forces transmitted through a single FN-integrin α5β1 pair from post-EMT cells were shown to be sufficient to rupture the binding between FN and integrin α5β1 on the cells, a result which is not observed on pre-EMT cells. This implies that post-EMT cells, by generating forces strong enough to break the FN-integrin binding, migrate and metastasize beyond the ovary, whereas pre-EMT cancer cells are confined in the ovary without such force generation. These results demonstrate quantitative and direct evidence for the role of actin dynamics in the enhanced motility of post-EMT ovarian cancer cells, providing a fundamental insight into the mechanism of ovarian cancer metastasis.

Polyplex-induced cytosolic nuclease activation leads to differential transgene expression

Cytosolic nucleases have been proposed to play an important role in limiting the effectiveness of polyplex-based gene delivery agents. In order to explore the effect of cell membrane disruption on nuclease activation, nuclease activity upon polyplex uptake and localization, and nuclease activity upon gene expression, we employed an oligonucleotide molecular beacon (MB). The MB was incorporated as an integral part of the polymer/DNA polyplex, and two-color flow cytometry experiments were performed to explore the relationship of MB cleavage with propidium iodide (PI) uptake, protein expression, and polyplex uptake. In addition, confocal fluorescence microcopy was performed to examine both polyplex and cleaved MB localization. The impact of cell membrane disruption was also probed using whole-cell patch clamp measurement of the plasma membrane's electrical conductance. Differential activation of cytosolic nuclease was observed with substantial activity for B-PEI and G5 PAMAM dendrimer (G5), less cleavage for jetPEI, and little activity for L-PEI. jetPEI and L-PEI exhibited substantially greater transgene expression, consistent with the lower amounts of MB oligonucleotide cleavage observed. Cytosolic nuclease activity, although dependent on the choice of polymer employed, was not related to the degree of cell plasma membrane disruption that occurred as measured by PI uptake or whole-cell patch clamp.

Theoretical and computational studies of dendrimers as delivery vectors

It is a great challenge for nanomedicine to develop novel dendrimers with maximum therapeutic potential and minimum side-effects for drug and gene delivery. As delivery vectors, dendrimers must overcome lots of barriers before delivering the bio-agents to the target in the cell. Extensive experimental investigations have been carried out to elucidate the physical and chemical properties of dendrimers and explore their behaviors when interacting with biomolecules, such as gene materials, proteins, and lipid membranes. As a supplement of the experimental techniques, it has been proved that computer simulations could facilitate the progress in understanding the delivery process of bioactive molecules. The structures of dendrimers in dilute solutions have been intensively investigated by monomer-resolved simulations, coarse-grained simulations, and atom-resolved simulations. Atomistic simulations have manifested that the hydrophobic interactions, hydrogen-bond interactions, and electrostatic attraction play critical roles in the formation of dendrimer-drug complexes. Multiscale simulations and statistical field theories have uncovered some physical mechanisms involved in the dendrimer-based gene delivery systems. This review will focus on the current status and perspective of theoretical and computational contributions in this field in recent years. (275 references).

Positively Charged Dendron Micelles Display Negligible Cellular Interactions

PEGylated dendron-based copolymers (PDC) with different end-group functionalities (-NH(2), -COOH, and -Ac) were synthesized and self-assembled into dendron micelles to investigate the effect of terminal surface charges on size, morphology, and cellular interactions of the micelles. All of the dendron micelles exhibited similar sizes (20-60 nm) and spherical morphologies, as measured using dynamic light scattering and transmission electron microscopy, respectively. The cellular interactions of dendron micelles were evaluated using confocal microscopy and flow cytometry. Surprisingly, although amine-terminated dendrimers are known to strongly interact with cells non-specifically, all of the surface-modified dendron micelles exhibited charge-independent low-levels of cellular interaction. The unexpected results, particularly from the amine-terminated dendron micelles, could be attributed to: i) minimal end-group effects, as each PDC has an approximately 10-fold lower charge-number-to-molecular-weight ratio compared to the dendrimer; and ii) intra- and intermolecular hydrogen bonding between positively charged terminal groups with poly(ethylene glycol) (PEG) backbones, which leads to the sequestration of the charges, as demonstrated by atomistic molecular dynamics simulations. With the narrow size distribution, uniform morphologies, and low levels of non-specific cellular interactions, the dendron micelles offer a promising drug delivery platform.

In vitro evaluation of dendrimer-polymer hybrid nanoparticles on their controlled cellular targeting kinetics

Although polymeric nanoparticles (NPs) and dendrimers represent some of the most promising cancer-targeting nanocarriers, each of them has drawbacks such as limited tissue diffusivity/tumor penetration and rapid in vivo elimination, respectively. To address these issues, we have designed a multiscale hybrid NP system (nanohybrid) that combines folate (FA)-targeted poly(amidoamine) dendrimers and poly(ethylene glycol)-b-poly(d,l-lactide) NPs. The nanohybrids (∼100 nm NPs encapsulating ∼5 nm targeted dendrimers) were extensively characterized through a series of in vitro experiments that validate the design rationale of the system, in an aim to simulate their in vivo behaviors. Cellular uptake studies using FA receptor (FR)-overexpressing KB cells (KB FR(+)) revealed that the nanohybrids maintained high FR selectivity resembling the selectivity of free dendrimers, while displaying temporally controlled cellular interactions due to the presence of the polymeric NP shells. The cellular interactions of the nanohybrids were clathrin-dependent (characteristic of polymer NPs) at early incubation time points (4 h), which were partially converted to caveolae-mediated internalization (characteristic of FA-targeted dendrimers) at longer incubation hours (24 h). Simulated penetration assays using multicellular tumor spheroids of KB FR(+) cells also revealed that the targeted dendrimers penetrated deep into the spheroids upon their release from the nanohybrids, whereas the NP shell did not. Additionally, methotrexate-containing systems showed the selective, controlled cytotoxicity kinetics of the nanohybrids. These results all demonstrate that our nanohybrids successfully integrate the unique characteristics of dendrimers (effective targeting and penetration) and polymeric NPs (controlled release and suitable size for long circulation) in a kinetically controlled manner.

Dendritic nanoparticles: the next generation of nanocarriers?

Dendritic polymers have attracted a great deal of scientific interest due to their well-defined unique structure and capability to be multifunctionalized. Here we present a comprehensive overview of various dendrimer-based nanomaterials that are currently being investigated for therapeutic delivery and diagnostic applications. Through a critical review of the old and new dendritic designs, we highlight the advantages and disadvantages of these systems and their structure-biological property relationships. This article also focuses on the major challenges facing the clinical translation of these nanomaterials and how these challenges are being (or should be) addressed, which will greatly benefit the overall progress of dendritic materials for theranostics.

Dendrimer-Fullerenol Soft-Condensed Nanoassembly

Nanoscale assembly is an area of research that has vast implications for molecular design, sensing, nanofabrication, supramolecular chemistry, catalysis, and environmental remediation. Here we show that poly(amidoamine) (PAMAM) dendrimers of both generations 1 (G1) and 4 (G4) can host 1 fullerenol per 2 dendrimer primary amines as evidenced by isothermal titration calorimetry, dynamic light scattering and spectrofluorometry. Thermodynamically, the interactions were similarly spontaneous between both generations of dendrimers and fullerenols, however, G4 formed stronger complexes with fullerenols resulting from their higher surface charge density and more internal voids, as demonstrated by spectrofluorometry. In addition to hydrogen bonding that existed between the dendrimer primary amines and the fullerenol oxygens, hydrophobic and electrostatic interactions also contributed to complex formation and dynamics. Such hybrid of soft and condensed nanoassembly may have implications for environmental remediation of discharged nanomaterials and entail new applications in drug delivery.

Effect of size, surface charge, and hydrophobicity of poly(amidoamine) dendrimers on their skin penetration

The barrier functions of the stratum corneum and the epidermal layers present a tremendous challenge in achieving effective transdermal delivery of drug molecules. Although a few reports have shown that poly(amidoamine) (PAMAM) dendrimers are effective skin-penetration enhancers, little is known regarding the fundamental mechanisms behind the dendrimer-skin interactions. In this Article, we have performed a systematic study to better elucidate how dendrimers interact with skin layers depending on their size and surface groups. Franz diffusion cells and confocal microscopy were employed to observe dendrimer interactions with full-thickness porcine skin samples. We have found that smaller PAMAM dendrimers (generation 2 (G2)) penetrate the skin layers more efficiently than the larger ones (G4). We have also found that G2 PAMAM dendrimers that are surface-modified by either acetylation or carboxylation exhibit increased skin permeation and likely diffuse through an extracellular pathway. In contrast, amine-terminated dendrimers show enhanced cell internalization and skin retention but reduced skin permeation. In addition, conjugation of oleic acid to G2 dendrimers increases their 1-octanol/PBS partition coefficient, resulting in increased skin absorption and retention. Here we report that size, surface charge, and hydrophobicity directly dictate the permeation route and efficiency of dendrimer translocation across the skin layers, providing a design guideline for engineering PAMAM dendrimers as a potential transdermal delivery vector.

Temporal control over cellular targeting through hybridization of folate-targeted dendrimers and PEG-PLA nanoparticles

Polymeric nanoparticles (NPs) and dendrimers are two major classes of nanomaterials that have demonstrated great potential for targeted drug delivery. However, their targeting efficacy has not yet met clinical needs, largely because of a lack of control over their targeting kinetics, which often results in rapid clearance and off-target drug delivery. To address this issue, we have designed a novel hybrid NP (nanohybrid) platform that allows targeting kinetics to be effectively controlled through hybridization of targeted dendrimers with polymeric NPs. Folate (FA)-targeted generation 4 poly(amidoamine) dendrimers were encapsulated into poly(ethylene glycol)-b-poly(D,L-lactide) (PEG-PLA) NPs using a double emulsion method, forming nanohybrids with a uniform size (~100 nm in diameter) at high encapsulation efficiencies (69-85%). Targeted dendrimers encapsulated within the NPs selectively interacted with FA receptor (FR)-overexpressing KB cells upon release in a temporally controlled manner. The targeting kinetics of the nanohybrids were modulated using three different molecular weights (MW) of the PLA block (23, 30, and 45 kDa). The release rates of the dendrimers from the nanohybrids were inversely proportional to the MW of the PLA block, which dictated their binding and internalization kinetics with KB cells. Our results provide evidence that selective cellular interactions can be kinetically controlled by the nanohybrid design, which can potentially enhance targeting efficacy of nanocarriers.

Discovery of cationic polymers for non-viral gene delivery using combinatorial approaches

Gene therapy is an attractive treatment option for diseases of genetic origin, including several cancers and cardiovascular diseases. While viruses are effective vectors for delivering exogenous genes to cells, concerns related to insertional mutagenesis, immunogenicity, lack of tropism, decay and high production costs necessitate the discovery of non-viral methods. Significant efforts have been focused on cationic polymers as non-viral alternatives for gene delivery. Recent studies have employed combinatorial syntheses and parallel screening methods for enhancing the efficacy of gene delivery, biocompatibility of the delivery vehicle, and overcoming cellular level barriers as they relate to polymer-mediated transgene uptake, transport, transcription, and expression. This review summarizes and discusses recent advances in combinatorial syntheses and parallel screening of cationic polymer libraries for the discovery of efficient and safe gene delivery systems.

Intrinsically fluorescent PAMAM dendrimer as gene carrier and nanoprobe for nucleic acids delivery: bioimaging and transfection study

This study successfully evaluated gene delivery and transfection toward rat C6 glioma cell lines mediated by intrinsic blue fluorescent poly(amido amine) (PAMAM) dendrimer. We used three antisense oligonucleotides, (AS-ODN) p75, NGF1, and NGF2 for knocking down specific protein expressions. The three oligonucleotides were electrostatically associated with the photoluminescent amino-terminated PAMAM dendrimer to yield fluorescent complexes at various nitrogen-to-phosphorus (N/P) ratios. Compared with pristine PAMAM dendrimer and hyperbranched polyethylenimine (PEI), the fluorescent PAMAM dendrimer revealed lower in vitro cytotoxicity toward C6 cells, allowing us to transfect the cells with the AS-ODN complexes under a higher N/P ratio. Due to the intrinsic fluorescence, cellular uptake behavior could be directly analyzed by fluorescence microscopy and flow cytometry, without additional fluorescence labeling. As expected, the result clearly suggested that the uptake efficiency increased as the N/P value increased. Furthermore, the quantified data obtained from flow cytometry indicated relatively higher uptake efficiency for the p75 complex, which is mainly due to different association patterns between the fluorescent dendrimer and AS-ODNs. At N/P = 20, atomic force microscopic analysis confirmed that the p75 complex formed well-condensed, spherical particles with dimensions less than 200 nm, but that NGF2 AS-ODN associated poorly with the dendrimer. Finally, Western blot analysis indicated that these complexes were capable of knocking down the specific protein expression to a certain level, being comparable to the hyperbranched PEI-mediated gene transfection. Our preliminary results clearly indicated that intrinsic fluorescent PAMAM dendrimers show promise as gene vehicles that can achieve delivery, transfection, and bioimaging at the same time.

Integrin targeted delivery of gene therapeutics

Integrins have become key targets for molecular imaging and for selective delivery of anti-cancer agents. Here we review recent work concerning the targeted delivery of antisense and siRNA oligonucleotides via integrins. A variety of approaches have been used to link oligonucleotides to ligands capable of binding integrins with high specificity and affinity. This includes direct chemical conjugation, incorporating oligonucleotides into lipoplexes, and use of various polymeric nanocarriers including dendrimers. The ligand-oligonucleotide conjugate or complex associates selectively with the integrin, followed by internalization into endosomes and trafficking through subcellular compartments. Escape of antisense or siRNA from the endosome to the cytosol and nucleus may come about through endogenous trafficking mechanisms, or because of membrane disrupting capabilities built into the conjugate or complex. Thus a variety of useful strategies are available for using integrins to enhance the pharmacological efficacy of therapeutic oligonucleotides.

Kinetically controlled cellular interactions of polymer-polymer and polymer-liposome nanohybrid systems

Although bioactive polymers such as cationic polymers have demonstrated potential as drug carriers and nonviral gene delivery vectors, high toxicity and uncontrolled, instantaneous cellular interactions of those vectors have hindered the successful implementation In Vivo. Fine control over the cellular interactions of a potential drug/gene delivery vector would be thus desirable. Herein, we have designed nanohybrid systems (100-150 nm in diameter) that combine the polycations with protective outer layers consisting of biodegradable polymeric nanoparticles (NPs) or liposomes. A commonly used polycation polyethylenimine (PEI) was employed after conjugation with rhodamine (RITC). The PEI-RITC conjugates were then encapsulated into (i) polymeric NPs made of either poly(lactide-co-glycolide) (PLGA) or poly(ethylene glycol)-b-poly(lactide-co-glycolide) (PEG-PLGA); or (ii) PEGylated liposomes, resulting in three nanohybrid systems. Through the nanohybridization, both cellular uptake and cytotoxicity of the nanohybrids were kinetically controlled. The cytotoxicity assay using MCF-7 cells revealed that liposome-based nanohybrids exhibited the least toxicity, followed by PEG-PLGA- and PLGA-based NPs after 24 h incubation. The different kinetics of cellular uptake was also observed, the liposome-based systems being the fastest and PLGA-based systems being the slowest. The results present a potential delivery platform with enhanced control over its biological interaction kinetics and passive targeting capability through size control.