Synthetic Anticancer Gene Medicine Exploits Intrinsic Antitumor Activity of Cationic Vector to Cure Established Tumors

Targeted Anticancer Agent with Original Mode of Action Prepared by Supramolecular Assembly of Antibody Oligonucleotide Conjugates and Cationic Nanoparticles

Despite their clinical success, Antibody-Drug Conjugates (ADCs) are still limited to the delivery of a handful of cytotoxic small-molecule payloads. Adaptation of this successful format to the delivery of alternative types of cytotoxic payloads is of high interest in the search for novel anticancer treatments. Herein, we considered that the inherent toxicity of cationic nanoparticles (cNP), which limits their use as oligonucleotide delivery systems, could be turned into an opportunity to access a new family of toxic payloads. We complexed anti-HER2 antibody-oligonucleotide conjugates (AOC) with cytotoxic cationic polydiacetylenic micelles to obtain Antibody-Toxic-Nanoparticles Conjugates (ATNPs) and studied their physicochemical properties, as well as their bioactivity in both in vitro and in vivo HER2 models. After optimising their AOC/cNP ratio, the small (73 nm) HER2-targeting ATNPs were found to selectively kill antigen-positive SKBR-2 cells over antigen-negative MDA-MB-231 cells in serum-containing medium. Further in vivo anti-cancer activity was demonstrated in an SKBR-3 tumour xenograft model in BALB/c mice in which stable 60% tumour regression could be observed just after two injections of 45 pmol of ATNP. These results open interesting prospects in the use of such cationic nanoparticles as payloads for ADC-like strategies.

Evaluation of the Cytotoxicity of Cationic Polymers on Glioblastoma Cancer Stem Cells

Cationic polymers such as polyethylenimine (PEI) have found a pervasive place in laboratories across the world as gene delivery agents. However, their applications are not limited to this role, having found a place as delivery agents for drugs, in complexes known as polymer-drug conjugates (PDCs). Yet a potentially underexplored domain of research is in their inherent potential as anti-cancer therapeutic agents, which has been indicated by several studies. Even more interesting is the recent observation that certain polycations may present a significantly greater toxicity towards the clinically important cancer stem cell (CSC) niche than towards more differentiated bulk tumour cells. These cells, which possess the stem-like characteristics of self-renewal and differentiation, are highly implicated in cancer drug resistance, tumour recurrence and poor clinical prognosis. The search for compounds which may target and eliminate these cells is thus of great research interest. As such, the observation in our previous study on a PEI-based PDC which showed a considerably higher toxicity of PEI towards glioblastoma CSCs (GSCs) than on more differentiated glioma (U87) cells led us to investigate other cationic polymers for a similar effect. The evaluation of the toxicity of a range of different types of polycations, and an investigation into the potential source of GSC's sensitivity to such compounds is thus described.

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

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

CD47-targeted cancer immunogene therapy: Secreted SIRPα-Fc fusion protein eradicates tumors by macrophage and NK cell activation

CD47 protects healthy cells from macrophage attack by binding to signal regulatory protein α (SIRPα), while its upregulation in cancer prevents immune clearance. Systemic treatment with CD47 antibodies requires a weakened Fc-mediated effector function or lower CD47-binding affinity to prevent side effects. Our approach combines “the best of both worlds,” i.e., maximized CD47 binding and full Fc-mediated immune activity, by exploiting gene therapy for paracrine release. We developed a plasmid vector encoding for the secreted fusion protein sCV1-hIgG1, comprising highly efficient CD47-blocking moiety CV1 and Fc domain of human immunoglobulin G1 (IgG1) with maximized immune activation. sCV1-hIgG1 exhibited a potent bystander effect, blocking CD47 on all cells via fusion protein secreted from only a fraction of cells or when transferring transfection supernatant to untransfected cells. The CpG-free plasmid ensured sustained secretion of sCV1-hIgG1. In orthotopic human triple-negative breast cancer in CB17-severe combined immunodeficiency (SCID) mice, ex vivo transfection significantly delayed tumor growth and eradicated one-third of tumors. In intratumoral transfection experiments, CD47 blockage and increased migration of macrophages into the tumor were observed within 17 h of a single injection. Natural killer (NK) cell-mediated lysis of sCV1-hIgG1-expressing cells was demonstrated in vitro. Taken together, this approach also opens the opportunity to block, in principle, any immune checkpoints.

In vivo gene delivery mediated by non-viral vectors for cancer therapy

Gene therapy by expression constructs or down-regulation of certain genes has shown great potential for the treatment of various diseases. The wide clinical application of nucleic acid materials dependents on the development of biocompatible gene carriers. There are enormous various compounds widely investigated to be used as non-viral gene carriers including lipids, polymers, carbon materials, and inorganic structures. In this review, we will discuss the recent discoveries on non-viral gene delivery systems. We will also highlight the in vivo gene delivery mediated by non-viral vectors to treat cancer in different tissue and organs including brain, breast, lung, liver, stomach, and prostate. Finally, we will delineate the state-of-the-art and promising perspective of in vivo gene editing using non-viral nano-vectors.

Antineoplastic Drug-Free Anticancer Strategy Enabled by Host-Defense-Peptides-Mimicking Synthetic Polypeptides

An antineoplastic drug-free anticancer strategy enabled by host defense peptides (HDPs)-mimicking synthetic polypeptides is reported. The polypeptide exhibits a broad spectrum of anticancer activity in 12 cancer cell lines, including drug-resistant and highly metastatic tumor cells. Detailed mechanistic studies reveal that the cationic anticancer polypeptide (ACPP) can directly induce rapid necrosis of cancer cells within minutes through a membrane-lytic mechanism. Moreover, a pH-sensitive zwitterionic derivative of ACPP (DA-ACPP) is prepared for in vivo application. DA-ACPP shows negligible hemolysis under neutral physiological conditions, and can be converted back to ACPP in slightly acidic tumor environments, resulting in selective killing of cancer cells. Consequently, DA-ACPP shows an effective inhibition of tumor growth in both 4T1 orthotopic breast tumor models and B16-F10 melanoma pulmonary metastatic models. Overall, these findings demonstrate that synthetic HDPs-mimicking polypeptides represent safe and effective antineoplastic agents, which sheds new light on the development of drug-free synthetic polymers for cancer therapy.

Local release of siRNA using polyplex-loaded thermosensitive hydrogels

One of the challenges for the clinical translation of RNA interference (RNAi)-based therapies concerns the deposition of therapeutically effective doses of the nucleic acids, like siRNA, at a local tissue level without severe off-target effects. To address this issue, hydrogels can be used as matrices for the local and sustained release of the siRNA cargo. In this study, the formation of polyplexes based on siRNA and poly(2-dimethylaminoethyl methacrylate) (PDMAEMA)-based polymers was investigated, followed by their loading in a thermosensitive hydrogel to promote local siRNA release. A multifunctional NPD triblock copolymer consisting of a thermosensitive poly(N-isopropylacrylamide) (PNIPAM, N), a hydrophilic poly(ethylene glycol) (PEG, P), and a cationic PDMAEMA (D) block was used to study the binding properties with siRNA taking the non-thermosensitive PD polymer as control. For both polymers, small polyplexes with sizes ranging from 10-20 nm were formed in aqueous solution (HBS buffer, 20 mM HEPES, 150 mM NaCl, pH 7.4) when prepared at a N/P charge ratio of 5 or higher. Formulating the siRNA into NPD or PD polyplexes before loading into the thermosensitive PNIPAM-PEG-PNIPAM hydrogel resulted in a more controlled and sustained release compared to free siRNA release from the hydrogel. The polyplexes were released for 128 hours in HBS, when changing the release medium twice a day, while free siRNA was completely released within 50 hours with already 40% being released after changing the release medium just once. The release of the polyplexes was dependent on the dissolution rate of the hydrogel matrix. Moreover, intact polyplexes were released from the hydrogels with a similar size as before loading, suggesting that the hydrogel material did not compromise the polyplex stability. Finally, it was shown that the released polyplexes were still biologically active and transfected FaDu cells, which was observed by siRNA-induced luciferase silencing in vitro. This study shows the development of an injectable thermosensitive hydrogel to promote local and sustained release of siRNA, which can potentially be used to deliver siRNA for various applications, such as the treatment of tumors.

Dendrimers: A versatile nanocarrier for drug delivery and targeting

Dendrimers are novel polymeric nanoarchitectures characterized by hyper-branched 3D-structure having multiple functional groups on the surface that increases their functionality and make them versatile and biocompatible. Their unique properties like nanoscale uniform size, high degree of branching, polyvalency, water solubility, available internal cavities and convenient synthesis approaches make them promising agent for biological and drug delivery applications. Dendrimers have received an enormous attention from researchers among various nanomaterials. Dendrimers can be used as a carrier for diverse therapeutic agents. They can be used for reducing drug toxicities and enhancement of their efficacies. The present review provide a comprehensive outline of synthesis of dendrimers, interaction of dendrimer with guest molecules, properties, characterization and their potential applications in pharmaceutical and biomedical field.

Polymers and hydrogels for local nucleic acid delivery

This review focusses on the rational design of materials (from polymers to hydrogel materials) to achieve successful local delivery of therapeutic nucleic acids.

Polymeric drugs: Advances in the development of pharmacologically active polymers

Synthetic polymers play a critical role in pharmaceutical discovery and development. Current research and applications of pharmaceutical polymers are mainly focused on their functions as excipients and inert carriers of other pharmacologically active agents. This review article surveys recent advances in alternative pharmaceutical use of polymers as pharmacologically active agents known as polymeric drugs. Emphasis is placed on the benefits of polymeric drugs that are associated with their macromolecular character and their ability to explore biologically relevant multivalency processes. We discuss the main therapeutic uses of polymeric drugs as sequestrants, antimicrobials, antivirals, and anticancer and anti-inflammatory agents.

Applications of dendrimers for brain delivery and cancer therapy

Dendrimers are emerging as potential nonviral vectors for the efficient delivery of drugs and nucleic acids to the brain and cancer cells. These polymers are highly branched, 3D macromolecules with modifiable surface functionalities and available internal cavities that make them attractive as delivery systems for drug and gene delivery applications. This article highlights the recent therapeutic advances resulting from the use of dendrimers for brain targeting and cancer treatment.

Recent advances in dendrimer-based nanovectors for tumor-targeted drug and gene delivery

Advances in the application of nanotechnology in medicine have given rise to multifunctional smart nanocarriers that can be engineered with tunable physicochemical characteristics to deliver one or more therapeutic agent(s) safely and selectively to cancer cells, including intracellular organelle-specific targeting. Dendrimers having properties resembling biomolecules, with well-defined 3D nanopolymeric architectures, are emerging as a highly attractive class of drug and gene delivery vector. The presence of numerous peripheral functional groups on hyperbranched dendrimers affords efficient conjugation of targeting ligands and biomarkers that can recognize and bind to receptors overexpressed on cancer cells for tumor-cell-specific delivery. The present review compiles the recent advances in dendrimer-mediated drug and gene delivery to tumors by passive and active targeting principles with illustrative examples.

Advances in the application of nanotechnology in the diagnosis and treatment of gastrointestinal tumors

Nanotechnology has broad application prospects in the diagnosis and treatment of cancer. Integrating chemistry, engineering, biology and medicine, nanotechnology is a multidisciplinary research field. Nanoscale imaging technology significantly improves the precision and accuracy of tumor diagnosis. Nanocarriers are able to significantly improve the accuracy of dose and targeted drug delivery and reduce the toxic side effects. This review focuses on the emerging roles of these innovative technologies in gastrointestinal cancer diagnostics and therapeutics. Although several problems and barriers are hampering the development of nanodevices, the potential for nanotechnologies to function as multimodal nanotheranostic agents will likely pave the way for the fight against gastrointestinal cancer.

A nano-enabled cancer-specific ITCH RNAi chemotherapy booster for pancreatic cancer

Gemcitabine is currently the standard therapy for pancreatic cancer. However, growing concerns over gemcitabine resistance mean that new combinatory therapies are required to prevent loss of efficacy with prolonged treatment. Here, we suggest that this could be achieved through co-administration of RNA interference agents targeting the ubiquitin ligase ITCH. Stable anti-ITCH siRNA and shRNA dendriplexes with a desirable safety profile were prepared using generation 3 poly(propylenimine) dendrimers (DAB-Am16). The complexes were efficiently taken up by human pancreatic cancer cells and produced a 40-60% decrease in ITCH RNA and protein expression in vitro (si/shRNA) and in a xenograft model of pancreatic cancer (shRNA). When co-administered with gemcitabine (100 mg/kg/week) at a subtherapeutic dose, treatment with ITCH-shRNA (3x 50 mg/week) was able to fully suppress tumour growth for 17 days, suggesting that downregulation of ITCH mediated by DAB-Am16/shRNA sensitizes pancreatic cancer to gemcitabine in an efficient and specific manner.

FROM THE CLINICAL EDITOR

Gemcitabine delivery to pancreatic cancer often results in the common problem of drug resistance. This team overcame the problem through co-administration of siRNA and shRNA dendriplexes targeting the ubiquitin ligase ITCH.

Transferrin-bearing polypropylenimine dendrimer for targeted gene delivery to the brain

The possibility of using genes as medicines to treat brain diseases is currently limited by the lack of safe and efficacious delivery systems able to cross the blood-brain barrier, thus resulting in a failure to reach the brain after intravenous administration. On the basis that iron can effectively reach the brain by using transferrin receptors for crossing the blood-brain barrier, we propose to investigate if a transferrin-bearing generation 3-polypropylenimine dendrimer would allow the transport of plasmid DNA to the brain after intravenous administration. In vitro, the conjugation of transferrin to the polypropylenimine dendrimer increased the DNA uptake by bEnd.3 murine brain endothelioma cells overexpressing transferrin receptors, by about 1.4-fold and 2.3-fold compared to that observed with the non-targeted dendriplex and naked DNA. This DNA uptake appeared to be optimal following 2h incubation with the treatment. In vivo, the intravenous injection of transferrin-bearing dendriplex more than doubled the gene expression in the brain compared to the unmodified dendriplex, while decreasing the non-specific gene expression in the lung. Gene expression was at least 3-fold higher in the brain than in any tested peripheral organs and was at its highest 24h following the injection of the treatments. These results suggest that transferrin-bearing polypropylenimine dendrimer is a highly promising gene delivery system to the brain.

Examination of structure-activity relationship of viologen-based dendrimers as CXCR4 antagonists and gene carriers

Chemokine receptors and their ligands play a central role in cancer metastasis, inflammatory disorders, and viral infections. Viologen dendrimers (VGD) emerged recently as a promising class of synthetic polycationic ligands for chemokine receptor CXCR4. The objective of this study was to evaluate the potential of VGD as novel dual-function polycations capable of simultaneous CXCR4 antagonism and gene delivery. As part of our systematic studies, we have synthesized a library of VGD with differences in molecular architecture, number of positive charges, and type of capping group. The ability of VGD to condense DNA was evaluated, and physicochemical and biological properties of the resulting polyplexes were studied. We have evaluated the effect of VGD surface charge, size, capping group, and molecular architecture on physicochemical properties of polyplexes, transfection efficiency, CXCR4 antagonism, and cytotoxicity in human epithelial osteosarcoma (U2OS) and in human liver hepatocellular carcinoma (HepG2) cells. We found that properties and behavior of the polyplexes are most dependent on the number of positive charges and molecular weight of VGD and to a lesser extent on the type of a capping group. Using TNFα plasmid, we have demonstrated that VGD prevents CXCR4-mediated cancer cell invasion and facilitates TNFα-mediated cancer cell killing. Such dual-function carriers have potential to enhance the overall therapeutic outcomes of cancer gene therapy.

Polymers for nucleic acid transfer-an overview

For the last five decades cationic polymers have been used for nucleic acids transfection. Our understanding of polymer-nucleic acid interactions and their rational use in delivery has continuously increased. The great improvements in macromolecular chemistry and the recognition of distinct biological extra- and intracellular delivery hurdles triggered several breakthrough developments, including the discovery of natural and synthetic polycations for compaction of nucleic acids into stable nanoparticles termed polyplexes; the incorporation of targeting ligands and surface-shielding of polyplexes to enable receptor-mediated gene delivery into defined target tissues; and strongly improved intracellular transfer efficacy by better endosomal escape of vesicle-trapped polyplexes into the cytosol. These experiences triggered the development of second-generation polymers with more dynamic properties, such as endosomal pH-responsive release mechanisms, or biodegradable units for improved biocompatibility and intracellular release of the nucleic acid pay load. Despite a better biological understanding, significant challenges such as efficient nuclear delivery and persistence of gene expression persist. The therapeutic perspectives widened from pDNA-based gene therapy to application of novel therapeutic nucleic acids including mRNA, siRNA, and microRNA. The finding that different therapeutic pay loads require different tailor-made carriers complicates preclinical developments. Convincing evidence of medical efficacy still remains to be demonstrated. Bioinspired multifunctional polyplexes resembling "synthetic viruses" appear as attractive opportunity, but provide additional challenges: how to identify optimum combinations of functional delivery units, and how to prepare such polyplexes reproducibly in precise form? Design of sequence-defined polymers, screening of combinatorial polymer and polyplex libraries are tools for further chemical evolution of polyplexes.

Poly(amidoamine) dendrimer complexes as a platform for gene delivery

INTRODUCTION

Gene therapy is one of the most effective ways to treat major infectious diseases, cancer and genetic disorders. It is based on several viral and non-viral systems for nucleic acid delivery. The number of clinical trials based on application of non-viral drug and gene delivery systems is rapidly increasing.

AREAS COVERED

This review discusses and summarizes recent advances in poly(amidoamine) dendrimers as effective gene carriers in vitro and in vivo, and their advantages and disadvantages relative to viral vectors and other non-viral systems (liposomes, linear polymers) are considered.

EXPERT OPINION

In this regard, dendrimers are non-immunogenic and have the highest efficiency of transfection among other non-viral systems, and none of the drawbacks characteristic for viral systems. The toxicity of dendrimers both in vitro and in vivo is an important question that has been addressed on many occasions. Several non-toxic and efficient multifunctional dendrimer-based conjugates for gene delivery, along with modifications to improve transfection efficiency while decreasing cytotoxicity, are discussed. Twelve paradigms that affected the development of dendrimer-based gene delivery are described. The conclusion is that dendrimers are promising candidates for gene delivery, but this is just the beginning and further studies are required before using them in human gene therapy.

Expand classical drug administration ways by emerging routes using dendrimer drug delivery systems: a concise overview

Drugs are introduced into the body by numerous routes such as enteral (oral, sublingual and rectum administration), parenteral (intravascular, intramuscular, subcutaneous and inhalation administration), or topical (skin and mucosal membranes). Each route has specific purposes, advantages and disadvantages. Today, the oral route remains the preferred one for different reasons such as ease and compliance by patients. Several nanoformulated drugs have been already approved by the FDA, such as Abelcet®, Doxil®, Abraxane® or Vivagel®(Starpharma) which is an anionic G4-poly(L-lysine)-type dendrimer showing potent topical vaginal microbicide activity. Numerous biochemical studies, as well as biological and pharmacological applications of both dendrimer based products (dendrimers as therapeutic compounds per se, like Vivagel®) and dendrimers as drug carriers (covalent conjugation or noncovalent encapsulation of drugs) were described. It is widely known that due to their outstanding physical and chemical properties, dendrimers afforded improvement of corresponding carried-drugs as dendrimer-drug complexes or conjugates (versus plain drug) such as biodistribution and pharmacokinetic behaviors. The purpose of this manuscript is to review the recent progresses of dendrimers as nanoscale drug delivery systems for the delivery of drugs using enteral, parenteral and topical routes. In particular, we focus our attention on the emerging and promising routes such as oral, transdermal, ocular and transmucosal routes using dendrimers as delivery systems.

Systemic tumor-specific gene delivery

The objective of a systemically administered cancer gene therapy is to achieve gene expression that is isolated to the tumor tissue. Unfortunately, viral systems have strong affinity for the liver, and delivery from non-viral cationic systems often results in high expression in the lungs. Non-specific delivery to these organs must be overcome if tumors are to be aggressively treated with genes such as IL-12 which activates a tumor immune response, and TNF-alpha which can induce tumor cell apoptosis. Techniques which have led to specific expression in tumor tissue include receptor targeting through ligand conjugation, utilization of tumor specific promoters and viral mutation in order to take advantage of proteins overexpressed in tumor cells. This review analyzes these techniques applied to liposomal, PEI, dendrimer, stem cell and viral gene delivery systems in order to determine the techniques that are most effective in achieving tumor specific gene expression after systemic administration.

Systemic TNFα gene therapy synergizes with liposomal doxorubicine in the treatment of metastatic cancer

Tumor necrosis factor alpha (TNFα) is a potent antitumoral cytokine, either killing tumor cells directly or affecting the tumor vasculature leading to enhanced accumulation of macromolecular drugs. Due to dose limiting side effects systemic administration of TNFα protein at therapeutically active doses is precluded. With gene vectors, tumor restricted TNFα expression can be achieved and in principle synergize with chemotherapy. Synthetic gene carriers based on polyamines were intravenously injected, which either passively accumulate within the tumor or specifically target the epidermal growth factor receptor. A single intravenous injection of TNFα gene vector promoted accumulation of liposomal doxorubicine (Doxil) in murine neuroblastoma and human hepatoma by enhancing tumor endothelium permeability. The expression of transgenic TNFα was restricted to tumor tissue. Three treatment cycles with TNFα gene vectors and Doxil significantly delayed tumor growth in subcutaneous murine Neuro2A neuroblastoma. Also tumors re-growing after initial treatment were successfully treated in a fourth cycle pointing at the absence of resistance mechanisms. Systemic Neuro2A metastases or human LS174T colon carcinoma metastases in liver were also successfully treated with this combined approach. In conclusion, this schedule opens the possibility for the efficient treatment of tumors metastases otherwise not accessible for macromolecular drug carriers.

Tumor regression following intravenous administration of a tumor-targeted p73 gene delivery system

The potential of gene therapy to treat cancer is hampered by the lack of safe and efficacious gene delivery systems able to selectively deliver therapeutic genes to tumors by intravenous administration. With the long-term aim of developing an efficacious cancer-targeted gene medicine, we demonstrated that transferrin-bearing polypropylenimine dendrimer complexed to a plasmid DNA encoding p73 led to an enhanced anti-proliferative activity in vitro, by up to 120-fold in A431 compared to the unmodified dendriplex. In vivo, the intravenous administration of this p73-encoding dendriplex resulted in a rapid and sustained inhibition of tumor growth over one month, with complete tumor suppression for 10% of A431 and B16-F10 tumors and long-term survival of the animals. The treatment was well tolerated by the animals, with no apparent signs of toxicity. These results suggest that the p73-encoding tumor-targeted polypropylenimine dendrimer should be further explored as a therapeutic strategy for cancer therapy.

Image-guided tumor-selective radioiodine therapy of liver cancer after systemic nonviral delivery of the sodium iodide symporter gene

We reported the induction of tumor-selective iodide uptake and therapeutic efficacy of (131)I in a hepatocellular carcinoma (HCC) xenograft mouse model, using novel polyplexes based on linear polyethylenimine (LPEI), shielded by polyethylene glycol (PEG), and coupled with the epidermal growth factor receptor-specific peptide GE11 (LPEI-PEG-GE11). The aim of the current study in the same HCC model was to evaluate the potential of biodegradable nanoparticle vectors based on pseudodendritic oligoamines (G2-HD-OEI) for systemic sodium iodide symporter (NIS) gene delivery and to compare efficiency and tumor specificity with LPEI-PEG-GE11. Transfection of HCC cells with NIS cDNA, using G2-HD-OEI, resulted in a 44-fold increase in iodide uptake in vitro as compared with a 22-fold increase using LPEI-PEG-GE11. After intravenous application of G2-HD-OEI/NIS HCC tumors accumulated 6-11% ID/g (123)I (percentage of the injected dose per gram tumor tissue) with an effective half-life of 10 hr (tumor-absorbed dose, 281 mGy/MBq) as measured by (123)I scintigraphic gamma camera or single-photon emission computed tomography computed tomography (SPECT CT) imaging, as compared with 6.5-9% ID/g with an effective half-life of only 6 hr (tumor-absorbed dose, 47 mGy/MBq) for LPEI-PEG-GE11. After only two cycles of G2-HD-OEI/NIS/(131)I application, a significant delay in tumor growth was observed with markedly improved survival. A similar degree of therapeutic efficacy had been observed after four cycles of LPEI-PEG-GE11/(131)I. These results clearly demonstrate that biodegradable nanoparticles based on OEI-grafted oligoamines show increased efficiency for systemic NIS gene transfer in an HCC model with similar tumor selectivity as compared with LPEI-PEG-GE11, and therefore represent a promising strategy for NIS-mediated radioiodine therapy of HCC.

Dendrimeric nanoarchitectures mediated transdermal and oral delivery of bioactives

Transdermal route is an evolving panorama in novel drug deliverance and with oral route they proffer immense potential. Most recently there is hastening in approaches for delivering bioactives via these routes, amongst them revolution has been made by dendrimers. Encapsulation and conjugation of bioactives with these virus sized robots have shown immense employment for delivery of hydrophobic and labile remedies. Transport of these nano-cruises from corner to corner of skin and through epithelial hurdle of gastrointestinal tract depends upon dendrimer characteristics. An improved thoughtful of these characteristics is an obligation for their use in these rambling fields. These characteristics embrace generation size, molecular weight, surface charge, incubation time and concentration. This context demarcates the imperative role of dendrimers in transdermal and oral drug delivery. This review also highlights concerning mechanism of convey of nanoarrays via epithelial hurdle of GIT.

Nanomaterials: applications in cancer imaging and therapy

The application of nanomaterials (NMs) in biomedicine is increasing rapidly and offers excellent prospects for the development of new non-invasive strategies for the diagnosis and treatment of cancer. In this review, we provide a brief description of cancer pathology and the characteristics that are important for tumor-targeted NM design, followed by an overview of the different types of NMs explored to date, covering synthetic aspects and approaches explored for their application in unimodal and multimodal imaging, diagnosis and therapy. Significant synthetic advances now allow for the preparation of NMs with highly controlled geometry, surface charge, physicochemical properties, and the decoration of their surfaces with polymers and bioactive molecules in order to improve biocompatibility and to achieve active targeting. This is stimulating the development of a diverse range of nanometer-sized objects that can recognize cancer tissue, enabling visualization of tumors, delivery of anti-cancer drugs and/or the destruction of tumors by different therapeutic techniques.

Polyamine aza-cyclic compounds demonstrate anti-proliferative activity in vitro but fail to control tumour growth in vivo

Cationic polyamines such as the poly(propylenimine) dendrimers (DAB16) are anti-tumour agents (Dufes et al., 2005, Cancer Res 65:8079-8084). Their mechanism of action is poorly understood, but the lack of in vivo toxicity suggests cancer specificity. To explore this polyamine pharmacophore we cross-linked the aza-cyclic compound, hexacyclen, with 1,4-dibromobutane or 1,8-dibromooctane to yield the polyamines [poly(butylhexacyclen)--CL4] or [poly(octylhexacyclen)--CL8] respectively, both free of primary amines. We characterised the compounds and their respective nanoparticles and examined their interaction with the putative targets of the cationic polyamines: the cell membrane and DNA. Like DAB 16, CL4 and CL8 bind plasmid DNA and all three compounds interrupted the cell cycle of A431 epidermoid carcinoma cells in the S-phase. Additionally all three compounds disrupted erythrocyte membranes, with CL8 and DAB 16 being more active, in this respect, than CL4. CL4 (IC(50) =775.1 µg mL(-1)) and CL8 (IC(50) =8.4 µg mL(-1)), in a similar manner to DAB 16, were anti-proliferative against A431 cells; although unlike DAB 16, CL4 and CL8 were not tumouricidal against A431 xenografts in mice, indicating that primary amines may play an important role in the in vivo activity of DAB 16.

Cationic nanosystems for the delivery of small interfering ribonucleic acid therapeutics: a focus on toxicogenomics

IMPORTANCE OF THE FIELD

siRNAs may serve as novel nanomedicines for sequence-specific gene silencing in the clinic. However, delivering siRNA to targeted tissue or cells remains a challenge. An appropriate delivery nanosystem such as cationic polymers or liposomes is required for effective gene silencing with siRNA in vivo but the available drug delivery vectors are not all biologically inert.

AREAS COVERED IN THIS REVIEW

A combination of highly focused and comprehensive literature searches to identify any relevant reports using Medline (from 1950 to 7 April 2010) through the OVID system.

WHAT THE READER WILL GAIN

Using cationic delivery nanosystems as examples, this review article highlights the importance of undertaking toxicogenomics studies - the application of transcription profiling to toxicology - to acquire gene expression signatures of siRNA delivery systems so as to determine and/or predict their impact on gene silencing activity and specificity. Such nanotoxicological information will be important for the optimal selection of siRNA-delivery system combinations in the many proposed clinical applications of RNA interference.

TAKE HOME MESSAGE

Cationic delivery nanosystems can elicit multiple gene expression changes in cells that may contribute to the 'off-target' effects of siRNAs and/or modulate their pharmacological activity. Thus, selection of delivery systems for siRNA applications should be based on both their delivery enhancing capability and toxicogenomics.

Nonviral vectors for the delivery of small interfering RNAs to the CNS

While efficient methods for cell line transfection are well described, for primary neurons a high-yield method different from those relying on viral vectors is lacking. Viral vector-based primary neuronal infection has several drawbacks, including complexity of vector preparation, safety concerns and the generation of immune and inflammatory responses, when used in vivo. This article will cover the different approaches that are being used to efficiently deliver genetic material (both DNA and small interfering RNA) to neuronal tissue using nonviral vectors, including the use of cationic lipids, polyethylenimine derivatives, dendrimers, carbon nanotubes and the combination of carbon-made nanoparticles with dendrimers. The effectiveness, both in vivo and in vitro, of the different methods to deliver genetic material to neural tissue is discussed.

Toxicity pathway focused gene expression profiling of PEI-based polymers for pulmonary applications

Polyethylene imine (PEI) based polycations, successfully used for gene therapy or RNA interference in vitro as well as in vivo, have been shown to cause well-known adverse side effects, especially high cytotoxicity. Therefore, various modifications have been developed to improve safety and efficiency of these nonviral vector systems, but profound knowledge about the underlying mechanisms responsible for the high cytotoxicity of PEI is still missing. In this in vitro study, we focused on stress and toxicity pathways triggered by PEI-based vector systems to be used for pulmonary application and two well-known lung toxic particles: fine crystalline silica (CS) and nanosized ZnO (NZO). The cytotoxicity profiles of all stressors were investigated in alveolar epithelial-like type II cells (LA4) to define concentrations with matching toxicity levels (cell viability >60% and LDH release <10%) for subsequent qRT-PCR-based gene array analysis. Within the first 6 h pathway analysis revealed for CS an extrinsic apoptotic signaling (TNF pathway) in contrast to the intrinsic apoptotic pathway (mitochondrial signaling) which was induced by PEI 25 kDa after 24 h treatment. The following causative chain of events seems conceivable: reactive oxygen species derived from particle surface toxicity triggers TNF signaling in the case of CS, whereby endosomal swelling and rupture upon endocytotic PEI 25 kDa uptake causes intracellular stress and mitochondrial alterations, finally leading to apoptotic cell death at higher doses. PEG modification most notably reduced the cytotoxicity of PEI 25 kDa but increased proinflammatory signaling on mRNA and even protein level. Hence in view of the lung as a sensitive target organ this inflammatory stimulation might cause unwanted side effects related to respiratory and cardiovascular disorders. Thus further optimization of the PEI-based vector systems is still needed for pulmonary application.

Evaluating the gene-expression profiles of HeLa cancer cells treated with activated and nonactivated poly(amidoamine) dendrimers, and their DNA complexes

Using dendrimers in cancer therapy as nonviral vectors for gene delivery seems promising. The biological performance of a dendrimer-based gene delivery system depends heavily on its molecular architecture. The transfection activity of dendrimers is significantly improved by processes activated in the heat degradation treatment of solvolysis. However, very little is known about the molecular mechanisms that dendrimers produce in cancer cells. We studied the changes in global gene-expression profiles in human cervical cancer HeLa cells exposed to nonactivated and activated poly(amidoamine) (PAMAM) dendrimers, alone or in complexes with plasmid DNA (dendriplexes). Real-time quantitative reverse transcriptase-polymerase chain reaction was used to confirm four regulated genes (PHF5A, ARNTL2, CHD4, and P2RX7) affected by activated dendrimers and dendriplexes. Activated and nonactivated dendrimers and dendriplexes alike induced multiple gene expression changes, some of which overlapped with their dendriplexes. Dendrimer activation improved transfection efficiency and induced additional gene expression changes in HeLa cells. Dendrimers and dendriplexes principally affect genes with the molecular functions of nucleic acid binding and transcription activity, metal-ion binding, enzyme activity, receptor activity, and protein binding. Our findings provide a deeper insight into the changes in gene expression patterns caused by the molecular structure of PAMAM dendrimers for gene-based cancer therapy.

Tumour and dendrimers: a review on drug delivery aspects

Tumour is a morbid state, characterized by spontaneous outgrowth of an abnormal mass of cells. The evolution of tumours is random, disorganized, a condition of numerous mutations. The properties are biased and incompletely comprehended. It is a malignant or benign condition that encompasses its own rules of morphogenesis, an immortal state that elucidates different physiology. It is a pathological crisis that still haunts the minds of scientists, physicians and patients, a complete cure of which is still a dream to be realized. The unpredictable microenvironment of cancerous cells in all of its existing forms i.e. leukaemic cells, solid tumours and sarcomas is well documented. This phenomenon expressed by cancerous sites in the body poses various obstacles towards drug efficacy. Thus, it has become necessary to address briefly the issues relating to tumour physiology, its vasculature and angiogenesis. The information could provide insight towards the development of tumour-targeted drug delivery. The salient features regarding these have been discussed.

The molecular shape of poly(propylenimine) dendrimer amphiphiles has a profound effect on their self assembly

The shape of dendrimer amphiphiles has an unexpected effect on their self-assembly. A series of diaminobutane poly(propylenimine) generation 3 dendrimer (DAB-dendr-(NH(2))(16)) amphiphiles has been synthesized, bearing an average of five (PD5), three (PD3) and one (PD1) palmitoyl group(s) per dendrimer molecule. Additionally DAB-dendr-(NH(2))(16) was derivatized with a layer of poly(ethylene glycol) (PEG, degree of polymerization = 12) groups and conjugated to an average of 1 palmitoyl group at the PEG end (PPD1). A final amphiphile resulted from the conjugation of DAB-dendr-(NH(2))(16) with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-succinimidylpropionate (DSPE-PEG(3400)-SPA), i.e.: DPD5 (with 4 DSPE-PEG arms). The critical micellar concentration in aqueous media followed the trend: DPD5 < PD5 = PD3 < PD1 < PPD1 and amphiphiles eventually formed 10-20 nm monomolecular or multimolecular micelles and/or 200 nm spheres or tubules. Aggregation was entropy driven, as expected, for DPD5, PD5 and PD1 and enthalpy driven with the most hydrophilic compound PPD1, but was unexpectedly enthalpy driven for PD3. PD3 aggregates formed low capacity hydrophobic domains with a limited capacity for encapsulation of cyclosporine A; encapsulation levels (mole drug per mole polymer) were 0.099, 0.014, 0.099, and 0.735 for PD1, PD3, PD5, and DPD5 and, respectively. We conclude that star shaped amphiphiles such as PD3 are sterically hindered from self-assembling into high capacity hydrophobic domains in aqueous media. Amphiphile-membrane interactions were promoted by hydrophobic groups, but diminished by PEG moieties. DPD5 is the most suitable amphiphile for biomedical applications.

Synthesis and in vivo antitumor efficacy of PEGylated poly(l-lysine) dendrimer-camptothecin conjugates

Polymer conjugates of camptothecin (CPT) have been pursued as a solution to the difficulties present in treating cancers with CPT and its derivatives. Covalent attachment of CPT to a polymer can improve solubility, increase blood circulation time, enhance tumor uptake, and significantly improve efficacy of the drug. In this report, we describe a novel polymer conjugate of CPT using a core-functionalized, symmetrically PEGylated poly(l-lysine) (PLL) dendrimer. The PEGylated dendrimer consisted of a lysine dendrimer functionalized with aspartic acid, which was used as an attachment site for poly(ethylene glycol) (PEG) and CPT. The final conjugate had a molecular weight of 40 kDa and was loaded with 4-6 wt % CPT. Polymer-bound CPT was shown to have a long blood circulation half-life of 30.9 +/- 8.8 h and a tumor uptake of 4.2 +/- 2.3% of the injected dose/g of tissue, compared to free CPT in which less than 1% was retained in the blood after 30 min and had a tumor accumulation of 0.29 +/- 0.04% of the injected dose/g of tissue. The PEGylated PLL-CPT showed superior efficacy in murine (C26) and human colon carcinoma (HT-29) tumor models when compared with no treatment or treatment with irinotecan. In the C26 tumor model, treatment resulted in significantly prolonged survival (P < 0.05) for all mice treated with a single injection of PEGylated PLL-CPT. In the HT-29 tumor model, all mice treated with multiple injections of a low dose survived to the end of the study, with three mice of eight surviving tumor-free.

How to study dendriplexes II: Transfection and cytotoxicity

This paper reviews different techniques for analyzing the transfection efficiencies and cytotoxicities of dendriplexes-complexes of nucleic acids with dendrimers. Analysis shows that three plasmids are mainly used in transfection experiments: plasmid DNA encoding luciferase from the firefly Photinus pyralis, beta-galactosidase, or green fluorescent protein. The effective charge ratio of transfection does not directly correlate with the charge ratio obtained from gel electrophoresis, zeta-potential or ethidium bromide intercalation data. The most popular cells for transfection studies are human embryonic kidney cells (HEK293), mouse embryonic cells (NIH/3T3), SV40 transformed monkey kidney fibroblasts (COS-7) and human epithelioid cervical carcinoma cells (HeLa). Cellular uptake is estimated using fluorescently-labeled dendrimers or nucleic acids. Transfection efficiency is measured by the luciferase reporter assay for luciferase, X-Gal staining or beta-galactosidase assay for beta-galactosidase, and confocal microscopy for green fluorescent protein. Cytotoxicity is determined by the MTT test and lactate dehydrogenase assays. On the basis of the papers reviewed, a standard essential set of techniques for characterizing dendriplexes was constructed: (1) analysis of size and shape of dendriplexes in dried/frozen state by electron or atomic force microscopy; (2) analysis of charge/molar ratio of complexes by gel electrophoresis or ethidium bromide intercalation assay or zeta-potential measurement; (3) analysis of hydrodynamic diameter of dendriplexes in solution by dynamic light scattering. For the evaluation of transfection efficiency the essential techniques are (4) luciferase reporter assay, beta-galactosidase assay or green fluorescent protein microscopy, and (5) cytotoxicity by the MTT test. All these tests allow the transfection efficiencies and cytotoxicities of different kinds of dendrimers to be compared.

Targeted radioiodine therapy of neuroblastoma tumors following systemic nonviral delivery of the sodium iodide symporter gene

PURPOSE

We recently reported the significant therapeutic efficacy of radioiodine therapy in various tumor mouse models following transcriptionally targeted sodium iodide symporter (NIS) gene transfer. These studies showed the high potential of NIS as a novel diagnostic and therapeutic gene for the treatment of extrathyroidal tumors. As a next crucial step towards clinical application of NIS-mediated radionuclide therapy we aim at systemic delivery of the NIS gene to target extrathyroidal tumors even in the metastatic stage.

EXPERIMENTAL DESIGN

In the current study, we used synthetic polymeric vectors based on pseudodendritic oligoamines with high intrinsic tumor affinity (G2-HD-OEI) to target a NIS-expressing plasmid (CMV-NIS-pcDNA3) to neuroblastoma (Neuro2A) cells.

RESULTS

Incubation with NIS-containing polyplexes (G2-HD-OEI/NIS) resulted in a 51-fold increase in perchlorate-sensitive iodide uptake activity in Neuro2A cells in vitro. Through (123)I-scintigraphy and ex vivo gamma counting Neuro2A tumors in syngeneic A/J mice were shown to accumulate 8% to 13% ID/g (123)I with a biological half-life of 13 hours, resulting in a tumor-absorbed dose of 247 mGy/MBq (131)I after i.v. application of G2-HD-OEI/NIS. Nontarget organs, including liver, lung, kidneys, and spleen revealed no significant iodide uptake. Moreover, two cycles of systemic NIS gene transfer followed by (131)I application (55.5 MBq) resulted in a significant delay in tumor growth associated with markedly improved survival.

CONCLUSIONS

In conclusion, our data clearly show the high potential of novel pseudodendritic polymers for tumor-specific NIS gene delivery after systemic application, opening the prospect of targeted NIS-mediated radionuclide therapy of nonthyroidal tumors even in metastatic disease.

Selective targeting of green fluorescent nanodiamond conjugates to mitochondria in HeLa cells

Fluorescent cellular biomarkers play a prominent role in biosciences. Most of the available biomarkers have some drawbacks due to either physical and optical or cytotoxic properties. In view of this, we investigated the potential of green fluorescent nanodiamonds as biomarkers in living cells. Nanodiamonds were functionalized by attaching antibodies that target intracellular structures such as actin filaments and mitochondria. Then, the nanodiamond conjugates were transfected into HeLa cells. Transfections were mediated by 4(th)-generation dendrimers, cationic liposomes and protamine sulfate. Using fluorescence microscopy, we confirmed successful transfections of the nanodiamonds into HeLa cells. Nanodiamond fluorescence could be easily differentiated from cellular autofluorescence. Furthermore, nanodiamonds could be targeted selectively to intracellular structures. Therefore, nanodiamonds are a promising tool for intracellular assays.