Poly(amidoamine)s as potential nonviral vectors: ability to form interpolyelectrolyte complexes and to mediate transfection in vitro

Cationic amino-acid functionalized polymethacrylamide vectors for siRNA transfection based on modification of poly(2-isopropenyl-2-oxazoline)

Poly(2-isopropenyl-2-oxazoline) (PiPOx) is a functional polymer showing great potential for the development of smart biomaterials. The straightforward synthesis and post-polymerization functionalization of PiPOx offers many opportunities for tailoring the properties of the polymer towards biomaterials. In this study we report for the first time PiPOx-based cationic charged polymethacrylamides with amino acid side chains that can complex siRNA and promote transfection in vitro. Therefore, PiPOx was fully modified via ring opening addition reactions with the carboxylic acid groups of a series of N-Boc-L-amino acids and their reaction kinetics were investigated. Based on the determined kinetic constants, another series of PiPOx-based copolymers with balanced hydrophilic/hydrophobic content of N-Boc-L-amino acids were obtained via one-pot modification reaction with two different N-Boc-L-amino acids. The N-Boc protected homopolymers and related copolymers were deprotected to obtain (co)polymers with the targeted side chain cationic charged units. The (co)polymers' structures were fully investigated via FT-IR and 1H NMR spectroscopy, size exclusion chromatography (SEC), and TGA-DSC-MS analysis. The polarimetry measurements revealed that the homopolymers retain their chiroptical properties after post-modification, and a sign inversion is noticed from (L) N-Boc-protected analogues to (D) for the TFA cationic charged homopolymers. Generally, cationically charged homopolymers with hydrophilic amino acids on the side chain showed efficient complexation of siRNA, but poor transfection while cationic copolymers having both tryptophan and valine or proline side chains revealed moderate siRNA binding, high transfection efficiency (> 90% of the cells) and potent gene silencing with IC50 values down to 5.5 nM. Particularly, these cationic copolymers showed higher gene silencing potency as compared to the commercial JetPRIME® reference, without reducing cell viability in the concentration range used for transfection, making this a very interesting system for in vitro siRNA transfection.

Dendrimers: Advancements and Potential Applications in Cancer Diagnosis and Treatment-An Overview

Cancer is a leading cause of death worldwide, and the main treatment methods for this condition are surgery, chemotherapy, and radiotherapy. These treatment methods are invasive and can cause severe adverse reactions among organisms, so nanomaterials are increasingly used as structures for anticancer therapies. Dendrimers are a type of nanomaterial with unique properties, and their production can be controlled to obtain compounds with the desired characteristics. These polymeric molecules are used in cancer diagnosis and treatment through the targeted distribution of some pharmacological substances. Dendrimers have the ability to fulfill several objectives in anticancer therapy simultaneously, such as targeting tumor cells so that healthy tissue is not affected, controlling the release of anticancer agents in the tumor microenvironment, and combining anticancer strategies based on the administration of anticancer molecules to potentiate their effect through photothermal therapy or photodynamic therapy. The purpose of this review is to summarize and highlight the possible uses of dendrimers regarding the diagnosis and treatment of oncological conditions.

Against the Resilience of High-Grade Gliomas: Gene Therapies (Part II)

Introduction: High-grade gliomas (HGGs) still have a high rate of recurrence and lethality. Gene therapies were projected to overcome the therapeutic resilience of HGGs, due to the intrinsic genetic heterogenicity and immune evasion pathways. The present literature review strives to provide an updated overview of the novel gene therapies for HGGs treatment, highlighting evidence from clinical trials, molecular mechanisms, and future perspectives. Methods: An extensive literature review was conducted through PubMed/Medline and ClinicalTrials.gov databases, using the keywords “high-grade glioma,” “glioblastoma,” and “malignant brain tumor”, combined with “gene therapy,” “oncolytic viruses,” “suicide gene therapies,” “tumor suppressor genes,” “immunomodulatory genes,” and “gene target therapies”. Only articles in English and published in the last 15 years were chosen, further screened based on best relevance. Data were analyzed and described according to the PRISMA guidelines. Results: Viruses were the most vehicles employed for their feasibility and transduction efficiency. Apart from liposomes, other viral vehicles remain largely still experimental. Oncolytic viruses and suicide gene therapies proved great results in phase I, II preclinical, and clinical trials. Tumor suppressor, immunomodulatory, and target genes were widely tested, showing encouraging results especially for recurrent HGGs. Conclusions: Oncolytic virotherapy and suicide genes strategies are valuable second-line treatment options for relapsing HGGs. Immunomodulatory approaches, tumor suppressor, and target genes therapies may implement and upgrade standard chemoradiotherapy. Future research aims to improve safety profile and prolonging therapeutic effectiveness. Further clinical trials are needed to assess the efficacy of gene-based therapies.

Disulfide Bridging Strategies in Viral and Nonviral Platforms for Nucleic Acid Delivery

Self-assembled nanostructures that are sensitive to environmental stimuli are promising nanomaterials for drug delivery. In this class, disulfide-containing redox-sensitive strategies have gained enormous attention because of their wide applicability and simplicity of nanoparticle design. In the context of nucleic acid delivery, numerous disulfide-based materials have been designed by relying on covalent or noncovalent interactions. In this review, we highlight major advances in the design of disulfide-containing materials for nucleic acid encapsulation, including covalent nucleic acid conjugates, viral vectors or virus-like particles, dendrimers, peptides, polymers, lipids, hydrogels, inorganic nanoparticles, and nucleic acid nanostructures. Our discussion will focus on the context of the design of materials and their impact on addressing the current shortcomings in the intracellular delivery of nucleic acids.

Light-Triggered Trafficking to the Cell Nucleus of a Cationic Polyamidoamine Functionalized with Ruthenium Complexes

Strategies for endosomal escape and access to the cell nucleus are highly sought for nanocarriers to deliver their load efficiently following endocytosis. In this work, we have studied the uptake and intracellular trafficking of a polycationic polyamidoamine (PAA) endowed with a luminescent Ru complex, Ru-PhenAN, that shows unique trafficking to the cell nucleus. Live cell imaging confirmed the capacity of this polymer to access the nucleus, excluding artifacts due to cell fixation, and clarified that the mechanism of escape is light-triggered and relies on the presence of the Ru complexes and their capacity to absorb light and act as photosensitizers for singlet oxygen production. These results open up the possibility to use PAA-ruthenium complexes for targeted light-triggered delivery of genetic material or drugs to the cytosol and nucleus.

Gene therapies for high-grade gliomas: from the bench to the bedside

Background:

Gene therapy is the most attractive therapeutic approach against high-grade gliomas (HGGs). This is because of its theoretical capability to rework gene makeup in order to yield oncolytic effects. However, some factors still limit the upgrade of these therapies at a clinical level of evidence. We report an overview of glioblastoma gene therapies, mainly focused on the rationale, classification, advances and translational challenges.

Methods:

An extensive review of the online literature on gene therapy for HGGs was carried out. The PubMed/MEDLINE and ClinicalTrials.gov websites were the main sources. Articles in English published in the last five years were sorted according to the best match with the multiple relevant keywords chosen. A descriptive analysis of the clinical trials was also reported.

Results:

A total of 85 articles and 45 clinical trials were selected. The main types of gene therapies are the suicide gene, tumor suppressor gene, immunomodulatory gene and oncolytic therapies (virotherapies). The transfer of genetic material entails replication-deficient and replication-competent oncolytic viruses and nanoparticles, such as liposomes and cationic polymers, each of them having advantages and drawbacks. Forty-eight clinical trials were collected, mostly phase I/II.

Conclusion:

Gene therapies constitute a promising approach against HGGs. The selection of new and more effective target genes, the implementation of gene-delivery vectors capable of greater and safer spreading capacity, and the optimization of the administration routes constitute the main translational challenges of this approach. (www.actabiomedica.it)

Recent advances in polymeric materials for the delivery of RNA therapeutics

Introduction: The delivery of nucleic acid therapeutics through non-viral carriers face multiple biological barriers that reduce their therapeutic efficiency. Despite great progress, there remains a significant technological gap that continues to limit clinical translation of these nanocarriers. A number of polymeric materials are being exploited to efficiently deliver nucleic acids and achieve therapeutic effects. Areas covered: We discuss the recent advances in the polymeric materials for the delivery of nucleic acid therapeutics. We examine the use of common polymer architectures and highlight the challenges that exist for their development from bench side to clinic. We also provide an overview of the most notable improvements made to circumvent such challenges, including structural modification and stimuli-responsive approaches, for safe and effective nucleic acid delivery. Expert opinion: It has become apparent that a universal carrier that follows 'one-size' fits all model cannot be expected for delivery of all nucleic acid therapeutics. Carriers need to be designed to exhibit sensitivity and specificity toward individual targets diseases/indications, and relevant subcellular compartments, each of which possess their own unique challenges. The ability to devise synthetic methods that control the molecular architecture enables the future development that allow for the construction of 'intelligent' designs.

Comparison of Gene Transfection and Cytotoxicity Mechanisms of Linear Poly(amidoamine) and Branched Poly(ethyleneimine) Polyplexes

PURPOSE

This study aimed to further explore the mechanisms behind the ability of certain linear polyamidoamines (PAAs) to transfect cells with minimal cytotoxicity.

METHODS

The transfection efficiency of DNA complexed with a PAA of a molecular weight over 10 kDa or 25 kDa branched polyethyleneimine (BPEI) was compared in A549 cells using a luciferase reporter gene assay. The impact of endo/lysosomal escape on transgene expression was investigated by transfecting cells in presence of bafilomycin A1 or chloroquine. Cytotoxicity caused by the vectors was evaluated by measuring cell metabolic activity, lactate dehydrogenase release, formation of reactive oxygen species and changes in mitochondrial membrane potential.

RESULTS

The luciferase activity was ~3-fold lower after transfection with PAA polyplexes than with BPEI complexes at the optimal polymer to nucleotide ratio (RU:Nt). However, in contrast to BPEI vectors, PAA polyplexes caused negligible cytotoxic effects. The transfection efficiency of PAA polyplexes was significantly reduced in presence of bafilomycin A1 while chloroquine enhanced or decreased transgene expression depending on the RU:Nt.

CONCLUSIONS

PAA polyplexes displayed a pH-dependent endo/lysosomal escape which was not associated with cytotoxic events, unlike observed with BPEI polyplexes. This is likely due to their greater interactions with biological membranes at acidic than neutral pH.

Redox-responsive polymeric micelles formed by conjugating gambogic acid with bioreducible poly(amido amine)s for the co-delivery of docetaxel and MMP-9 shRNA

A novel redox-sensitive system for co-delivering hydrophobic drugs and hydrophilic siRNA or shRNA was developed by conjugating gambogic acid (GA) with poly(amido amine)s (PAAs) through amide bonds, which is called GA-conjugated PAAs (PAG). PAG can self-assemble into micelles as amphiphilic block copolymers, which exhibits an excellent loading ability for the co-delivery of docetaxel (DTX) and MMP-9 shRNA with adjustable dosing ratios. In addition, confocal microscopy, flow cytometry and in vitro transfection analyses demonstrated more efficient cellular internalization of DTX and MMP-9 shRNA after incubation with PAG/DTX- MMP-9 shRNA micelles (PAG/DTX-shRNA) than with free drugs. Unlike traditional amphiphilic copolymer micelles, GA conjugated in PAG possesses an intrinsic anticancer efficacy. The presence of disulfide bonds in PAAs enables rapid disassembly of PAG micelles in response to reducing agents, inducing the release of loaded drugs (DTX, GA and MMP-9 shRNA). In vitro cellular assays revealed that PAG/DTX-shRNA micelles inhibited MCF-7 cell proliferation more efficiently than the single drug or single drug-loaded micelles. In vivo biodistribution and anti-tumor effect studies using an MCF-7 breast cancer xenograft mouse model have indicated that PAG/DTX-shRNA micelles can enhance drug accumulation compared with the free drug, thereby sustaining the therapeutic effect on tumors. Additionally, PAG/DTX-shRNA micelles displayed a greater anti-tumor efficacy than Taxotere® and PAG-shRNA micelles. These results suggest that the redox-sensitive PAG platform is a promising co-delivery system for combining drugs and gene therapy for the treatment of cancer.

STATEMENT OF SIGNIFICANCE

The PAG micelles were designed by conjugating gambogic acid (GA) with poly(amido amine)s (PAAs), which would serve dual purposes as both gene and drugs co-delivery carrier and an anti-tumor prodrug. Unlike traditional amphiphilic micelles, GA conjugated in PAG could exert its intrinsic efficacy and provide synergistic antiproliferative effects with docetaxel (DTX) on MCF-7 cells. Disulfide bonds in PAG enables a rapid disassembly of PAG micelles in response to reducing agents and to release all loaded drugs (DTX, GA and MMP-9 shRNA) at tumor sites. PAG/DTX-shRNA micelles displayed greater anti-tumor efficacy than that of Taxotere®, indicating the design concept for PAG works well. And the strategy for PAG could be used to develop a series of similar co-delivery systems through conjugations of other small-molecule drugs with PAAs, such as doxorubicin, methotrexate and other drugs with carboxy groups in their structure.

Stimuli-Responsive Cationic Hydrogels in Drug Delivery Applications

Stimuli-responsive, smart, intelligent, or environmentally sensitive polymers respond to changes in external stimuli such as pH, temperature, ionic strength, surfactants, pressure, light, biomolecules, and magnetic field. These materials are developed in various network architectures such as block copolymers, crosslinked hydrogels, nanogels, inter-penetrating networks, and dendrimers. Stimuli-responsive cationic polymers and hydrogels are an interesting class of "smart" materials that respond reversibly to changes in external pH. These materials have the ability to swell extensively in solutions of acidic pH and de-swell or shrink in solutions of alkaline pH. This reversible swelling-shrinking property brought about by changes in external pH conditions makes these materials useful in a wide range of applications such as drug delivery systems and chemical sensors. This article focuses mainly on the properties of these interesting materials and their applications in drug delivery systems.

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.

The AGMA1 polyamidoamine mediates the efficient delivery of siRNA

AGMA1, a prevailingly cationic, guanidine-bearing, linear, amphoteric polyamidoamine is an effective siRNA condensing agent. Here two AGMA1 samples of different molecular weight, i.e. AGMA1-5 and AGMA1-10 were evaluated as siRNA condensing agents and transfection promoters. AGMA1-10 formed stable polyplexes with a size lower than 50 nm and positive zeta potential. AGMA1-5 polyplexes were larger, about 100 nm in size. AGMA1-10 polyplexes, but not AGMA1-5 proved to be an effective intracellular siRNA carrier, able to trigger gene silencing in Hela and PC3 cell lines without eliciting cytotoxic effects. AGMA1-10 knocked down AKT-1 expression upon transfection with an AKT-1 specific siRNA. The polyplex entry mechanism was investigated and was mediated by macropinocytosis. In conclusion, AGMA1 has potential as an efficient, non-toxic tool for the intracellular delivery of siRNA and warrants further investigation.

Use of New Aminosugar Derivatives as Comonomers for the Synthesis of Glycosylated Poly(Amido-Amines)

New sugar functionalized poly(amido-amines) (PAA) polymers were synthesized. The PAA made by the addition polymerization of 2-methylpiperazine-2,2-bisacrylamidoacetic acid (ISA) was chosen for its potential applications in the biomedical field and the sugar monomers were obtained by chemical and enzymatic synthetic strategies. Specifically, the 2-aminoethyl fi-D-galactopyranosyl monomer was directly obtained by enzymatic catalysis, while the 2-aminoethyl amide and the 3-aminopropyl amide of lactobionic acid were obtained by ning-opening reactions of the corresponding lactone. The presence of sugar moieties in the polymer chains was confirmed by FT-IR, 'H NMR, 13C NMR analysis and calorimetric assay. The sugar content of polymer derivatives is sufficient for targeting purpose, making these compounds potential soluble drug carriers.

Polyamidoamine nanoparticles as nanocarriers for the drug delivery to malaria parasite stages in the mosquito vector

Malaria is arguably one of the main medical concerns worldwide because of the numbers of people affected, the severity of the disease and the complexity of the life cycle of its causative agent, the protist Plasmodium spp. With the advent of nanoscience, renewed hopes have appeared of finally obtaining the long sought-after magic bullet against malaria in the form of a nanovector for the targeted delivery of antimalarial compounds exclusively to Plasmodium-infected cells, thus increasing drug efficacy and minimizing the induction of resistance to newly developed therapeutic agents. Polyamidoamine-derived nanovectors combine into a single chemical structure drug encapsulating capacity, antimalarial activity, low unspecific toxicity, specific targeting to Plasmodium, optimal in vivo activity and affordable synthesis cost. After having shown their efficacy in targeting drugs to intraerythrocytic parasites, now polyamidoamines face the challenge of spearheading a new generation of nanocarriers aiming at the malaria parasite stages in the mosquito vector.

Polymerization Kinetics of Poly(amidoamine)s in Different Solvents

The polyaddition kinetics of 2-methylpiperazine to 1,4-bisacryloylpiperazine was determined in water, methanol, ethylene glycol, formamide, and dimethylformamide, respectively. In the protic solvents, the polyaddition proceeded through a two-step mechanism, each step involved one of the two different secondary amino groups; the difference in amine reactivity was ascribed to the different steric hindrance by the neighbouring groups. Each step followed pseudo-second-order kinetics; the kinetic constants included the catalytic protonic species. In the case of dimethylformamide, the polyaddition proceeded through third-order kinetics; this accounted for the autocatalytic activity of the amino groups. The apparent kinetic constants in the protic solvents increased with the increase in the autoprotolysis constant values and decreased with the increase of the dipole moment.

Synthesis, Acid-Base Properties and Preliminary Cell Compatibility Evaluation of Amphoteric Poly(Amido-Hydrazine)s

Amphoteric poly(amido-hydrazine)s (PAHYs) were obtained by hydrogen-transfer polyaddition of hydrazine, 1,2-dimethylhydrazine and 1,1-dimethylhydrazine to 2,2-bisacrylamidoacetic acid. These polymers were studied for biomedical applications, such as degradability in water solution, acid-base properties, and cell toxicity. They degraded rapidly in aqueous media under physiological conditions, their molecular weight was reduced to about one-fourth, that of the original polymer in less than two days. They exhibited a typical polyelectrolyte behavior with isoelectric points between 4 and 5 and are prevailingly anionic in the blood. In preliminary cell toxicity essays they proved to be remarkably biocompatible, comparable in this respect to amphoteric poly(amido-amine)s (PAAs), and much less toxic than poly-L-lysine and polyethylenimine.

Intracellular Delivery and Triggered Release of DNA Using Biodegradable Poly(2-hydroxypropylene imine)s Containing Cystamine Units

Poly(2-hydroxypropylene imine)s containing segments of cystamine (PHPI-CA) are synthesized by polycondensation of 1,3-dibromo-2-propanol with a mixture of 1,3-diamino-2-propanol and cystamine. High molecular weight fractions of these polymers are collected by ultrafiltration and characterized by chemical analysis, ¹ H and ¹³ C-NMR spectroscopy, size-exclusion chromatography with triple detection, and potentiometric titration, and are tested for DNA delivery in vitro. It is shown that PHPI-CA are highly branched polymers containing disulfide linkages. Transfection efficiency of PHPI-CA for DNA gives similar results to that of PHPI with GFP⁺ cell percent reaching 80-90%. Cytotoxicity levels for PHPI-CA are lower than that of PHPI. Novel polymers containing different amounts of disulfide linkages are able to disintegrate and release DNA following the treatment with reducing agent 1,4-dithiothreitol. Downstream application of PHPI-CA transfected cells for RNA purification shows that RNA yield is not affected even after the double transfection suggesting that these polymers could be great candidates for in vitro and in vivo transfection.

Cationic Polymers for Intracellular Delivery of Proteins

Many therapeutic proteins exert their pharmaceutical action inside the cytoplasm or onto individual organelles inside the cell. Intracellular protein delivery is considered to be the most direct, fastest and safest approach for curing gene-deficiency diseases, enhancing vaccination and triggering cell transdifferentiation processes, within other curative applications. However, several hurdles have to be overcome. For this purpose the use of polymers, with their ease of modification in physical and chemical properties, is attractive in protein drug carriers. They can protect their therapeutic protein cargo from degradation and enhance their bioavailability at targeted sites. In this chapter, potential and currently used polymers for fabrication of protein delivery systems and their applications for intracellular administration are discussed. Special attention is given to the use of cationic polymers for their ability to promote the cellular uptake of therapeutic proteins.

Timed-release polymers as novel transfection reagents

Timed-release polymer with 95% gene expression, which was greater than a commercial transfection reagent.

Bioresponsive poly(amidoamine)s designed for intracellular protein delivery

Poly(amidoamine)s with bioreducible disulfide linkages in the main chain (SS-PAAs) and pH-responsive, negatively charged citraconate groups in the sidechain have been designed for effective intracellular delivery and release of proteins with a net positive charge at neutral pH. Using lysozyme as a cationic model protein these water soluble polymers efficiently self-assemble into nanocomplexes by charge attraction. At pH5 (the endosomal pH) the amide linkages connecting the citraconate groups in the sidechains of the SS-PAAs are hydrolyzed by intramolecular catalysis, resulting in expulsion of the negative citraconate groups and formation of protonated amine groups, resulting in charge reversal of the polymeric carrier from negative to positive. The concomitant endosomal buffering effect and increased polymer-endosomal membrane interactions are considered to lead to increased protein delivery into the cytosol. Besides destabilization of the polymer-protein nanoparticles by the charge reversal effect, intracellular cleavage of disulfide linkages in the polymer ensure further unpacking of the protein in the cytosol. Cellinternalization and cytotoxicity experiments with primary human umbilical vein endothelial cells (HUVEC) showed that the SS-PAA-based nanocomplexes were essentially non-toxic, and that lysozyme is successfully internalized into HUVEC. The results indicate that these charge reversal SS-PAAs have excellent properties as non-toxic intracellular delivery systems for cationic proteins.

Dendrimers for siRNA Delivery

Since the discovery of the “starburst polymer”, later renamed as dendrimer, this class of polymers has gained considerable attention for numerous biomedical applications, due mainly to the unique characteristics of this macromolecule, including its monodispersity, uniformity, and the presence of numerous functionalizable terminal groups. In recent years, dendrimers have been studied extensively for their potential application as carriers for nucleic acid therapeutics, which utilize the cationic charge of the dendrimers for effective dendrimer-nucleic acid condensation. siRNA is considered a promising, versatile tool among various RNAi-based therapeutics, which can effectively regulate gene expression if delivered successfully inside the cells. This review reports on the advancements in the development of dendrimers as siRNA carriers.

Poly(amidoamine) polymers: soluble linear amphiphilic drug-delivery systems for genes, proteins and oligonucleotides

Polymer-drug and polymer-protein conjugates are emerging as a robust and well-characterized class of therapeutic entity. Although there are no low-molecular-weight soluble polymer conjugates in routine clinical use, there are many examples of routinely used high-molecular-weight drugs conjugated to soluble polymers (e.g., Oncospar). Advances in synthetic polymer chemistry have fostered the development of linear poly(amidoamine)s (PAA)s that impart both biodegradability, 'smart' (pH responsive) biological activity and biocompatibility. In their linear form, such as hyper-branched poly(amidoamine) (PAMAM) dendrimers, linear PAAs can be used to deliver large therapeutic entities such as peptides, proteins and genes to either the cytosol or nucleus. Furthermore, these polymers offer great potential in vivo due to their ability to either target the liver or be directed away from the liver and enter tumor mass via the enhanced permeability and retention (EPR) effect. PAAs also exhibit minimal toxicity (dependent upon backbone chemistry), relative to well-characterized polymers used for gene delivery. The propensity of PAAs to modulate intracellular trafficking resulting in their cytosolic translocation has also recently been quantified in vivo and is the primary focus of this article.

Effects of branched or linear architecture of bioreducible poly(amido amine)s on their in vitro gene delivery properties

In this study, the gene delivery properties of new hyperbranched poly(amido amine)s (PAAs) with disulfide linkages in the main chain were investigated in comparison with their linear analogs. Eight different bioreducible PAAs were prepared by Michael addition of N,N'-bisacryloylpiperazine (BP) with cystamine (CYST) or N,N'-dimethylcystamine (DMC) and of N,N'-cystaminebisacrylamide (CBA) with N,N'-ethylenediamine (EDA) or N,N'-dimethylethylenediamine (DMEDA). In order to study the effect of terminal groups on the transfection efficiency, each polymer was terminated with 4-aminobutanol (ABOL) or with 2-aminoethanol (ETA). The hyperbranched and the linear PAAs generally formed polyplexes with plasmid DNA with sizes around 200nm and positive zeta potentials ranging from +10 to +22mV at polymer/DNA weight ratios equal or higher than 3/1. Remarkably low or no cytotoxicity was observed for both hyperbranched and linear PAAs. Hyperbranched CBA-containing PAAs showed higher gene expression in DNA transfection tests with COS-7 cells than their linear analogs and up to two times higher than linear PEI that was used as the reference polymer. Transfection efficiencies of the branched PAAs were generally enhanced by the presence of serum, which is a promising property for future in vivo studies with these hyperbranched PAAs. In this study the ease of synthetic modification of both linear and hyperbranched poly(amido amide)s and the versatility of hyperbranched PAAs in regulating DNA transfection and cytotoxicity are demonstrated. The results show the large possibilities for this class of polymers to provide polymeric vectors with controllable properties for gene therapy applications.

Advanced materials for co-delivery of drugs and genes in cancer therapy

With cancer being the major cause of mortality worldwide, the continued development of safe and efficacious treatments is warranted. A better understanding of the molecular mechanism and genetic basis of tumor initiation and progression, coupled with advances in chemistry, molecular biology and engineering have led to discovery of a wide range of therapeutic agents for cancer therapy. However, multidrug-resistance, which is mainly caused by malfunction of genes, has become a major problem in chemotherapy. To overcome this problem, the simultaneous delivery of genes to cancer cells has been proposed to correct the malfunctioned genes to sensitize the cells to chemotherapeutics. This progress report summarizes key advances in drug and gene delivery with focus on the development of polymers, peptides, liposomes and inorganic materials as nanocarriers for co-delivery of small molecular drugs and macromolecular genes or proteins. In addition, challenges and future perspectives in the design of nanocarriers for the co-delivery of therapeutic drugs and genes are discussed.

Surface conjugation of triphenylphosphonium to target poly(amidoamine) dendrimers to mitochondria

Dendrimers have emerged as promising carriers for the delivery of a wide variety of pay-loads including therapeutic drugs, imaging agents and nucleic acid materials into biological systems. The current work aimed to develop a novel mitochondria-targeted generation 5 poly(amidoamine) (PAMAM) dendrimer (G(5)-D). To achieve this goal, a known mitochondriotropic ligand triphenylphosphonium (TPP) was conjugated on the surface of the dendrimer. A fraction of the cationic surface charge of G(5)-D was neutralized by partial acetylation of the primary amine groups. Next, the mitochondria-targeted dendrimer was synthesized via the acid-amine-coupling conjugation reaction between the acid group of (3-carboxypropyl)triphenyl-phosphonium bromide and the primary amines of the acetylated dendrimer (G(5)-D-Ac). These dendrimers were fluorescently labeled with fluorescein isothiocyanate (FITC) to quantify cell association by flow cytometry and for visualization under confocal laser scanning microscopy to assess the mitochondrial targeting in vitro. The newly developed TPP-anchored dendrimer (G(5)-D-Ac-TPP) was efficiently taken up by the cells and demonstrated good mitochondrial targeting. In vitro cytotoxicity experiments carried out on normal mouse fibroblast cells (NIH-3T3) had greater cell viability in the presence of the G(5)-D-Ac-TPP compared to the parent unmodified G(5)-D. This mitochondria-targeted dendrimer-based nanocarrier could be useful for imaging as well as for selective delivery of bio-actives to the mitochondria for the treatment of diseases associated with mitochondrial dysfunction.

2011 Rita Schaffer lecture: nanoparticles for intracellular nucleic acid delivery

Nanoparticles are a promising technology for delivery of new types of therapeutics. A polymer library approach has allowed engineering of polymeric particles that are particularly effective for the delivery of DNA and siRNA to human cells. Certain chemical structural motifs, degradable linkages, hydrophobicity, and biophysical properties are key for successful intracellular delivery. Small differences to biomaterial structure, and especially the type of degradable linkage in the polymers, can be critical for successful delivery of siRNA vs. DNA. Furthermore, subtle changes to biomaterial structure can facilitate cell-type gene delivery specificity between human brain cancer cells and healthy cells as well as between human retinal endothelial cells and epithelial cells. These polymeric nanoparticles are effective for nucleic acid delivery in a broad range of human cell types and have applications to regenerative medicine, ophthalmology, and cancer among many other biomedical research areas.

Functionalized linear poly(amidoamine)s are efficient vectors for intracellular protein delivery

An effective intracellular protein delivery system was developed based on functionalized linear poly(amidoamine)s (PAAs) that form self-assembled cationic nanocomplexes with oppositely charged proteins. Three differently functionalized PAAs were synthesized, two of these having repetitive disulfide bonds in the main chain, by Michael-type polyaddition of 4-amino-1-butanol (ABOL) to cystamine bisacrylamide (CBA), histamine (HIS) to CBA, and ABOL to bis(acryloyl)piperazine (BAP). These water-soluble PAAs efficiently condense β-galactosidase by self-assembly into nanoscaled and positively-charged complexes. Stable under neutral extracellular conditions, the disulfide-containing nanocomplexes rapidly destabilized in a reductive intracellular environment. Cell-internalization and cytotoxicity experiments showed that the PAA-based nanocomplexes were essentially non-toxic. β-Galactosidase was successfully internalized into cells, with up to 94% of the cells showing β-galactosidase activity, whereas the enzyme alone was not taken up by the cells. The results indicate that these poly(amidoamine)s have excellent properties as highly potent and non-toxic intracellular protein carriers, which should create opportunities for novel applications in protein delivery.