A novel polyphosphoester (PPE) with vinyl ether side chain functionality was developed as a versatile template for postpolymerization modifications, and its degradability and biocompatibility were evaluated. An organocatalyzed ring-opening polymerization of ethylene glycol vinyl ether-pendant cyclic phosphotriester monomer allowed for construction of poly(ethylene glycol vinyl ether phosphotriester) (PEVEP). This vinyl ether-functionalized PPE scaffold was coupled with hydroxyl- or thiol-containing model small molecules via three different types of conjugation chemistries−thiol−ene “click” reaction, acetalization, or thio−acetalization reaction−to afford modified polymers that accommodated either stable thio−ether or hydrolytically labile acetal or thio−acetal linkages. Amphiphilic diblock copolymers of poly(ethylene glycol) and PEVEP formed well-defined micelles with a narrow and monomodal size distribution in water, as confirmed by dynamic light scattering (DLS), transmission electron microscopy, and atomic force microscopy. The stability of the micelles and the hydrolytic degradability of the backbone and side chains of the PEVEP block segment were assessed by DLS and nuclear magnetic resonance spectroscopy (1H and 31P), respectively, in aqueous buffer solutions at pH values of 5.0 and 7.4 and at temperatures of 25 and 37°C. The hydrolytic degradation products of the PEVEP segments of the block copolymers were then identified by electrospray ionization, gas chromatography, and matrix-assisted laser desorption/ionization mass spectrometry. The parent micelles and their degradation products were found to be non-cytotoxic at concentrations up to 3 mg/mL, when evaluated with RAW 264.7 mouse macrophages and OVCAR-3 human ovarian adenocarcinoma cells.

Linear and star-shape PGMAs were synthesized by atom transfer radical polymerization and then functionalized with four different amines by ring-opening addition. This resulted in the formation of polyglycerol-like polymers having both hydroxyl and amine moieties and different water-solubility. The water insoluble polymers could form pH-sensitive nanoassemblies, while the soluble derivatives efficiently complexed a short strand polynucleotide. The aminated polyglycerol interacted more avidly with the oligonucleotide than the control polyethylenimine, and high transfection efficacy could be obtained with the linear derivative.

Gene therapy holds the promise of correcting a genetic defect. It can be achieved with the introduction of a normal wild-type transgene into specific cells of the patient where the endogenous gene is underexpressing or by the introduction of a therapeutic agent, such as, antisense oligonucleotides (AON) or small interfering RNA (siRNA) to inhibit transcription and/or translation of an overexpressing endogenous gene or a cancer causing oncogene. Gene therapy has been utilized for vaccination and for the treatment of several diseases, such as, cancer, viral infections and dermatological diseases. However, there are many hurdles to overcome in developing effective gene-based therapeutics, including cellular barriers, enzymatic degradation and rapid clearance after administration. Successful transfer of nucleic acids (e.g. plasmid DNA, AON, siRNA, small hairpin RNA and micro RNA) into cells usually relies on the use of efficient carriers, commonly viral or non-viral vectors. Presently, viral vectors are more efficient than non-viral systems. However, immunogenicity, inflammatory reactions and problems associated with scale-up limit their clinical use. The ideal carriers for gene delivery should be safe and yet ensure that the DNA/RNA survives the extra- and intracellular environment and efficiently transfer to the appropriate cellular compartments. This review discusses some of the strategies that have been employed to overcome the barriers towards successful gene delivery.

Over the past 10 years, polyglycerols and their structurally related analogs have received considerable attention in the biomedical field. Poly(glycidyl methacrylate) (PGMA) is a versatile polymer because its pendant epoxide groups can be opened with different functional groups to generate poly(glycerol methacrylate)s (PGOHMA) derivatives. In this work, linear and star-shape PGMAs were synthesized by atom transfer radical polymerization and then functionalized with four different amines by ring-opening addition. This resulted in the formation of polyglycerol-like polymers having both hydroxyl and amine moieties and different water-solubility. The water-insoluble polymers could form pH-sensitive nanoassemblies, while the soluble derivatives efficiently complexed a short strand polynucleotide. The aminated polyglycerol interacted more avidly with the oligonucleotide than the control poly(ethyleneimine), and high transfection efficacy could be obtained with the linear derivative. Such polymers could find practical applications for the delivery of drugs and nucleic acids.

Gene therapy is a technique utilized to treat diseases caused by missing, defective or overexpressing genes. Although viral vectors transfect cells efficiently, risks associated with their use limit their clinical applications. Nonviral delivery systems are safer, easier to manufacture, more versatile and cost effective. However, their transfection efficiency lags behind that of viral vectors. Many groups have dedicated considerable effort to improve the efficiency of nonviral gene delivery systems and are investigating complexes composed of DNA and soft materials such as lipids, polymers, peptides, dendrimers and gemini surfactants. The bottom-up approach in the design of these nanoparticles combines components essential for high levels of transfection, biocompatibility and tissue-targeting ability. This article provides an overview of the strategies employed to improve in vitro and in vivo transfection, focusing on the use of cationic lipids and surfactants as building blocks for nonviral gene delivery systems.

The objectives of the current study were to design and characterize poly(ethylene glycol) (PEG)-based carriers for antisense oligonucleotide (AON) delivery that would gradually release the AON upon the enzymatic degradation of a complementary nuclease-sensitive sequence (SON). A phosphodiester SON was conjugated to one extremity or to the central part of PEG (molecular weight 10 or 20 K). The PEG-SON was hybridized to a nuclease-resistant phosphorothioate AON analog. Compared to the non-PEGylated duplex, the PEG-SON/AON derivative had a modest impact on the degradation kinetics of SON as monitored by a fluorescence dequenching assay performed in the presence of DNase 1. The reaction rate depended on the grafting position of SON and on the PEG’s molecular weight. To further control the release rate, PEG-SON/AON conjugates were complexed to poly(amidoamine) (PAMAM) dendrimers of different generations (G). Interaction with PAMAMs of G3 and G5 yielded monodisperse polyion complex micelles (PICMs) with average mean sizes ranging from 70 to 100 nm. The PICMs were found to decrease the catalytic reaction rate by 20 to 100 fold; the slowest release kinetics being achieved with PEG10K-SON/AON/G5 PAMAM. The PEGylated conjugates reported in this manuscript as well as their self-assemblies with PAMAMs, could prove potentially useful to confer prolonged circulating properties to nucleic acid drugs and release them in a sustained manner.

Purpose. To optimize oligonucleotide (ODN)-based polyion complex micelles (PICMs) by studying the effects of polymer composition and length on their properties. Methods. Atom transfer radical polymerization was used to synthesize copolymers with increasing hydrophilic nonionic and cationic block lengths. PICMs were prepared by mixing the copolymers and ODN at various nitrogen-to-phosphate (N/P) ratios and characterized by gel electrophoresis and dynamic light scattering. The stability of the complexes towards dissociation was tested using a competitive assay with heparin. Finally, protection of the incorporated ODN against DNAse I degradation was evaluated. Results. A library of copolymers composed of poly(ethylene glycol) (PEG) and poly(aminoethyl methacrylate) (PAEMA) and/or poly(dimethylamino)-ethylmethacrylate) (PDMAEMA) was synthesized. All polymers efficiently interacted with the ODN at N/P ratios approaching 1.5. Narrowly distributed but easily dissociable PICMs were obtained using PEG 5000 and short DMAEMA chains. Shortening the PEG block to 2000, increasing the number of cationic units and using AEMA produced more stable complexes but at the cost of colloidal properties. All polymers were able to protect the ODN from nuclease degradation. Conclusions. PEG 3000-based PICMs possess good colloidal properties, intermediate stability towards dissociation and adjustable buffering capacity, making thempotentially useful for the delivery of nucleic acid drugs.

Poly(ethylene oxide)-block-poly(styrene oxide) (PEO-b-PSO) and PEO-b-poly(butylene oxide) (PEO-b-PBO) of different chain lengths were synthesized and characterized for their self-assembling properties in water by dynamic/static light scattering, spectrofluorimetry, and transmission electron microscopy. The resulting polymeric micelles were evaluated for their ability to solubilize and protect the anticancer drug docetaxel (DCTX) from degradation. The drug release kinetics as well as the cytotoxicity of the loaded micelles were assessed in vitro. All polymers formed micelles with a highly viscous core at low critical association concentrations (10 mg/L). Micelle morphology depended on the nature of the hydrophobic block, with PBO- and PSO-based micelles yielding monodisperse spherical and cylindrical nanosized aggregates, respectively. The maximum solubilization capacity for DCTX ranged from 0.7 to 4.2% and was the highest for PSO micelles exhibiting the longest hydrophobic segment. Despite their high affinity for DCTX, PEO-b-PSO micelles were not able to efficiently protect DCTX against hydrolysis under accelerated stability testing conditions. Only PEO-b-PBO bearing 24 BO units afforded significant protection against degradation. In vitro, DCTX was released slower from the latter micelles, but all formulations possessed a similar cytotoxic effect against PC-3 prostate cancer cells. These data suggest that PEO-b-P(SO/BO) micelles could be used as alternatives to conventional surfactants for the solubilization of taxanes.

Inhibition of c-secretase, one of the enzymes responsible for the cleavage of the amyloid precursor protein (APP) to produce pathogenic Ab peptides, is an attractive approach for the treatment of Alzheimer’s disease. We designed a c-secretase inhibitor bearing an ascorbic acid moiety which allows a specific delivery of the drug to the brain. Through, on the one hand, Ab peptide production measurements by specific in vitro assays (c-secretase cell free assay and cell based assay on HEK 293 APP transfected cells) and on the other hand through pharmacokinetic studies on animal models, the new inhibitor shows a good pharmacokinetic profile as well as a potent c-secretase inhibitory activity in vitro. From the obtained results, it is expected that drug 2 will be mainly delivered to the CNS with a low diffusion in the peripheral tissues. Consequently the side effects of this c-secretase inhibitor on the immune cells could be reduced.

Naproxen is one of the most potent NSAIDs and plays an important role in the treatment of neurodegenerative diseases. Poor brain delivery of naproxen at therapeutic doses, in addition to its serious gastrointestinal side effects, has prompted research into the development of a specific carrier system that is capable of delivering naproxen to the brain at smaller doses. The purpose of this study was to evaluate two brain-specific carrier systems of naproxen. The first was the dihydropyridine/pyridinium redox system that utilized a lipophilic chemical delivery system coupled to the carboxylic acid group of naproxen through an ethanolamine linker. Secondly, an ascorbic acid system, which has reducing properties and acts as a biological carrier through sodiumdependent vitamin-C transporter, was used for brain-specific delivery of naproxen. The prepared prodrugs were stable in aqueous buffers (pH 1.2 and 7.4) and rapidly hydrolyzed in biological fluids. Bioavailability studies revealed that both prodrugs 10 and 17 were rapidly cleared from blood with half lives of about 1 h, which will likely decrease systemic adverse effects. The rapid clearance from the blood was accompanied by an increase in the prodrug concentration in the brain, which occurred as a result of the prodrug being more locked in compared to the parent drug naproxen.