Adeno-associated virus mediated gene transfer into primary rat brain neuronal and glial cultures: enhancement with the pH-sensitive surfactant dodecyl 2-(1'-imidazolyl) propionate

Cyclic peptide-capped gold nanoparticles for enhanced siRNA delivery

Previously, we have reported the synthesis of a homochiral l-cyclic peptide [WR]₅ and its use for delivery of anti-HIV drugs and biomolecules. A physical mixture of HAuCl₄ and the peptide generated peptide-capped gold nanoparticles. Here, [WR]₅ and [WR]₅-AuNPs were tested for their efficiency to deliver a small interfering RNA molecule (siRNA) in human cervix adenocarcinoma (HeLa) cells. Flow cytometry investigation revealed that the intracellular uptake of a fluorescence-labeled non-targeting siRNA (200 nM) was enhanced in the presence of [WR]₅ and [WR]₅-AuNPs by 2- and 3.8-fold when compared with that of siRNA alone after 24 h incubation. Comparative toxicity results showed that [WR]₅ and [WR]₅-AuNPs were less toxic in cells compared to other available carrier systems, such as Lipofectamine.

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.

Synthesis and aqueous solution properties of stimuli-responsive triblock copolymers

Two series of poly(di(methylamino)ethyl methacrylate)--poly(di(ethylene glycol)methyl ether methacrylate)--poly(di(methylamino)ethyl methacrylate), pDMAEMA--pDEGMEMA--pDMAEMA, and poly(di(ethylamino)ethyl methacrylate)--poly(di(ethylene glycol)methyl ether methacrylate)--poly(di(ethylamino)ethyl methacrylate), pDEAEMA--pDEGMEMA--pDEAEMA, triblock copolymers have been synthesized using copper-mediated living radical polymerization. Kinetic studies showed that the polymerizations were controlled yielding copolymers with MWt similar to predicted values with narrow polydispersities. UV/Vis experiments in aqueous solution indicate that the incorporation of pDMAEMA hydrophilic segments into the pDEGMEMA polymeric chains causes an increase in the lower critical solution temperature (LCST). Conversely, the incorporation of pDEAEMA hydrophobic segments has the reverse effect. It has been demonstrated that the cloud points of the copolymers increase when blocks pDMAEMA and pDEAEMA are protonated. At acidic pH and above 35-40 °C, the pDEGMEMA inner blocks become insoluble and, consequently, upon contact with water they form micellar aggregates constituted of a pDEGMEMA hydrophobic core with a pDMAEMA or pDEAEMA hydrophilic shell. At pH = 8.3 and 25 °C, the pDMAEMA--pDEGMEMA--pDMAEMA triblock copolymers form ordered aggregates of larger size. In addition under these conditions, in aqueous solution the pDEGMEMA form aggregates of smaller size than those found in the case of copolymers with pDMAEMA. Surface-tension measurements suggest that homopolymers, as well as copolymers, are surface active. The pDEGMEMA polymers present low values of the critical aggregation concentration (cac), due to their amphiphilic properties. The combination of pDEGMEMA thermosensitive segments with pDMAEMA and pDEAEMA blocks sensitive to pH and temperature has given rise to the formation of intelligent materials with responses to both stimuli. Their behavior depends on the MWt and the composition of the copolymers.

Molecular-thermodynamic theory of micellization of multicomponent surfactant mixtures: 2. pH-sensitive surfactants

In article 1 of this series, we developed a molecular-thermodynamic (MT) theory to model the micellization of mixtures containing an arbitrary number of conventional (pH-insensitive) surfactants. In this article, we extend the MT theory to model mixtures containing a pH-sensitive surfactant. The MT theory was validated by examining mixtures containing both a pH-sensitive surfactant and a conventional surfactant, which effectively behave like ternary surfactant mixtures. We first compared the predicted micellar titration data to experimental micellar titration data that we obtained for varying compositions of mixed micelles containing the pH-sensitive surfactant dodecyldimethylamine oxide (C12DAO) mixed with either a cationic surfactant (dodecyltrimethylammonium bromide, C12TAB), a nonionic surfactant (dodecyl octa(ethylene oxide), C12E8), or an anionic surfactant (sodium dodecyl sulfate, SDS) surfactant. The MT theory accurately modeled the titration behavior of C12DAO mixed with C12E8. However, C12DAO was observed to interact more favorably with SDS and with C12TAB than was predicted by the MT theory. We also compared predictions to data from the literature for mixtures of C12DAO and SDS. Although the pH values of solutions with no added acid were modeled with only qualitative accuracy, the MT theory resulted in quantitatively accurate predictions of solution pH for mixtures containing added acid. In addition, the predicted degree of counterion binding yielded a lower bound to the experimentally measured value. Finally, we predicted the critical micelle concentration (cmc) of solutions of two pH-sensitive surfactants, tetradecyldimethylamine oxide (C14DAO) and hexadecyldimethyl betaine (C16Bet), at varying solution pH and surfactant composition. However, at the pH values considered, the pH sensitivity of C16Bet could be neglected, and it was equivalently modeled as a zwitterionic surfactant. The cmc's predicted using the MT theory agreed well with the experimental cmc's and were found to be comparable to and sometimes better than the cmc's determined using the regular solution theory (RST), even though the empirical RST utilizes experimentally measured cmc's as an input. The MT theory presented here represents the first molecular-based quantitative description of the micellization behavior of mixtures of pH-sensitive surfactants and conventional surfactants, and allows qualitative and quantitative predictions of the micellization behavior of a variety of surfactant systems.

pH-dependence of the properties of hydrophobically modified polyvinylamine

A series of N-alkyl or N-benzyl substituted polyvinylamines (PVAm) were prepared and the properties of aqueous solutions were measured as functions of pH. The polymer solutions showed almost no surface activity under acidic conditions whereas surface tension was reduced to 40-50 mN/m around pH 9. Increasing either the degree of hydrophobic substitution or the hydrophobic chain length lowered the pH at which surface tension lowering was observed. Hydrophobic substitution also shifted plots of the degree of ionization versus pH toward lower pH which means lower pH values were required to achieve a given value of polymer charging. The hydrophobically modified PVAm associated in water giving species whose apparent diameter measured by dynamic light scattering decreased with increasing pH, whereas the electrophoretic mobilities of the associated species increased with decreasing pH. Although many hydrophobically modified and pH sensitive polymers have been described in the literature for applications in biomaterials, drug release and as pH sensitive surfactants, the hydrophobically modified PVAms are particularly attractive because they are easily prepared from commercially available polyvinylamines.

Efficient gene delivery to primary neuron cultures using a synthetic peptide vector system

A bi-functional, 31 amino acid synthetic peptide (polylysine-molossin) was evaluated for gene delivery to primary cultures of rat cerebral cortex neurons. Polylysine-molossin consists of an amino terminal domain of 16 lysines for electrostatic binding of DNA, and a 15 amino acid, integrin-binding domain at the carboxyl terminal. High levels of gene delivery were obtained with 20-30 microM chloroquine, with a synthetic fusogenic peptide at an optimal DNA:polylysine-molossin:fusogenic peptide w/w ratio of 1:3:0.2, and with the addition of low concentrations of Lipofectamine 2000 at an optimal DNA:polylysine-molossin:Lipofectamine 2000 w/w ratio of 1:3:0.5. With the best combination, >30% of neurons strongly expressed the beta-galactosidase reporter gene, with no observable toxicity. DNA concentrations >2 microgram/ml were essential for efficient gene delivery. This synthetic peptide provides a safe, readily standardised and flexible DNA vector system well suited to ex vivo gene delivery to neurons for experimental and clinical applications.

Non-classical nuclear localization signal peptides for high efficiency lipofection of primary neurons and neuronal cell lines

Gene transfer into CNS is critical for potential therapeutic applications as well as for the study of the genetic basis of neural development and nerve function. Unfortunately, lipid-based gene transfer to CNS cells is extremely inefficient since the nucleus of these post-mitotic cells presents a significant barrier to transfection. We report the development of a simple and highly efficient lipofection method for primary embryonic rat hippocampal neurons (up to 25% transfection) that exploits the M9 sequence of the non-classical nuclear localization signal of heterogeneous nuclear ribonucleoprotein A1 for targeting beta(2)-karyopherin (transportin-1). M9-assistant lipofection resulted in 20-100-fold enhancement of transfection over lipofection alone for embryonic-derived retinal ganglion cells, rat pheochromocytoma (PC12) cells, embryonic rat ventral mesencephalon neurons, as well as the clinically relevant human NT2 cells or retinoic acid-differentiated NT2 neurons. This technique can facilitate the implementation of promoter construct experiments in post-mitotic cells, stable transformant generation, and dominant-negative mutant expression techniques in CNS cells.