Dendritic polyglycerol with secondary amine shell as an efficient gene delivery vector with reduced toxicity

Dendritic polycation (PG‐BEN) using polyglycerol as a core and secondary amine shell consisting of N¹,N¹¹‐bisethylnorspermine (BEN) was synthesized. Polymers containing primary amines in the shell (PG‐Nor and PG‐NH₂) were synthesized as controls to allow evaluation of the shell effect on physicochemical and transfection properties of the polymers. All studied polymers condensed DNA and formed polyplexes with sizes less than 110 nm. PG‐BEN and PG‐Nor had a similar transfection activity that was fully comparable with that of the control polyethylenimine. Amongst the studied polymers, PG‐BEN demonstrated the lowest cytotoxicity, suggesting that PG‐BEN is a promising gene delivery vector with favorable transfection/toxicity profile. Copyright © 2014 John Wiley & Sons, Ltd.     

Phospholipid–Detergent Conjugates as Novel Tools for siRNA Delivery

One of the potential benefits of drug delivery systems in medicine is the creation of nanoparticle‐based vectors that deliver a therapeutic cargo in sufficient quantity to a target site to enable a selective effect, width of the therapeutic window depending on the toxicity of the vector and the cargo. In this work, we intended to improve the siRNA delivery efficiency of a new kind of nucleic acid carrier, which is the result of the conjugation of the membrane phospholipid 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine (DOPC) to the membrane‐active species Triton X‐100 (TX100). We hypothesized that by improving the biodegradability the cytotoxicity of the conjugate might by reduced, whereas its original transfection potential would be tentatively preserved. DOPC was conjugated to Triton X‐100 through spacers displaying various resistance to chemical hydrolysis and enzyme degradation. The results obtained through in vitro siRNA delivery experiments showed that the initial phosphoester bond can be replaced with a phospho(alkyl)enecarbonate group with no loss in the transfection activity, whereas the associated cytotoxicity was significantly decreased, as assessed by metabolic activity and membrane integrity measurements. The toxicity of the conjugates incorporating a phospho(alkyl)enesuccinnate moiety proved even lower but was clearly balanced with a reduction of the siRNA delivery efficiency. Hydrolytic stability and intracellular degradation of the conjugates were investigated by NMR spectroscopy and mass spectrometry. A general trend was that the more readily degraded conjugates were those with the lower toxicity. Otherwise, the phospho(alkyl)enecarbonate conjugates revealed some hemolytic activity, whereas the parent phosphoester did not. The reason why these conjugates behave differently with respect to hemolysis might be a consequence of unusual fusogenic properties and probably reflects the difference in the stability of the conjugates in the intracellular environment.     

Synthesis and cell transfection properties of cationic uracil-morpholino tetramer

Synthesis and cell transfection properties of guanidinium-functionalized uracil morpholino tetramer have been reported for the first time. Due to the basic nature of guanidinium groups they remain protonated under physiological conditions. Such cationic tetramer exhibits efficient cellular uptake properties as visualized by microscopy imaging using fluorescent dye BODIPY. 7′-End of this morpholino tetramer was functionalized with an azide group for conjugation with various types of biomolecules or drugs for cellular delivery.     

An inflammation self-adaptive nanocarrier for highly efficient gene therapy

Inflammation represents a real micromilieu of many diseases as well as the actual application environment of nanocarriers. However, few studies have focused on the influence of the inflammatory environment on the effects of nanoparticle delivery. Herein, a novel inflammation self-adaptive nanocarrier is designed and fabricated by attaching the ascorbyl palmitate (AP) onto the surface of gene-entrapped polymeric nanocomplexes through the formation of phenylboronate bond. In vitro and in vivo studies demonstrate that the introduction of AP enhances considerably the accumulation of entrapped gene in inflammation and facilitates the intracellular uptake of gene-loading nanoparticles. Meanwhile, the gene transfection efficiency of DNA and in vivo gene therapy of nanocomplexes under an inflammation stimulus is significantly enhanced. Hence, our delicate design concept opens up a new pathway to develop an inflammation self-adaptive drug delivery system for precise drug/gene delivery and therapy.     

Temperature‐Sensitive Amphiphilic Non‐Ionic Triblock Copolymers for Enhanced In Vivo Skeletal Muscle Transfection

It is reported that low concentration of amphiphilic triblock copolymers of pMeOx‐b‐pTHF‐b‐pMeOx structure (TBCPs) improves gene expression in skeletal muscle upon intramuscular co‐injection with plasmid DNA. Physicochemical studies carried out to understand the involved mechanism show that a phase transition of TBCPs under their unimer state is induced when the temperature is elevated from 25 to 37 °C, the body temperature. Several lines of evidences suggest that TBCP insertion in a lipid bilayer causes enough lipid bilayer destabilization and even pore formation, a phenomenon heightened during the phase transition of TBCPs. Interestingly, this property allows DNA translocation across the lipid bilayer model. Overall, the results indicate that TBCPs exhibiting a phase transition at the body temperature is promising to favor in vivo pDNA translocation in skeletal muscle cells for gene therapy applications.     

Inorganic nanoparticles as carriers of nucleic acids into cells

The transfer of nucleic acids (DNA or RNA) into living cells, that is, transfection, is a major technique in current biochemistry and molecular biology. This process permits the selective introduction of genetic material for protein synthesis as well as the selective inhibition of protein synthesis (antisense or gene silencing). As nucleic acids alone are not able to penetrate the cell wall, efficient carriers are needed. Besides viral, polymeric, and liposomal agents, inorganic nanoparticles are especially suitable for this purpose because they can be prepared and surface-functionalized in many different ways. Herein, the current state of the art is discussed from a chemical viewpoint. Advantages and disadvantages of the available methods are compared.     

In Vitro Drug and Gene Delivery Using Random Cationic Copolymers Forming Stable and pH‐Sensitive Polymersomes

Stimuli‐sensitive polymeric vesicles or polymersomes as self‐assembled colloidal nanocarriers have received paramount importance for their integral role as delivery system for therapeutics and biotherapeutics. This work describes spontaneous polymersome formation at pH 7, as evidenced by surface tension, steady state fluorescence, dynamic light scattering, and microscopic studies, by three hydrophilic random cationic copolymers synthesized using N ,N‐(dimethylamino)ethyl methacrylate (DMAEM) and methoxy poly(ethylene glycol) monomethacrylate in different mole ratios. The results suggest that methoxy poly(ethylene glycol) chains constitute the bilayer membrane of the polymersomes and DMAEM projects toward water constituting the positively charged surface. The polymersomes have been observed to release their encapsulated guest at acidic pH as a result of transformation into polymeric micelles. All these highly biocompatible cationic polymers show successful gene transfection ability as nonviral vector on human cell line with different potential. Thus these polymers prove their utility as a potential delivery system for hydrophilic model drug as well as genetic material.