A PEG-b-poly(disulfide-l-lysine) based redox-responsive cationic polymer for efficient gene transfection

Photothermally Responsive siRNA Delivery by PEGylated Poly(amido amine)s for Improved Tumor Therapy

Polycations have a high siRNA binding efficiency, however, their cytotoxicity and poor transfection efficiency prevent their use in siRNA delivery. This study combined PEGylation for enhanced safety with a photothermally controlled endolysosomal escape to improve the cytoplasmic delivery of polycations.We first synthesized PEGylated cationic polymers (denoted as PEG-PHD), which were then used to prepare polyplexes with siRNA and ICG through electrostatic interactions. We found that the cytotoxicity of PEG-PHD and its polyplexes were significantly decreased compared with unPEGylated PHD. The prepared polyplexes successfully induced endolysosomal escape under laser irradiation, thereby showing better siRNA delivery efficiency in vitro and in vivo. Finally, polyplexes carrying siBcl-2 achieved significant inhibition of 4T1 tumor mediated by specific gene silencing after intravenous injection. In conclusion, this biocompatible photothermal controlled delivery platform is suitable for improving the efficiency of siRNA transfection. Overall, this study suggests that combing PEGylation and photoresponsive delivery is a promising strategy for designing siRNA delivery carriers.

Poly(disulfide)s: From Synthesis to Drug Delivery

Bioresponsive polymers have been widely used in drug delivery because of their degradability. For example, poly(disulfide)s with repeating disulfide bonds in the main chain have attracted considerable research attention. The characteristics of the disulfide bonds, including their dynamic and reversible properties and their responsiveness to stimuli such as reductants, light, heat, and mechanical force, make them ideal platforms for on-demand drug delivery. This review introduces the synthesis methods and applications of poly(disulfide)s. Furthermore, the synthesis methods of poly(disulfide)s are classified on the basis of the monomers used: oxidative step-growth polymerization with dithiols, ring-opening polymerization with cyclic disulfides, and polymerization with linear disulfides. In addition, recent advances in poly(disulfide)s for the delivery of small-molecule or biomacromolecular drugs are discussed. Quantum-dot-loaded poly(disulfide) delivery systems for imaging are also included. This review provides an overview of the various design strategies employed in the construction of poly(disulfide) platforms to inspire new applications in the field of drug delivery.

Agmatine-grafted bioreducible poly(l-lysine) for gene delivery with low cytotoxicity and high efficiency

Bioreducible cationic polymers have gained considerable attention in gene delivery due to their low cytotoxicity and high efficiency. In the present work, we reported a cationic polymer, poly(disulfide-l-lysine)-g-agmatine (denoted as SSL-AG), and evaluated its ability to transfer pEGFP-ZNF580 plasmid (pZNF580) into human umbilical vein endothelial cells (HUVECs). This SSL-AG polymeric carrier efficiently condensed pZNF580 into positively charged particles (<200 nm) through electrostatic interaction. This carrier also exhibited excellent buffering capacity in the physiological environment, good pDNA protection against enzymatic degradation and rapid pDNA release in a highly reducing environment mainly because of the responsive cleavage of disulfide bonds in the polymer backbone. The hemolysis assay and in vitro cytotoxicity assay suggested that the SSL-AG carrier and corresponding gene complexes possessed both good hemocompatibility and great cell viability in HUVECs. The cellular uptake of the SSL-AG/Cy5-oligonucleotide group was 3.6 times that of the poly(l-lysine)/Cy5-oligonucleotide group, and its mean fluorescence intensity value was even higher than that of the PEI 25 kDa/Cy5-oligonucleotide group. Further, the intracellular trafficking results demonstrated that the SSL-AG/Cy5-oligonucleotide complexes exhibited a high nucleus co-localization rate (CLR) value (36.0 ± 2.8%, 3.4 times that of the poly (l-lysine)/Cy5-oligonucleotide group, 1.6 times that of the poly(disulfide-l-lysine)-g-butylenediamine/Cy5-oligonucleotide group) at 24 h, while the endo/lysosomal CLR value was relatively low. This suggested that SSL-AG successfully delivered plasmid into HUVECs with high cellular uptake, rapid endosomal escape and efficient nuclear accumulation owing to the structural advantages of the bioreducible and agmatine groups. In vitro transfection assay also verified the enhanced transfection efficiency in the SSL-AG/pZNF580 group. Furthermore, the results of CCK-8, cell migration and in vitro/vivo angiogenesis assays revealed that pZNF580 delivered by SSL-AG could effectively enhance the proliferation, migration and vascularization of HUVECs. In a word, the SSL-AG polymer has great potential as a safe and efficient gene carrier for gene therapy.

Polymeric nano-carriers for on-demand delivery of genes via specific responses to stimuli

Polymeric nano-carriers have been developed as a most capable and feasible technology platform for gene therapy. As vehicles, polymeric nano-carriers are obliged to possess high gene loading capability, low immunogenicity, safety, and the ability to transfer various genetic materials into specific sites of target cells to express therapeutic proteins or block a process of gene expression. To this end, various types of polymeric nano-carriers have been prepared to release genes in response to stimuli such as pH, redox, enzymes, light and temperature. These stimulus-responsive nano-carriers exhibit high gene transfection efficiency and low cytotoxicity. In particular, dual- and multi-stimulus-responsive polymeric nano-carriers can respond to a combination of signals. Markedly, these combined responses take place either simultaneously or in a sequential manner. These dual-stimulus-responsive polymeric nano-carriers can control gene delivery with high gene transfection both in vitro and in vivo. In this review paper, we highlight the recent exciting developments in stimulus-responsive polymeric nano-carriers for gene delivery applications.

Delivery of pOXR1 through an injectable liposomal nanoparticle enhances spinal cord injury regeneration by alleviating oxidative stress

Oxidation resistance 1 (OXR1) is regarded as a critical regulator of cellular homeostasis in response to oxidative stress. However, the role of OXR1 in the neuronal response to spinal cord injury (SCI) remains undefined. On the other hand, gene therapy for SCI has shown limited success to date due in part to the poor utility of conventional gene vectors. In this study, we evaluated the function of OXR1 in SCI and developed an available carrier for delivering the OXR1 plasmid (pOXR1). We found that OXR1 expression is remarkably increased after SCI and that this regulation is protective after SCI. Meanwhile, we assembled cationic nanoparticles with vitamin E succinate-grafted ε-polylysine (VES-g-PLL) (Nps). The pOXR1 was precompressed with Nps and then encapsulated into cationic liposomes. The particle size of pOXR1 was compressed to 58 nm, which suggests that pOXR1 can be encapsulated inside liposomes with high encapsulation efficiency and stability to enhance the transfection efficiency. The agarose gel results indicated that Nps-pOXR1-Lip eliminated the degradation of DNA by DNase I and maintained its activity, and the cytotoxicity results indicated that pOXR1 was successfully transported into cells and exhibited lower cytotoxicity. Finally, Nps-pOXR1-Lip promoted functional recovery by alleviating neuronal apoptosis, attenuating oxidative stress and inhibiting inflammation. Therefore, our study provides considerable evidence that OXR1 is a beneficial factor in resistance to SCI and that Nps-Lip-pOXR1 exerts therapeutic effects in acute traumatic SCI.

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OXR1 is upregulated after SCI and may provide a protective effect in response to neural injury.

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OXR1 plasmid is condensed by VES-g-PLL micelles and then encapsulated into cationic liposomes.

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Liposome complexes significantly enhance the OXR1 protein expression in vivo and in vitro.

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Overexpressed OXR1 relieving oxidative stress after SCI through Nrf-2/HO-1 pathway.

Progress of cationic gene delivery reagents for non-viral vector

Gene delivery systems play a vital role in gene therapy and recombinant protein production. The advantages of using gene delivery reagents for non-viral vector include the capacity to accommodate a large packaging load and their low or absent immunogenicity. Furthermore, they are easy to produce at a large scale and preserve. Gene delivery reagents for non-viral vector are commonly used for transfecting a variety of cells and tissues. It is mainly composed of liposomes and non-liposome cationic polymers. According to the different head structures used, the non-viral cationic transfection reagents include a quaternary ammonium salt, amine, amino acid or polypeptide, guanidine salt, and a heterocyclic ring. This article summarizes these approaches and developments of types and components of transfection reagents and optimization of gene delivery. The optimization of mammalian cell transient recombinant protein expression system and cationic reagents for clinical or clinical trials are also discussed.

Preparation and Biological Property Evaluation of Novel Cationic Lipid-Based Liposomes for Efficient Gene Delivery

Novel cationic lipid-based liposomes prepared using an amphiphilic cationic lipid material, N,N-dimethyl-(N',N'-di-stearoyl-1-ethyl)1,3-diaminopropane (DMSP), have been proposed to enhance the transfection of nucleic acids. Herein, we designed and investigated liposomes prepared using DMSP, soybean phosphatidylcholine, and cholesterol. This novel gene vector has high gene loading capabilities and excellent protection against nuclease degradation. An in vitro study showed that the liposomes had lower toxicity and superior cellular uptake and transfection efficiency compared with Lipofectamine 2000. An endosomal escape study revealed that the liposomes demonstrated high endosomal escape and released their genetic payload in the cytoplasm efficiently. Mechanistic studies indicated that the liposome/nucleic acid complexes entered cells through energy-dependent endocytosis that was mediated by fossa proteins. These results suggest that such cationic lipid-based liposome vectors have potential for clinical gene delivery.

Targeting Delivery Nanocarriers for (+)-Terrein to Enhance Its Anticancer Effects

As a compound from marine fungi, (+)-terrein showed significant anticancer activity. In this study, (+)-terrein was extracted from the marine-derived fungus and showed significant cytotoxicity against cancer cells, especially in A549 cells. To enhance its anticancer effects, redox-responsive nanocarriers based on folic acid-chitosan decorating the mesoporous silica nanoparticles were designed to control (+)-terrein target delivery into cancer cells. (+)-Terrein was loaded in the holes, and folic acid-chitosan worked as a gatekeeper by disulfide linkage controlling (+)-terrein release in the tumor microenvironment. The (+)-terrein drug delivery systems exhibited cytotoxicity toward A549 cells through induction of apoptosis. The apoptosis effect was confirmed by the increase in the expression of cleaved caspase-3, caspase-9, and PARP. Taken together, this work evaluates for the first time the (+)-terrein delivery system and provides a promising nanomedicine platform for (+)-terrein.

A dual-functional buformin-mimicking poly(amido amine) for efficient and safe gene delivery

Biguanides (i.e. metformin, phenformin and buformin) are antidiabetic drugs with potential antitumor effects. Herein, a polycationic polymer, N,N'-bis(cystamine)acrylamide-buformin (CBA-Bu), containing multiple biodegradable disulphide bonds and buformin-mimicking side chains was synthesised. CBA-Bu was equipped with high efficiency and safety profile for gene delivery, meanwhile exhibiting potential antitumor efficacy. As a gene vector, CBA-Bu was able to condense plasmid DNA (pDNA) into nano-sized (<200 nm), positively-charged (>30 mV) uniform polyplexes that were well resistant to heparin and DNase I. Due to the reduction responsiveness of the disulphide bonds, CBA-Bu/pDNA polyplexes could release the loaded pDNA in the presence of dithiothreitol, and induce extremely low cytotoxicity in NIH/3T3 and U87 MG cells. The transfection results showed that CBA-Bu had a cellular uptake efficiency comparable to 25 kDa PEI, while a significantly higher gene expression level. Additionally, CBA-Bu had a lower IC50 value than its non-biguanide counterpart in two cancer cell lines. Furthermore, CBA-Bu could activate AMPK and inhibit mTOR pathways in U87 MG cells, a mechanism involved in the antitumor effect of biguanides. Taken together, CBA-Bu represented an advanced gene vector combining desirable gene delivery capability with potential antitumor activity, which was promising to achieve enhanced therapeutic efficacy in antitumor gene therapy.

From single to a dual-gene delivery nanosystem: coordinated expression matters for boosting the neovascularization in vivo

A dual-gene delivery system with coordinated expression function boosted the neovascularization.