pH-sensitive degradable hydrophobe modified 1.8 kDa branched polyethylenimine as “artificial viruses” for safe and efficient intracellular gene transfection

Biodegradable Poly(Amino Ester) with Aromatic Backbone as Efficient Nonviral Gene Delivery Vectors

The development of gene delivery vectors with high efficiency and biocompatibility is one of the critical points of gene therapy. Two biodegradable poly(amino ester)s were synthesized via ring-opening polymerization between low molecular weight (LMW) PEI and diepoxide. The molecular weights of poly(amino ester)s were measured by GPC. Agarose gel retardation assays showed that these materials have good DNA-binding ability and can retard the electrophoretic mobility of plasmid DNA (pDNA) at a weight ratio of 1. The formed polyplexes have proper sizes of around 200 nm and zeta-potential values of about 30-40 mV for cellular uptake. In vitro experiments revealed that polymer P2 gave higher transfection efficiency than PEI 25KDa and Lipofectamine 2000 with less toxicity, especially in 293 cells. Results demonstrate that such a type of degradable poly(amino ester) may serve as a promising non-viral gene vector.

Defined pH-sensitive nanogels as gene delivery platform for siRNA mediated in vitro gene silencing

An advanced cationic carrier system which combines high transfection efficiency with low cytotoxicity and a control over the release of the encapsulated genetic material by the reduction of the multivalent architecture upon pH triggered degradation was developed.

Synthesis and in vitro evaluation of pH-sensitive PEG-I-dC16 block polymer micelles for anticancer drug delivery

Objectives

To develop an acid trigger release of antitumour drug delivery carriers, pH-sensitive amphiphilic poly (ethyleneglycol)-imine-benzoic-dipalmitate (PEG-I-dC16) polymers were designed and synthesized and the drug-loaded micelles were evaluated in vitro.

Methods

PEG-I-dC16 synthesized by Schiff base synthetic method and characterized by 1H-NMR. To determine the drug-loading capacity, doxorubicin (DOX) was encapsulated in the micelles using membrane dialysis method. Zeta potential, particle size, drug-loading capacity, in vitro drug release in different pH conditions and cytotoxicity evaluation of micelles were carried out comparing with non-acid liable PEG–amide–benzoic–dipalmitate (PEG-A-dC16) polymers micelles. The cellular uptake and intracellular distribution of DOX were detected by flow cytometry and confocal laser scanning microscope.

Key findings

Drug-loading capacity and encapsulation efficiency of micelle (PEG molecular weight 2k) were 12.7 ± 1.1% and 49.8 ± 2.2%, respectively. The average particle size was 72.3 ± 2.5 nm. The DOX release rate of PEG-I-dC16 micelles is much higher at pH 6.5 than at pH 7.4. DOX cellular uptake and nuclear accumulation of PEG-I-dC16 micelles were more efficiency than that of PEG-A-dC16 micelles.

Conclusion

The pH-sensitive PEG-I-dC16 micelles could be a promising drug delivery system for anticancer drugs.

pVEGF-loaded lipopolysaccharide-amine nanopolymersomes for therapeutic angiogenesis

Therapeutic angiogenesis via gene delivery is promising for tissue survival and regeneration after injury or ischemia. A stable, safe and efficient gene vector is essential for successful angiogenesis. We have demonstrated that our newly developed lipopolysaccharide-amine nanopolymersomes (LNPs) have higher than 95% transfection efficiency when delivering pEGFP into mesenchymal stem cells (MSCs). To explore their clinical potential in therapeutic angiogenesis, in this study, we studied their toxicity, storage stability, protection ability to genes and efficacy to deliver therapeutic genes of pVEGF in MSCs and zebrafish. The results show that LNPs can condense pVEGF to form pVEGF-loaded nanopolymersomes (VNPs), and protect pVEGF against DNase digestion in 6 h. Both LNPs and VNPs have low toxicity to MSCs, erythrocytes and zebrafish embryos. LNPs are stable at 4 °C for at least two years with unchanged size and transfection efficiency. MSCs transfected by VNPs continuously synthesize VEGF for at least four days under control, with a peak (21.25 ng ml(-1)) ∼35-fold greater than that for the untreated group. VNPs induce significant and dose-dependent angiogenesis in zebrafish without causing death, deformity or delay in growth and development, and the induced maximal vessel area of subintestinal vessel plexus is 2.5-fold higher than that for the untreated group. Our study suggests that VNP has high potential in therapeutic angiogenesis.

Delivery of a granzyme B inhibitor gene using carbamate-mannose modified PEI protects against cytotoxic lymphocyte killing

Cytotoxic T lymphocytes (CTL) and natural killer (NK) cells protect vertebrates by killing infected or transformed cells using granzyme B (GrB) to induce apoptosis. However, GrB-induced apoptosis of target cells causes inflammatory disease and chronic transplant rejection and so is an important disease target. The aim of this study was to prevent apoptosis of the target cells by delivering a plasmid encoding GrB inhibitor proteinase inhibitor-9 (PI-9) using cationic polymers as a non-viral vector. Polyethyleneimine (PEI, branched, Mn 10 kDa) gives a high degree of gene transfection efficiency in many types of cell lines, but it is highly cytotoxic. To reduce this cytotoxicity, we modified PEI by blocking primary amine groups through nucleophilic addition between primary amine and a protected mannose-functionalized cyclic carbonate (MTC-ipman), generating a carbamate linkage through the ring-opening of the cyclic carbonate. Deprotection of the mannose yielded a PEI polymer that is decorated with the carbohydrate. PEI with 7 or 20 of 67 primary amine groups substituted by the carbohydrate had similar gene binding ability compared to unmodified PEI, leading to almost 100% transfection efficiency of a GFP-reporter plasmid in HEK293T human embryonic kidney cells. Furthermore, modification of PEI resulted in a decrease in the cytotoxicity of PEI/DNA complexes. However, PEI with all primary amine groups blocked was unable to form a complex with DNA, and so reporter transfection was negligible. The PI-9 encoding plasmid was transfected into HEK293T cells effectively using the modified PEIs with the optimal degree of primary amine substitution, protecting up to 80% HEK293T cells from killing by human natural killer-like leukemic YT cells. Therefore, these carbamate-mannose modified PEI/PI-9 encoding plasmid complexes have potential clinical utility in the prevention of chronic transplant rejection and inflammatory disease caused by GrB.