Dendrimer catiomers like dendrigraft poly-L-lysine (DGL) have been very popular vectors for gene delivery recently; however, they generally suffer from serious cytotoxicity for high density of positive charge. PEGylated DGL engineered using the PEG cleavable mechanism (DGL(R)-SS-mPEG) was first developed as a non-viral gene vector for cancer intervention. Cleavable PEGylation of the DGL catiomer in tumor relevant glutathione (GSH) conditions enables us to dramatically decrease the cytotoxicity as well as to promote the intracellular release and expression of the genetic payload. Like DGL, DGL(R)-SS-mPEG is capable of efficiently complexing with plasmid DNA (pDNA) to afford homogeneous compact nano-complexes. Those gene carrying nanostructures could be stably dispersed in the regular serum medium without GSH, but with fast PEG dis-assembly if subject to 10 mM GSH. Compared with the non-cleavable counterpart, PEG-cleavable dendrigraft poly-L-lysine exhibited significantly higher enhanced green fluorescence protein (EGFP) expression against 293T cells. By using small interfering RNA (siRNA-VEGF) as the therapeutic gene payload, the complex nanoparticles demonstrated the pronounced inhibition effect on cell growth in vitro and tumor growth in vivo. The promising results revealed a universal strategy to balance disadvantages and advantages of dendrimer catiomers for future non-viral gene delivery vector.

Polymeric catiomers, which can mimic viruses for gene packing and delivery, have received considerable attention as nonviral vectors for gene therapy. Inspired by the critically important role of the sequence of structural units in various biomolecules, including DNA and protein, in this study, we intend to investigate how the monomer sequence of a polymeric catiomer affects its gene packing capacity and delivery efficiency. The well-documented poly(histidine-co-lysine) was chosen as the scaffold for gene carrier. Four reducible polycations (RPCs) based on sequence-regulated peptides monomers were synthesized. Chemical parameters (namely, composition and molecular weight) of four RPCs were controlled at comparable level except for the monomer sequence. All of the RPCs exhibited low cytotoxicity and effective DNA binding ability. However, these RPCs displayed distinct diversity from each other, especially in their ability of binding to DNA, buffering capacity and transfection efficiency. Using 293T cell as the mode, we found that the regulation of the monomer sequence of polycations could significantly affect their properties for gene delivery, with differences of 100 fold. The sequence effect might be correlated with different chain folding as well as physiochemical properties of RPCs/pDNA complexes, providing new insight for designing gene vector with promising prospects in gene therapy.

In this work, sheddable, degradable, cationic micelles were designed and developed based on intermediate disulfide-linked poly(ε-caprolactone)-b-poly(N,N-dimethylamino-2-ethylmethacrylate) (PCL-SS-PDMA) diblock copolymers, for glutathione (GSH)-mediated intracellular delivery of anticancer drug doxorubicin (DOX) and gene. The PCL-SS-PDMA diblock polymers with different PDMA block lengths were prepared by a combination of ring opening polymerization (ROP) and atom transfer radical polymerization (ATRP). Driven by hydrophobic interaction, these polymers self-assembled into nanoscaled micelles with size ranging from 70 to 200 nm, and positive surface charges from +24 to +37 mV. The PDMA length was found to determine the surface charge and in turn affect the physiochemical properties and cumulative drug release. More importantly, glutathione mediated intracellular drug release was observed by intracellular fluorescence arising from DOX for the GSH treated cells. The accelerated drug release was induced by the structural disassembly after disulfide cleavage. The PCL-SS-PDMA block polymers exhibited high DNA binding affinity and cellular uptake efficiency. The gene transfection efficiency of PCL-SS-PDMA/DNA complex showed relatively low transfection efficiency in 293 T and HeLa cells, compared to PEI 25K. However, the transfection efficacy dramatically outperformed PEI 25K in human oral carcinoma cell lines (KB and CAL-27 cells). A ten-fold population of the transfected cells was found for the PS-SS-PDMA polymer, compared with PEI. The experimental results show the great potential of the new micelles in gene and drug delivery for cancer therapy.

We report on the preparation and drug delivery application of shell sheddable micelles based on disulfide-linked star-shaped copolymer of poly(ε-caprolactone) and poly(ethyl glycol) (6sPCL-SS-PEG). Interestingly, the micelles exhibit high stability normally and rapid destabilization under a reduction environment, eliciting GSH dependent cytotoxicity of drug-loaded formulations on tumor cells.

Dendrimer catiomers like dendrigraft poly-L-lysine (DGL) have been very popular vectors for gene delivery recently; however, they generally suffer from serious cytotoxicity for high density of positive charge. PEGylated DGL engineered using the PEG cleavable mechanism (DGL(R)-SS-mPEG) was first developed as a non-viral gene vector for cancer intervention. Cleavable PEGylation of the DGL catiomer in tumor relevant glutathione (GSH) conditions enables us to dramatically decrease the cytotoxicity as well as to promote the intracellular release and expression of the genetic payload. Like DGL, DGL(R)-SS-mPEG is capable of efficiently complexing with plasmid DNA (pDNA) to afford homogeneous compact nano-complexes. Those gene carrying nanostructures could be stably dispersed in the regular serum medium without GSH, but with fast PEG dis-assembly if subject to 10 mM GSH. Compared with the non-cleavable counterpart, PEG-cleavable dendrigraft poly-L-lysine exhibited significantly higher enhanced green fluorescence protein (EGFP) expression against 293T cells. By using small interfering RNA (siRNA-VEGF) as the therapeutic gene payload, the complex nanoparticles demonstrated the pronounced inhibition effect on cell growth in vitro and tumor growth in vivo. The promising results revealed a universal strategy to balance disadvantages and advantages of dendrimer catiomers for future non-viral gene delivery vector.