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Cationic polymer nanogels, positively-charged submicrometer polymeric particles that swell in water, have attracted an increasing research attentions in recent years because of their potential applications as gene carriers. In this paper, we report a novel method to synthesize polyethylenimine (PEI) nanogels with sizes ranging from 80 nm to 200 nm via UV irradiation at room temperature in aqueous solution without adding any kind of surfactants. The morphology of the nanoparticles is determined to be spherical. The nanogels are of high stability, high transfection efficiency, low toxicity and low immunogenicity, as having been confirmed by in vivo tests with mice as an animal model, and by in vitro tests with human lung and liver cancer cells as well.

Graphene oxide nanosheet (NGO) was covalently functionalized with positively charged, branched polyethylenimine (bPEI) via an amide bond, coated with serum proteins by electrostatic interaction. Operating as a newly fashioned, multifunctional nanocarrier, the processed NGO showed promise for use in combined gene therapy, chemotherapy, photothermal therapy, bioimaging and as a biosensor of cancer cells. Our current research is focused on the systematic studies of mechanisms of cancer cellular uptake, subcellular location, cytotoxicity and the cellular exclusion of the NGO–bPEI nanocarriers. It was observed that NGO–bPEI accumulated in the mitochondria and that long-term retention of NGO–bPEI led to a decrease in mitochondrial membrane potential while levels of reactive oxygen species increased. The mitochondrial effects associated with long-term retention of NGO–bPEI have potential as a synergistic enhancer of the cytotoxic effects of anti-cancer drugs or genes in human lung carcinoma (A549) cells. This work demonstrated the utility of NGO–bPEI-based multifunctional nanocarriers while detailing the mechanism at the cellular level and providing guidance for further research in cancer therapy.

A series of UiO-66-PEI materials were obtained by impregnating UiO-66 with different amounts of polyethylenimine (PEI) with UiO-66 as the basic skeleton material. The materials were used as adsorbents to remove Ni${}^{2+}$ and Cu${}^{2+}$ from water. The prepared UiO-66-PEI-30 had good adsorption capacity on Ni${}^{2+}$ and Cu${}^{2+}$ at 30% PEI. The adsorption of Ni${}^{2+}$ and Cu${}^{2+}$ with UiO-66-PEI-30 was further studied. The role of eluent types, elution time, concentration and volume on the effect of Cu${}^{2+}$ elution was investigated. The adsorption of Ni${}^{2+}$ and Cu${}^{2+}$ by UiO-66-PEI-30 followed the pseudo-second-order kinetic model and Langmuir adsorption model. The maximum adsorption capacities obtained by Langmuir fitting for Ni${}^{2+}$ and Cu${}^{2+}$ were 11.54mgg${}^{-1}$ and 24.87mgg${}^{-1}$, respectively. After four desorption/adsorption experiments, UiO-66-PEI-30 still showed good adsorption performance. UiO-66 impregnated with PEI was an adsorbent with adsorption potential.

Gene therapy is a treatment for inborn and acquired diseases, although the development of safe and effective gene delivery system is a great challenge to make a gene therapy a success. Viral vectors have been used in a majority of clinics because of their high transfection efficiency in vitro and in vivo. However, their use has been limited because of several drawbacks, such as induction of immune response, recombination of wild-type viruses, limitation in the size of inserted gene, and difficulty in large-scale production. Nonviral vectors have been widely proposed safe alternatives to viral vectors because they have low immunogenicity, flexibility in the size of gene to be delivered, cell targetibility, and easy scalability of production, although they have low transfection efficiency compared to viral vectors. Among nonviral vectors, polyethylenimine (PEI) has been widely used as a standard gene carriers due to its high pH-buffering capacity for endosomal escape although high-molecular-weight PEI is too toxic owing to non-degradability. Recently, many types of degradable PEI have been studied due to high transfection efficiency with lower cytotoxicity. This review explains recent progress on the development of degradable PEIs as nonviral vectors. The present paper summarizes the transfection efficiency of DNA or silencing efficiency of small interfering RNA (siRNA) based on the kinds of degradable linkage between low PEI and crosslinkers. Degradable linkages, such as ester, disulfide, imines, carbamate, amide and ketal in the degradable PEIs are covered.