Contribution of cholesterol moieties attached on MPEG-b-PCL-b-PLL to the cell uptake, endosomal escape and gene knockdown of the micelleplexes of siRNA

Recent Advances in Engineering Carriers for siRNA Delivery

RNA interference (RNAi) technology has been a promising treatment strategy for combating intractable diseases. However, the applications of RNAi in clinical are hampered by extracellular and intracellular barriers. To overcome these barriers, various siRNA delivery systems have been developed in the past two decades. The first approved RNAi therapeutic, Patisiran (ONPATTRO) using lipids as the carrier, for the treatment of amyloidosis is one of the most important milestones. This has greatly encouraged researchers to work on creating new functional siRNA carriers. In this review, the recent advances in siRNA carriers consisting of lipids, polymers, and polymer-modified inorganic particles for cancer therapy are summarized. Representative examples are presented to show the structural design of the carriers in order to overcome the delivery hurdles associated with RNAi therapies. Finally, the existing challenges and future perspective for developing RNAi as a clinical modality will be discussed and proposed. It is believed that the addressed contributions in this review will promote the development of siRNA delivery systems for future clinical applications.

Poly(l-glutamic acid)-Based Zwitterionic Polymer in a Charge Conversional Shielding System for Gene Therapy of Malignant Tumors

Recently, pH-sensitive polymers have received extensive attention in tumor therapy. However, the rapid response to pH changes is the key to achieving efficient treatment. Here, a novel shielding system with a rapidly pH-responsive polymer (PAMT) is synthesized by click reaction between poly(γ-allyl-l-glutamate) and thioglycolic acid or 2-(Boc-amino)ethanethiol. The zwitterionic biodegradable polymer PAMT, which is negatively charged at physiological pH, can be used to shield positively charged nanoparticles. PAMT is electrostatically attached to the surface of the positively charged PEI/pDNA complex to form a ternary complex. The zwitterionic PAMT-shielded complex exhibits rapid charge conversion when the pH decreases from 7.4 to 6.8. For the in vivo tumor inhibition experiment, PAMT/PEI/shVEGF injected intravenously shows a more significant inhibitory effect on tumor growth. The excellent results are mainly attributed to introduction of the zwitterionic copolymer PAMT, which can shield the positively charged PEI/shVEGF complex in physiological conditions, while the surface potential of the shielded complexes changes to a positive charge in the acidic tumor environment.

miRNA oligonucleotide and sponge for miRNA-21 inhibition mediated by PEI-PLL in breast cancer therapy

MicroRNA-21 (miR-21) inhibition is a promising biological strategy for breast cancer therapy. However its application is limited by the lack of efficient miRNA inhibitor delivery systems. As a cationic polymer transfection material for nucleic acids, the poly (l-lysine)-modified polyethylenimine (PEI-PLL) copolymer combines the high transfection efficiency of polyethylenimine (PEI) and the good biodegradability of polyllysine (PLL). In this work, PEI-PLL was successfully synthesized and confirmed to transfect plasmid and oligonucleotide more effectively than PEI in MCF-7 cells (human breast cancer cells). In this regard, two kinds of miR-21 inhibitors, miR-21 sponge plasmid DNA (Sponge) and anti-miR-21 oligonucleotide (AMO), were transported into MCF-7 cells by PEI-PLL respectively. The miR-21 expression and the cellular physiology were determined post transfection. Compared with the negative control, PEI-PLL/Sponge or PEI-PLL/AMO groups exhibited lower miR-21 expression and cell viability. The anti-tumor mechanism of PEI-PLL/miR-21 inhibitors was further studied by cell cycle and western blot analyses. The results indicated that the miR-21 inhibition could induce the cell cycle arrest in G1 phase, upregulate the expression of Programmed Cell Death Protein 4 (PDCD4) and thus active the caspase-3 apoptosis pathway. Interestingly, the PEI-PLL/Sponge and PEI-PLL/AMO also sensitized the MCF-7 cells to anti-tumor drugs, doxorubicin (DOX) and cisplatin (CDDP). These results demonstrated that PEI-PLL/Sponge and PEI-PLL/AMO complexes would be two novel and promising gene delivery systems for breast cancer gene therapy based on miR-21 inhibition.

STATEMENT OF SIGNIFICANCE

This work was a combination of the high transfection efficiency of polyethylenimine (PEI), the good biodegradability of polyllysine (PLL) and the breast cancer-killing effect of miR-21 inhibitors. The poly (l-lysine)-modified polyethylenimine (PEI-PLL) copolymer was employed as the vector of miR-21 sponge plasmid DNA (Sponge) or anti-miR-21 oligonucleotide (AMO). PEI-PLL showed more transfection efficiency and lower cytotoxicity in human breast cancer cells than PEI. Moreover, the breast cancer cells exhibited significantly lower miR-21 expression and cell viability post transfection with sponge or AMO. Interestingly, the PEI-PLL/miR-21 inhibitor complexes also sensitized the cancer cells to anti-cancer chemotherapy drugs, doxorubicin (DOX) and cisplatin (CDDP). This synergistic effect provides a good application prospect of co-delivery miR-21 inhibitors and chemical drugs in breast cancer therapy.

A multifunctional perylenediimide derivative (DTPDI) can be used as a recyclable specific Hg2+ ion sensor and an efficient DNA delivery carrier

A multifunctional perylenediimide derivative (DTPDI) can be used as a recyclable specific Hg²⁺ ion sensor and an efficient DNA delivery carrier.