Degradable Polyethylenimine-Based Gene Carriers for Cancer Therapy.

Gene therapy using recombinant DNA or gene silencing using siRNA have become a prominent area of research in cancer therapy. However, their use in clinical applications is limited due to overall safety concerns and suboptimal efficacy. Although non-viral vectors such as polycationic polymers do not offer the same level of transfection efficiency as their viral counterparts, they still demonstrate immense potential as alternatives to viral vectors, given their versatility, low immunogenicity, ease of large-scale production, and ability to accelerate gene transfer with well-designed delivery platforms. Among these polymers, polyethylenimine (PEI) is considered a state-of-the-art gene carrier, owing to its ability to improve gene transfer capacity and intracellular delivery. Nonetheless, PEI suffers from the critical shortcoming of non-degradability that can lead to severe cytotoxic effects, despite the fact that the level of this toxicity decreases with molecular weight (MW). As a result, a considerable amount of effort has been devoted to designing low-MW PEI derivatives with degradable linkages. This review will categorize the recent advances in these degradable PEI derivatives based on their degradable chemistries, including ester, disulfide, imine, carbamate, amide, and ketal linkages, and summarize their application in gene therapies against various major cancer malignancies.