Biodegradable polyamino acid-based polycations as safe and effective gene carrier minimizing cumulative toxicity.
Gene delivery using cationic polymers has attracted much attention due to their potential advantages, such as large DNA loading capacity, ease of large-scale production, and reduced immunogenicity. We recently reported that polyplexes from poly[N-[N-(2-aminoethyl)-2-aminoethyl]aspartamide] (P[Asp(DET)]), having an efficient endosomal escape due to pH-selective membrane destabilization, showed high transfection efficiency with minimal toxicity. Pharmacogenomic analysis demonstrated that P[Asp(DET)] also provided long-term security after transfection. We hypothesized that the biodegradability of P[Asp(DET)] played a significant role in achieving effective transfection. Gel permeation chromatography (GPC) and electrospray ionization mass spectrometry (ESI-MS) measurements of P[Asp(DET)] revealed their ability to undergo rapid degradation. In contrast, a derivative polycation, N-substituted polyglutamide (P[Glu(DET)]), showed no degradability, indicating that the degradation of P[Asp(DET)] was induced by a specific self-catalytic reaction between the PAsp backbone and the side-chain amide nitrogen. Degradation products of P[Asp(DET)] caused no cytotoxicity, even at high concentrations in the culture medium. Repeated transfection by administering the polyplexes for every 24h showed that biodegradable P[Asp(DET)] provided a continuous increase in transgene expression, while non-degradable P[Glu(DET)] showed a decrease in transgene expression after 48h, coupled with fluctuations in expression profiles of endogenous genes. In vivo intraperitoneal injection of P[Asp(DET)] induced minimal inflammatory cytokine induction to a level comparable to that of normal saline. These results indicate that the biodegradability of P[Asp(DET)] played a key role in achieving safe and sustained transgene expression, by minimizing cumulative toxicity caused by polycations remaining in cells or in the body.
Division of Clinical Biotechnology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Keiji
K
Itaka
Takehiko
T
Ishii
Yoko
Y
Hasegawa
Kazunori
K
Kataoka
D000596:Amino Acids / Q000378:metabolism*; D002384:Catalysis; D002412:Cations / Q000008:administration & dosage* / Q000633:toxicity; D002460:Cell Line; D002850:Chromatography, Gel; D016207:Cytokines / Q000096:biosynthesis; D005822:Genetic Vectors; D006706:Homeostasis; D006801:Humans; D021241:Spectrometry, Mass, Electrospray Ionization
D000596:Amino Acids; D002412:Cations; D016207:Cytokines