Dually Stabilized Triblock Copolymer Micelles with Hydrophilic Shell and Hydrophobic Interlayer for Systemic Antisense Oligonucleotide Delivery to Solid Tumor

Beob Soo Kim; Hyun Jin Kim; Shigehito Osawa; Kotaro Hayashi; Kazuko Toh; Mitsuru Naito; Hyun Su Min; Yu Yi; Ick Chan Kwon; Kazunori Kataoka; Kanjiro Miyata

doi:10.1021/acsbiomaterials.9b00384

Dually Stabilized Triblock Copolymer Micelles with Hydrophilic Shell and Hydrophobic Interlayer for Systemic Antisense Oligonucleotide Delivery to Solid Tumor

ACS Biomater Sci Eng. 2019 Nov 11;5(11):5770-5780. doi: 10.1021/acsbiomaterials.9b00384. Epub 2019 Aug 15.

Authors

Beob Soo Kim^{1

2}, Hyun Jin Kim, Shigehito Osawa^{3

4}, Kotaro Hayashi³, Kazuko Toh³, Mitsuru Naito, Hyun Su Min¹, Yu Yi¹, Ick Chan Kwon², Kazunori Kataoka³, Kanjiro Miyata¹

Affiliations

¹ Department of Materials Engineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
² Center for Theragnosis, Biomedical Research Institute, Korea Institute of Science and Technology (KIST), Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791, Republic of Korea.
³ Innovation Center of NanoMedicine, Kawasaki Institute of Industrial Promotion, 3-25-14 Tonomachi, Kawasaki-ku, Kawasaki 210-0821, Japan.
⁴ Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan.

PMID: 33405669
DOI: 10.1021/acsbiomaterials.9b00384

Abstract

For intravenous delivery of antisense oligonucleotides (ASOs) to solid tumors, a triblock copolymer was synthesized from poly(2-ethyl-2-oxazoline) (PEtOx), poly(2-n-propyl-2-oxazoline) (PnPrOx), and poly(l-lysine) (PLL) segments. The triblock copolymer, PEtOx-PnPrOx-PLL, was utilized to fabricate a compartmentalized polymeric micelle featuring a hydrophilic PEtOx shell, thermoresponsive PnPrOx interlayer, and ASO/PLL polyion complex (PIC) core. In this formulation, the PnPrOx-derived interlayer underwent the phase transition from hydrophilic elongated state to hydrophobic collapsed state at a lower critical solution temperature (LCST) to enhance the micelle stability. Three triblock copolymers comprising varying lengths of PEtOx segment (2k, 7k, and 12 kDa) were compared to investigate the effect of hydrophilic chain length on the micelle properties. The triblock copolymer micelles (TCMs) were prepared in a two-step manner: mixing between triblock copolymer and ASO in a buffer solution at 4 °C and then increasing the temperature of the solution up to 37 °C. This protocol was crucial for the fabrication of TCMs with both smaller size and narrower size distribution, probably due to the formation of the well-compartmentalized hydrophobic interlayer in the micelle structure. The presence of the PnPrOx segment dramatically enhanced the stability of TCMs in serum-containing media and elicited more efficient cellular uptake of ASO payloads, resulting in higher gene silencing efficiency in cultured prostate cancer (PC-3) cells, compared with a control diblock copolymer micelle (DCM). The blood circulation property of TCMs was prolonged with an increase in the length of PEtOx segment, permitting the efficient accumulation of ASO payloads in a subcutaneous PC-3 tumor model. Ultimately, the systemic delivery of ASO targeting a long noncoding RNA (lncRNA) by the TCMs significantly reduced the expression level of lncRNA in the subcutaneous PC-3 tumor in a sequence-specific manner. These results demonstrate the superiority of TCMs equipped with the hydrophilic shell and hydrophobic interlayer to the cancer-targeted systemic ASO delivery.

Keywords: antisense oligonucleotide; long noncoding RNA; polymeric micelle; prostate cancer; thermoresponsive; triblock copolymer.