2018 Fiscal Year Research-status Report
Reticuloendothelial system blockade by PEG-oligo(amino acid) block copolymers: A strategy for functional tuning of nanomedicine pharmacokinetics
| Project/Area Number |
18K18393
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| Research Institution | Kawasaki Institute of Industrial Promotion Innovation Center of NanoMedicine |
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Principal Investigator |
ディリサラ アンジャネユル 公益財団法人川崎市産業振興財団(ナノ医療イノベーションセンター), ナノ医療イノベーションセンター, 研究員 (70794353)
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| Project Period (FY) |
2018-04-01 – 2021-03-31
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| Keywords | RES blockade / PEG coating to liver / Single arm PEG-OLys / Double arm PEG-OLys / Bile clearance |
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| Outline of Annual Research Achievements |
To tune binding behavior of PEGylated oligo(L-lysine) (OLys) to the highly polyanionic liver sinusoidal wall, the architecture of PEG was studied. A short OLys with a degree of polymerization 20 was PEGylated in two formulations: One polymer with a single linear chain of 80-kDa (sPEG-OLys) and other with double linear chains of 40-kDa (dPEG-OLys). Biodistribution revealed that both s- and dPEG-OLys showed almost similar level of PEG coating to liver at 30 min, but dPEG-OLys showed lower accumulation to the kidney compared to sPEG-OLys, suggesting that dPEG-OLys has selectivity towards liver wall. The binding behavior of polymers to vessel walls of liver sinusoid and non-liver sinusoids was observed by direct imaging with intravital confocal microscopy (IVM) in living mice. Both s- and d-PEG-OLys were not attached to earlobe vessel wall, while non-PEGylated OLys was rapidly attached. In sharp contrast, both s- and d-PEG-OLys, as well as non-PEGylated OLys, attached to liver sinusoidal wall within 5 min. Interestingly, concentration of dPEG-OLys at sinusoidal wall was decreased with the time and became almost undetectable at 6 h, whereas sPEG-OLys remained localized to the wall even at 9 h with a minimal decrease. IVM revealed that dPEG-OLys was progressively accumulated to the bile canaliculi from 3 h after the injection, whereas sPEG-OLys exhibited fairly low accumulation even at 9 h. Both s- and d-PEG-OLys did not show ex vivo hemolysis and also no detectable change in lactate dehydrogenase (LDH), while non-PEGylated OLys induced hemolysis and in vivo LDH release.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The work is progressing smoothly as proposed in the plan. Instead of focusing on the conventional benchmark strategy on modulating the nature and length of cationic segment in PEGylated oligo-cation copolymers to tune the affinity to the anionic sinusoidal wall, we mainly focused on the molecular structure of PEG either with a single- and double-arm. The steric clash between the two arms of PEG in dPEG-OLys resulting from the large excluded volume of PEG does not facilitate them to overlap, thus generated force might increase the sticking force of OLys to the anionic receptors of sinusoidal wall.
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| Strategy for Future Research Activity |
The selectivity in binding nature of s- and d-PEG-OLys in comparison with non-PEGylated OLys to other reticuloendothelial walls will be monitored by intravital confocal microscopy directly in living mice. dPEG-OLys attached to liver sinusoidal wall selectively and transiently without inducing detectable toxicity, we would like to use this polymer for PEG coating of the sinusoidal wall to prevent sinusoidal clearance of a wide-variety of nanoparticles including PEGylated polyplex micelle as a model of PEGylated soft nanoparticle, Cationic liposomes and anionic liposomes as representative of non-PEGylated soft nanoparticle, Adeno virus and adeno associated virus as a model of nature derived nanoparticle and Quantum dot as a representative of hard nanoparticle.
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| Causes of Carryover |
The platform PEGylated oligo(L-lysine) copolymer with two-arms of PEG (dPEG-OLys) for blockading the liver sinusoidal wall was well characterized in the last fiscal year. Due to transient PEG coating of dPEG-OLys to the liver sinusoidal wall, we would like to forward this polymer for preventing the clearance of different therapeutic or diagnostic nanoparticles, which originally cleared by the cells of liver sinusoidal wall. The research direction of the applications of liver blockade using dPEG-OLys pre-injection was changed for focusing more on rising the impact of the research and versatility in applications. For that reason, the amount left in the last year will be used for this fiscal year for buying various viral and non-viral (both soft and hard) nanoparticles.
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