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방석호,김규원,이원종,심민석 한국고분자학회 2018 Macromolecular Research Vol.26 No.12
A polyspermine-derived bioreducible polymer was synthesized as efficient siRNA carriers. Spermine was polymerized using disulfide-bearing cross-linkers, resulting in poly(disulfide spermine) (PDS). PDS was also conjugated with poly(ethylene glycol) (PEG) to tailor siRNA condensation efficiency of the polymer. PEG-conjugated PDS (PEG-PDS) was able to condense siRNA into nano-sized polyplexes at high N/P ratios. siRNA condensation efficiency of PDS was reduced by PEGylation due to its weakened interaction with siRNA caused by its decreased cationic charge density. An ethidium bromide exclusion assay demonstrated that siRNA was more efficiently released from the less stable PEG-PDS polyplexes compared to stable PDS polyplexes. In addition, bioreducible siRNA/PEG-PDS polyplexes were efficiently disassembled in the reductive conditions, leading to facilitated siRNA release into the cytoplasm. The lowered siRNA condensation but efficient cytoplasmic release of siRNA by PEG-PDS induced higher gene silencing efficiency in comparison with PDS. Moreover, PEG-PDS exhibited lower cytotoxicity compared to PDS and non-biodegradable branched polyethylenimine. These results suggest that siRNA delivery efficiency of cationic gene carriers can be improved by tailoring their siRNA complexation through PEG conjugation. This study demonstrates that bioreducible PEG-PDS is a promising candidate for safe and efficient siRNA delivery.
방석호 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1
In order to enhance the osteogenic differentiation of human mesenchymal stem cells (hMSCs) and induce angiogenesis, zinc (Zn) and iron (Fe) were synthesized together into a nanoparticle with a pH-sensitive degradation property. Zn and Fe were loaded within the nanoparticles to promote early osteogenic gene expression and to induce angiogenic paracrine factor secretion for hMSCs. In vitro studies revealed that treating an optimized concentration of our zinc-based iron oxide nanoparticles to hMSCs delivered Zn and Fe ion in a controlled release manner and supported osteogenic gene expression with improved vascular endothelial growth factor secretion. Simultaneous intracellular release of Zn and Fe ions through the endocytosis of the nanoparticles further modulated the mild reactive oxygen species generation level in hMSCs without cytotoxicity and thus improved the osteogenic capacity of the stem cells.
방석호,유태경,김병수 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
Here, we report that Mn ion at high concentrations can be delivered to pheochromocytoma 12 (PC12) cells using gold nanoparticles (AuNPs) to enhance cellular neurodevelopment without toxicity. Mn2+ release from AuNPs was designed to be pH-responsive so that low pH condition of the cell endosomes can trigger in situ release of Mn2+ from AuNPs after cellular uptake of Mn-incorporated AuNPs (MnAuNPs). Due to the differences in reduction potentials of Mn and Au, only Mn ionized and released while Au remained intact when MnAuNPs were uptaken by cells. Compared to PC12 cells treated with a high concentration of free Mn2+, PC12 cells treated with an equal concentration of MnAuNPs resulted in significantly enhanced cellular neurodevelopment with decreased apoptosis and necrosis.