京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18294号 / 工博第3886号 / 新制||工||1596(附属図書館) / 31152 / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 中條 善樹, 教授 吉﨑 武尚, 教授 秋吉 一成 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第19758号 / 農博第2154号 / 新制||農||1039(附属図書館) / 学位論文||H28||N4974(農学部図書室) / 32794 / 京都大学大学院農学研究科応用生物科学専攻 / (主査)教授 佐藤 健司, 教授 山下 洋, 准教授 豊原 治彦 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

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Yes / Complex biological tissues are highly viscoelastic and dynamic. Efforts to repair or replace cartilage, tendon, muscle, and vasculature using materials that facilitate repair and regeneration have been ongoing for decades. However, materials that possess the mechanical, chemical and resorption characteristics necessary to recapitulate these tissues have been difficult to mimic using synthetic resorbable biomaterials. Herein, we report a series of resorbable elastomer-like materials that are compositionally identical and possess varying ratios of cis:trans double bonds in the backbone. These features afford concomitant control over the mechanical and surface eroding degradation properties of these materials. We show the materials can be functionalized post-polymerization with bioactive species and enhance cell adhesion. Furthermore, an in vivo rat model demonstrates that degradation and resorption are dependent on succinate stoichiometry in the elastomers and the results show limited inflammation highlighting their potential for use in soft tissue regeneration and drug delivery.

Thesis advisor: Jia Niu / This dissertation discusses two main projects focusing on synthesizing degradable vinyl copolymers. The first project describes the development of a general approach to synthesizing degradable vinyl random copolymers through photocontrolled radical ring-opening cascade copolymerization (rROCCP). The rROCCP of a macrocyclic allylic sulfone with acrylates or acrylamides mediated by visible light at ambient temperature achieved near-unity comonomer reactivity ratios over the entire range of feed compositions. Such a powerful approach provides degradable vinyl random copolymers with comparable material properties to their non-degradable counterparts. Experimental and computational evidence also revealed an unusual reversible inhibition of chain propagation by in situ generated sulfur dioxide (SO2), which was successfully overcome by reducing the solubility of SO2 during polymerization. The second project depicts a general method for organocatalyzed photocontrolled radical copolymerization of a macrocyclic allylic sulfone and various types of vinyl monomers, including acrylates, acrylamides, styrene, and methacrylate. Catalyzed by Eosin Y under visible light irradiation, copolymerization of the macrocyclic allylic sulfone and acrylic monomers displayed near unity comonomer reactivity ratios by fitting the copolymer composition to the Beckingham-Sanoya-Lynd integrated model. The macrocyclic allylic sulfone was also successfully copolymerized with styrene or methyl methacrylate to generate degradable polystyrene and poly(methyl methacrylate). These degradable vinyl copolymers exhibited tunable thermal properties correlated with the incorporation of degradable main-chain diester motif. / Thesis (PhD) — Boston College, 2023. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Different structures of non-viral cationic polymer delivery vehicles, including charge center type, molecular weight and degradability, could significantly affect toxicity, release of nucleic acid and transfection efficiency. Poly(glycoamidoamine)s (PGAAs) contained different carbohydrate and secondary amine moieties and showed high transfection efficiency to different cell lines in a nontoxic manner. The "proton sponge hypothesis" has attempted to relate the buffering capacity to endosomal release of polyethylenimine (PEI) based polyplexes, which could contribute to high transfection efficiency. Secondary amine structures rendered PGAAs buffering capacity around physiological pH. To test the feasibility of the mechanism for PGAAs, new no buffering capacity guanidine or methylguanidine containing poly(glycoamidoguanidine)s (PGAGs) were synthesized. PGAGs formed stable polyplexes with pDNA from N/P (# secondary amine or guanidine group on polymer backbone / # phosphate group on pDNA backbone) ratio 3. PGAG based polyplexes expressed low cytotoxicity and were internalized by 90% of cells at N/P 25. Furthermore, two PGAG based polyplexes showed higher transfection efficiency from N/P 5 to 30 than their PGAA based analogs. These data suggested the low transfection could be due to the difficulties to release pDNA from polyplexes; also, the "proton sponge theory" could not explain the higher transfection efficiency by some PGAGs. Degradation of delivery vehicles could potentially release pDNA in cells and increase transfection efficiency. PGAAs degraded rapidly at physiological conditions and the proposed mechanism was amide hydrolysis. Typically, amide groups are stable and hydrolyze slowly in absence of enzyme. Different models mimicking PGAAs were synthesized to study the fast hydrolysis. Amide groups showed asymmetric hydrolysis. Different hydrolysis behaviors suggested neighboring group participation of two terminal groups to induce rapid amide hydrolysis. These new models could potentially be used to design new polymer delivery vehicles with various degradation profiles. / Master of Science

L’embolisation thérapeutique est devenu le traitement de choix pour l’hémorragie, les malformations artériovéneuses ou certains types de cancer. Parmi différents agents d’embolisation,les microsphères non dégradables (Embozene®, Bead BlockTM,…) sont les plus utilisées. Leur forme bien sphérique et leur taille calibrée permettent un meilleur ciblage dans les vaisseaux et une bonne qualité de l’occlusion. Dans certains cas cliniques, l’embolisation temporaire, envisageable avec l’utilisation des microsphères résorbables peut être bénéfique pour les patients. Le but du travail réalisé au cours de cette thèse a été le développement de microsphères résorbables satisfaisant les différents critères pour être employées comme matériaux d’embolisation (taille calibrée,biocompatibles, élastique pour être injectée au travers des cathéters mais suffisamment rigide pour résister à la pression sanguine). Dans cet objectif, nous avons développé une méthode de synthèse de microsphères constituées d’hydrogels hydrolysables par polymérisation en suspension. Une large gamme de microsphères ont été synthétisées en modulant la nature du réticulant et/ou la composition des milieux de polymérisation. Les expériences in vitro ont démontré que les microsphères obtenues sont satisfaisantes pour permettre leur injection au travers des cathéters. La dégradation rapide des ponts de réticulation a été confirmée à travers la diminution du module élastique G’ et du pH du surnageant, accompagnée d’une augmentation du taux de gonflement.Malgré une dégradation partielle des microsphères (due à une réaction secondaire formant des liaisons de réticulation non dégradables), le temps de l’hydrolyse a répondu parfaitement au cahier de charges (entre 7 et 49 jours). Des études complémentaires pour optimiser la réaction de polymérisation vont permettre le développement de microsphères totalement dégradables. / Therapeutic embolization is nowadays a first line treatment for haemorrhage, arteriovenous malformation or tumors. Among different embolization agents, non degradable microspheres(Embozene®, Bead BlockTM,…) are the most employed thanks to their well calibrated spherical shape which allows good occlusion. In some cases including treatment of uterine fibroids or chemo-sensitive tumors, it may be interesting to achieve a temporary embolization to avoid definitive destruction of the tissue. Temporary embolization would be possible using biodegradable microspheres. The aim of our work was to develop degradable microspheres having all requiredcharacteristics to be used as embolization material (well calibrated in size, biocompatible, rigide enough to resist blood pressure but elastic enough to remain intact during injection through catheter). To this purpose, we have developed hydrolysable hydrogel based microspheres by suspension polymerization. A wide range of microspheres was synthesized by varying the type of crosslinker and composition of the polymerization medium. In vitro test showed that the microspheres have suitable characteristics to pass through catheter. Degradation studies revealed a rapid diminution of G’ modulus and the pH of the supernatants, accompanied by an increase of swelling ratio due to the hydrolysis of the crosslinkings. Although microspheres were not totally degradable as expected (since a side reaction had created non degradable crosslinking during the polymerisation), characterisations showed promising results that the degradation did occur within a suitable time scale requirements for temporal embolization.

abstract: Minimally invasive endovascular embolization procedures decrease surgery time, speed up recovery, and provide the possibility for more comprehensive treatment of aneurysms, arteriovenous malformations (AVMs), and hypervascular tumors. Liquid embolic agents (LEAs) are preferred over mechanical embolic agents, such as coils, because they achieve homogeneous filling of aneurysms and more complex angioarchitectures. The gold standard of commercially available LEAs is dissolved in dimethyl sulfoxide (DMSO), which has been associated with vasospasm and angiotoxicity. The aim of this study was to investigate amino acid substitution in an enzyme-degradable side group of an N-isopropylacrylamide (NIPAAm) copolymer for the development of a LEA that would be delivered in water and degrade at the rate that tissue is regenerated. NIPAAm copolymers have a lower critical solution temperature (LCST) due to their amphiphilic nature. This property enables them to be delivered as liquids through a microcatheter below their LCST and to solidify in situ above the LCST, which would result in the successful selective occlusion of blood vessels. Therefore, in this work, a series of poly(NIPAAm-co-peptide) copolymers with hydrophobic side groups containing the Ala-Pro-Gly-Leu collagenase substrate peptide sequence were synthesized as in situ forming, injectable copolymers.. The Gly-Leu peptide bond in these polypeptides is cleaved by collagenase, converting the side group into the more hydrophilic Gly-Ala-Pro-Gly-COOH (GAPG-COOH), thus increasing the LCST of the hydrogel after enzyme degradation. Enzyme degradation property and moderate mechanical stability convinces the use of these copolymers as liquid embolic agents. / Dissertation/Thesis / Masters Thesis Biomedical Engineering 2019

A degradable/polar/hydrophobic/ionic (D-PHI) polyurethane with properties intended to promote tissue regeneration in a small diameter peripheral artery vascular graft was evaluated for cell biocompatibility and growth. Films were cast in polypropylene 96 well plates for monocyte/endothelial cell (EC) co-culture in vitro studies and porous scaffold discs were implanted in an in vivo subcutaneous mouse model. After 7 days in culture the co-culture demonstrated cell adhesion and growth, low esterase activity (a measure of degradative potential and cell activation), no detectable release of pro-inflammatory cytokine (tumour necrosis factor -α) but measurable anti-inflammatory interleukin (IL)-10. The EC and the co-culture expressed the EC biomarker CD31, whereas the monocyte monoculture did not. Cytokine array analysis of the in vivo characterization of D-PH supported an anti-inflammatory phenotype of cells at the site of the implant. Levels of IL-6 significantly decreased over time while IL-10 was significantly higher at 6 weeks post implant. TNF-α levels did not change significantly from 24 hours onwards, however the trend was towards lesser amounts following the initial time point. Histological analysis of the explanted scaffolds showed excellent tissue ingrowth and vascularization. A live/dead stain showed that the cells infiltrating the scaffolds were viable. Both the in vitro and in vivo results of this thesis indicate that D-PHI is a good candidate material for tissue engineering a peripheral artery vascular graft.

A degradable/polar/hydrophobic/ionic (D-PHI) polyurethane with properties intended to promote tissue regeneration in a small diameter peripheral artery vascular graft was evaluated for cell biocompatibility and growth. Films were cast in polypropylene 96 well plates for monocyte/endothelial cell (EC) co-culture in vitro studies and porous scaffold discs were implanted in an in vivo subcutaneous mouse model. After 7 days in culture the co-culture demonstrated cell adhesion and growth, low esterase activity (a measure of degradative potential and cell activation), no detectable release of pro-inflammatory cytokine (tumour necrosis factor -α) but measurable anti-inflammatory interleukin (IL)-10. The EC and the co-culture expressed the EC biomarker CD31, whereas the monocyte monoculture did not. Cytokine array analysis of the in vivo characterization of D-PH supported an anti-inflammatory phenotype of cells at the site of the implant. Levels of IL-6 significantly decreased over time while IL-10 was significantly higher at 6 weeks post implant. TNF-α levels did not change significantly from 24 hours onwards, however the trend was towards lesser amounts following the initial time point. Histological analysis of the explanted scaffolds showed excellent tissue ingrowth and vascularization. A live/dead stain showed that the cells infiltrating the scaffolds were viable. Both the in vitro and in vivo results of this thesis indicate that D-PHI is a good candidate material for tissue engineering a peripheral artery vascular graft.