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Self-Photopolymerization of Poly(disulfide) Oligomers.

ABSTRACT: Base catalyst and oxidant are usually necessary to promote the polymerization of poly(disulfide) oligomers through oxidative coupling of the terminal SH groups into S-S bonds. In this study, we prove that self-polymerization of bifunctional (disulfide) oligomer films can take place in a matter of minutes under UVC irradiation (254 nm, 10.5 mW cm^-2). The resulting insoluble polymer is characterized using solid-state NMR, ¹H T² NMR relaxation measurements, thermal analysis, and Fourier-transform infrared spectroscopy and proves to have similar composition as a model poly(disulfide) prepared under oxidative conditions, but distinct physical properties. These differences are explained by a change in polymer architecture due to a higher ratio of cyclization relative to linear polymerization. Homolytic photocleavage of internal S-S bonds creates thiyl groups close to each other, driving an increased kinetic feasibility for the cyclization reaction by radical coupling. The subsequent formation of mechanically interlocked macrocycles (polycatenane network) is proposed to account for film properties analogous to those of a cross-linked polymer.

SUBMITTER: Chemtob A

PROVIDER: S-EPMC6647947 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature

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Self-Photopolymerization of Poly(disulfide) Oligomers.

Chemtob Abraham A Feillée Noémi N Vaulot Cyril C Ley Christian C Le Nouen Didier D

ACS omega 20190322 3

Base catalyst and oxidant are usually necessary to promote the polymerization of poly(disulfide) oligomers through oxidative coupling of the terminal SH groups into S-S bonds. In this study, we prove that self-polymerization of bifunctional (disulfide) oligomer films can take place in a matter of minutes under UVC irradiation (254 nm, 10.5 mW cm-2). The resulting insoluble polymer is characterized using solid-state NMR, 1H T2 NMR relaxation measurements, thermal ...[more]

PMID: 31459725

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Project description:Recently, biomaterials have been designed to contain redox-sensitive moieties, such as thiols and disulfides, to impart responsive degradation and/or controlled release. However, due to the high sensitivity of cellular redox-based systems which maintain free-radical homeostasis (e.g. glutathione/glutathione disulfide), if these biomaterials modify the cellular redox environment, they may inadvertently affect cellular compatibility and/or oxidative stress defenses. In this work, we hypothesize that the degradation products of a poly(β-amino ester) (PBAE) hydrogel formed with redox sensitive disulfide (cystamine) crosslinking could serve as a supplement to the environmental cellular antioxidant defenses. Upon introduction into a reducing environment, these disulfide-containing hydrogels cleave to present bound-thiol groups, yet remain in the bulk form at up to 66 mol% cystamine of the total amines. By controlling the molar fraction of cystamine, it was apparent that the thiol content varied human umbilical vein endothelial cell (HUVEC) viability IC50 values across an order of magnitude. Further, upon introduction of an enzymatic oxidative stress generator to the cell culture (HX/XO), pre-incubated thiolated hydrogel degradation products conferred cellular and mitochondrial protection from acute oxidative stress, whereas non-reduced disulfide-containing degradation products offered no protection. This polymer may be an advantageous implantable drug delivery system for use in acute oxidative stress prophylaxis and/or chronic oxidative stress cell therapies due to its solid/liquid reversibility in a redox environment, controlled thiolation, high loading capacity through covalent drug-addition, and simple post-synthesis modification which bound-thiols introduce.Statement of significanceIn this work, we demonstrate a unique property of disulfide containing degradable biomaterials. By changing the redox state of the degradation products (from oxidized to reduced), it is possible to increase the IC50 of the material by an order of magnitude. This dramatic shift is linked directly to the oxidative stress response of the cells and suggests a possible mechanism by which one can tune the cellular response to degradable biomaterials.

Project description:A family of bioreducible poly(disulfide amine)s, which differ in the length of polymethylene spacer [-(CH(2))(n)-] in the main chain and the side chain, has been synthesized. These bioreducible poly(disulfide amine)s exhibit local environment specific degradability and are associated with lower cytotoxicity than branched poly(ethylenimine) (bPEI, 25 kDa). These cationic polymers also show higher buffering capacity and protonation degree than bPEI, facilitating the endosomal escape of carried genetic materials. The transfection efficiency of these agents is oligomethylene length dependent. Poly(cystaminebisacrylamide-spermine) [poly(CBA-SP)], poly(cystaminebisacrylamide-bis(3-aminopropyl)-1,3-propanediamine) [poly(CBA-APPD)], and poly(cyxtaminebisacrylamide-bis(3-aminopropyl)-ethylenediamine) [ploy(CBA-APED)] with longer propylene [-(CH(2))(3)-] side spacer, demonstrate higher transfection efficacy than the counterpart poly(cystaminebisacrylamide-bis(2-aminoethyl)-1,3-propanediamine) [poly(CBA-AEPD)] and poly(cystaminebisacrylamide-triethylenetetramine) [poly(CBA-TETA)], which have shorter ethylene [-(CH(2))(2)-] side spacer. The poly(CBA-SP), poly(CBA-APPD), poly(CBA-APED) with the main chain spacer of -(CH(2))(4)-, -(CH(2))(3)-, -(CH(2))(2)- demonstrate similar transfection efficiency, indicating the length of polymer main chain spacer has less influence on transfection efficiency. However, with the same short ethylene [-(CH(2))(2)-] side spacer, poly(CBA-AEPD), with the longer main chain oligomethylene units [-(CH(2))(3)-], showed relatively higher transfection efficiency than poly(CBA-TETA), having shorter main chain oligomethylene units [-(CH(2))(2)-]. Of these polymeric carriers, poly(CBA-SP) demonstrated the highest transfection in the C2C12 cell line, while poly(CBA-APED) showed the highest transfection in the HeLa cell line. All of these agents showed greater transfection activity than commercialized bPEI 25 kDa. The poly(disulfide amine)s are promising safe and efficient non-viral vectors for gene delivery.

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Self-Photopolymerization of Poly(disulfide) Oligomers.

Publications

Self-Photopolymerization of Poly(disulfide) Oligomers.

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