Catalytic Synthesis and Characterization of Biodegradable ...

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Chapter 1 The introduction of polyelectrolytes led to the materials being hydrophilic enough to swell in water, which allows the easy diffusion of entrapped protein. When the PPy was reduced by negative potential, the anions were quickly expulsed in less than one minute. The in vitro test demonstrated that the released NGF still retained activity. Generally the polymeric carriers will affect the entrapped protein’s folding and activity due to the strong hydrophobic nature of the polymer. However, this approach employed polyelectrolytes to increase the hydrophilicity of the materials, which had solved this problem in some extent. In another investigation, authors incorporated streptavidin into the PPy films doped with both biotin and dodecylbenzenesulfonate. Then the biotinylated NGF was immobilized to this film. When the film was electrically stimulated, NGF was exclusively released. The activity of the released protein was also confirmed in vitro. This method can be expanded to most of drugs that could be delivered through biotin-streptavidin strategy. Hydrogels have been studied for a long time as drug carrier. The release behaviors of “smart” hydrogels can be controlled by many stimuli, including pH, temperature, biomacromolecues and electrical stimulation. For example, PVA hydrogels were covalently immobilized onto aldehyde groups modified PPy films (Figure. 1.5.16). The heparin was loaded into the hydrogels and could be released through the diffusion without electrically stimulation. 165 When PPy was electrically stimulated, the release of heparin from the hydrogel was accelerated. Many factors were considered by the authors that could affect the results, such as changes in temperature, electrophoresis, changes in pH as a result of electrolysis, and the polyanionic nature of heparin. Besides the film, electroactive polymers can be fabricated into other shapes for drug delivery. For example, PEDOT nanotubes were synthesized on the electrospun PLGA fibers (~100 nm diameter) template (Figure. 1.5.17). 164 Then the PLGA loaded with dexamethasone was removed to produce PEDOT nanotubes encapsulating small molecules. The drug release of PEDOT nanotubes drug delivery system can be controlled by the electrical stimulation, probably as a consequence of expansion/reduction of polymer cavities induced by the expulsion of anions. ‐ 36 ‐
- 37 - Polymerization and Applications of Biodegradable Polyesters Figure. 1.5.17 (A) Electrospun PLGA fibers are loaded with drug (dexamethasone). (B) Degradation of PLGA fibers release the drug. (C) PEDOT is electropolymerized around PLGA fibers loaded with drug. (D) After degradation of PLGA fibers, PEDOT nanotubes are loaded with drug. (E) PEDOT nanotubes do not release drug in a neutral electrical condition. (F) PEDOT nanotubes release the drug upon external electrical stimulation with a positive voltage, which produces contraction of the nanotubes and the subsequent expulsion of the drug. (G) SEM image. Electropolymerized PEDOT nanotubes on the electrode site of an acute neural microelectrode after removing the PLGA core fibers. (H) Higher magnification of a single PEDOT nanotube on a neural microelectrode array. 164 The volume change of electroactive polymers responding to electrical stimulation has also been explored to develop actuators as “artificial muscle” devices. For example, Otero et al. placed two layers of PPy in a triple layer arrangement separated by a non-conductive material, as illustrated in Figure. 1.5.18. 166, 167 When current applied across the two conductive films, one of the films is oxidized and the other is reduced. The oxidized film exhibited an inflow of dopant ions and an associated expansion, whereas the reduced film expels ions and shrinks. 166, 168 The combined effect is changed into a mechanical force that bends the films, which has been compared to the mechanisms in natural muscles. In order to increase the electromechanical actuation of the materials, carbon nanotubes (CNTs) were blended with
Page 1 and 2: Catalytic Synthesis and Characteriz
Page 3 and 4: Preface Biodegradable polyesters ha
Page 5 and 6: Chapter 3 Polymerization of Lactic
Page 7 and 8: Chapter 1 Polymerization and Applic
Page 9 and 10: - 3 - Polymerization and Applicatio
Page 13 and 14: 1.2.2 Aluminum Catalysts - 7 - Poly
Page 17 and 18: 1.3 Polylactide 1.3.1 Introduction
Page 19 and 20: - 13 - Polymerization and Applicati
Page 21 and 22: 1.3.4 Application of PLA Figure 1.3
Page 27 and 28: 1.5.1.4 Polyaniline (PANi) - 21 - P
Page 41: - 35 - Polymerization and Applicati
Page 47 and 48: 1.6.1 Radical Polymers for Organic
Page 51 and 52: initialization of the device by app
Page 55 and 56: 1.6.2.4 Others - 49 - Polymerizatio
Page 63 and 64: 182. R. B. Weller, J. Invest. Derma
Page 65 and 66: Chapter 2 Synthesis and Electrochem
Page 67 and 68: Synthesis and Electrochemistry of S
Page 79: Synthesis and Electrochemistry of S
Page 84 and 85: Chapter 3 3.1 Introduction Poly(lac
Page 86 and 87: Chapter 3 polydispersity index (PDI
Page 88 and 89: Chapter 3 aluminum based complexes
Page 90 and 91: Chapter 3 3.5 Conclusions Co(III) c
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Chapter 3 22. Z. H. Tang, X. S. Che
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Chapter 4 4.1 Introduction Stimulus
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Chapter 4 the proton of methenyl gr
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Chapter 4 attributed to the amide g
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Chapter 4 4.4 Thermal Properties Th
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Chapter 4 Figure 4.8 MTT assay for
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Chapter 4 The 1 H NMR and 13 C NMR
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Chapter 4 Cell viability (%) = (Asa
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Chapter 5 Synthesis of Triblock Cop
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5.2 Synthesis of Triblock Copolymer
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Sample Table 1. Feed and result com
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= 25 μm. B: MTT assay for the cyto
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‐ 109 ‐ Synthesis of Triblock C
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‐ 111 ‐ Synthesis of Triblock C
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Chapter 6 6.1 Introduction Since th
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Chapter 6 6.3 Synthesis of MPEG-b-P
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Chapter 6 used to characterize the
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Chapter 6 Figure 6.6 Cyclic voltamm
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Chapter 6 vivo cytotoxicity was als
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Chapter 6 NMR. Characterization of
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Chapter 6 CO2 for 24 h. RSC96 cells
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Chapter 7 Conclusion and Future Pro
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‐ 131 ‐ Conclusion and Future P
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‐ 133 ‐ Conclusion and Future P
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13. Xuan Pang, Xuesi Chen, Xiuli Zh
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Acknowledgments The present thesis
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