|
|
Rheological properties of biodegradable thermosensitive copolymers
Chamradová, Ivana ; Poláček, Petr (oponent) ; Vojtová, Lucy (vedoucí práce)
The general goal of the proposed diploma work was preparation, characterization and rheological study of well-defined “smart” injectable hydrogels from biodegradable, biocompatible, controlled life-time copolymers based on hydrophilic poly(ethylene glycol) (PEG) and hydrophobic poly(lactic acid)—co—poly(glycolic acid) (PLA/PGA) copolymer. Resulted thermosensitive PLGA—PEG—PLGA copolymer, which gels at body temperature, was additionally functionalized by itaconic anhydride (ITA) from renewable resources, bringing both reactive carbon double bonds and functional —COOH groups to polymer ends. Additionally, the PLGA—PEG—PLGA copolymer was modified by inorganic bioactive hydroxyapatite (HAp) for usage as injectable bone bioadhesive. Both functionalized ITA/PLGA—PEG—PLGA/ITA copolymer and PLGA—PEG—PLGA/HAp polymer composite affected rheological properties of original PLGA—PEG—PLGA copolymer deciding whether or not would be the new polymeric material suitable as injectable drug carrier or bone adhesive in medical applications. Experimental part of this thesis describes mainly characterization of viscoelastic properties of both unmodified and ITA or HAp modified PLGA—PEG—PLGA copolymer by test tube inverting method (TTIM) and dynamic rheological analysis. Advantage of TTIM is sol-gel visualization with determination of the critical gelation temperature and the critical gelation concentration. The rheological measurements provide information about viscosity and elasticity of the gel by the changes storage (G´) and loss (G´´) modulus. The prepared copolymers were additionally characterized by 1H NMR and GPC. Surface and HAp particles size was determined by both SEM and Laser Particles Size Analyzer. Both unmodified and ITA or HAp modified PLGA—PEG—PLGA copolymers exhibited sol-gel transitions induced by increasing temperature. Rheological properties of copolymers’ 6 to 24 wt% water solutions investigated either by TTIM or by rheometer were in good agreement. Evaluating by rheometer, the copolymers showed two cross-points, where G´= G´´. The first one very well corresponded with the first sol-gel transition found via TTIM. The maximum values of G´ representing the highest gel stiffness lie in the white gel observed by TTIM. The second cross-point constituted to the gel-suspension transition where white polymer is precipitated from the water. The gel stiffness grows with increasing polymer concentration in water. In comparison, ITA modification or addition of HAp (0, 10, 20, 30, 40, 50 wt%) caused increasing the gel stiffness of unmodified PLGA—PEG—PLGA copolymer and approximating the temperature of G´max closer to body temperature (37 °C). Investigated both ITA/PLGA—PEG—PLGA/ITA copolymer and PLGA—PEG—PLGA/HAp composite were proved to be suitable candidates as injectable systems for drug delivery or regenerative medicine in orthopedics or dental applications, respectively.
|
|
|
Rheological properties of biodegradable thermosensitive copolymers
Chamradová, Ivana ; Poláček, Petr (oponent) ; Vojtová, Lucy (vedoucí práce)
The general goal of the proposed diploma work was preparation, characterization and rheological study of well-defined “smart” injectable hydrogels from biodegradable, biocompatible, controlled life-time copolymers based on hydrophilic poly(ethylene glycol) (PEG) and hydrophobic poly(lactic acid)—co—poly(glycolic acid) (PLA/PGA) copolymer. Resulted thermosensitive PLGA—PEG—PLGA copolymer, which gels at body temperature, was additionally functionalized by itaconic anhydride (ITA) from renewable resources, bringing both reactive carbon double bonds and functional —COOH groups to polymer ends. Additionally, the PLGA—PEG—PLGA copolymer was modified by inorganic bioactive hydroxyapatite (HAp) for usage as injectable bone bioadhesive. Both functionalized ITA/PLGA—PEG—PLGA/ITA copolymer and PLGA—PEG—PLGA/HAp polymer composite affected rheological properties of original PLGA—PEG—PLGA copolymer deciding whether or not would be the new polymeric material suitable as injectable drug carrier or bone adhesive in medical applications. Experimental part of this thesis describes mainly characterization of viscoelastic properties of both unmodified and ITA or HAp modified PLGA—PEG—PLGA copolymer by test tube inverting method (TTIM) and dynamic rheological analysis. Advantage of TTIM is sol-gel visualization with determination of the critical gelation temperature and the critical gelation concentration. The rheological measurements provide information about viscosity and elasticity of the gel by the changes storage (G´) and loss (G´´) modulus. The prepared copolymers were additionally characterized by 1H NMR and GPC. Surface and HAp particles size was determined by both SEM and Laser Particles Size Analyzer. Both unmodified and ITA or HAp modified PLGA—PEG—PLGA copolymers exhibited sol-gel transitions induced by increasing temperature. Rheological properties of copolymers’ 6 to 24 wt% water solutions investigated either by TTIM or by rheometer were in good agreement. Evaluating by rheometer, the copolymers showed two cross-points, where G´= G´´. The first one very well corresponded with the first sol-gel transition found via TTIM. The maximum values of G´ representing the highest gel stiffness lie in the white gel observed by TTIM. The second cross-point constituted to the gel-suspension transition where white polymer is precipitated from the water. The gel stiffness grows with increasing polymer concentration in water. In comparison, ITA modification or addition of HAp (0, 10, 20, 30, 40, 50 wt%) caused increasing the gel stiffness of unmodified PLGA—PEG—PLGA copolymer and approximating the temperature of G´max closer to body temperature (37 °C). Investigated both ITA/PLGA—PEG—PLGA/ITA copolymer and PLGA—PEG—PLGA/HAp composite were proved to be suitable candidates as injectable systems for drug delivery or regenerative medicine in orthopedics or dental applications, respectively.
|
host ::
RSS.