BEH.462/3. 962J Molecular Principles of Biomaterials Spring 2003 Lecture 7: Hydrogel Biomaterials: Structure and Physical Chemistry Last Day: programmed/regulated/multifactor controlled release for drug delivery and tissue engineering Today Applications of hydrogels in bioengineering Covalent hydrogels Physical hydrogels Synthesis of hydrogel biomaterials Synthesis of hydrogel biomaterials Physical gels Formation Aq son-==zs Associating hydrophobic groups synthesis in organic solvent readily assembled in situ Synthesis of pluronics? Anionic polymerization? Formation of ionic gels: coacervates, nanoparticles LCST polymer gelation 1- △T Associating hydrophobic group Thermodynamics of LCST Lecture 7-Hydrogels 1 1 of 2
BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Lecture 7: Hydrogel Biomaterials: Structure and Physical Chemistry Last Day: programmed/regulated/multifactor controlled release for drug delivery and tissue engineering Today: Applications of hydrogels in bioengineering Covalent hydrogels Physical hydrogels Synthesis of hydrogel biomaterials Synthesis of hydrogel biomaterials Physical gels Formation: Aq soln Associating hydrophobic groups synthesis in organic solvent readily assembled in situ Synthesis of pluronics? Anionic polymerization? Formation of ionic gels: coacervates, nanoparticles LCST polymer gelation: ∆T Associating hydrophobic groups Thermodynamics of LCST Lecture 7 – Hydrogels 1 1 of 2
BEH.462/3. 962J Molecular Principles of Biomaterials Spring 2003 Covalent gels Formation: simultaneous with polymerization Approaches Free radical polymerization -+M+M+M→|+M+M+M→|-M'+M+M→|-M-M"+M Thermal initiation: Ammonium persulfate(APS) Catalyzed initiation Mechanism of APS sodium metabisulfite/ TEMED polymerization allows polymerization at room temperature or 37 C ( not a thermal initiation mechanism) Photo polymerization Mechanism Acetophenone initiation 1→"→|M→LM-M'etc. can be used in situ/in vivo during surgery DEMOS: examples of rapidity of gelation in class: APS TEMED and photopolymerization Advantages: rapid polymerization does not require organic solvents Limitations: degree of conversion typically limited Enzymatic polymerization Sperinde work with transglutaminase Hubbell work with fibrin-based hydrogels Kinetics of gelation ntn→口 conversion Lecture 7-Hydrogels 1 20f2
BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Covalent gels Formation: simultaneous with polymerization Approaches: Free radical polymerization I-I + M + M + M → I’ + M + M + M → I-M’ + M + M → I-M-M’ + M Thermal initiation: Ammonium persulfate (APS) Catalyzed initiation: Mechanism of APS + sodium metabisulfite/TEMED polymerization allows polymerization at room temperature or 37°C (not a thermal initiation mechanism) Photo polymerization Mechanism Acetophenone initiation I → I’ → I-M’ → I-M-M’ etc. can be used in situ/in vivo during surgery DEMOS: examples of rapidity of gelation in class: APS + TEMED and photopolymerization Advantages: rapid polymerization does not require organic solvents Limitations: degree of conversion typically limited Enzymatic polymerization Sperinde work with transglutaminase Hubbell work with fibrin-based hydrogels Kinetics of gelation gel point η ⇒ � η % conversion t Lecture 7 – Hydrogels 1 2 of 2