Lecture 7 Hydrogel Biomaterials Structure and Physical Chemistry.pdf

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 structure and chemistry of biomedical gels
Thermodynamics of hydrogel swelling
Reading: . Peppas et al., ‘Physicochemical foundations and structural design of hydrogels in
medicine and biology,’ Annu. Rev. Biomed. Eng., 2, 9-29 (2000).
Supplementary Reading: . Flory, ‘Principles of Polymer Chemistry,’ Cornell University Press, Ithaca, pp. 464-
469, pp. 576-581 (Statistical thermodynamics works work swelling)
Applications of hydrogels in bioengineering
• Hydrogels: work of polymer chains that swell in aqueous solutions
• Gels can be classified by the type of crosslinker:1
• Covalent - covalent junctions
• Physical - non-covalent junctions
Lecture 7 – Hydrogels 1 1 of 15
Molecular Principles of Biomaterials Spring 2003
Physical gels: example- Hydrophobic
interactions in physical gels
water
Physical gels are formed by noncovalent
cross-links Example blocks:
Poly(ethylene glycol) (PEG)
Hydrophilic B blocks
Hydrophobic A blocks
Poly(propylene oxide) (PPO)
Poly(butylene oxide) (PBO)
• Key properties of gels for bioengineering applications:
1. in situ formability
2. degradability
3. responsive swelling
4. tissue-like structure/properties
• In situ formability
ƒ Gelation of liquid solutions by:
• Irradiation with light
• Temperature change (. 4°C to 37°C)
• Cross-linking enzymes
• Presence of divalent salts
ON BOARD:
In situ formation
¥h ν
¥Heat
¥Crosslinking by enzymes
¥Introduction of divalent
cations (. Ca++, Mg++)
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Molecular Principles of Biomaterials Spring 2003
Key propert