Synthesis and Properties of Hydrogels Used for Drug Delivery

• Published in: Transport Processes in Pharmaceutical Systems pp. 486 - 559
• Main Authors: Amidon, Gordon L, Topp, Elizabeth M, Lee, Ping I
• Format: Book Chapter
• Language: English
• Published: United States CRC Press 1999; Taylor & Francis Group
• Subjects: Pharmacology; Swelling Degree; Ionizing Radiation; Partition Coefficient; Sol Fraction; Linear Polymers; Ethylene Glycol Dimethacrylate; Transport Exponent; Diffusion Coefficient; Cross-link Density; Glassy Polymers; Equilibrium Swelling Degree; Polymer Solvent Interaction Parameter; MDCK Cell Monolayer; Effective Cross-link Density; Solubility Parameter; Controlled Porosity Osmotic Pump; Hydrogel Synthesis; Polyelectrolyte Gels; Sorption Rate; Solvent Sorption; EGDMA; Sorption Kinetics; PVA Gel; Swelling Kinetics
• ISBN: 9780824746322; 0824746325
• DOI: 10.1201/9780203909478-16

In colloquial definitions, the term ‘‘gel’’ applies to states of matter intermediate between solids and liquids in some sense, while a ‘‘hydrogel’’ is simply an aqueous gel. In fact, the latter word has its origins in the Latin gelare, meaning ‘‘to congeal.’’ Over the decades, numerous authors have attempted to formulate more precise definitions; thus, there are probably as many definitions for the term as there are authors on the subject. A most astute statement on the subject was the pronouncement by D. Jordon-Lloyd in the 1920s that ‘‘the gel is . . . easier to recognize than to define’’ [1]. The basis of all definitions is that a gel possesses a continuous macroscopic structure giving the sense of solidity-that is, exhibiting an elastic response to stress, at least up to a certain yield stress-while having a significant liquid component as well. Opinions diverge on whether a dried gel can still be termed a gel.