title: On the unusual stability of succinimidyl esters in pNIPAm-AAc microgels.
abstract: In this contribution, we describe the effects of amide coupling reactions on the physical properties of thermoresponsive hydrogel microparticles (microgels). These microgels, when treated via aqueous carbodiimide/sulfo-succinimide coupling protocols, displayed a dramatic modulation of the microgel phase transition thermodynamics. UV spectrophotometry was used to determine that this modulation was due to remarkably stable hydrogel conjugates of sulfo-NHS that resisted degradation under standard hydrolysis protocols. These intermediates result in a shift of the phase transition, along with a large increase in equilibrium microgel swelling degree, due to an increase in chain-chain Coulombic repulsion. Only aggressive hydrolysis protocols resulted in the recovery of the native microgel phase transition, suggesting that an unusually stable succinimidyl ester is formed in the microgel during coupling.
authors.affiliation: School of Chemistry and Biochemistry & Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA.
authors.forename: Justin D
authors.initials: JD
authors.lastname: Debord
authors.forename: L Andrew
authors.initials: LA
authors.lastname: Lyon
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000464:Alginates / Q000737:chemistry*; D000536:Aluminum Hydroxide / Q000737:chemistry*; D001672:Biocompatible Materials; D004338:Drug Combinations; D004952:Esters / Q000737:chemistry*; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry*; D006868:Hydrolysis; D011108:Polymers; D012824:Silicic Acid / Q000737:chemistry*; D017693:Sodium Bicarbonate / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D000180:Acrylic Resins; D000464:Alginates; D001672:Biocompatible Materials; D004338:Drug Combinations; D004952:Esters; D011108:Polymers; D012824:Silicic Acid; C052970:poly-N-isopropylacrylamide; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D000536:Aluminum Hydroxide; C007829:alginate, aluminium hydroxide, magnesium trisilicate, sodium bicarbonate drug combination; D017693:Sodium Bicarbonate