Enhancing stability of 3-(aminopropyl)triethoxysilane (APTES) and glutaraldehyde (GA)-anchored glass coatings through Schiff base reduction

Glass functionalization with 3-aminopropyltriethoxysilane (APTES) is widely used to introduce surface amines; however, these films hydrolyze within minutes under physiologic conditions, limiting their utility in subsequent conjugation steps. Glutaraldehyde (GA) treatment stabilizes these coatings while introducing pendant aldehyde groups for conjugation with amine-bearing molecules, yet the resulting Schiff base linkages are also hydrolytically labile. Here, we show the importance of a reductive amination step in enhancing the stability of APTES-GA-based coatings. After conjugating a model thermoresponsive copolymer to APTES-GA coatings, we evaluate temperaturedependent surface wettability of reduced and unreduced polymer coatings following incubation in phosphate buffered saline (PBS) for 24 h. While prior to PBS incubation, both coatings demonstrated an ~11º difference in contact angle between temperatures above and below the lower critical solution temperature (LCST), only reduced polymer coatings maintained this behavior after incubation. By demonstrating Schiff base reduction as a critical step in surface functionalization workflows, this work highlights a strategy for stabilizing grafted coatings in aqueous/physiologic environments.