Silica Subsurface Amine Effect on the Chemical Stability and Chromatographic Properties of End-Capped Immobilized Artificial Membrane Surfaces

Article abstract of DOI:10.1021/ac00017a034

The silica surface of immobilized artificial membranes containing phosphatidylcholine (IAM.PC) has approximately two aminopropyl groups per immobilized phosphatidylcholine molecule.Primary amines near the silica subsurface adsorb biomolecules and also decrease the chemical stability of IAM.PC surfaces.Consequently, subsurface amines were end-capped by several methods including silylating reagents, acetyl analogues, glycidol, methyl glycolate, short-chain anhydrides (3-6 carbons/anhydride chain), and long-chain anhydrides (10-12 carbons/anhydride chain).All end-capping reactions resulted in loss of the initially immobilized phosphatidylcholine molecule.However, the amount of PC loss during end capping was very low (for alkyl anhydride end-capping reactions).After end capping, IAM.PC showed increased chemical stability compared to non end-capped IAM.PC surfaces.The chemical stability of IAM packing material was monitored by phospholipid leaching from IAM surfaces exposed to organic and aqeous solvents using thin-layer chromatography, 1H-NMR spectroscopy, infrared spectroscopy, and mass spectroscopy.IAM.PC packing material end capped with long-chain anhydrides exhibited the greatest chemical stability, i. e., little or no detectable phospholipid leaching when challenged with aqueous and/or organic solvents.The chromatography of acidic and basic compounds of end-capped and non end-capped IAM.PC surfaces was studied.Compared to non end-capped IAM.PC HPLC columns, the chromatographic retention times of acidic compounds (deoxynucleotides) decreased after end caping.In contrast, the retention times of basic compounds (amphetamine analogues) increased on end-capped IAM.PC HPLC columns.This indicates that these solutes have access to the silica subsurface amine during chromatography.