Carbodiimide/NHS derivatization of COOH-terminated SAMs: activation or byproduct formation?
COOH-terminated self-assembled monolayers (SAMs) are widely used in biosensor technology to bind different amine-containing biomolecules. A covalent amide bond, however, can be achieved only if the carboxylic acids are activated. This activation process usually consists of forming an N-hydroxysuccinimidyl ester (NHS-ester) by consecutively reacting carboxylic acids with a carbodiimide and NHS. Though many papers report using this method,1-8 the experimental conditions vary greatly between them and chemical characterization at this stage is often omitted. Evidence of an efficient activation is therefore rarely shown. Furthermore, recent publications9-11 have highlighted the complexity of this process, with the possible formation of different byproducts. In this paper, we have conducted a study on NHS activation under different conditions with chemical characterization by polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). Our results indicate that the nature of the solvent and carbodiimide and the reactant concentrations play crucial roles in activation kinetics and efficiency.
Université de Lyon , Institut des Nanotechnologies de Lyon, Site École Centrale de Lyon, CNRS UMR 5270, 36 Avenue Guy-de-Collongue, 69134 Écully, France.
Francisco
F
Palazon
Cindy Montenegro
CM
Benavides
Didier
D
Léonard
Éliane
É
Souteyrand
Yann
Y
Chevolot
Jean-Pierre
JP
Cloarec
D015374:Biosensing Techniques; D002234:Carbodiimides / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D018629:Spectrometry, Mass, Secondary Ion; D013499:Surface Properties
D002234:Carbodiimides; D002264:Carboxylic Acids; D012997:Solvents