Semiconductor nanowires (NWs) are gaining significant importance in various biological applications, such as biosensing and drug delivery. Efficient and controlled immobilization of biomolecules on ...the NW surface is crucial for many of these applications. Here, we present for the first time the use of the CuI‐catalyzed alkyne–azide cycloaddition and its strain‐promoted variant for the covalent functionalization of vertical NWs with peptides and proteins. The potential of the approach was demonstrated in two complementary applications of measuring enzyme activity and protein binding, which is of general interest for biological studies. The attachment of a peptide substrate provided NW arrays for the detection of protease activity. In addition, green fluorescent protein was immobilized in a site‐specific manner and recognized by antibody binding to demonstrate the proof‐of‐concept for the use of covalently modified NWs for diagnostic purposes using minute amounts of material.
Click on nanowires: A method for highly reproducible, covalent functionalization of oxidized semiconductor nanowires with peptides and proteins is reported. The method combines silanization with the CuI‐catalyzed and strain‐promoted alkyne–azide cycloaddition (CuAAC and SPAAC) reactions. A protease FRET substrate and green fluorescent protein were site‐specifically immobilized on GaAs nanowires.
Stable primary functionalization of metal surfaces plays a significant role in reliable secondary attachment of complex functional molecules used for the interfacing of metal objects and ...nanomaterials with biological systems. In principle, this can be achieved through chemical reactions either in the vapor or liquid phase. In this work, we compared these two methods for oxidized silicon surfaces and thoroughly characterized the functionalization steps by tagging and fluorescence imaging. We demonstrate that the vapor‐phase functionalization only provided transient surface modification that was lost on extensive washing. For stable surface modification, a liquid‐phase method was developed. In this method, silicon wafers were decorated with azides, either by silanization with (3‐azidopropyl)triethoxysilane or by conversion of the amine groups of an aminopropylated surface by means of the azido‐transfer reaction. Subsequently, D‐amino acid adhesion peptides could be immobilized on the surface by use of CuI‐catalyzed click chemistry. This enabled the study of cell adhesion to the metal surface. In contrast to unmodified surfaces, the peptide‐modified surfaces were able to maintain cell adhesion during significant flow velocities in a microflow reactor.
Stuck tight: The fully optimized coating of silicon surfaces with a monolayer of (3‐azidopropyl)siloxide allowed attachment of secondary complex molecules. D‐Amino acid adhesion peptides k‐l‐h‐r‐l‐r‐a and k‐l‐y‐r‐v‐r‐a were immobilized through CuAAC, and their interaction with cells was investigated by flow shear. Stable adhesion of HEK293 cells was achieved even at high flow rates.
