Synthesis and characterization of novel organic/inorganic hybrid material with short peptide brushes generated on the surface

A novel route to synthesize an organic/inorganic hybrid material containing short peptide chains attached on the surface (e.g., oligo(S-benzyl-L-cysteine)) was developed. PolyN-(beta-aminoethylene)acrylamide] (PAEA) adsorbed onto silica particles surface (main diameter between 15 and 40 microm) was irreversibly fixed by the reaction between the accessible primary amino groups of the PAEA and 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTCDA). After the deposition of PAEA from a salt-free aqueous solution onto microporous silica particles and stabilization by a cross-linking reaction with BTCDA, five repeated coupling reactions of boc-S-benzyl-L-cysteine were performed. Changes in surface charges during the polyelectrolyte adsorption were studied by electrokinetic measurements. The cross-linking degree was a tool to control the surface charge of the PAEA/silica hybrid particles. X-ray photoelectron spectroscopy (XPS) was employed to obtain information about the amount of the adsorbed polyelectrolyte as well as the amount of the amino acid S-benzyl-L-cysteine that was covalently bound to the hybrid particle surface and polycondensed there. In the XPS spectra, the sulfur peaks (S 2p3/2, S 2p1/2, and S 2s) qualitatively and quantitatively indicated the presence of the amino acid on the hybrid material surface. After each step of coupling, the intensity of the S 2s peak was increased by a constant value. This indicates the oligopeptide growth. The novel hybrid material offers possibilities for subsequent derivatization reactions such as coupling other amino acids, peptides, obtaining hybrid ion exchange resins, and so forth.