Specific peptide for functionalization of GaN E. Estephan* a , C. Larroque § , T. Cloitre*, F. J.G. Cuisinier # and C. Gergely* * Groupe d’Etude des Semi-conducteurs, UMR 5650, CNRS-Université Montpellier II, 34095 Montpellier, France § Centre Régional de Lutte contre le Cancer, Université Montpellier I, 34298 Montpellier, France # EA 4203, Université Montpellier I, Montpellier, France Abstract Nanobiotechnology aims to exploit biomolecular recognition and self-assembly capabilities for integrating advanced materials into medicine and biology. However frequent problems are encountered at the interface of substrate-biological molecule, as the direct physical adsorption of biological molecules is dependent of unpredictable non-specific interactions with the surface, often causing their denaturation. Therefore, a proper functionalization of the substrate should avoid a loss of biological activity. In this work we address the functionalization of the semiconductor GaN (0001) for biosensing applications. The basic interest of using III-V class semiconductors is their good light emitting properties and a fair chemical stability that allows various applications of these materials. The technology chosen to elaborate GaN-specific peptides is the combinatorial phage-display method, a biological screening procedure based on affinity selection. An M13 bacteriophage library has been used to screen 10 10 different peptides against the GaN (0001) surface to finally isolate one specific peptide. The preferential attachment of the biotinylated selected peptide onto the GaN (0001), in close proximity to a surface of different chemical and structural composition has been demonstrated by fluorescence microscopy. Further physicochemical studies have been initiated to evaluate the semiconductor-peptide interface and understand the details in the specific recognition of peptides for semiconductor substrates. Fourier Transform Infrared spectroscopy in Attenuated Total Reflection mode (FTIR-ATR) has been employed to prove the presence of peptides on the surface. Our Atomic Force Microscopy (AFM) studies on the morphology of the GaN surface after functionalization revealed a total surface coverage by a very thin, homogeneous peptide layer. Due to its good biocompatibility, functionalized GaN devices might evolve in a new class of implantable biosensors for medical applications. Keywords: Functionalization, bacteriophage, specific peptide, semiconductors, biosensor. 1. Introduction Biosensor applications of semiconductor devices are currently a topic of intense research. Immobilization of functional molecules onto a solid substrate constitutes an important research area in material sciences, biomedical engineering and biotechnologies. We are interested in developing label-free biosensors due to their simplicity and the lack of unwanted modification of molecule structure while staining. The nowadays commercially available devices are affinity-based optical biosensors (ex. Biacore), which are generally based on methods that are measuring refractive index change like the plasmon surface resonance. These methods have some inconvenient such as the needed large sensing area, as well as the underlying unspecific interactions. The adsorption processes thus become difficult to handle and are giving rise to serious limitations in the detection accuracy and detection threshold. Therefore our interest focused on developing new sensing substrates presenting high binding selectivity for biological molecules. During the last years much effort has been focused on identifying biomolecules with molecular specificity for inorganic materials towards the elaboration of smart biomaterials for medical applications.[1, 2] Specific interactions to GaAs and InP III-V semiconductor materials, ZnS and CdS II-VI semiconductor materials and magnetic materials including FePt, CoPt and Co using commercially available phage display peptide libraries (New England Biolabs) were demonstrated . [3-5] Biophotonics: Photonic Solutions for Better Health Care, edited by Jürgen Popp, Wolfgang Drexler, Valery V. Tuchin, Dennis L. Matthews, Proc. of SPIE Vol. 6991, 699121, (2008) · 1605-7422/08/$18 · doi: 10.1117/12.781205 Proc. of SPIE Vol. 6991 699121-1