Protein Adsorption on the Surface Functionalized Planar Si
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0901-Ra06-05.1
Protein Adsorption on the Surface Functionalized Planar Si Li-Lin Tay1, Nelson Rowell1, Rabah Boukherroub2 and David J. Lockwood1 1 National Research Council , Ottawa, Ontario, Canada K1A 0R6 2 Interdisciplinary Research Institute, IRI-IEMN, 59652 Villeneuve d'Ascq, France ABSTRACT The peak energy of photoluminescence (PL) from an undecylenic acid functionalized porous Si demonstrated a large PL red-shift (~ 75 nm) during 2.5 hours of protein incubation in our previous work. [1] Here we present a similar in-situ PL study of surface functionalized planar Si (Si:COOH). The PL of Si:COOH exhibited a 5 nm red-shift in its peak frequency and an approximately 10% drop in its intensity after incubation in a protein solution. Vibrational spectroscopic characterization was carried out upon the Si:COOH sample for which we observed the PL red-shift. The infrared absorption spectra showed clear evidence of protein adsorption on Si:COOH. This correlation study between the PL peak energy and the vibrational spectrum provided strong evidence that the observed red-shift was due to the formation of semiconductorprotein (Si:COOH:BSA) complexes. INTRODUCTION Electrochemically prepared porous Si (pSi) has several advantages which render it an attractive material for biosensor applications. Many of the recently proposed pSi optical biosensors are based on the interferometric effect. [2, 3] In these devices, the porous matrix simply acts as a Fabry-Perot cavity. Molecular species incorporated in the pSi layer modulate the overall optical density of the Fabry-Perot cavity resulting in a small shift in the interferogram. These interferometer-based pSi biosensors utilize the unique binding specificity of a biological recognition molecule to its conjugated analyte to achieve a label-free detection scheme. It is, therefore, critically important to understand the interaction between biomolecules and semiconductor substrates. We have recently investigated the interaction of bovine serum albumin (BSA) protein and surface functionalized pSi[4] where we utilized the unique luminescence property of pSi to detect protein incorporation in the porous matrix. The one- and twodimensional Si nanocrystallites present in the pSi matrix imposed a quantum confinement effect on its charge carrier. This resulted in the bright room temperature photoluminescence (PL) in pSi. In this previous work we studied the variation of the pSi PL peak energy in order to monitor the incorporation of protein molecules inside the porous matrix. The in-situ monitoring of the protein and pSi interaction showed large red shift (~ 75 nm) in PL peak energy after protein incubation. Although it was suspected such a shift was due to the protein incorporation into the pSi matrix, the heterogeneous nature of the pSi material made it difficult to prove this correlation. To understand the origin and nature of the shift, we carried out similar protein adsorption studies on surface functionalized planar Si. In this paper, we will present the results of an in-situ PL study o
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