Silicon dioxide surfaces, functionalized by two aminosilane compounds (3-amino-propyl-triethoxysilane, APTES; 3-amino-propyl-dimethylethoxysilane, APDMES) both dissolved in different solvents (dry ethanol and toluene), have been investigated by standard techniques such as spectroscopic ellipsometry (SE), water contact angle (WCA), and atomic force microscopy (AFM). Silane thicknesses between 5 and 80 Å have been found, depending on deposition conditions; surface wettabilities change, accordingly. These organic-inorganic interfaces have also been modified by a cross-linker (bis-sulfosuccinimidyl suberate) in order to covalently bind a fluorescein labeled protein A. The amount of protein linked to functional surfaces has been quantified by SE and fluorescence microscopy. These results could be very useful in developing new platforms for optical biosensing.

Human α-thrombin (TB) is a serine protease with a crucial role in coagulation and hemostasis. The monitoring of the TB level in blood serum could be of great importance in order to prevent serious damage to human health. In this work, an aptasensor is realized by in situ synthesis of a 17-mer Thrombin Binding Aptamer analogue (TBATT) on silanized macroporous silica (PSi). The interaction between TBATT and TB at different concentrations is monitored by a label-free optical method, spectroscopic reflectometry, and quantified by fast Fourier transform (FFT) analysis. A TBATT-TB affinity constant of 14 ± 8 nM and limit of detection of 1.5 ± 0.3 nM are demonstrated. The selectivity and reversibility of the aptasensor are also proved

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