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A well-organized immobilization of bio-receptors is a crucial goal in biosensing, especially to achieve high reproducibility, sensitivity and specificity. These requirements are usually attained with a controlled chemical/biochemical functionalization that creates a stable layer on a sensor surface. In this work, a chemical modification protocol for silicon-based surfaces to be applied in biosensing devices is presented. An anhydrous silanization step through 3-aminopropylsilane (APTES), followed by a further derivatization with succinic anhydride (SA), is optimized to generate an ordered flat layer of carboxylic groups. The properties of APTES/SA modified surface were compared with a functionalization in which glutaraldehyde (GA) is used as crosslinker instead of SA, in order to have a comparison with an established and largely applied procedure. Moreover, a functionalization based on the controlled deposition of a plasma polymerized acrylic acid (PPAA) thin film was used as a reference for carboxylic reactivity. Advantages and drawbacks of the considered methods are highlighted, through physico-chemical characterizations (OCA, XPS, and AFM) and by means of a functional Protein G/Antibody immunoassay. These analyses reveal that the most homogeneous, reproducible and active surface is achieved by using the optimized APTES/SA coupling., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Plasma Enhanced Chemical Vapor Deposition (PECVD) technique is used to polymerize Acrylic Acid for the surface functionalization of porous silicon samples with different pore dimensions. The polymer shows free COOH groups also at the pores inner surface, suitable for the immobilization of fluorescent labeled Protein A. The stability of the polymer, its role in the protection from aging of the porous matrix and the efficiency of the functionalization for the binding of protein A have been characterized by ATR-FTIR, SEM, Optical Contact Angle and Fluorescence Microscopy. The polymerization process is well controllable and suitable for the functionalization of porous silicon leaving free carboxylic groups at the surface ready for the immobilization of biochemical species for sensing applications., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Functionalization is a key element in biodetection technologies such as micro/nano-mechanical sensors. Since assay sensitivity and stability drastically depends on a proper bioreceptor immobilization, the sensing surface must be first chemically modified with uniform, well-packed, and robust layers. Here, we describe three functionalization protocols that we developed for the surface modification with amino, aldehyde, and carboxyl groups of micro/nano-mechanical biosensors.