Development of a photoluminescence affinity porous silicon biosensor

• Grant number: 12/00454-9
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: April 01, 2012
• End date: December 31, 2013
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Andrés Vercik
• Grantee: Thiago Antônio Villa Menezes
• Host Institution: Faculdade de Zootecnia e Engenharia de Alimentos (FZEA). Universidade de São Paulo (USP). Pirassununga , SP, Brazil

Abstract

Porous silicon is a material obtained by anodic corrosion of crystalline silicon in HF and ethanol electrolyte. It has good properties such as large area per volume ratio, biocompatibility and ability to adjust its pore diameter and thin film thickness. Porous silicon is photoluminescent, and the origin of this effect is attributed to quantum confinement and a siloxene layer on the surface of the pore. The oxidation of porous silicon right after etching stabilizes the photoluminescent properties and creates a layer of silanol on which biological molecules such as proteins, enzymes and antibodies can be immobilized. Biosensors reported in the literature use porous silicon to immobilize antibodies with potentiometric transducers by capacitance-voltage curves or interferometric fringes. The most common method of antibody immobilization on the substrate is by covalent bonding between a substrate and a silanizating agent, and a bifunctional aldehyde and the silanizating agent. The antibody binds to the other end of the aldehyde. The pair 3-aminopropyl triethoxysilane (APTES) and glutaraldehyde (GTA) appears in most studies. Less reported are biosensors that exploit the photoluminescent effect of the substrate, whose intensity decreases linearly with the affinity binding reaction between the antigen and its antibody immobilized on the surface of the pore. This configuration is advantageous from a technical point of view, because no other transduction is required other than optical, and oxidation serves its two purposes, as well as an economic point of view because, unlike an ELISA that uses two antibodies to detect a antigen, the porous silicon biosensor with photoluminescence only needs one. The present work aims to develop and study a prototype of porous silicon biosensor with immobilized antibody by APTES and GTA via photoluminescence. A model antibody will be used: anti-mouse IgG in goat and its antigen mouse IgG, since it is well characterized and appears in other works, which allows comparison. Porous silicon will be synthesized in situ by the reaction mentioned, as previous experience of this laboratory has yielded satisfactory results. The oxidation will be via thermal path. The biosensor will be morphologically characterized by SEM and AFM, the FTIR and XPS spectra, the capacitance-voltage curve and the fall of the photoluminescent effect. It is hoped that the results are in agreement with the literature, showing linearity between the concentration of antigen and photoluminescence. This platform will serve for future projects for affinity biosensors, since the simple exchange of the antibody allows to detect different targets, with applications in food science, veterinary medicine, agriculture, biomedicine and defense.(AU)