PDMS biofunctionalization study for the development of a microfluidic device: Application to salivary cortisol

The authors acknowledge to Sofia Neves from ICVS for her help in the antibodies selection.

This paper presents the study of the PDMS (poly(dimethylsiloxane)) surface functionalization for the development of a microfluidic immunosensor that quantitatively analyss salivary cortisol by optical detection. The functionalization was performed using different antibodies immobilization methods on PDMS surface: (a) immobilization by passive adsorption on pristine PDMS; (b) silanization of PDMS surface with (3-aminopropyl)-triethoxysilane (APTES) to generate amino groups and posterior covalent immobilization of antibodies on APTES-PDMS using cross-linker glutaraldehyde (GA); (c) coating the PDMS surface with BSA to block non-specific protein adsorption, and then covalent bond of the protein A via GA. In this last approach, the antibodies were covalently immobilized to protein A due to its high affinity with the constant fraction (Fc) region of the antibodies. Atomic force microscope (AFM) and spectrophotometric analysis demonstrated that the immobilization method using protein A is more efficient since a higher roughness and uniformity on the PDMS surface and higher absorbance signals were obtained

This work is funded by FEDER funds through the "Eixo I do Programa Operacional Fatores de Competitividade (POFC) QREN, project references COMPETE: FCOMP-01-0124FEDER-020241 and by FCT – Fundação para a Ciência e a Tecnologia, project reference PTDC/EBB-EBI/120334/2010. V. C. Pinto thanks the FCT for the SFRH/BD/81526/2011 PhD grant. The authors acknowledge to Sofia Neves from ICVS for her help in the antibodies selection.