Attachment of biomolecules on porous silicon for biosensor application

Abstract

Nanostructured porous silicon has properties that make it a very promising biomaterial, particularly for sensing devices that need to be linked to the biological system. The unique feature of the material is its large surface area within small volume, controllable pore size, convenient surface chemistry and its compatibility with conventional silicon microfabrication technologies. Porous silicon (PS) can be prepared by chemical or electrochemical etching processes and consists of nano- and microcrystalline domains with defined pore morphologies. The diameter, geometric shape and direction of the pores depend on surface orientation, doping level and type, temperature, the composition of the etching solution and the current density. Porous silicon is also a biocompatible material and could prove to be the bridge that allows signals and informations to be transmitted between a semiconductor device and a biological system. It is a luminescent semiconductor that could play the roles of both transducer and the matrix. The PS matrix is suitable for biomolecule immobilization, provides a protective environment for the biomolecule and can transduce biorecognition events such as antigen-antibody binding, DNA, protein, enzymatic reactions, etc. An objective of the proposal is to study the growth of porous silicon on the silicon wafer by electrochemical method. PS surface was amino-silanised by a simple three-step method using 3-aminopropyltriethoxylsilane (APTS) that provides amine terminated surface. The primary amine terminated PS surface reacted with either of two cross-linkers, glutaraldehyde and sulfo-NHS-biotin. The biofunctionalised newlinenanostructured surface was used to attach immunoglobulin and DNA using glutaraldehyde. Sulfo-NHS-biotin was used to immobilize streptavidin. Similar protocol has been adopted for DNA hybridization and streptavidin-biotin interaction on silicon nanowires.