Porous silicon Bloch surface and sub-surface wave structure for simultaneous detection of small and large molecules

Abstract

A porous silicon (PSi) Bloch surface wave (BSW) and Bloch sub-surface wave (BSSW) composite biosensor is designed and used for the size-selective detection of both small and large molecules. The BSW/BSSW structure consists of a periodic stack of high and low refractive index PSi layers and a reduced optical thickness surface layer that gives rise to a BSW with an evanescent tail that extends above the surface to enable the detection of large surface-bound molecules. Small molecules were detected in the sensor by the BSSW, which is a large electric field intensity spatially localized to a desired region of the Bragg mirror and is generated by the implementation of a step or gradient refractive index profile within the Bragg mirror. The step and gradient BSW/BSSW sensors are designed to maximize both resonance reflectance intensity and sensitivity to large molecules. Size-selective detection of large molecules including latex nanospheres and the M13KO7 bacteriophage as well as small chemical linker molecules is reported.

Detection of Echinococcus granulosus antigen by a quantum dot/porous silicon optical biosensor

“…PSi has many advantages, such as large specific surface area, good biological compatibility, easy to be prepared into various optical devices, making it an ideal platform for biosensors [6][7][8]. There are two main types sensing mechanism of PSi optical sensors for biological detection.…”

The analytical performance of a porous silicon Bloch surface wave biosensors as protease biosensor

“…This advantage is due to the structural reason that Bloch surface wave structures possess an open sensing space that made it easy for protease molecule to digest and ease of diffusion of the biomolecule fragments to leave the pores [27][28][29]. The versatility of Bloch surface and sub-surface wave structure PSi was also recently shown by Rodriguez et al where it could be used for simultaneous detection of small chemical molecules and bacteriophage [29]. We perform protease assays on the BSW sensors using subtilisin as a model protease and study the reaction kinetics of the enzyme acting on the gelatin substrate.…”

“…The use of BSW modes is chosen due to its intrinsic advantages over other porous silicon photonic structures, such as microcavities [23,25] and rugate filters [26]. This advantage is due to the structural reason that Bloch surface wave structures possess an open sensing space that made it easy for protease molecule to digest and ease of diffusion of the biomolecule fragments to leave the pores [27][28][29]. The versatility of Bloch surface and sub-surface wave structure PSi was also recently shown by Rodriguez et al where it could be used for simultaneous detection of small chemical molecules and bacteriophage [29].…”

Electromagnetic field enhancement in Bloch surface waves

“…In the last decade, we witnessed a growing interest in Bloch surface waves (BSWs) [15][16][17][18][19][20][21][22], which are electromagnetic modes that propagate at the interface between a truncated periodic multilayer and a dielectric external medium. Light confinement in BSWs occurs near the multilayer surface and is caused by TIR from the homogeneous layer and by the presence of a photonic band gap (PBG) from the multilayer.…”