A microfluidics assisted porous silicon array for optical label-free biochemical sensing

Abstract

A porous silicon (PSi) based microarray has been integrated with a microfluidic system, as a proof of concept device for the optical monitoring of selective label-free DNA-DNA interaction. A 4 × 4 square matrix of PSi one dimensional photonic crystals, each one of 200 μm diameter and spaced by 600 μm, has been sealed by a polydimethylsiloxane (PDMS) channels circuit. The PSi optical microarray elements have been functionalized by DNA single strands after sealing: the microfluidic circuit allows to reduce significantly the biologicals and chemicals consumption, and also the incubation time with respect to a not integrated device. Theoretical calculations, based on finite element method, taking into account molecular interactions, are in good agreement with the experimental results, and the developed numerical model can be used for device optimization. The functionalization process and the interaction between DNA probe and target has been monitored by spectroscopic reflectometry for each PSi element in the microchannels.

Aminosilane functionalizations of mesoporous oxidized silicon for oligonucleotide synthesis and detection

“…The reaction is not trivial, and the quality of the interface is not always the same, depending on the silane and the procedure conditions [6]. Recently, we have demonstrated in situ synthesis of oligonucleotides (ONs) on the surface of porous silica structures, characterized by optical monitoring [7,8]; the advantages of in situ synthesis with respect to ex situ immobilization are not only the increasing of DNA probe density but also the process automation, and the possibility of surface local functionalization [9]. Porous silicon (PSi) is obtained by electrochemical partial dissolution of crystalline silicon in a hydrofluoridic solution, and therefore exhibits a sponge-like morphology, characterized by very high specific surface, up to hundreds of m 2 cm -3 .…”

“…Moreover, PSi is by far one of the most intriguing materials in optical sensing: the refractive index is widely tuneable, namely between the silicon refractive index and that of air, and it is changed by each substance that penetrates into its pores. Owing to these characteristics, a lot of optical structures, such as photonic filters and microcavities, have been proposed in the literature for chemical [10] and biological sensing [9]. Unfortunately, the PSi structures suffer instability from oxidation and corrosion in aqueous solutions, especially simulating biological conditions.…”

Oxidized Porous Silicon Nanostructures Enabling Electrokinetic Transport for Enhanced DNA Detection

“…[ 25,27,35 ] To date, the lowest measured LoD for DNA detection using PSi Fabry-Pérot is ≈6 × 10 −6 M , [ 13 ] and efforts have been directed toward enhancing sensitivity by applying different passivation chemistries and designing more complex optical devices. [ 16,18,26,27,[36][37][38] Indeed, Weiss and co-workers were able to accomplish DNA detection in sub micromolar range by employing sophisticated optical nanostructures and advanced optical measurement confi gurations. [ 16,27,39 ] The integration of PSi-based biosensors with microfl uidic systems has gained considerable interest in recent years.…”

A zero-flow microfluidics for long-term cell culture and detection

“…Cells in this chamber undergo direct laminar flow by convective mass transport in one direction. 12 This design has been adopted by a variety of microfluidic perfusion devices. 13,14 However, in this case, the high speed generates a high shear stress, which is generally harmful for cells.…”

“…9 In addition, Toh et al designed the cell culture chambers consisting of a 3D matrix, with 10 and without micropillar arrays, 11 to support cells in 3D, while isolating them from convective flow. 12 By implementing the design to mechanically decouple cells from the fluid, the aforementioned issues could be addressed successfully. 13,14 In this paper, a novel microfluidic structure is proposed to acquire a stable and isolated microenvironment.…”