On Chip Protein Pre-Concentration for Enhancing the Sensitivity of Porous Silicon Biosensors

Abstract

Porous silicon (PSi) nanomaterials have been widely studied as label-free optical biosensors for protein detection. However, these biosensors' performance, specifically in terms of their sensitivity (which is typically in the micromolar range), is insufficient for many applications. Herein, we present a proof-of-concept application of the electrokinetic isotachophoresis (ITP) technique for real-time preconcentration of a target protein on a PSi biosensor. With ITP, a highly concentrated target zone is delivered to the sensing area, where the protein target is captured by immobilized aptamers. The detection of the binding events is conducted in a label-free manner by reflective interferometric Fourier transformation spectroscopy (RIFTS). Up to 1000-fold enhancement in local concentration of the protein target and the biosensor's sensitivity are achieved, with a measured limit of detection of 7.5 nM. Furthermore, the assay is successfully performed in complex media, such as bacteria lysate samples, while the selectivity of the biosensor is retained. The presented assay could be further utilized for other protein targets, and to promote the development of clinically useful PSi biosensors.

One Spot—Two Sensors: Porous Silicon Interferometers in Combination With Gold Nanostructures Showing Localized Surface Plasmon Resonance

“…Furthermore, key properties of the porous silicon, such as layer thickness and porosity, can be satisfyingly controlled by the most often utilized fabrication method—electrochemical etching (Zhang, 2005). Tailor-made fabrication strategies for more sophisticated devices (Rodriguez et al, 2019), well-thought through surface functionalization methods (Mariani et al, 2018b), and smartly chosen conditions for detecting target analytes (Arshavsky-Graham et al, 2017; Mariani et al, 2018a) provided optical porous silicon sensors whose performance can compete with other optical sensing platforms. A comprehensive review has recently been published (Arshavsky-Graham et al, 2019).…”

Mass Transfer Limitations of Porous Silicon-Based Biosensors for Protein Detection

“… 16 , 21 − 25 Nevertheless, common detection thresholds in such systems revealed an inferior performance, with micromolar detection limits for protein and DNA targets in direct and label-free optical detection. 15 , 22 , 25 − 29 Therefore, many have focused on developing assays for improving the sensitivity and performance of such systems, 15 , 26 , 27 , 29 − 31 while others investigated the limiting characteristics of the platform and suggested solutions for overcoming these issues. 28 , 32 − 34 The latter includes mass transfer limitations, which are affected by the nanostructure characteristics such as pore size, height, porosity, surface area, and roughness.…”

Aptasensors for Point-of-Care Detection of Small Molecules

“…Such aptasensors were successfully demonstrated for label-free detection of various targets [ 52 , 53 , 54 ]. Nanostructured graphene materials, such as graphene oxide (GO), are another class of promising candidates for aptasensor surfaces.…”