Label-Free Optical Biosensors Based on Aptamer-Functionalized Porous Silicon Scaffolds

Abstract

A proof-of-concept for a label-free and reagentless optical biosensing platform based on nanostructured porous silicon (PSi) and aptamers is presented in this work. Aptamers are oligonucleotides (single-stranded DNA or RNA) that can bind their targets with high affinity and specificity, making them excellent recognition elements for biosensor design. Here we describe the fabrication and characterization of aptamer-conjugated PSi biosensors, where a previously characterized his-tag binding aptamer (6H7) is used as model system. Exposure of the aptamer-functionalized PSi to the target proteins as well as to complex fluids (i.e., bacteria lysates containing target proteins) results in robust and well-defined changes in the PSi optical interference spectrum, ascribed to specific aptamer-protein binding events occurring within the nanoscale pores, monitored in real time. The biosensors show exceptional stability and can be easily regenerated by a short rinsing step for multiple biosensing analyses. This proof-of-concept study demonstrates the possibility of designing highly stable and specific label-free optical PSi biosensors, employing aptamers as capture probes, holding immense potential for application in detection of a broad range of targets, in a simple yet reliable manner.

Synthesis and characterization of a nanostructured porous silicon/carbon dot-hybrid for orthogonal molecular detection

“…The HRSEM image of a cross-section of the untreated PSiO 2 provided in Figure 3a shows the typical aligned pore structure of the PSiO 2 matrix. 28 The comparative HRSEM micrographs of the PSiO 2 /C-dot hybrid shown in Figure 3b and c reveal the nanostructure of the hybrid and the presence of organic material throughout the porous scaffold. 34 Moreover, electron-charging effects were encountered throughout the entire cross-sections shown in Figure 3b and c, which was ascribed to the abundant C-dots-an organic substance-within the PSiO 2 pores.…”

“…27,28 The resulting porous layers were~5 μm thick, and the calculated porosity was~80%. 28 In situ synthesis of C-dots within PSiO 2 The incorporation of C-dots in the porous nanostructure was achieved by in situ synthesis within the pores.…”

“…27,28 The resulting porous layers were~5 μm thick, and the calculated porosity was~80%. 28 In situ synthesis of C-dots within PSiO 2 The incorporation of C-dots in the porous nanostructure was achieved by in situ synthesis within the pores. A C-dot precursor solution (25 mg ml − 1 p-phenylenediamine aqueous solution) was introduced onto the PSiO 2 upper surface and allowed to infiltrate the pores, followed by evaporation of the water and mild, slow heating in an oven (180°C, 12 h).…”

Optical Biosensing and Bioimaging With Porous Silicon and Silicon Quantum Dots (Invited Review)

“…Lately, aptamers, short single-strand oligonucleotides that have high and specific binding affinity to proteins, have become new bioreceptors for the detection of various analytes [49][50][51][52]. Aptamers have advantages over antibodies in fast, low-cost and controllable synthesis and chemical stability [53][54][55].…”

Oxidized Porous Silicon Nanostructures Enabling Electrokinetic Transport for Enhanced DNA Detection

“…[ 19,20 ] Extensive research efforts to improve the performance of PSi biosensors, specifi cally their sensitivity, have focused on designing sophisticated optical structures, e.g., multilayered 1D and 2D photonic crystals, [ 21,22 ] nonperiodic multilayered structures as Thue-Morse and Cantor, [ 14 ] and other architectures. [ 17,23,24 ] Detection of a wide range of biomolecular targets, including oligonucleotides, [ 3,13,16,[24][25][26][27] proteins, [ 15,[28][29][30] enzymes, [ 8,31 ] and cells, [ 32 ] has been reported using PSi biosensors. While detection of DNA targets is of critical importance in numerous applications, including clinical diagnosis, environmental monitoring, and antibioterrorism, [ 33,34 ] its sensitive and reproducible monitoring using PSi biosensors is challenging mostly due to the enhanced corrosion of the PSi scaffold by DNA.…”