A Monolithic Silicon Optoelectronic Transducer as a Real-Time Affinity Biosensor

Abstract

An optical real-time affinity biosensor, which is based on a monolithic silicon optoelectronic transducer and a microfluidic module, is described. The transducer monolithically integrates silicon avalanche diodes as light sources, silicon nitride optical fibers, and p/n junction detectors and efficiently intercouples these elements through a self-alignment technique. The transducer surface is hydrophilized by oxygen plasma treatment, silanized with (3-aminopropyl)triethoxysilane and bioactivated through adsorption of the biomolecular probes. The use of a microfluidic module allows real-time monitoring of the binding reaction of the gold nanoparticle-labeled analytes with the immobilized probes. Their binding within the evanescent field at the surface of the optical fiber causes attenuated total reflection of the waveguided modes and reduction of the detector photocurrent. The biotin-streptavidin model assay was used for the evaluation of the analytical potentials of the device developed. Detection limits of 3.8 and 13 pM in terms of gold nanoparticle-labeled streptavidin were achieved for continuous- and stopped-flow assay modes, respectively. The detection sensitivity was improved by silver plating of the immobilized gold nanoparticles, and a detection limit of 20 fM was obtained after 20-min of silver plating. In addition, two different analytes, streptavidin and anti-mouse IgG, were simultaneously assayed on the same chip demonstrating the multianalyte potential of the sensor developed.

Patterning of thick polymeric substrates for the fabrication of microfluidic devices

“…The final PDMS replica is shown in 'figure 4', where 100µm deep and 150 µm wide micro-channels are shown connecting the 800 µm circular inlet and outlet tubing plugs, used for fluid delivery to the microfluidic device. For the latter, the micro-channels will be sealed by pressure application on part of a biosensor, where bio-fluid delivery will be used for spotting of proteins on the biosensor [7]. ii.…”

Recent developments in detection for microfluidic systems

“…An advantage of this configuration is that the microfluidics can be disposable, while the optics can be reused. The fluorescence signal from 0.04 mm diameter carboxylate-modified microspheres was measured with a lowest detectable concentration of 1.2610 27 M. Misiakos et al [31] presented a light-emitting silicon avalanche diode in an intriguing device that also contained a single-mode planar waveguide, a Si photodetector, and a microfluidic channel cast in PDMS as shown in Fig. 2.…”

“…Quite a few articles have been dedicated to photodetectors for microfluidic systems (beside the already mentioned work [31,32,35]). Namasivayam et al [37] and Jorgensen et al [38] used a monolithic approach, where the photodiodes were fabricated in the same substrate as the bottom of the microfluidic channels.…”

Novel Highly Sensitive Protein Sensors Based on Tapered Optical Fibres Modified with Au-Based Nanocoatings

“…SV molecules have very high affinity for biotin, as their binding is one of the strongest noncovalent interactions in nature [32]. In a previous report, biotin was attached covalently to gold immobilized on an optoelectronic silicon transducer [33]. The biotin-SV binding process produces measurable variations in the external refractive index surrounding the tapered optical fibre and modifies the optical transmission spectra, thus acting as the sensing mechanism.…”