J. G. Castelló

Label-free antibody detection using band edge fringes in SOI planar photonic crystal waveguides in the slow-light regime

We report experimental results of label-free anti-bovine serum albumin (anti-BSA) antibody detection using a SOI planar photonic crystal waveguide previously bio-functionalized with complementary BSA antigen probes. Sharp fringes appearing in the slow-light regime near the edge of the guided band are used to perform the sensing. We have modeled the presence of these band edge fringes and demonstrated the possibility of using them for sensing purposes by performing refractive index variations detection, achieving a sensitivity of 174.8 nm/RIU. Then, label-free anti-BSA biosensing experiments have been carried out, estimating a surface mass density detection limit below 2.1 pg/mm2 and a total mass detection limit below 0.2 fg.

Single-strand DNA detection using a planar photonic-crystal-waveguide-based sensor

We report an experimental demonstration of single-strand DNA (ssDNA) detection at room temperature using a photonic-crystal-waveguide-based optical sensor. The sensor surface was previously biofunctionalized with ssDNA probes to be used as specific target receptors. Our experiments showed that it is possible to detect these hybridization events using planar photonic-crystal structures, reaching an estimated detection limit as low as 19.8 nM for the detection of the complementary DNA strand.

Real-time and low-cost sensing technique based on photonic bandgap structures

A technique for the development of low-cost and high-sensitivity photonic biosensing devices is proposed and experimentally demonstrated. In this technique, a photonic bandgap structure is used as transducer, but its readout is performed by simply using a broadband source, an optical filter, and a power meter, without the need of obtaining the transmission spectrum of the structure; thus, a really low-cost system and real-time results are achieved. Experimental results show that it is possible to detect very low refractive index variations, achieving a detection limit below 2×10(-6) refractive index units using this low-cost measuring technique.

Real-time observation of antigen–antibody association using a low-cost biosensing system based on photonic bandgap structures

In this letter, we present experimental results of antibody detection using a biosensor based on photonic bandgap structures, which are interrogated using a power-based readout technique. This interrogation method allows a real-time monitoring of the association process between the antigen probes and the target antibodies, allowing the instantaneous observation of any interaction event between molecules. because etunable lasers and optical spectrum analyzers are avoided for the readout, a drastic reduction of the final cost of the platform is obtained. Furthermore, the performance of the biosensing system is significantly enhanced due to the large number of data values obtained per second.

Single strand DNA hybridization sensing using photonic crystal waveguide based sensor

We report an experimental demonstration of single-strand DNA detection at room temperature using a photonic crystal waveguide based optical sensor. A detection limit of 19.8nM is obtained.

Experimental Study of the Oriented Immobilization of Antibodies on Photonic Sensing Structures by Using Protein A as an Intermediate Layer

A proper antibody immobilization on a biosensor is a crucial step in order to obtain a high sensitivity to be able to detect low target analyte concentrations. In this paper, we present an experimental study of the immobilization process of antibodies as bioreceptors on a photonic ring resonator sensor. A protein A intermediate layer was created on the sensor surface in order to obtain an oriented immobilization of the antibodies, which enhances the interaction with the target antigens to be detected. The anti-bovine serum albumin (antiBSA)-bovine serum albumin (BSA) pair was used as a model for our study. An opto-fluidic setup was developed in order to flow the different reagents and, simultaneously, to monitor in real-time the spectral response of the photonic sensing structure. The antiBSA immobilization and the BSA detection, their repeatability, and specificity were studied in different conditions of the sensor surface. Finally, an experimental limit of detection for BSA recognition of only 1 ng/mL was obtained.

Real-time analysis of antigen-antibody association kinetics using a low-cost SOI photonic biosensor

We present an analysis of the association kinetics of the BSA-antiBSA (antigen-antibody) complex by using a photonic bandgap biosensor. The readout of the biosensor is done using a real-time and low-cost power-based technique.

Low-cost biosensing systems based on integrated photonic devices

The development of lab-on-a-chip (LoC) devices able to perform complex sample analysis quickly and easily, and at reduced cost, is crucial for many different fields of application. Examples include medical diagnostics, food and water safety control, and drug discovery. Transduction elements for these LoC devices based on integrated photonic technology are particularly promising. Their extremely high sensitivity and reduced size make them well suited for detecting target analytes (molecules of interest) at extremely low concentrations without the use of any type of marker (i.e., label-free). Hundreds or even thousands of these sensing elements can be arrayed on chips smaller than 1mm2, enabling both multiparameter analysis and more complete and valuable information. CMOS-compatible materials and processes borrowed from the microelectronics industry can be used to fabricate very low cost photonic sensing devices. But their practical application in developing commercial LoCs is limited by the significant cost of the readout instruments required for these chips. This is because the sensor relies on tracking the shift in the spectral response of the photonic structure, which involves either a tunable laser or an optical spectrum analyzer at a cost generally ranging from

Label-Free Biosensing Using Photonic Crystal Waveguides

30,000 to

Measurement technique for real-time and low-cost biosensing using photonic bandgap structures

60,000. Moreover, these components tend to be bulky and heavy, and thus not amenable to genuinely compact and portable readout systems. To overcome these problems, we have proposed a sensing system that indirectly tracks the spectral shift of a photonic bandgap (PBG) structure using a power-based readout technique.1 PBG structures are periodic dielectric structures that show a forbidden band in their transmission spectrum The position of Figure 1. Top: Scanning electron microscope image of a silicon-oninsulator 1D photonic bandgap structure used for sensing. Bottom: Close-up view of the periodic transversal elements.