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The development of effective array biosensorsrelies heavily on careful control of the density of surface-immobilized ligands on the transducing platform. In this paperwe describe the synthesis of new dextran−lipase conjugates foruse in immobilizing low molecular weight haptens onto glassplanar waveguides for immunosensor development. Theconjugates were synthesized by immobilizing bacterial thermoalkalophilic lipases (Geobacillus thermocatenulatuslipase 2,BTL2) on agarose macroporous beads, followed by covalent coupling to dextran networks of variable molecular weight (1500−40000). The chimeras were immobilized via nonspecific hydrophobic interactions onto glass planar waveguides modified with1,1,1,3,3,3-hexamethyldisilazane to obtain highly ordered and homogeneous molecular architectures as confirmed by atomic forcemicroscopy. Microcystin LR (MCLR) was covalently bound to the dextran−BTL2 conjugates. The usefulness of this approach inimmunosensor development was demonstrated by determining amounts of MCLR down to a few picograms per liter with anautomated array biosensor and evanescent wave excitation forfluorescence measurements of attached DyLight649-labeledsecondary antibody. Modifying BTL2 with dextrans of an increased molecular weight (>6000) provided surfaces with anincreased loading capacity that was ascribed to the production of three-dimensional surfaces by the effect of analyte binding deepin the volume, leading to expanded dynamic ranges (0.09−136.56 ng L−1), lower limits of detection (0.007±0.001 ng L−1), andlower IC50values (4.4±0.7 ng L−1). These results confirm the effectiveness of our approach for the development of high-performance biosensing platforms., Depto. de Química en Ciencias Farmacéuticas, Fac. de Farmacia, TRUE, pub

We have developed a photonic nano-immunosensor platform for the on-site analysis of harmful organic ocean pollutants, intended to be allocated in stand-alone buoys. The main aim is bringing the monitoring tools directly to the contaminated place, resulting in cost and time savings as compared to the standard analytical techniques. As sensor we have employed an integrated asymmetric Mach-Zehnder interferometer (aMZI) of micro/nano dimensions, based on silicon photonic technology. In order to obtain a multiplexed system, a four-channel microfluidic cell has been designed, manufactured and incorporated in the miniaturized sensor. Additionally, a microfluidic delivery module enabling automatic sample analysis has been designed, evaluated and assembled. Moreover, we have implemented the optical interconnections of the sensor chip by fiber optics, as well the electronics and the required software and data processing. Pollutant detection is based on a competitive immunoassay using bioreceptors previously biofunctionalized on the aMZI sensor arms and incubation with a specific antibody. As proof of concept, two types of pollutants have been analysed: the biocide Irgarol 1051, and the antibiotic Tetracycline. Results show limits of detection in the range of few ng/mL, accomplished the European legislation.

The field of environmental monitoring has experienced a substantial progress in the last years but still the on-site control of contaminants is an elusive problem. In addition, the growing number of pollutant sources is accompanied by an increasing need of having efficient early warning systems. Several years ago biosensor devices emerged as promising environmental monitoring tools, but their level of miniaturization and their fully operation outside the laboratory prevented their use on-site. In the last period, nanophotonic biosensors based on evanescent sensing have emerged as an outstanding choice for portable point-of-care diagnosis thanks to their capability, among others, of miniaturization, multiplexing, label-free detection and integration in lab-on-chip platforms. This review covers the most relevant nanophotonic biosensors which have been proposed (including interferometric waveguides, grating-couplers, microcavity resonators, photonic crystals and localized surface plasmon resonance sensors) and their recent application for environmental surveillance.

Portable point-of care (POC) devices for in vitro diagnostics will be a milestone for the achievement of universal healthcare and environmental protection. The main goal is to reach a rapid, user-friendly and highly sensitive portable tool which can provide immediate results in any place at any time while having a competitive cost. Integrated optical (IO) waveguide based-biosensors are the most suitable candidates to achieve this ambitious objective. They are able to operate in real samples (such as blood, urine, wastewater…) affording relevant sensitivities even under a label-free scheme. In addition, arrays of IO sensors for multiplexed analysis can be integrated in lab-on-chip (LOC) platforms, providing a truly cost-effective fabrication and miniaturization. Among the different IO biosensors, interferometric ones have demonstrated the highest sensitivity for label-free detection ever reported. Although the first interferometric biosensors were developed in the early nineties, they focused mainly on preliminary proof-of-concept studies; only recently the resilient potential of interferometric biosensors as highly advanced POC devices has firmly emerged. This review provides an overview of the state-of-the art in photonic interferometric biosensors, their main biofunctionalisation routes and their integration in LOC platforms, while maintaining a special focus on the real analytical applications achieved so far.

[EN] Sub-wavelength diameter holes in thin metal layers can exhibit remarkable optical features that make them highly suitable for (bio)sensing applications. Either as efficient light scattering centers for surface plasmon excitation or metal-clad optical waveguides, they are able to form strongly localized optical fields that can effectively interact with biomolecules and/or nanoparticles on the nanoscale. As the metal of choice, aluminum exhibits good optical and electrical properties, is easy to manufacture and process and, unlike gold and silver, its low cost makes it very promising for commercial applications. However, aluminum has been scarcely used for biosensing purposes due to corrosion and pitting issues. In this short review, we show our recent achievements on aluminum nanohole platforms for (bio)sensing. These include a method to circumvent aluminum degradation-which has been successfully applied to the demonstration of aluminum nanohole array (NHA) immunosensors based on both, glass and polycarbonate compact discs supports-the use of aluminum nanoholes operating as optical waveguides for synthesizing submicron-sized molecularly imprinted polymers by local photopolymerization, and a technique for fabricating transferable aluminum NHAs onto flexible pressure-sensitive adhesive tapes, which could facilitate the development of a wearable technology based on aluminum NHAs.

Sub-wavelength diameter holes in thin metal layers can exhibit remarkable optical features that make them highly suitable for (bio)sensing applications. Either as efficient light scattering centers for surface plasmon excitation or metal-clad optical waveguides, they are able to form strongly localized optical fields that can effectively interact with biomolecules and/or nanoparticles on the nanoscale. As the metal of choice, aluminum exhibits good optical and electrical properties, is easy to manufacture and process and, unlike gold and silver, its low cost makes it very promising for commercial applications. However, aluminum has been scarcely used for biosensing purposes due to corrosion and pitting issues. In this short review, we show our recent achievements on aluminum nanohole platforms for (bio)sensing. These include a method to circumvent aluminum degradation—which has been successfully applied to the demonstration of aluminum nanohole array (NHA) immunosensors based on both, glass and polycarbonate compact discs supports—the use of aluminum nanoholes operating as optical waveguides for synthesizing submicron-sized molecularly imprinted polymers by local photopolymerization, and a technique for fabricating transferable aluminum NHAs onto flexible pressure-sensitive adhesive tapes, which could facilitate the development of a wearable technology based on aluminum NHAs.

The development of effective array biosensors relies heavily on careful control of the density of surface-immobilized ligands on the transducing platform. In this paper we describe the synthesis of new dextran-lipase conjugates for use in immobilizing low molecular weight haptens onto glass planar waveguides for immunosensor development. The conjugates were synthesized by immobilizing bacterial thermoalkalophilic lipases (Geobacillus thermocatenulatus lipase 2, BTL2) on agarose macroporous beads, followed by covalent coupling to dextran networks of variable molecular weight (1500-40000). The chimeras were immobilized via nonspecific hydrophobic interactions onto glass planar waveguides modified with 1,1,1,3,3,3-hexamethyldisilazane to obtain highly ordered and homogeneous molecular architectures as confirmed by atomic force microscopy. Microcystin LR (MCLR) was covalently bound to the dextran-BTL2 conjugates. The usefulness of this approach in immunosensor development was demonstrated by determining amounts of MCLR down to a few picograms per liter with an automated array biosensor and evanescent wave excitation for fluorescence measurements of attached DyLight649-labeled secondary antibody. Modifying BTL2 with dextrans of an increased molecular weight (>6000) provided surfaces with an increased loading capacity that was ascribed to the production of three-dimensional surfaces by the effect of analyte binding deep in the volume, leading to expanded dynamic ranges (0.09-136.56 ng L -1), lower limits of detection (0.007 ± 0.001 ng L -1), and lower IC50 values (4.4 ± 0.7 ng L -1). These results confirm the effectiveness of our approach for the development of high-performance biosensing platforms. © 2013 American Chemical Society.