Nanoplasmonic biosensing approach for endotoxin detection in pharmaceutical field

none7noThe outer membrane of Gram-negative bacteria contains bacterial endotoxins known as Lipopolysaccharides (LPS). Owing to the strong immune responses induced in humans and animals, these large molecules have a strong toxic effect that can cause severe fever, hypotension, shock, and death. Endotoxins are often present in the environment and medical implants and represent undesirable contaminations of pharmaceutical preparations and medical devices. To overcome the limitations of the standard technique, novel methods for early and sensitive detection of LPS will be of crucial importance. In this work, an interesting approach for the sensitive detection of LPS has been realized by exploiting optical features of nanoplasmonic transducers supporting Localized Surface Plasmon Resonances (LSPRs). Ordered arrays of gold nano-prisms and nano-disks have been realized by nanospheres lithography. The realized transducers have been integrated into a simple and miniaturized lab-on-a-chip (LOC) platform and functionalized with specific antibodies as sensing elements for the detection of LPS. Interactions of specific antibodies anchored on protein A-modified sensor chips with the investigated analyte resulted in a spectral shift in the plasmonic resonance peak of the transducers. A good linear relationship between peak shifts and the LPS concentration has been demonstrated for the fabricated nano-structures with a detection limit down to 5 ng/mL. Integration with a proper microfluidic platform demonstrates the possibility of yielding a prototypal compact device to be used as an analytical test for quality determination of pharmaceutical products.openColombelli A.; Primiceri E.; Rizzato S.; Monteduro A.G.; Maruccio G.; Rella R.; Manera M.G.Colombelli, A.; Primiceri, E.; Rizzato, S.; Monteduro, A. G.; Maruccio, G.; Rella, R.; Manera, M. G

Magneto-Optical properties of noble-metal nanostructures: functional nanomaterials for bio sensing

Metallic nanostructures supporting Localized Surface Plasmon Resonances (LSPR) are characterized by their unique ability to control and manipulate light at the nanoscale. Noble metal nanostructures, such as gold nanostructures, are demonstrating to exhibit magneto-optic activity in the presence of modulated magnetic field of low intensity in transversal configuration (T-MOKE). Validation of experimental findings was achieved by numerical simulations based on Finite Element Method (FEM) techniques. The developed numerical models allowed studying the combination of the T-MOKE effect with the localized surface plasmon resonance of metal nanoparticles. Numerical optical and magneto-optical spectra provided a deep insight on the physical aspects behind the magneto-optical activity of metal nanostructures strictly related to direction of oscillations electrical dipoles generated in resonance conditions. Additionally the MO signal was characterized as a transducing signal for refractive index sensing in liquid conditions. The outcome is an increase in the limit of detection of magneto optical transducer with respect to traditional plasmonic sensors. A new strategy for magneto-plasmonic sensing based on the use of glass supported -Au nanostructures based on their MO properties has put forward.The authors want to acknowledge G. Montagna and E. Melissano for technical support and the financial support from Italian MIUR through FIRB project RBFR10OAI0 Nanoplasmag. A. G.-M. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (Contract No.MAT2014-58860-P), and the Comunidad de Madrid (Contract No. S2013/MIT-2740).Peer reviewe

Nanoparticle Langmuir-Blodgett Arrays for Sensing of CO and NO2 Gases

Metal oxide sensors with active Fe2O3 and CoFe2O4 nanoparticle arrays were studied. Sensing nanoparticle films from 1, 2, 4 or 7 monolayers were deposited by Langmuir-Blodgett technique. Sensors are formed on the alumina substrates equipped with heating meander. Langmuir-Blodgett layers were heated or UV irradiated to remove the insulating surfactant. Sensing properties were studied towards CO or NO2 gases in concentrations between 0.5 and 100 ppm in mixture with the dry air. Best response values Igas/Iair were obtained with CoFe2O4 device being 3 for 100 ppm of CO and with Fe2O3 device being (38)-1 for 0.5 ppm of NO2

Enhanced gas sensing performance of TiO2 functionalized magneto-optical SPR sensors

9 páginas, 7 figurasPorous TiO2 thin films deposited by glancing angle deposition are used as sensing layers to monitor their sensing capabilities towards Volatile Organic Compounds both in a standard Surface Plasmon Resonance (SPR) sensor and in Magneto-Optical Surface Plasmon Resonance (MO-SPR) configuration in order to compare their sensing performances. Here our results on the enhanced sensing capability of these TiO2 functionalized MO-SPR sensors with Au/Co/Au transducers with respect to traditional SPR gas sensors are presented.This work has been funded by the European Commission (NMP3-SL-2008-214107-Nanomagma), the Spanish MICINN (CSD 2008-00023, MAT 2008-06765-C02-01/NAN, MAT2010-21228), CSIC (JAE fellowship for E. F.-V.) and Comunidad de Madrid (S2009 / MAT – 1726, S2009/TIC – 1476).Peer reviewe

Magnetophotonics for sensing and magnetometry toward industrial applications

Magnetic nanostructures sustaining different types of optical modes have been used for magnetometry and label-free ultrasensitive refractive index probing, where the main challenge is the realization of compact devices that are able to transfer this technology from research laboratories to smart industry. This Perspective discusses the state-of-the-art and emerging trends in realizing innovative sensors containing new architectures and materials exploiting the unique ability to actively manipulate their optical properties using an externally applied magnetic field. In addition to the well-established use of propagating and localized plasmonic fields, in the so-called magnetoplasmonics, we identified a new potential of the all-dielectric platforms for sensing to overcome losses inherent to metallic components. In describing recent advances, emphasis is placed on several feasible industrial applications, trying to give our vision on the future of this promising field of research merging optics, magnetism, and nanotechnology

Shape Modulation of Plasmonic Nanostructures by Unconventional Lithographic Technique

Conventional nano-sphere lithography techniques have been extended to the fabrication of highly periodic arrays of sub-wavelength nanoholes in a thin metal film. By combining the dry etching processes of self-assembled monolayers of polystyrene colloids with metal physical deposition, the complete transition from increasing size triangular nanoprism to hexagonally distributed nanoholes array onto thin metal film has been gradually explored. The investigated nano-structured materials exhibit interesting plasmonic properties which can be precisely modulated in a desired optical spectral region. An interesting approach based on optical absorbance measurements has been adopted for rapid and non-invasive inspections of the nano-sphere monolayer after the ion etching process. By enabling an indirect and accurate evaluation of colloid dimensions in a large area, this approach allows the low-cost and reproducible fabrication of plasmonic materials with specifically modulated optical properties suitable for many application in biosensing devices or Raman enhanced effects

Peroxides and Bisphenols Detection in Extra Virgin Olive Oil (EVOO) by Plasmonic Nanodomes Transducers

Large-area nanostructured transducer for absorption opto-plasmonic measurements in the ultraviolet visible UV-VIS spectral range have been realized by colloidal lithography. The design and simulation performed guarantee the optical behaviour of the nanostructured transducers. Morphological characterization by AFM microscopy evidences the nanodome structure of the object realized in array configuration. A microfluidic device was optimized to perform measurements in real time. Qualitative evaluation of the peroxides’ and bisphenols’ concentration in extra virgin olive oil (EVOO) have been obtained by following the variation in the plasmonic resonance monitoring of a suitable array nanodome structure deposited onto a glass substrate. Comparison of the obtained results with laboratory-standard methodologies gives us guaranteed support of the potential of the realized technology

Tunable Nanoplasmonic Transducers: Performance Analysis and Potential Application

Plasmonic nanostructures with tunable optical properties can have many different applications, including high-sensitivity optical sensing for biological and chemical analyses in different field such as medical, environmental and food safety. The realization of an optimized sensing platform is closely related to the ability to finely control optical properties of nanostructures, which are, in turn, intimately linked to their geometrical and compositional characteristics. In this paper, an efficient and reproducible fabrication protocol, based on nanosphere lithography, for the realization of metal nanostructures with tunable plasmonic features is presented. In particular, the relationships between the geometric characteristics of different types of nanostructures with related optical phenomena such as enhanced absorption or extraordinary transmission are investigated in detail. These properties, together with electric field enhancement and confinement, are characterized and optimized in view of the employment of the fabricated nanostructures as optical transducers in nanoplasmonic chemosensor platforms working in the UV-VIS spectral range