Two-photon fluorescent immunosensor for androgenic hormones using resonant grating waveguide structures (original) (raw)
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Nonlinear immunofluorescent assay for androgenic hormones based on resonant structures
Optics Express, 2008
We report for the first time the use of two photon fluorescence as detection method of affinity binding reactions. We use a resonant grating waveguide structure as platform enhancement for detecting the interaction between fluorescent labeled Boldenone, a non-natural androgenic hormone, and a specific anti-anabolic antibody. We were able to detect a surface coverage of approximately 0.7 ng/mm 2 .
Optical Guided-wave Chemical and Biosensors I
Springer Series on Chemical Sensors and Biosensors, 2009
Electron transfer processes to/from monolayers or submonolayers of surface-confined molecules are at the core of several established or emerging sensor technologies. Spectroelectrochemical techniques to monitor these redox processes combine spectroscopic information with the normally monitored electrochemical parameters, such as changes in current or voltage, and can be much more sensitive to changes in optical properties coupled with electron transfer than electrochemical techniques alone. Spectroelectrochemical techniques based on absorbance measurements typically suffer from low sensitivity owing to the low concentrations of redox active species on the surface, and their low absorptivities. Electro-active, single-mode waveguide technologies, developed over the last decade, have provided more than adequate sensitivity to characterize electron transfer to surface-confined molecules where the coverage can be as low as a few percent of a monolayer. In this chapter, we review the major developments in combining electrochemical analysis with optical platforms that maximize optical sensitivity, through the development of electro-active integrated planar waveguides operating in the single-mode optical regime. We provide here a general overview of the theoretical formalisms associated with light propagation and absorbance measurements in integrated optical waveguides, and their electro-active counterparts. We also describe the major implementations of the technology, including the extension of the single-mode configuration into a broadband spectroscopic tool to facilitate the interrogation of the entire visible wavelength region during the redox event, and review some specific applications of these techniques, which demonstrate its sensitivity and broad utility.
Applied Physics Letters, 2005
We report a strong enhancement of two-photon fluorescence ͑TPF͒ excitation in the evanescent field of a double grating waveguide structure ͑DGWS͒. For a suitable combination of wavelength, polarization, and angular orientation of the incident laser light DGWSs show resonant behavior resulting in a large field enhancement at the waveguide surface. We demonstrate that at resonance, TPF spectroscopy reveals a 330-fold enhancement of the fluorescence signal of a tetramethylrhodamine thin film prepared from a picomolar aqueous solution. This shows the large potential of DGWSs as TPF-based high-sensitivity sensor platforms for biotechnological and biophysical application.
Food Chemistry, 2008
A direct-binding optical waveguide lightmode spectroscopy-based immunosensor detecting sulfamethazine (SMZ) was prepared, followed by the measurement of its specificity and sensitivity. System construction was undertaken with a peristaltic pump, an injector and the main unit comprising a sensor holder, two signal-harvesting photodiodes, a beam mirror, shutter and He-Ne laser source emitting a monochrome light (k = 632.8 nm), plus a PC. Antibody immobilization was performed in situ by covalent binding of an anti-SMZ antibody over the surface of a glutaraldehyde-activated 3-aminopropyltriethoxysilane-treated sensor chip. The reaction buffer for the system was 4 mM Tris-HCl (pH 7.2) that showed a medium surface coverage and stable baseline. Sensor response was quite specific to antibody-antigen complexation, as judged from no sensor response caused by bovine serum albumin immobilization. The sensor responses according to SMZ concentrations from 10 À8 to 10 À2 M increased linearly in a semi-logarithmic scale, with the limit of detection of 10 À8 M. The immunosensor was favorably reusable for SMZ screening.
Analytical and Bioanalytical Chemistry, 2014
Doped organically modified silica nanoparticles (ORMOSIL NPs) with luminescent molecules represent a potent approach to signal amplification in biomolecule labeling. Herein, we report the synthesis of new ORMOSIL NPs incorporating thermochemiluminescent (TCL) 1,2-dioxetane derivatives to prepare TCL labels for ultrasensitive immunoassay, displaying a detectability comparable to those offered by other conventional luminescence-based systems. Aminofunctionalized ORMOSIL NPs were synthesized for inclusion of acridine-containing 1,2-dioxetane derivatives with a fluorescence energy acceptor. The doped ORMOSIL NPs were further functionalized with biotin for binding to streptavidinlabeled species to be used as universal detection reagents for immunoassays. A quantitative non-competitive immunoassay for streptavidin has been developed by immobilizing antistreptavidin antibody to capture streptavidin, then the antibody-bound streptavidin was detected by the biotinylated TCL ORMOSIL NPs. The analytical performance was similar to that obtained by chemiluminescent (CL) detection using horseradish peroxidase (HRP) as label, being the limits of detection 2.5-3.8 and 0.8 ng mL −1 for TCL and CL detection, respectively. In addition, since the TCL emission is simply initiated by thermolysis of the label, chemical reagents were not required, thus allowing reagentless detection with a simplification of the analytical protocols. A compact mini dark box device based on the use of a cooled charge-coupled device (CCD) and a miniaturized heater has been developed and used to quantify the light emission after heat decomposition of the label at a temperature of 90-120°C. These characteristics make TCL-doped ORMOSIL NPs ideal universal nanoprobes for ultrasensitive bioassays such as immuno-and DNA-based assay.
Heliyon, 2020
A new fluorescent chemosensor based on quinoxaline was successfully synthesized through a facile and green catalytic reaction of ortho-phenylenediamine (O-PDA) and acenaphthylene-1,2-dione in the presence of SBA-Pr-SO 3 H. Prepared a "switch-off" quinoxaline-based receptor to recognized Hg 2þ ion in high selectively and, without any interference from other metal ions, was developed. The photophysical behavior of this fluorophore was studied in acetonitrile by using fluorescence spectra. The fluorescence properties of several cations to acenaphtoquinoxaline were investigated in acetonitrile, and the competition test displayed that the probe fluorescence changes were specific for Hg 2þ ion. The obtained results have shown high selectivity and sensitivity only for Hg 2þ. Also, the detection limit was as low as 42 ppb, and a top linear trend was observed between the concentration of Hg 2þ ions and fluorescence intensity. The binding stoichiometry between chemosensor L and Hg 2þ was found to be 1:1. Moreover, a computational study was performed to obtain an electronic description of the fluorescence emission and quenching mechanisms. The optimized structures and binding mechanisms were supported with a high correlation and agreement by spectroscopy and DFT calculations.
Two-Dimensional Photonic Crystal Chemical and Biomolecular Sensors
Analytical Chemistry, 2015
We review recent progress in the development of two-dimensional (2-D) photonic crystal (PC) materials for chemical and biological sensing applications. Self-assembly methods were developed in our laboratory to fabricate 2-D particle array monolayers on mercury and water surfaces. These hexagonal arrays strongly forward Bragg diffract light to report on their array spacings. By embedding these 2-D arrays onto responsive hydrogel surfaces, 2-D PC sensing materials can be fabricated. The 2-D PC sensors utilize responsive polymer hydrogels that are chemically function-alized to show volume phase transitions in selective response to particular chemical species. Novel hydrogels were also developed in our laboratory by cross-linking proteins while preserving their native structures to maintain their selective binding affinities. The volume phase transitions swell or shrink the hydrogels, which alter their 2-D array spacings, and shift their diffraction wavelengths. These shifts can be visually detected or spectrally measured. These 2-D PC sensing materials have been used for the detection of many analytes, such as pH, surfactants, metal ions, proteins, anionic drugs, and ammonia. We are exploring the use of organogels that use low vapor pressure ionic liquids as their mobile phases for sensing atmospheric analytes. T he need for sensitive and selective detection of hazardous chemicals and biological species has increased in importance due to the concern associated with environmental toxins and terrorist chemical threats. 1−8 It is important to identify and quantitate hazardous chemicals and biological agents before their concentrations reach dangerous levels. The ideal sensing technology would be portable, inexpensive, and able to selectively and sensitively detect hazardous species with few false positives. There are numerous methods presently used to detect chemical species. These include sophisticated analytical techniques such as chromatography, mass spectrometry, electrochemistry, fluorescence, Raman, and many others. 9−16 However, these approaches have the disadvantages of being expensive because they utilize sophisticated equipment and require the use of highly trained personnel. The optimal chemical and biomolecular sensing technology would be inexpensive and require minimal sample preparation. Photonic crystal (PC) sensors have the possibility to be developed into point-of-care type devices that will give fast, visual detection of analytes through colorimetric determinations of concentration. These two-dimensional (2-D) PC sensors, along with the similar three-dimensional (3-D) PC sensors, could revolutionize at home testing for chemical or biological analytes like the glucose sensor did for diabetics. These sensors could also be useful for detection in the field to give timely results when facilities with advanced instrumentation are hundreds of miles away. Some time ago, we pioneered a visually evident chemical sensing technology that utilized 3-D photonic crystals (PCs). 17−28 This technology incorporates face-centered-cubic (fcc) arrays of colloidal particles within smart responsive hydrogels, which contain chemical recognition agents that actuate hydrogel volume changes (Figure 1a). These volume changes alter the interparticle spacings, which shift their array diffraction wavelengths. The diffracted wavelengths have very bright, easily visually determined diffraction colors. For the 3-D PC sensors, the array embedded in the hydrogel was formed by the electrostatic self-assembly of particles in aqueous solutions that contain polymerizable monomers. The monomers were then photopolymerized around the nonclose packed 3-D PC array (Figure 1a). The array spacing was much larger than the particle diameter. The swelling or shrinkage of the responsive hydrogel leads to the change in the Bragg diffraction of the 3-D PCs. Thus, the sensing could occur either through swelling or shrinking of the responsive hydrogel. The PC hydrogel was then functionalized with molecular recognition agents that actuated the hydrogel volume changes. 3-D PC sensors were fabricated for analytes such as glucose, metal cations, creatinine, organophosphorus compounds, pH, etha-nol, and ammonia. 2,11,17−25,28 More recently other research groups used related methods to fabricate 3-D PC sensing hydrogels by polymerizing hydrogels around particle arrays. 29−37 Sensors were developed for detection of protein kinase activity, 30 glucose, 31−33 Hg 2+ , 34 ionic strength, 35 humidity, 36,37 etc. These hydrogel sensors were able to sense