In this paper, we present an array of biosensors for vapour phase detection of odorant molecules based on surface acoustic wave (SAW) resonators coated with odorant-binding proteins (OBPs). For the ...first time, the sensing capabilities of three different OBPs, as sensitive layers for SAW devices, are studied and compared. The SAW biosensor array is composed of three SAW devices coated by the droplet method with the wild-type OBP from cow (wtbOBP), a double mutant of the OBP from cow (dmbOBP) and the wild-type OBP from pig (wtpOBP). An uncoated device is used to compensate the variations of the environmental parameters. The SAW devices consist of two-port resonators fabricated on quartz (ST-cut, x propagation) with electrodes made of aluminium covered with a thin gold film (2nm thick). The obtained surface densities of OBP layers are between 1.18×10−6kg/m2 and 2.31×10−6kg/m2 and were calculated measuring the resonant frequency shift of the SAW devices after the coating. The SAW biosensor array was tested in nitrogen upon exposure to vapours of R-(–)-1-octen-3-ol (octenol), in the range of concentration between 13 and 61ppm, and R-(–)-carvone (carvone), in the range between 9 and 80ppm. The highest sensitivity for detection of octenol (25.9Hz/ppm) was obtained using the wtpOBP-based SAW biosensor, while the highest sensitivity for detection of carvone (9.2Hz/ppm) was obtained using the dmbOBP-based SAW biosensor.
► Sensor array of three surface acoustic wave biosensors and one reference is proposed. ► Three different odorant-binding proteins deposited on three SAW resonators. ► A sensor system with electronic oscillators and sealed chamber was fabricated. ► Detection of small concentrations of octenol and carvone vapours in air. ► From the comparison of the sensitivities of the OBPs they resulted to be different
Background and purpose
Bilateral globus pallidus deep brain stimulation (GPi‐DBS) represents an effective and relatively safe therapy for different forms of refractory dystonia. The aim of this study ...was to assess, retrospectively, the effect of two different stimulation settings during GPi‐DBS in 22 patients affected by primary generalized or multi‐segmental dystonia.
Methods
Thirteen patients were stimulated using a voltage‐controlled setting whilst in the other nine patients a current‐controlled setting was used. Clinical features were evaluated for each patient at baseline, 6 months and 12 months after surgery by means of the Burke−Fahn−Marsden Dystonia Rating Scale.
Results
Globus pallidus deep brain stimulation was effective in all patients. However, comparing constant‐current and constant‐voltage stimulation, a better outcome was found in the current‐controlled group during the last 6 months of follow‐up.
Conclusions
Current‐controlled stimulation is effective during GPi‐DBS for primary dystonia and it could be a better choice than voltage‐controlled stimulation over long‐term follow‐up.
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High sensitivity detection of DNA is essential for genomics. The intrinsic fluorescence from DNA is very weak and almost all methods for detecting DNA rely on the use of extrinsic fluorescent probes. ...We show that the intrinsic emission from DNA can be enhanced many-fold by spatial proximity to silver island films. Silver islands are subwavelength size patches of metallic silver on an inert substrate. Time-resolved measurements show a decreased lifetime for the intrinsic DNA emission near the silver islands. These results of increased intensity and decreased lifetime indicate a metal-induced increase in the radiative rate decay of the DNA bases. The possibility of increased radiative decay rates for DNA bases and other fluorophores suggest a wide variety of DNA measurements and other biomedical assays based on metal-induced increases in the fluorescence quantum yield of weakly fluorescent substances.
In this work, a "bio-electronic nose" for vapour phase detection of odorant molecules based on surface acoustic wave (SAW) resonators is presented. The biosensor system is composed of an array of ...five SAW resonators coated with three types of odorant-binding proteins (OBPs): the wild-type OBP from bovine (wtbOBP), a double-mutant of the OBP from bovine (dmbOBP), and the wild-type OBP from pig (wtpOBP). High resolution deposition of OBPs onto the active area of SAW resonators was implemented through laser-induced forward transfer (LIFT). The resonant frequency shifts of the SAW resonators after the deposition of the biomolecules confirmed the immobilisation of the proteins onto the Al/Au inter-digital transducers (IDTs). In addition, a low increase of insertion losses with a limited degradation of Q-factors is reported. The "bio-electronic nose" fabricated by LIFT is tested in nitrogen upon exposure to separated concentrations of R-(-)-1-octen-3-ol (octenol) and R-(-)-carvone (carvone) vapours. The "bio-electronic nose" showed low detection limits for the tested compounds (i.e. 0.48 ppm for the detection of octenol, and 0.74 ppm for the detection of carvone). In addition, the bio-sensing system was able to discriminate the octenol molecules from the carvone molecules, making it pertinent for the assessment of food contamination by moulds, or for the evaluation of indoor air quality in buildings.
•A novel SAW biosensor for the detection of d-serine was developed.•Fabrication of a SH-SAW delay-line on a piezoelectric quartz substrate covered by a SiO2 guiding layer.•A reduced-PLP d-serine ...dehydratase protein has been used as a specific probe for d-serine detection.•Detection of small concentrations of d-serine in liquid.
d-serine is an amino acid that has an important role in the regulation of N-methyl-d-aspartate (NMDA) signalling in the central nervous system. In fact, it acts as an endogenous co-agonist molecule for the NMDA receptor activation. Since an abnormal body level of d-amino acids is usually associated to different neurological diseases, it appears evident that it is of high interest to develop a fast and specific biosensor for the determination of d-serine.
In this work, we report on the design and development of a surface acoustic wave (SAW) biosensor to detect the level of d-serine. The SAW-biosensor is based on the utilization of an inactivated form of the d-serine dehydratase isolated from Saccharomyces cerevisiae, a biomolecule that is able to specifically bind d-serine. In particular, we produced a PLP-reduced d-serine dehydratase biomolecule that was still able to bind d-serine and not to transform it into the product. The binding event between the “inactivated” d-serine dehydratase and d-serine was monitored by SAW delay-lines.
Capybaras (Hidrochoeris hidrochoeris) are 1 of the largest rodents used for meat in South and Central America. Prevalence of anti–Toxoplasma gondii antibodies in 149 feral H. hidrochoeris from the ...state of São Paulo, Brazil, was evaluated using the indirect immunofluorescent antibody test (IFAT) and the modified agglutination test (MAT). Using IFAT, antibodies (>1:16) were found in 104 (69.8%) and with the MAT, antibodies (>1:25) were found in 63 (42.3%) capybaras. This is the first report of prevalence of T. gondii antibodies in this host.
The effect of temperature and glucose binding on the structure of the galactose/glucose-binding protein from Escherichia coli was investigated by circular dichroism, Fourier transform infrared ...spectroscopy, and steady-state and time-resolved fluorescence. The data showed that the glucose binding induces a moderate change of the secondary structure content of the protein and increases the protein thermal stability. The infrared spectroscopy data showed that some protein stretches, involved in alpha-helices and beta strand conformations, are particularly sensitive to temperature. The fluorescence studies showed that the intrinsic tryptophanyl fluorescence of the protein is well represented by a three-exponential model and that in the presence of glucose the protein adopts a structure less accessible to the solvent. The new insights on the structural properties of the galactose/glucose-binding protein can contribute to a better understanding of the protein functions and represent fundamental information for the development of biotechnological applications of the protein.
•MAPLE deposition technique was used to deposit OBPs onto SAW devices.•The surface density of the OBP coating was dependent on the laser parameters.•The biochemical structure of OBPs was not modified ...by the deposition process.•The functionality of the OBPs was established by measurements with SAW sensor.•The obtained sensitivities were proportional to the thickness of the OBP layers.
In this study, wild type bovine odorant-binding proteins (wtbOBPs) were deposited by matrix-assisted pulsed laser evaporation (MAPLE) and utilized as active material on surface acoustic wave (SAW) biosensors. Fourier transform infrared spectroscopy (FTIR), and atomic force microscopy (AFM) were used to determine the chemical, morphological characteristics of the protein thin films. The FTIR data demonstrates that the functional groups of wtbOBPs do not suffer significant changes in the MAPLE-deposited films when compared to the reference one. The topographical studies show that the homogeneity, density and the roughness of the coatings are related mainly to the laser parameters (fluence and number of pulses). SAW biosensor responses to different concentrations of R-(–)-1-octen-3-ol (octenol) and R-(–)-carvone (carvone) were evaluated. The obtained sensitivities, achieved through the optimization of deposition parameters, demonstrated that MAPLE is a promising deposition technique for SAW biosensor implementation.
•We described the thermal denaturation process of mKO.•mKO shows a high thermostability and an irreversible three-state unfolding process.•Changes in chromophore protonation lead to variations of ...fluorescence intensity.•Changes in chromophore protonation are coupled to small structural rearrangements.
The mKO is the monomeric version of Kusabira Orange, a GFP-like protein emitting bright orange fluorescence at 559nm. This protein shows the characteristic β-barrel motif typical of the fluorescent protein family which it belongs to, similar spectral properties to the tetrameric form and an exceptional photo-stability to pH changes. Here, we demonstrate that mKO in solution at physiological pH exhibits a secondary structure analogue to that of the crystal. Moreover, we describe the thermal unfolding, revealing an outstanding structural stability with a denaturation temperature close to 90°C and identifying the existence of a thermodynamic intermediate. The denaturation process of mKO results to be absolutely irreversible because of the complete lost of the native structure and the consequent aggregation, while the presence of the intermediate state is most likely due to coexistence of two different species of mKO, with protonated and deprotonated chromophore respectively, that affects the fluorescence properties and the structural stability of the protein.
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