Corrosion Resistant FBG-Based Quasi-Distributed Sensor for Crude Oil Tank Dynamic Temperature Profile Monitoring.

This article presents a corrosion resistant, maneuverable, and intrinsically safe fiber Bragg grating (FBG)-based temperature optical sensor. Temperature monitoring is a critical activity for the oil and gas industry. It typically involves acquiring the desired parameters in a hazardous and corrosive environment. The use of polytetrafluoroethylene (PTFE) was proposed as a means of simultaneously isolating the optical fiber from the corrosive environment and avoiding undesirable mechanical tensions on the FBGs. The presented sensor head is based on multiple FBGs inscribed in a lengthy single mode fiber. The sensor presents an average thermal sensitivity of 8.82 ± 0.09 pm/°C, resulting in a typical temperature resolution of ~0.1 °C and an average time constant value of 6.25 ± 0.08 s. Corrosion and degradation resistance were verified by infrared spectroscopy and scanning electron microscopy during 90 days exposure to high salinity crude oil samples. The developed sensor was tested in a field pilot test, mimicking the operation of an inland crude tank, demonstrating its abilities to dynamically monitor temperature profile.

Localized Surface Plasmon Resonance-Based Nanosensor for Rapid Detection of Glyphosate in Food Samples.

In this study, we developed a biosensor based on the localized surface plasmon resonance (LSPR) phenomenon of gold nanoparticles (AuNPs) to detect the widely used herbicide glyphosate in food samples. To do so, either cysteamine or a specific antibody for glyphosate were conjugated to the surface of the nanoparticles. AuNPs were synthesized using the sodium citrate reduction method and had their concentration determined via inductively plasma coupled mass spectrometry. Their optical properties were analyzed using UV-vis spectroscopy, X-ray diffraction, and transmission electron microscopy. Functionalized AuNPs were further characterized via Fourier-transform infrared spectroscopy, Raman scattering, Zeta potential, and dynamic light scattering. Both conjugates succeeded in detecting the presence of glyphosate in the colloid, although nanoparticles functionalized with cysteamine tended to aggregate at high concentrations of the herbicide. On the other hand, AuNPs functionalized with anti-glyphosate functioned at a broad concentration range and successfully identified the presence of the herbicide in non-organic coffee samples and when it was added to an organic coffee sample. This study demonstrates the potential of AuNP-based biosensors to detect glyphosate in food samples. The low-cost and specificity of these biosensors make them a viable alternative to current methods for detecting glyphosate in foodstuffs.

Rapid and sensitive detection of ochratoxin A using antibody-conjugated gold nanoparticles based on Localized Surface Plasmon Resonance.

The regulation of tolerable levels of ochratoxin A in food for human and animal consumption has been defined in some countries. To meet these levels, simpler, more efficient, and faster analytical methods are being developed to facilitate the identification of this dangerous contaminant in food. Here, we combined gold nanoparticles (AuNPs) with anti-ochratoxin A (OTA) IgG to detect elementary levels of OTA based on Localized Surface Plasmon Resonance. AuNPs were prepared with trisodium citrate and characterized by UV-visible spectroscopy, X-ray, dynamic light scattering, and transmission electron microscopy. The conjugation of AuNPs to IgG anti-OTA was confirmed by bathochromic shift (UV-vis) and RAMAN spectroscopy. The sensitivity of the nanosensor was investigated by measuring LSPR band λmax shifts. Our results suggest this assay is highly sensitive, with a lower detection limit of about 0.001 pg mL-1. The LSPR nanosensor reduced detection limits by roughly 10 times compared to other methods. We demonstrated that the approach investigated here is a rapid and sensitive method for OTA detection.

Impact of conjugation strategies for targeting of antibodies in gold nanoparticles for ultrasensitive detection of 17ß-estradiol.

Antibody-coated nanoparticles have recently attracted considerable attention, with the focus falling on diagnostics. Nevertheless, controlled antibody bioconjugation remains a challenge. Here, we present two strategies of bioconjugation with the aim of evaluating the best approach for the coupling of antibodies on the surface of nanomaterials in an oriented way. We employed electrostatic interaction (physical adsorption) and covalent conjugation in the orientation of antibodies on the metallic surface as coupling methods, and their influence on the detection of 17ß-estradiol was addressed with localized surface plasmon resonance. The understanding of these mechanisms is fundamental for the development of reproducible inorganic bioconjugates with oriented surface as well sensibility of immunoassays.

Controlled biosynthesis of gold nanoparticles with Coffea arabica using factorial design.

Green synthesis of metallic nanoparticles has become incredibly popular, mainly by minimizing problems of environmental contamination and by being able to reduce, stabilize and potentially functionalize nanomaterials. Such compounds have possible applications in various areas, e.g., pharmaceuticals (drug delivery systems, cosmetics), textile industry (clothing with antimicrobial properties), diagnostic medicine (imaging, high efficiency biosensors), energy (solar panels), bioremediation, among others. However, the lack of reproducibility and information on the control mechanisms during synthesis have made the application of green-synthesized nanoparticles unfeasible. Thus, this study proposed the investigation of the main mechanisms affecting synthesis control, using factorial design for the preparation of gold nanoparticles with extract of Coffea arabica. We obtained stable (Zeta Potential, UV-vis and DLS), monodisperse, and quasi-spherical (TEM) nanoparticles, which presented adsorbed aromatic molecules (FTIR and RAMAN) and defined crystal structure (XRD), proving that the plant extract acted as a reducing agent, as well as a stabilizer and functionalizer for the synthesized nanostructures. The factorial design employed here to obtain gold nanoparticles with Coffea arabica extract allowed for a controlled and reproducible synthesis, enabling new possibilities for the application in several fields.

A non-linear mathematical model using optical sensor to predict heart decellularization efficacy.

One of the main problems of the decellularization technique is the subjectivity of the final evaluation of its efficacy in individual organs. This problem can result in restricted cell repopulation reproducibility and worse responses to transplant tissues. Our proposal is to analyze the optical profiles produced by hearts during perfusion decellularization, as an additional method for evaluating the decellularization process of each individual organ. An apparatus comprised of a structured LED source and photo detector on an adjustable base was developed to capture the relationship between transmitted light during the perfusion of murine hearts, and residual DNA content. Voltage-time graphic records were used to identify a nonlinear mathematical model to discriminate between decellularizations with remaining DNA above (Incomplete Decellularization) and below (Complete Decellularization) the standardized limits. The results indicate that temporal optical evaluation of the process enables inefficient cell removal to be predicted in the initial stages, regardless of the apparent transparency of the organ. Our open system also creates new possibilities to add distinct photo detectors, such as for specific wavelengths, image acquisition, and physical-chemical evaluation of the scaffold, in order to collect different kinds of information, from dozens of studies. These data, when compiled and submitted to machine learning techniques, have the potential to initiate an exponential advance in tissue bioengineering research.