Sensing and Bio-Sensing Research最新文献

Among the non-destructive techniques capable of obtaining information on biological systems even in vivo, terahertz-based techniques are emerging due to their specificity to the water content, which can represent an important indicator of the presence of microorganisms and, in general, of the health status, particularly in plants. Nevertheless, the analysis of the extracted data (especially for images) and the exploitation of the potential of the technique for the study of the complex phenomena that occur in living tissues are still almost unexplored fields. In this work, the hydration status of leaves both in vivo and ex vivo was monitored continuously and non-destructively by acquiring videos in the sub-terahertz range through a portable imaging system. A model for describing the water flow in space and time in the midvein of a leaf is obtained which is suitable for the analysis of the data extracted from the portable sub-terahertz imaging system. These results show that terahertz-based technology can be used to study biological phenomena even in vivo; moreover, they pave the way for the introduction of a general method for the analysis of terahertz data based on surface fits in space and in time as well.

Early detection of prostate cancer, the second main cause of death in men, with robust assay platforms by using the appropriate biomarkers is of great importance for diagnosis and follow-up of disease under treatment. The aim of this research is to investigate how novel TiS₃ nanoribbons can be used as a channel material in the microfluidic electrolyte-gated field-effect transistor (FET), with the goal of developing a label-free immunosensor for the sensitive, selective, and rapid detection of PSA as a cancer marker in both PBS and human serum samples. To create an active channel material, the TiS₃ nanoribbons were deposited onto the FET surface through a drop-casting process, and the surface of the channel was subsequently modified with an anti-PSA monoclonal antibody. The electrical properties of the microfluidic electrolyte-gated TiS₃ nanoribbon-based FET were characterized, and the results showed that it exhibited a depletion-mode n-type behavior with a field-effect mobility of 2.3 × 10⁻³ cm²/Vs, an I_on/I_off current ratio of 4.12, and a subthreshold swing (SS) of 914.1 mV/decade. As the concentration of PSA increased from 0.1 fg/mL to 10 pg/mL, there was a corresponding increase in the drain current with a high sensitivity of 2.2665 nA/decade and a detection limit of 0.04 fg/mL. Integrating the electrolyte-gated FET with the microfluidic channel resulted in improved performance of the microfluidic electrolyte-gated FET immunosensor. The combination of these two components led to better control and delivery of small sample volumes to the surface of the electrolyte-gated FET, which improved the repeatability of the obtained data. Based on the results obtained from the microfluidic immunosensor, it can be inferred that the developed platform has the potential to be an excellent candidate for point-of-care cancer diagnosis and therapeutic monitoring.

Several studies have demonstrated that Ag₂S QDs are promising near-infrared II-emitting nanoprobes. They Ag₂S QDs can be used in the fields of bio-imaging, fluorescence detection and photodetectors. In this work, we achieved the first successful construction of a dual-input logic gate IMPLICATION gate based on the specific detection of Fe³⁺ by silver sulfide quantum dots and the reduction of Fe³⁺ by ascorbic acid. The Ag₂S QDs were successfully prepared from glutathione and silver nitrate and characterized by fluorescence spectroscopy analysis, XPS analysis, and transmission electron microscopy TEM analysis. The prepared Ag₂S QDs can achieve selective detection of Fe³⁺ with a detection limit of LOD of 0.15 mM. This work provides a new method for the detection of Fe³⁺.

This study introduces a dual-core photonic crystal fiber incorporating a highly responsive plasmonic refractive index (RI) sensor. The performance of the RI sensor is evaluated based on amplitude sensitivity, wavelength resolution, wavelength sensitivity, and the linearity of the resonance wavelength. Employing the finite element technique (FEM), a numerical analysis of the proposed design is conducted. Results indicate that employing the amplitude interrogation method yields a peak amplitude sensitivity of 605.82 RIU⁻¹ for y-polarization. Furthermore, the wavelength interrogation approach for y-polarized modes demonstrates a maximum wavelength sensitivity of approximately 17,000 nm/RIU and a maximum wavelength resolution of 5.88 × 10⁻⁶ RIU. The proposed sensor exhibits a figure of merit of approximately 298 and effectively responds to refractive index variations within the range of 1.28 to 1.40. These promising outcomes, coupled with the broad sensing range, establish the suggested sensor as a promising candidate for the detection of organic chemical solutions.

The application of a recombination sensor for real-time detection of Lactate Dehydrogenase (LDH) activities has been demonstrated. LDH activity in biological fluids, particularly in blood serum, is a critical diagnostic indicator of human health. Therefore, the development of methods for monitoring it remains a crucial task in modern bioengineering. The parameter directly measured in real-time is the photocurrent through a deep-barrier structure under light illumination from the region of strong optical absorption in silicon. The detection of enzyme presence can be achieved because the flow of the dehydrogenase reaction (in the presence of LDH activation) is accompanied by changes in charge at the system's interface. Such a change in the effective charge of the reactants can be detected through the amplitude of the sensor structure's photocurrent. The main factor in this approach is the influence on the recombination center parameters at the interface. It has been shown that the combined use of modulated signal illumination and constant illumination allows obtaining additional information about the analyte and reaction kinetics. A promising approach is proposed, which can be considered a simple and sensitive method for real-time detection of lactate dehydrogenase activity.

The main shortcoming of the Surface Plasmon Resonance (SPR) method is its inability to detect low molecular weight (<400 Da) and dilute samples. Moreover, the study of protein-DNA interactions using SPR is one of the most challenging one. Due to these difficulties, the enhancement of SPR signals has been less explored. According to the proposition that the Rif1 protein can be considered a biomarker in breast cancer, further investigations are needed to understand the mechanism of Rif1 and G4 interaction. For this purpose, we studied different platforms to obtain kinetic data on their interaction and to investigate the increase in the SPR signal using quantum dot (Qdot) nanoparticles. Finally, the nickel-NTA chip was used to immobilize the protein, and the streptavidin was attached to Qdot through the EDC-NHS mechanism to bind the 5′-biotinylated G4 structure that was prepared. Different concentrations of biotinylated-G4 were injected, and the enhancement in the signals was studied by injecting the streptavidin-conjugated Qdots onto the chip. Our results indicate a very low dissociation constant of 6.8 ± 0.9 nM which is in consistent with our previous studies. We could enhance the signals by approximately 6 times which is believed to be due to the high bulk density and refractive index of Qdots.

Numerical values of important parameters associated with a piezoelectric material containing an electrolyte and subjected to external stress were obtained; the applied stress produced, almost instantly, induced charges on the material's surface; these charges move the ions of the electrolyte toward the charged surfaces forming the electric double layer EDL; these two charged surfaces give place to the formation, in the interior of the material, of a particular type of capacitor called double layer capacitor DLC. The values of these parameters associated with DLC show interesting and important characteristics: DLC can store considerable amounts of energy and electric charge, as well as high electric fields; these characteristics can explain the extreme sensitivity of the human body to sense extraordinarily small mechanical actions. While the time to induce the charge on the surface τ_e is instantaneous, the time τ_i to form EDL is not; this time controls the shape of the output voltage signals. The presence of glucose modifies the piezoelectric signals allowing to use these profiles to diagnose diabetes. Additionally, expressions were obtained for the chemical capacitance C_μ as a function of voltage and glucose concentration.

Lanthanum fluoride (LaF₃) and other rare-earth halides are commonly used in sensor and optical equipment. A deep eutectic solvent (DES) based LaF₃ passivated porous silicon (PS) sensor for sensing the pH of buffer solution has been fabricated in this research. An electrochemically etched PS structure has been prepared and passivated with novel DES-based LaF₃ to fabricate pH sensor. For the deposition of LaF₃ thin film to create heterostructure devices, a variety of complex and costly processes have been employed. In a quest to find a facile technique to fabricate a pH sensor, this research presents the justification of sensing characteristics of DES-based spin-deposited LaF₃/PS structure. Energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses both supported the almost stoichiometric and highly crystalline nature of LaF₃. Scanning electron microscopy (SEM) was used to confirm the uniform morphological structure. The sensing characteristics of fabricated pH sensors have been confirmed by studying the capacitance-voltage (CV) characteristics of prepared structure in a different buffer solution with different pH values. From the experimental results, it was observed that DES-based LaF₃ passivated PS structure shows voltage shift at the inflexion point of CV characteristics for different pH solutions. In light of this, it can be said that a pH sensor for sensing the pH levels of any buffer solution may be fabricated by depositing novel DES-based LaF₃ both inside the pores of PS and on top of it using the spin coating approach.

Coffee known for its diverse aromas shaped by postharvest treatments, particularly the roasting process, plays a pivotal role in determining the quality of the brewed beverage. This study focuses on classifying the aroma of Arabica coffee beans based on roasting temperature, employing an electronic nose equipped with a TGS gas array sensor. The classification methodology integrates deep learning through an artificial neural network (ANN), along with a calculation analysis utilizing the Pearson correlation coefficient. Raw Robusta coffee beans were subjected to five distinct roasting treatments (185 °C, 195 °C, 205 °C, 215 °C, and 225 °C), resulting in light roasts, light to medium roasts, medium to dark roasts, medium to dark roasts, and dark roasts. The repeatability test affirms the TGS sensor's reliability, exhibiting a standard deviation (STD) below 20%. Notably, the TGS 2612 and TGS 2611 sensors, dedicated to odor detection, demonstrated excellent validity with an STD below 10% across various roasting temperatures. Classification results from deep learning cross-validation showcase impressive accuracy: 98.2% for Light Roasts, 98.4% for Light to Medium Roasts, 98.8% for Medium Roasts, 97.8% for Medium Roasts, and 95.9% for Dark Roasts. In conclusion, this study reveals that the E-nose, utilizing the TGS gas sensor array with deep learning analysis, effectively detects and classifies coffee types based on roasting time with high accuracy.