Urinary tract infections (UTIs) are caused mainly by uropathogenic Escherichia coli (UPEC), accounting for both uncomplicated (75%) and complicated (65%) UTIs. Detecting UPEC in a specific, rapid, ...and timely manner is essential for eradication, and optical biosensors may be useful tools for detecting UPEC. Recently, biosensors have been developed for the selective detection of antigen–antibody-specific interactions. In this study, a methodology based on the principle of an optical biosensor was developed to identify specific biomolecules, such as the PapG protein, which is located at the tip of P fimbriae and promotes the interaction of UPEC with the uroepithelium of the human kidney during a UTI. For biosensor construction, recombinant PapG protein was generated and polyclonal anti-PapG antibodies were obtained. The biosensor was fabricated in silicon supports because its surface and anchor biomolecules can be modified through its various properties. The fabrication process was carried out using self-assembled monolayers (SAMs) and an immobilized bioreceptor (anti-PapG) to detect the PapG protein. Each stage of biosensor development was evaluated by Fourier transform infrared (FTIR) spectroscopy. The infrared spectra showed bands corresponding to the C–H, CO, and amide II bonds, revealing the presence of the PapG protein. Then, the spectra of the second derivative were obtained from 1600 to 1700 cm–1 to specifically determine the interactions that occur in the secondary structures between the biological recognition element (anti-PapG antibodies) and the analyte (PapG protein) complex. The analyzed secondary structure showed β-sheets and β-turns during the detection of the PapG protein. Our data suggest that the PapG protein can be detected through an optical biosensor and that the biosensor exhibited high specificity for the detection of UPEC strains. Furthermore, these studies provide initial support for the development of more specific biosensors that can be applied in the future for the detection of clinical UPEC samples associated with ITUs.
Escherichia coli (E. coli) may be harmful to humans. Hence, a rapid, low cost, and easy detection method is needed, and optical biosensors are an excellent option. Here a new platform based upon ...silicon carbide and titanium (SiC-Ti) was used to determine enteropathogenic E. coli by Fourier transform infrared (FTIR) spectroscopy. Self-assembly monolayer (SAM) approach was used to modify the platform. Antibody anti-E. coli flagella were obtained and utilized as the biological recognition element. Three concentrations of bacteria (10, 100, and 1000 CFU/mL) were determined. The detection region was from 1330 to 1480 cm
−1
, where characteristic bands associated with E. coli were determined. An increase in the absorption intensity was observed with the bacteria concentration, demonstrating suitability for quantitative analysis.
Salmonella is one of the main microorganisms that causes food-borne illnesses worldwide, although there are standard procedures to determine its presence or absence in food samples. However, these ...methodologies are time consuming and cumbersome, so the development of devices that rapidly and accurately determine bacteria is necessary. Various materials have been used to construct these devices. Hydrogenated amorphous silicon carbide (a-SiC:H) is one of the least studied. Therefore, in the present work, self-assembled monolayers were applied on a-SiC:H thin films to determine Salmonella Typhimurium ATCC 14028 by Fourier transform infrared spectroscopy. The detection of this microorganism was performed between 1060 and 960 cm
−1
corresponding to carbohydrate and phosphate groups of the bacteria. The lowest detected concentration was 10 CFU/mL. This work confirms the utility of a-SiC:H to reliably and rapidly determine Salmonella.
•The a-SiC:H platform as an alternative for development biosensors.•Antibodies immobilized by non-specific physical adsorption have better bioactivity than by covalent attachment.•Wrong orientation ...and the excess of the immobilized antibodies can impair the capture of the antigen in the development of immunosensors.
In this work, we evaluate the performance of two biofunctionalization processes on silicon and hydrogenated amorphous silicon carbide (a-SiC:H). The biofunctionalization processes were designed to immobilize antibodies via non-specific physical adsorption or covalent attachment. The impact of the two surface types (crystalline and amorphous) on the resulting immunosensing layer is discussed in terms of the possible orientation, stability, and bioactivity of the immobilized antibodies. To evaluate the formation of active groups on the surface before and after the immobilization process, we used Fourier-transform infrared (FTIR) spectroscopy. On the other hand, to visualize the topography changes on the different surfaces with immobilized antibodies, we used atomic force microscopy (AFM). ELISA assay was conducted to obtain a quantitative parameter associated with the density of immobilized antibodies on the platforms. The results showed that the antibodies were immobilized on both platforms by any of the two immobilization mechanisms. The antigen capture did not show a direct relationship with the antibody estimation made by ELISA. According to the results, the a-SiC:H platforms by covalent attachment achieved the highest density of immobilized antibodies compared to silicon. However, its performance in the antigen detection assay was lower compared to silicon platforms. We concluded that the performance of the silicon platform was better in terms of its biofunctionalization and antigen detection. The orientation and structural integrity of the antibodies on the platforms was crucial to its performance on antigen detection.
The fabrication of biosensors has different future applications mainly from the perspective of eco-friendly technologies. Label-free strategies, recyclable materials and low-temperature processing ...are parameters to consider for the development of a new generation of biosensor devices. In this work, Zinc oxide (ZnO) Thin-film Transistors (TFTs) using recyclable plastic substrates were used for real-time enteropathogenic Escherichia coli detection as an approach for biosensing (bio-TFTs). Fourier Transform Infrared Spectroscopy was used to verify the characteristic absorption peaks at the different steps of the bio-TFT assembly process. The bio-TFTs are ready to observe the bacterial detection by electrical characterization. Finally, detection was validated by a coupled strategy that fuses the genomic DNA extraction from bacteria attached in situ over bio-TFTs surface and, the development of the Polymerase Chain Reaction to amplify specific genes from enteropathogenic Escherichia coli.
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•Solution-processed ZnO TFTs on recyclable plastic substrates allow real-time bacterial detection.•Recyclable plastic substrate PET has compatibility with flexible electronics and contribute its use in a low-cost biosensor.•Electrical modifications are associated to the bacterial concentration and validated in situ by PCR.
The antibody immobilization compatible with low-cost materials and label-free strategies is a challenge for biosensor device fabrication. In this study, ZnO thin film deposition was carried out on ...corning glass substrates by ultrasonic spray pyrolysis at 200 °C. The thin films were analyzed as platforms for enteropathogenic Escherichia coli (E. coli EPEC) antibody immobilization. The modification of thin films from the functionalization and antibody immobilization steps was visualized using Fourier transform infrared spectroscopy (FTIR) spectroscopy, and surface changes were observed by atomic force microscopy. The obtained FTIR spectra after functionalization showed a contribution of the amino group (NH2) derived from silane (3-aminopropyltrimethoxysilane). The antibody immobilization showed an amide I conserved signal corresponding to the CO stretching vibrations and the amide II signal related to the N–H scissor vibration mode. In this way, the signals observed are correlated with the presence of antibody immobilized on the film. The ZnO film morphology changes after every stage of the process and allows observing the antibody distribution on the immobilized surface. In order to validate the antibody recognition capability as well as the E. coli EPEC detection in situ, polymerase chain reaction was used.
•Al and AZO are used as source/drain electrodes in room-temperature based Zn3N2 TFTs.•The fabrication and characterization of fully transparent Zn3N2 TFTs is presented.•The fabrication procedure is ...compatible with flexible electronics.
In this work, the comparison of source/drain electrodes in thin film transistors (TFTs) based on room temperature deposited Zinc Nitride (Zn3N2) films is presented. Aluminum and aluminum doped zinc oxide (AZO) films are used as electrodes. Both devices exhibit an on/off-current ratio of 104 and a subthreshold slope close to 1 V/Dec. The extracted field-effect mobility was 4.5 cm2/Vs and 1 cm2/Vs for TFTs using aluminum and AZO, respectively. Better electrical characteristics are achieved with aluminum electrodes. However, AZO electrodes made possible the fabrication of fully transparent Zn3N2 TFTs, reported for first time in this work.
In this work, the study of annealing effects on electrical properties of Zinc Oxide Thin-film Transistors is presented. The samples were annealed at 180°C under Nitrogen ambient. The conductivity and ...contact resistance of ZnO films with Aluminum electrodes are studied by Transmission Line Method. Also, the Zinc Oxide films obtained by ultrasonic spray pyrolysis at 200°C are studied by X-ray diffraction and Fourier transform infrared spectroscopy. A comparison of the electrical properties as a function of annealing time is presented. The results show an optimal annealing time and after this time, the metal-ZnO interface deteriorates.
•The study of annealing effects on aluminum/ZnO contacts is presented.•There is an optimal time of annealing and after this time, the contact tends to degrade.•ZnO bonds clearly shows a reduction as the annealing time is increased.•Output characteristics present a clear saturation regime after 30min of annealing.
Dengue and Zika are two major vector-borne diseases. Dengue causes up to 25,000 deaths and nearly a 100 million cases worldwide per year, while the incidence of Zika has increased in recent years. ...Although Zika has been associated to fetal microcephaly and Guillain-Barré syndrome both it and dengue have common clinical symptoms such as severe headache, retroocular pain, muscle and join pain, nausea, vomiting, and rash. Currently, vaccines have been designed and antivirals have been identified for these diseases but there still need for more options for treatment. Our group previously obtained some fractions from medicinal plants that blocked dengue virus (DENV) infection
. In the present work, we explored the possible targets by molecular docking a group of molecules contained in the plant fractions against DENV and Zika virus (ZIKV) NS3-helicase (NS3-hel) and NS3-protease (NS3-pro) structures. Finally, the best ligands were evaluated by molecular dynamic simulations.
To establish if these molecules could act as wide spectrum inhibitors, we used structures from four DENV serotypes and from ZIKV. ADFR 1.2 rc1 software was used for docking analysis; subsequently molecular dynamics analysis was carried out using AMBER20.
Docking suggested that 3,5-dicaffeoylquinic acid (DCA01), quercetin 3-rutinoside (QNR05) and quercetin 3,7-diglucoside (QND10) can tightly bind to both NS3-hel and NS3-pro. However, after a molecular dynamics analysis, tight binding was not maintained for NS3-hel. In contrast, NS3-pro from two dengue serotypes, DENV3 and DENV4, retained both QNR05 and QND10 which converged near the catalytic site. After the molecular dynamics analysis, both ligands presented a stable trajectory over time, in contrast to DCA01. These findings allowed us to work on the design of a molecule called MOD10, using the QND10 skeleton to improve the interaction in the active site of the NS3-pro domain, which was verified through molecular dynamics simulation, turning out to be better than QNR05 and QND10, both in interaction and in the trajectory.
Our results suggests that NS3-hel RNA empty binding site is not a good target for drug design as the binding site located through docking is too big. However, our results indicate that QNR05 and QND10 could block NS3-pro activity in DENV and ZIKV. In the interaction with these molecules, the sub-pocket-2 remained unoccupied in NS3-pro, leaving opportunity for improvement and drug design using the quercetin scaffold. The analysis of the NS3-pro in complex with MOD10 show a molecule that exerts contact with sub-pockets S1, S1', S2 and S3, increasing its affinity and apparent stability on NS3-pro.
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