Wyllerson Evaristo Gomes

Interfacial water layers attached to both hydrophobic and hydrophilic substrates have low dielectric permittivity. Measured structural differences between hydrophobic and hydrophilic arrangements are presented in this work. Nanosized water clusters (∼50 nm) are observed in air/water interfacial regions characterized by an ice-like structure forming walls surrounding regions with a dielectric constant ε ∼7.6. Walls are formed by an ice-like II structural arrangement. This condensed phase of water possesses an extremely small dielectric constant (ε ∼3.6) and forms wired water structures. Two nonequilibrium arrangements are then responsible for the measured spatially variable dielectric constant profiles observed in Atomic Force Microscopy.

Early disease detection is vital. Biosensors using phospholipid films or core-shell lipid-based nanostructures can aid this process. This study examined the influence of gold surface functionalization with self-assembled monolayers (SAMs) on liposome adsorption using Atomic Force Microscopy and Quartz Crystal Microbalance. Comparing hydrophobic octanethiol and hydrophilic 3-mercaptopropionic acid (3-MPA) SAMs, we found that liposome adsorption on the hydrophilic surface occurred significantly faster, requiring only 20 seconds, compared to hydrophobic surfaces which took over 1,000 seconds. Furthermore, the hydrophilic surface exhibited a higher adsorbed mass of approximately 200 ng, suggesting multilayer formation, while hydrophobic surfaces showed around 150 ng of deposited liposomes. These results highlight the crucial role of surface wettability, dictated by SAM polarity, in controlling the kinetics and extent of lipid bilayer formation for applications in biosensors and drug delivery nanotechnology.

SARS-CoV-2 is a matter of concern. Here, biosensors were prepared using iron magnetic nanoparticles containing antibodies against the receptor binding domain (RBD) of the spike protein. Antibodies were adsorbed to nanoparticles in three configurations, including direct adsorption without functionalization (DANPs). Nanoparticles were added to a glassy carbon electrode and connected to an electrochemical cell. Electrochemical impedance spectroscopy and ELISA experiments indicated that antibodies were desorbed from the DANPs upon the addition of the RBD. DANPs-based biosensors produced linear curves with decreasing charge transfer resistance due to the removal of antibodies. Thus, a detection method can be based on antibody desorption.

This work shows the efficiency of wash waters from lipopeptide production as a remediation strategy to treat urban water samples contaminated with p-cresol. The harvesting step in surfactin production involved a centrifugation step, generating a major soluble fraction and a fraction that is adsorbed to the biomass. The adsorbed fraction was recovered by washing steps. These wash waters containing lipopeptides (mostly surfactins), were successfully used to adsorb and solubilize p-cresol. The method of decontamination applied to an artificially contaminated natural water was monitored using a biosensor based on laccase/magnetic nanoparticles. Given the amount of surfactin within the wash water, the removal of p-cresol from artificially contaminated water was approximately 46.0%. This result confirms the successful and sustainable application of surfactin-rich wash waters to remove p-cresol from artificially contaminated natural water. The adsorption mechanism is potentially based on a multi-layer adsorption process, considering Langmuir and Freundlich adsorption isotherms. GRAPHICAL ABSTRACT

This work shows that the cup-stacked carbon nanotube/carbon fiber felt composite electrode (CSCNT/felt) is a promising electronic conductive matrix to develop biosensors. The device was prepared by combining this matrix with the well-studied enzyme tyrosinase. Atomic force microscopy and scanning electron microscopy confirm that tyrosinase remained well dispersed in the whole electrode and completely covered the CSCNT network surface deposited on the surface of each graphitic felt electrode fiber. The studied combination allows preparing a disposable biosensor to determine hydroquinone in water with remarkable selectivity and accuracy when applied in real samples. The limit of detection was 1.4 µM with a wide linear range between 9 and 545 µM. The device presented good reproducibility for construction, with relative error of 2.4% (n = 7). These results confirm that a simple and sensitive device has been constructed to quantify hydroquinone in natural water and that the CSCNT structure is attractive for the immobilization of tyrosinase without functionalization of their walls or the use of surfactants.

A atual busca por melhores condições de vida, com o excesso de produção e o contínuo crescimento demográfico, levou a um significativo aumento de problemas ambientais. Isto ocorre devido aos efeitos da industrialização, que geram uma grande exploração dos recursos naturais, além de resíduos tóxicos e degradantes que são erroneamente descartados no meio ambiente, contaminando diversos recursos naturais, em especial, os recursos hídricos. O lançamento de efluentes domésticos e industriais gera a poluição das águas, sendo que os principais contaminantes são agrotóxicos, como herbicidas e inseticidas, contaminantes orgânicos como fenóis, solventes orgânicos, plásticos, entre outros. Nesta perspectiva, o fenol é um dos poluentes orgânicos mais representativos, devido ao seu efeito tóxico. Portanto, sua identificação é muito importante para auxiliar na descontaminação da água. A pesquisa e o desenvolvimento de métodos para a detecção destes poluentes têm se intensificado nos últimos anos. Um desses métodos parte do uso de biossensores, um mecanismo bastante disseminado para experimentos laboratoriais. Entretanto, um desafio que se apresenta consiste na utilização dessa técnica para a detecção de compostos fenólicos no meio urbano, in loco, sem a necessidade de recolher e armazenar amostras para análise em laboratório. Para isso, é necessário tornar essa técnica “portátil” e de baixo custo para que ela possa ser efetivamente utilizada no meio urbano. Nesse sentido, este trabalho visou integrar a metodologia para detecção de compostos fenólicos via biossensores a uma plataforma que permitisse a coleta de dados e seu monitoramento de maneira remota. Assim, este trabalho teve como propósito implementar um biossensor portátil, utilizando tecnologia Wi-Fi, para detectar compostos fenólicos na água em ambiente urbano.

A clear molecular description of excess hydrated protons and their local hydrogen bond transport network remains elusive. Here, the hydrogen bond network of excess hydrated protons in water bridges was probed by measuring their Raman spectra and comparing them to the spectra of protons in ice and water. The proton vibrational spectrum and the hydrogen bond network translational and librational spectra were recorded. The spectra of the water bridge and water exhibit clear differences, indicating the presence of a structure in water bridges when subjected to an electric field of ∼10⁶ V/m that has not been previously reported. The intermolecular Raman spectrum of the floating water bridge exhibits a hydrogen bond stretching band at 150–250 cm⁻¹, librational bands within the 300–1000 cm⁻¹ spectral range, and a large band at 1500–3000 cm⁻¹, which corresponds to the vibrational signature of excess hydrated protons in the water bridge structure. The excess protons are shown to move predominantly at the air/water interface, and the effect of this distribution is a measurable change in the air/water interfacial tension from ∼80 to ∼32 N/m. Therefore, hydrated protons must have a unique water arrangement that enables them to propagate without sinking into bulk water. This local polarized hydrogen bond network in the interfacial water region is characterized by a translational spectrum similar to that of ice V.