Prattakorn Metem

The elastic properties of nanoscale extracellular vesicles (EVs) are believed to influence their cellular interactions, thus having a profound implication in intercellular communication. However, accurate quantification of their elastic modulus is challenging due to their nanoscale dimensions and their fluid-like lipid bilayer. We show that the previous attempts to develop atomic force microscopy-based protocol are flawed as they lack theoretical underpinning as well as ignore important contributions arising from the surface adhesion forces and membrane fluctuations. We develop a protocol comprising a theoretical framework, experimental technique, and statistical approach to accurately quantify the bending and elastic modulus of EVs. The method reveals that membrane fluctuations play a dominant role even for a single EV. The method is then applied to EVs derived from human embryonic kidney cells and their genetically engineered classes altering the tetraspanin expression. The data show a large spread; the area modulus is in the range of 4 to 19 mN/m and the bending modulus is in the range of 15 to 33 k B T , respectively. Surprisingly, data for a single EV, revealed by repeated measurements, also show a spread that is attributed to their compositionally heterogeneous fluid membrane and thermal effects. Our protocol uncovers the influence of membrane protein alterations on the elastic modulus of EVs.

Extracellular vesicles (EVs) are nanoparticles encapsulated with a lipid bilayer, and they constitute an excellent source of biomarkers for multiple diseases. However, the heterogeneity in their molecular compositions constitutes a major challenge for their recognition and profiling, thereby limiting their application as an effective biomarker. A single-EV analysis technique is crucial to both the discovery and the detection of EV subpopulations that carry disease-specific signatures. Herein, a plasmonic nanohole array is designed for capturing single EVs and subsequently performing fluorescence detection of their membrane proteins by exploiting plasmonic amplification of the fluorescence signal. Unlike other reported methods, our design relies on an exclusive detection of single EVs captured inside nanoholes, thus allowing us to study only plasmonic effects and avoid other metal-induced phenomena while leveraging on the proximity of emitters to the plasmonic hotspots. The method is optimized through numerical simulations and verified by a combination of atomic force, scanning electron microscopy, and fluorescence microscopy. Fluorescence enhancement is then estimated by measuring the CD9 expression of small EVs derived from the human embryonic kidney (HEK293) cell line and carefully considering the spatial distribution of emission and excitation intensities. Fluorescence intensities of immunostained EVs show a moderate overall enhancement of intensity and follow the intensity trend predicted by simulation for nanohole arrays with different nanohole periods. Moreover, the number of observed EVs in the best-performing nanohole array increases by more than 12 times compared with EVs immobilized on a reference substrate, uncovering a vast amount of weakly fluorescent EVs that would remain undetected with the regular fluorescent method. Our nanohole array provides a basis for a future platform of single-EV analyses, also promising to capture the signature arising from low-expressing proteins.

Anion-exchange-membrane water electrolysis (AEMWE) is a nascent green hydrogen production technology. Its main advantage lies in its ability to utilize non-platinum group metals (PGMs) as catalysts and PFSA-free polymer as a membrane, unlike proton-exchange-membrane water electrolysis (PEMWE). It is well-known that, unlike PEMWE, AEMWE suffers greatly from substituting the electrolytic feed solution with a solution of a lower pH (e.g., pure water). Literature has attributed the loss of performance to the lower reaction kinetics of both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) and the drastic loss of electrolyte conductivity, which is further exacerbated at higher current density [1]. Notably, it is shown that addition of salt to improve the conductivity of electrolyte does not always equate to a better performance over time, depending on the feed configuration, highlighting the importance of understanding mass transport during cell operation [2]. Therefore, to decouple the causes of the drastic losses of performance in-situ, we have developed a system capable of feeding vapor and liquid into AEMWE asymmetrically. The cell is constructed using a membrane electrode assembly (MEA) fabricated by the catalyst coated membrane (CCM) method, where platinum on carbon (Pt/C) and iridium oxide (IrO_x) are coated directly on PiperION^® anion exchange membranes. Moreover, we have studied hydroxide crossover both statically using an h-cell test and dynamically in an AEMWE cell. We have shown that, by utilizing various combinations of feeds, including humidified gas, pure water, or KOH, through both cathode and anode, it is possible to study cell performance and hydroxide transport under different conditions. Through which, we have elucidated the performance loss, the importance of hydroxide transport, and a strategy to overcome such losses, thus showing the possibility of advancing toward pure water and low-temperature vapor electrolysis. [1] Liu, Jiangjin, et al. "Elucidating the role of hydroxide electrolyte on anion-exchange-membrane water electrolyzer performance." Journal of the electrochemical society 168.5 (2021): 054522. [2] Rossi, Ruggero, Rachel Taylor, and Bruce E. Logan. "Increasing the electrolyte salinity to improve the performance of anion exchange membrane water electrolyzers." ACS Sustainable Chemistry & Engineering 11.23 (2023): 8573-8579. Figure 1. Schematic of the developed feeding system capable of feeding water vapor and liquid into the electrolyzer. Figure 1

Ammonia (NH₃) is globally one of the most produced chemicals. Despite being known for its use as a fuel and as a precursor of multiple chemicals, during its production, it is responsible for more than 1.2 % of the total global CO₂ emission and consumes a large amount of energy. In this work, we studied a flow‐through membrane‐free electrocatalytic device (CMED) to produce continuous stream of NH₃ from a common water contaminant, nitrate (NO₃⁻). Indium‐palladium (In−Pd) nanoparticles were impregnated in activated carbon cloth (ACC) and used as a cathode in the electrochemical device. It is found that in the counter electrode, adding oxygen evolution reaction (OER) active catalysts like platinum (Pt) for the regeneration of hydrogen ions enhances the rate of ammonia conversion to 7.28 μmol min⁻¹ cm⁻², eliminate the production of toxic nitrite by‐products, as well as provide a platform for a stable energy consumption over long periods of time. This method for the conversion of NO₃⁻ into NH₃ promises a way forward for sustainable resource utilization while generating fuel from waste and contributing to future circular economies, and managing the nitrogen cycle in water that is a major challenge of the 21st century society.

This work demonstrated a ZnO-coated optical fiber sensor for the detection of a volatile organic compound (VOC) biomarker for diabetes for detecting isopropanol (IPA) markers. A coreless silica fiber (CSF) was connected to a single-mode fiber (SMF) at both ends to achieve a SMF–CSF–SMF structure. CSF is the sensing region where multimode interference (MMI) generates higher light interaction at the interface between the fiber and sensing medium, leading to enhanced sensitivity. Optimization of the CSF length was conducted numerically to attain the highest possible coupling efficiency at the output. Surface functionalization was achieved via hydrothermal growth of ZnO nanorods directly onto the CSF at low temperatures. The optical fiber-based sensor was successfully fabricated and tested with 20%, 40%, 60%, 80%, and 100% of IPA. The sensor response was recorded using an optical spectrometer and analyzed for sensor sensitivity. The fabricated sensor shows the potential to detect isopropanol with the sensitivity of 0.053 nm/%IPA vapor. Further improvement of the sensor sensitivity and selectivity is also proposed for future work.