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2022 ◽  
Vol 124 ◽  
pp. 107352
Author(s):  
Haobo Jin ◽  
Yi Sun ◽  
Jiajing Pan ◽  
Yue Fang ◽  
Yongguo Jin ◽  
...  

Molecules ◽  
2022 ◽  
Vol 27 (2) ◽  
pp. 394
Author(s):  
Esra Kocaman ◽  
Davide Rabiti ◽  
Juan Sebastian Murillo Moreno ◽  
Asli Can Karaca ◽  
Paul Van der Meeren

The permeation of amino acids and di-peptides with different hydrophobicities across the oil phase in W/O/W double emulsions was investigated at different concentrations, considering the pH of the aqueous phase. Moreover, the particle size, yield of entrapped water and release kinetics of the double emulsions was evaluated as a function of time. Regarding the release of the entrapped amino acids and di-peptides, their hydrophobicity and the pH had a significant effect, whereas the concentration of the dissolved compound did not lead to different release kinetics. The release of the amino acids and di-peptides was faster at neutral pH as compared to acidic pH values due to the increased solute solubility in the oil phase for more hydrophobic molecules at neutral pH. Regarding the effect of the type of oil, much faster amino acid transport was observed through MCT oil as compared to LCT oil, which might be due to its higher solubility and/or higher diffusivity. As di-peptides released faster than amino acids, it follows that the increased solubility overruled the effect from the decreased diffusion coefficient of the dissolved compound in the oil phase.


Author(s):  
Moritz Doering ◽  
Jochen Kieninger ◽  
Gerald Urban ◽  
Andreas Weltin

Abstract Objective. The stability of platinum and other noble metal electrodes is critical for neural implants, electrochemical sensors, and energy sources. Beyond the acidic or alkaline environment found in most electrochemical studies, the investigation of electrode corrosion in neutral pH and chloride containing electrolytes is essential, particularly regarding the long-term stability of neural interfaces, such as brain stimulation electrodes or cochlear implants. In addition, the increased use of microfabricated devices demands the investigation of thin-film electrode stability. Approach. We developed a procedure of electrochemical methods for continuous tracking of electrode degradation in situ over the complete life cycle of platinum thin-film microelectrodes in a unique combination with simultaneous chemical sensing. We used chronoamperometry and cyclic voltammetry to measure electrode surface and analyte redox processes, together with accelerated electrochemical degradation. Main results. We compared degradation between thin-film microelectrodes and bulk electrodes, neutral to acidic pH, different pulsing schemes, and the presence of the redox active species oxygen and hydrogen peroxide. Results were confirmed by mechanical profilometry and microscopy to determine material changes on a nanometer scale. We found that electrode degradation is mainly driven by repeated formation and removal of the platinum surface oxide, also within the electrochemical stability window of water. There was no considerable difference between thin-film micro- and macroscopic bulk electrodes or in the presence of reactive species, whereas acidic pH or extending the potential window led to increased degradation. Significance. Our results provide valuable fundamental information on platinum microelectrode degradation under conditions found in biomedical applications. For the first time, we deployed a unified method to report quantitative data on electrode degradation up to a defined endpoint. Our method is a widely applicable framework for comparative long-term studies of sensor and neural interface stability.


2021 ◽  
Author(s):  
Jim Warwicker

Existence of a SARS-CoV-2 spike protein trimer form with closer packing between monomers when receptor binding domains (RBDs) are all down, locked as opposed to closed, has been associated with linoleic acid (LA) binding at neutral pH, or can occur at acidic pH in the absence of LA binding. The relationship between degree of closure of the LA binding pocket of the RBD, and monomer burial in the trimer, is examined for a range of spike protein structures, including those with D614G mutation, and that of the Delta variant (which also carries D614G). Some spike protein structures with this aspartic acid mutation show monomer packing approaching that of the locked form (at neutral pH, without LA binding) for two segments, a third (around the RBD) remains less closely packed. Analysis of other coronavirus RBD structures suggests that mutation of the RBD in spike protein of the Omicron variant could lead to LA binding pocket changes. It is proposed that these changes could lead to one of two consequences for the Omicron variant spike protein (which also has the D614G mutation), at neutral pH and without LA binding, either easier access to a locked form throughout that leads to cooperative transitions between all RBD down and all RBD up, or maintenance of a spike trimer with locked characteristics C-terminal to the RBD at the same time as the RBD is free to transit between down and up states. The situation may also be impacted by spike protein charge mutations in the Omicron lineage that alter pH-dependence around the RBD, in a similar way to the changes induced elsewhere by D614G.


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