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Povzetek: Benzisothiazolinone (BIT) is a commonly used biocide in water-based products, which can enter the environment from household and personal care products, as well as from leaching off building facades and roofs due to rainfall, eventually reaching rivers through stormwater runoff and raising ecological concerns due to its high aquatic toxicity. Detecting benzisothiazolinone, particularly in the environment is crucial due to health and regulatory requirements. This study explores electrochemical techniques and conductive nanomaterials for detecting BIT in environmental samples. Carbon- and gold-based screen-printed electrodes (SPEs) with distinct morphologies were investigated: carbon electrodes as nanoparticles (SPE-C) and single-wall carbon nanotubes (SPE-SWCNTs), and gold electrodes as nanoparticles (SPE-Au-BT) and thin films (SPE-Au-AT). Cyclic voltammetry and square-wave voltammetry (SWV) were optimized, with SWV demonstrating superior sensitivity—showing a two-order improvement with carbon-based electrodes and a 30-fold enhancement with gold-based electrodes. The lowest detection limits were 40 nM for carbon and 80 nM for gold nanoparticle-based electrodes. SPE-C achieved good recovery in river water, confirming its effectiveness for BIT monitoring with minimal interference from common ions or saccharin. These sensors can be easily used for everyday detection and monitoring of BIT in river water, ensuring a screening programme that supports the development of adequate regulatory guidelines.
Ključne besede: screen-printed electrodes, square-wave voltammetry, electrochemical detection, isothiazolinones
Objavljeno v DiRROS: 11.03.2026; Ogledov: 294; Prenosov: 239
Celotno besedilo (8,22 MB)
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Povzetek: Electrochemical signals are traditionally interpreted in the time domain, where overlapping faradaic and non-faradaic currents, noise, and drift obscure frequency-dependent behaviour. This study introduces a frequency-domain framework that complements time-domain analysis by decomposing voltammetric signals into their harmonic components through Fourier methods. AC voltammetry provides experimental evidence of how increasing excitation frequency progressively suppresses faradaic clarity, while a modified Randles equivalent circuit model explains this response through the interplay of charge-transfer, diffusion, and double-layer charging processes. Fourier series analysis of canonical voltammetric techniques, including linear sweep, cyclic, differential pulse, and square wave voltammetry, shows that waveform geometry uniquely defines harmonic structure. Fast Fourier transform analysis of practical data reveals artefacts introduced by finite sampling, binning, and spectral leakage. These effects highlight the need for conceptual awareness when interpreting experimental spectra. Quantitative spectral descriptors such as the centroid, bandwidth, flatness, and low-frequency power fraction link waveform design directly to faradaic visibility and measurement clarity. Frequency-domain analysis therefore establishes that electrochemical measurement is inherently frequency-structured. By combining experimental data, equivalent circuit modelling and spectral metrics within a single framework, this approach provides a general route to optimise waveform parameters, reduce capacitive interference, and improve interpretability across electrochemical techniques. Viewed more broadly, this perspective reframes the process of the measurement itself, showing that time-domain signals are projections of an underlying spectral reality.
Ključne besede: frequency domain, spectral decomposition, electrochemical sensors, benzenediols
Objavljeno v DiRROS: 22.12.2025; Ogledov: 936; Prenosov: 298
Celotno besedilo (6,14 MB)
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Povzetek: Extracellular vesicles (EVs) are nanosized lipid bilayer particles released by various cellular organisms that carry an array of bioactive molecules. EVs have diagnostic potential, as they play a role in intercellular interspecies communication, and could be applied in drug delivery. In contrast to mammalian cell-derived EVs, the study of EVs from bacteria, particularly Gram-positive bacteria, received less research attention. This study aimed to investigate the production of EVs by lactic acid bacterium Lactococcus cremoris NZ9000 and to examine the impact of recombinant protein expression on their formation and protein content. Four different recombinant proteins were expressed in L. cremoris NZ9000, in different forms of expression and combinations, and the produced EVs were isolated using the standard ultracentrifugation method. The presence of vesicular structures (50–200 nm) in the samples was confirmed by transmission electron microscopy and by flow cytometry using membrane-specific stain. Mass spectrometry analyses confirmed the presence of recombinant proteins in the EVs fraction, with amounts ranging from 13.17 to 100%, highlighting their significant incorporation into the vesicles, together with intrinsic L. cremoris NZ9000 proteins that were either more abundant in the cytoplasm (ribosomal proteins, metabolic enzymes) or present in the membrane. The presence of the most abundant lactococcal proteins in EVs fraction suggests that protein cargo-loading of EVs in L. cremoris NZ9000 is not regulated. However, our data suggests that L. cremoris NZ9000 genetically engineered to express recombinant proteins can produce EVs containing these proteins in scalable manner. As L. cremoris NZ9000 is considered safe bacterium, EVs from L. cremoris NZ9000 could have several advantages over EVs from other bacteria, implying possible biotechnological applications, e.g. in therapeutic protein delivery.
Ključne besede: Lactococcus cremoris, extracellular vesicles, recombinant proteins, delivery vehicle
Objavljeno v DiRROS: 16.01.2025; Ogledov: 1588; Prenosov: 659
Celotno besedilo (4,38 MB)
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