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  1. ; ; ; ( , Journal of Industrial Microbiology and Biotechnology)
    Abstract  

    Microbial biofilm contamination is a widespread problem that requires precise and prompt detection techniques to effectively control its growth. Microfabricated electrochemical impedance spectroscopy (EIS) biosensors offer promise as a tool for early biofilm detection and monitoring of elimination. This study utilized a custom flow cell system with integrated sensors to make real-time impedance measurements of biofilm growth under flow conditions, which were correlated with confocal laser scanning microscopy (CLSM) imaging. Biofilm growth on EIS biosensors in basic aqueous growth media (tryptic soy broth, TSB) and an oil–water emulsion (metalworking fluid, MWF) attenuated in a sigmoidal decay pattern, which lead to an ∼22–25% decrease in impedance after 24 Hrs. Subsequent treatment of established biofilms increased the impedance by ∼14% and ∼41% in TSB and MWF, respectively. In the presence of furanone C-30, a quorum-sensing inhibitor (QSI), impedance remained unchanged from the initial time point for 18 Hrs in TSB and 72 Hrs in MWF. Biofilm changes enumerated from CLSM imaging corroborated impedance measurements, with treatment significantly reducing biofilm. Overall, these results support the application of microfabricated EIS biosensors for evaluating the growth and dispersal of biofilm in situ and demonstrate potential for use in industrial settings.

     One-Sentence Summary

    This study demonstrates the use of microfabricated electrochemical impedance spectroscopy (EIS) biosensors for real-time monitoring and treatment evaluation of biofilm growth, offering valuable insights for biofilm control in industrial settings.

     
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  2. ; ; ; ; ; ( , ECS Sensors Plus)

    During the growth of a polycrystalline ice lattice, microorganisms partition into veins, forming an ice vein network highly concentrated in salts and microbial cells. We used microfabricated electrochemical impedance spectroscopy (EIS) sensors to determine the effect of microorganisms on the electrochemical properties of ice. Solutions analyzed consisted of a 176μS cm−1conductivity solution, fluorescent beads, andEscherichia coliHB101-GFP to model biotic organisms. Impedance spectroscopy data were collected at −10 °C, −20 °C, and −25 °C within either ice veins or ice grains (i.e., no veins) spanning the sensors. After freezing, the fluorescent beads andE. coliwere partitioned into the ice veins. The corresponding impedance data were discernibly different in the presence of ice veins and microbial impurities. The presence of microbial cells in ice veins was evident by decreased electrical characteristics (electrode polarization between electrode and ice matrix) relative to solid ice grains. Further, this electrochemical behavior was reversed in all bead-doped solutions, indicating that microbial processes influence sensor response. Linear mixed-effects models empirically corroborated the differences in polarization associated with the presence and absence of microbial cells in ice. We show that EIS has the potential to detect microbes in ice and differentiate between veins and solid grains.

     
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  3. ; ; ; ( , Biosensors and Bioelectronics: X)
    Free, publicly-accessible full text available September 1, 2024
  4. ; ; ; ( , Effects of Escherichia coli K12 Biofilm on Sensor Thin Film Materials)
    Micro-fabricated sensors enable the study of chemical and physical dynamics in aqueous environments such as rivers, lakes or oceans at low cost. Sensors must work reliably in these environments, which include both biological and chemical challenges. However, sensor thin films have not been studied in detail for aqueous applications, and more specifically how biotic interactions may change sensor material properties. In this study, the long-term effects of biofilm formation on the properties of aluminum (electric conductor) and a-Si x N y :H (insulating material) were investigated. Material degradation caused by Escherichia coli K12 biofilm growth was determined by electrical sheet resistance measurements (collinear four-point-probe) and Fourier-transform infrared spectroscopy (FTIR) absorption spectra over a time period of 7 weeks. Changes of the surface topography were tested using scanning electron microscopy (SEM) and white light interferometry. Aluminum was found to be heavily degraded at three weeks, whereas a-Si x N y :H was inert during the entire investigation period. As differences between thin film sensor materials are evident, more detailed investigations including a broader range of materials should be explored. 
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  5. ; ; ; ; ( , Journal of Industrial Microbiology & Biotechnology)
    Microbial contamination in metalworking systems is a critical problem. This study determined the microbial communities in metalworking fluids (MWFs) from two machining shops and investigated the effect of quorum sensing inhibition (QSI) on biofilm growth. In both operations, biofilm-associated and planktonic microbial communities were dominated by Pseudomonadales (60.2–99.7%). Rapid recolonization was observed even after dumping spent MWFs and meticulous cleaning. Using Pseudomonas aeruginosa PAO1 as a model biofilm organism, patulin (40 µM) and furanone C-30 (75 µM) were identified as effective QSI agents. Both agents had a substantially higher efficacy compared to α-amylase (extracellular polymeric substance degrading enzyme) and reduced biofilm formation by 63% and 76%, respectively, in MWF when compared to untreated controls. Reduced production of putatively identified homoserine lactones and quinoline in MWF treated with QS inhibitors support the effect of QSI on biofilm formation. The results highlight the effectiveness of QSI as a potential strategy to eradicate biofilms in MWFs. 
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