Monitoring biofilm growth and dispersal in real-time with impedance biosensors

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.

Mitigation and use of biofilms in space for the benefit of human space exploration

Biofilms are self-organized communities of microorganisms that are encased in an extracellular polymeric matrix and often found attached to surfaces. Biofilms are widely present on Earth, often found in diverse and sometimes extreme environments. These microbial communities have been described as recalcitrant or protective when facing adversity and environmental exposures. On the International Space Station, biofilms were found in human-inhabited environments on a multitude of hardware surfaces. Moreover, studies have identified phenotypic and genetic changes in the microorganisms under microgravity conditions including changes in microbe surface colonization and pathogenicity traits. Lack of consistent research in microgravity-grown biofilms can lead to deficient understanding of altered microbial behavior in space. This could subsequently create problems in engineered systems or negatively impact human health on crewed spaceflights. It is especially relevant to long-term and remote space missions that will lack resupply and service. Conversely, biofilms are also known to benefit plant growth and are essential for human health (i.e., gut microbiome). Eventually, biofilms may be used to supply metabolic pathways that produce organic and inorganic components useful to sustaining life on celestial bodies beyond Earth. This article will explore what is currently known about biofilms in space and will identify gaps in the aerospace industry's knowledge that should be filled in order to mitigate or to leverage biofilms to the advantage of spaceflight.

Ulkusheilung nach Varizen-OP – Ergebnisse nach fünf Jahren

Ziel: Die Langzeitergebnisse der Varizenoperation zur Behandlung eines Ulcus cruris venosum sollten überprüft werden. Methode: Bei 63 Patienten mit vor fünf Jahren durch Operation einer Varikose der V. saphena magna behandeltem venösen Ulkus wurde der Langzeitheilungserfolg überprüft. Ergebnis: Von 63 unteren Extremitäten war in 49 Fällen innerhalb von sechs Monaten nach der Operation eine dauerhafte Abheilung des Ulkus eingetreten. Bei vier weiteren Patienten erfolgte die Heilung innerhalb von eineinhalb Jahren nach der Varizenoperation. Eine Langzeitheilung des venösen Ulkus wurde bei 84% der Patienten erreicht. Hierbei handelt es sich ausschließlich um Patienten mit einem Ulkus infolge einer Stammvarikosis. Bei 6% der Patienten (4 Beine) kam es zu rezidivierenden Ulzera, die z. Zt. unter Behandlung abgeheilt sind. Bei 6 Patienten (10%) blieb das Ulkus trotz zusätzlicher konservativer Therapie dauerhaft nach fünf Jahren weiter bestehen. Diese Patienten haben zusätzlich zur Varikose schwerwiegende Begleiterkrankungen (malignes Geschehen, PTS, AVK, Diabetes, ausgeprägte Lymphödeme etc.). Schlußfolgerung: Bei Patienten mit einer Stammvarikose und venösem Ulkus führt die Varizenoperation zu einem sehr guten dauerhaften Heilungserfolg. Eine zusätzliche schwerwiegende Begleiterkrankung beeinträchtigt die Prognose der Ulkusheilung erheblich.

MEMS measurements of single cell stiffness decay due to cyclic mechanical loading

The goal of this study was to measure the mechanical stiffness of individual cells and to observe changes due to the application of repeated cell mechanical loads. 28 single baker's yeast cells (Saccharomyces cerevisiae) were fatigue tested and had their stiffness measured during repetitive loading cycles performed by a MEMS squeezer in aqueous media. Electrothermal micro-actuators compressed individual cells against a reference back spring; cell and spring motions were measured using a FFT image analysis technique with ~10 nm resolution. Cell stiffness was calculated based on measurements of cell elongation vs. applied force which resulted in stiffness values in the 2-10 N/m range. The effect of increased force was studied for cells mechanically cycled 37 times. Cell stiffness decreased as the force and the cycle number increased. After 37 loading cycles (~4 min), forces of 0.24, 0.29, 0.31, and 0.33 μN caused stiffness drops of 5%, 13%, 31% and 41% respectively. Cells force was then set to 0.29 μN and cells were tested over longer runs of 118 and 268 cycles. After 118 cycles (~12 min) cells experienced an average stiffness drop of 68%. After 268 cycles (~25 min) cells had a stiffness drop of 77%, and appeared to reach a stiffness plateau of 20-25% of the initial stiffness after approximately 200 cycles.

Submicron displacement measurements of MEMS using optical microphotographs in aqueous media: Enhancement using color image processing

The measurement of precise submicron displacements is essential in several MEMS applications. For instance, the measurement of the mechanical parameters of biological cells requires repeatable measurement of displacements in the nanometer regime. This paper presents a method to make displacement measurements in an aqueous MEMS environment with a ± 10 nm accuracy by using the blue channel of RGB pictures in combination with a FFT phase shift analysis.