Real-time Monitoring of Bacterial Biofilms Metabolic Activity by a Redox-Reactive Nanosensors Array

Abstract

Background: Bacterial biofilms are communities of surface-associated microorganisms living in cellular clusters or micro-colonies, encapsulated in a complex matrix composed of an extracellular polymeric substance, separated by open water channels that act as a circulatory system that enable better diffusion of nutrients and easier removal of metabolic waste products. The monitoring of biofilms can provide important information on fundamental biofilm-related processes. That information can shed light on the bacterial processes and enable scientists to find ways of preventing future bacterial infections. Various approaches in use for biofilm analysis are based on microscopic, spectrochemical, electrochemical and piezoelectrical methods. All these methods provide significant progress in understanding the bio-process related to biofilm formation and eradication, nevertheless, the development of novel approaches for the real-time monitoring of biochemical, in particular metabolic activity, of bacterial species during the formation, life and eradication of biofilms is of great potential importance.Results: Here, detection and monitoring of the metabolic activity of bacterial biofilms in high-ionic-strength solutions were enabled as a result of novel surface modification by an active redox system, composed of 9,10-dihydroxyanthracene/9,10-anthraquinone, on the oxide layer of the SiNW, yielding a chemically-gated FET array. With the use of enzymatic reactions of oxidases, metabolites can be converted to and monitored by the nanosensors. Here, the successful detection of glucose consumption in high-ionic-strength solutions, such as bacterial media, without pre-processing of small volume samples under different conditions and treatments, has been demonstrated. The biofilms were treated with antibiotics differing in their mechanisms of action and were compared to untreated biofilms. Further examination of biofilms under antibiotic treatment with SiNW-FET devices could shed light on the bioprocess that occurs within the biofilm. Moreover, finding a proper treatment that eliminates the biofilm could be examined by the novel nanosensor array as a monitoring tool.Conclusions: To summarize, the combination of redox-reactive SiNW-FET devices with microfluidic techniques enables the performance of label-free, rapid, automated, multiplex and real-time noninvasive metabolites detection for the investigation of bacterial biofilms. This novel platform can be used as an extremely sensitive tool for detection and establishing medical solutions for bacterial-biofilm eradication and for finding a proper treatment to eliminate biofilm contaminations. Moreover, the sensing system can be used as a research tool for further understanding of the metabolic processes that occur within the bacterial biofilm population.

Instantaneous Clearing of Biofilm (iCBiofilm): an optical approach to revisit bacterial and fungal biofilm imaging

“…2f and Supplementary Movies 3-5). A slight decay of fluorescence was observed, likely due to a reduction in membrane potential as metabolic activity within the biofilm decreased 31 . In addition, biofilm formation by S. aureus MR4 was visualized by iCBiofilm-based live cell imaging (Supplementary Movie 7), and the process was distinct from that of SE21 or MR23 (Supplementary Movies 5 and 6).…”

The efficacy of antiseptic agents against staphylococcal biofilm can be quantitatively assessed with the use of processed microscopic images

“…Biofilm (in general) is considered to be an adhered, three-dimensional, spatial structure consisting of microbial cells embedded within an extracellular matrix, displaying high tolerance to environmental factors (with regard to medical biofilms, these factors are usually antimicrobials and the immune system) [11]. The metabolic differentiation within biofilm parts is also frequently mentioned [12–14]. Such a definition is derived from the early observations of dental plaque biofilms [15] and is repeated frequently in the introductory parts of scientific manuscripts.…”