Rapid Chromatic Detection of Bacteria by Use of a New Biomimetic Polymer Sensor

Abstract

We present a new platform for visual and spectroscopic detection of bacteria. The detection scheme is based on the interaction of membrane-active compounds secreted by bacteria with agar-embedded nanoparticles comprising phospholipids and the chromatic polymer polydiacetylene (PDA). We demonstrate that PDA undergoes dramatic visible blue-to-red transformations together with an intense fluorescence emission that are induced by molecules released by multiplying bacteria. The chromatic transitions are easily identified by the naked eye and can also be recorded by conventional high-throughput screening instruments. Furthermore, the color and fluorescence changes generally occur in shorter times than the visual appearance of bacterial colonies on the agar. The chromatic technology is generic and simple, does not require identification a priori of specific bacterial recognition elements, and can be applied for detection of both gram-negative and grampositive bacteria. We demonstrate applications of the new platform for reporting on bacterial contaminations in foods and for screening for bacterial antibiotic resistance.The emerging global risks of bioterrorism, the recurring incidents of bacterial food contaminations, and the need to monitor sterile environments in health care applications and other industries have pushed the development of methods for detection of pathogens to the forefront of technological and scientific research. Numerous technologies for reporting on bacterial presence have been developed (3,5,9,25,26). There are, however, limitations to existing bacterial detection techniques as rapid and generic approaches. Specifically, many bioanalytical techniques employed for pathogen detection (such as culture-based methods) provide results after relatively long time spans (several hours to days) (10). Other currently employed technologies often involve complex detection mechanisms that require specialized instrumentation, application by trained personnel, and the need for active operation (addition of reagents, initiation of chemical reactions, etc.), which overall do not lend their use in settings other than laboratory environments (3, 6). Furthermore, a prerequisite for many detection methods is the detailed understanding of the biochemical and structural properties of the bacterial species sought, limiting applications in the case of unknown pathogens or variants (9, 31).Various membrane-active compounds are released by bacteria to their environments (2, 30), a process that often has an essential functional role as a means for overcoming host defense mechanisms, allowing colony proliferation, and facilitating bacterial communication (17). Membrane-active peptides and toxins, in particular, are produced by bacteria, for example, pneumolysins secreted by streptococci (27) and ␣-toxin, which is the major cytolysin emitted by Staphylococcus aureus (1). Secretion of pore-forming exotoxins by bacteria is abundant, and endotoxins, such as lipopolysaccharides, which are often released by gram-negative bacteria, ...

The application of polymerized lipid vesicles as colorimetric biosensors for real-time detection of pathogens in drinking water

“…From the results described above and in studies published by other authors (Ma et al 2002;Silbert et al 2006), we learned that the transition from blue-red colour observed in the agar matrix, is related directly with the diffusion of substances secreted by the bacteria during growth. Since the aqueous medium allows a more direct contact between the environmental elements and bacteria, tests were conducted to evaluate the TRCDA/DMPC vesicles challenged with bacteria in aqueous phase.…”

“…In the case of vesicles TRCDA/DMPC, we observed the same phenomenon, but the colour change occurred 30 min later, suggesting that the tryptophan receptor favours the response time in those chromatic vesicles. This phenomena associated to colour change occurring during bacterial growth has also being described by other authors (Silbert et al 2006;Pires et al 2011). A bacterial concentration of 10 10 CFU/mL was detected 5 hrs after inoculation a+nd a concentration of 10 8 CFU/mL was detected 7 hrs after inoculation.…”

“…The TRCDA is a molecule that can be incorporated into artificial lipid vesicles adding the possibility of exhibiting a visible and rapid colorimetric transition based on the interaction of the vesicle with a variety of biological compounds (Ma et al 2000;Silbert et al 2006).…”

Conducting Polymers and Their Applications to Biosensors: Emphasizing on Foodborne Pathogen Detection

“…Silbert et al [50] presented a new platform for visual and spectroscopic detection of bacteria based on colorimetric and fluorescence transformations induced within lipid-polymer assemblies by bacterially released substances. The detection scheme in their study was based on the interaction of membrane-active compounds secreted by bacteria with agar-embedded nanoparticles comprising phospholipids and the chromatic polymer polydiacetylene (PDA).…”

Polydiacetylene Vesicles for Detecting Surfactants: Understanding the Driven Forces of Polydiacetylene-Surfactant Interaction

“…As is well known, polydiacetylene vesicle building by self-organized diacetylene monomers and then polymerized by UV light could be used as nanosensors due to its molecules undergo spectrophotometric transitions in J ournal of Food Chemistry & Nanotechnology response to different stimuli, such as temperature change [4][5][6], pH [5,7,8], mechanical stress [9,10], solvents [5,11,12], and interaction with other molecules, such as surfactants [13][14][15][16][17][18][19].…”