Label-free detection of Staphylococcus aureus in skin using real-time potentiometric biosensors based on carbon nanotubes and aptamers
Published in 'Biosensors & Bioelectronics', 2011
In this paper we report the first biosensor that is able to detect Staphylococcus aureus in real-time. A network of... more In this paper we report the first biosensor that is able to detect Staphylococcus aureus in real-time. A network of single-walled carbon nanotubes (SWCNTs) acts as an ion-to-electron potentiometric transducer and anti-S. aureus aptamers are the recognition element. Carbon nanotubes were functionalized with aptamers using two different approaches: (1) non-covalent adsorption of drop-casted pyrenil-modified aptamers onto the external walls of the SWCNTs; and (2) covalent bond formation between amine-modified aptamers and carboxylic groups previously introduced by oxidation at the ends of the SWCNTs. Both of these approaches yielded functional biosensors but there were large differences in the minimum detectable bacteria concentration and sensitivity values. With covalent functionalization, the minimum concentration detected was 8 × 102 colony-forming units (CFU)/mL and the sensitivity was 0.36 mV/Decade. With the non-covalent approach, the sensitivity was higher (1.52 mV/Decade) but the minimum concentration detected was greatly affected (107 CFU/mL). In both cases, potential as a function of Decade of bacteria concentration was linear. Functional biosensors were used to test real samples from freshly excised pig skin, contaminated with the target microorganism, as a surrogate for human skin.
Download (.pdf) Immediate Detection of Living Bacteria at Ultralow Concentrations Using a Carbon Nanotube Based Potentiometric Aptasensor
Published in 'Angewandte Chemie', 2009
So braucht's keinen Arzt: Ein Aptamer, das an eine mit einwandigen Kohlenstoffnanoröhren bedeckte Elektrode gebunden... more So braucht's keinen Arzt: Ein Aptamer, das an eine mit einwandigen Kohlenstoffnanoröhren bedeckte Elektrode gebunden ist, wechselwirkt selektiv mit Bakterien (siehe Bild). Das daraus resultierende elektrochemische Signal ist sehr genau und reproduzierbar und setzt bei äußerst niedrigen Bakterienkonzentrationen ein. Damit handelt es sich um eine einfache, selektive Methode zum Nachweis von Pathogenen.
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Immediate Detection of Living Bacteria at Ultralow Concentrations Using a Carbon Nanotube Based Potentiometric Aptasensor
Published in 'Angewandte Chemie Int. Ed.', 2009 (featured in the Frontispiece Cover as a VIP Communication)
Keeping the doctor away: An aptamer attached to an electrode coated with single-walled carbon nanotubes interacts... more Keeping the doctor away: An aptamer attached to an electrode coated with single-walled carbon nanotubes interacts selectively with bacteria (see picture). The resulting electrochemical response is highly accurate and reproducible and starts at ultralow bacteria concentrations, thus providing a simple, selective method for pathogen detection.
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Real-Time Potentiometric Detection of Bacteria in Complex Samples
Published in 'Analytical Chemistry', 2010
Detecting and identifying pathogen bacteria is essential to ensure quality at all stages of the food chain and to... more Detecting and identifying pathogen bacteria is essential to ensure quality at all stages of the food chain and to diagnose and control microbial infections. Traditional detection methods, including those based on cell culturing, are tedious and time-consuming, and their further application in real samples generally implies more complex pretreatment steps. Even though state-of-the-art techniques for detecting microorganisms enable the quantification of very low concentrations of bacteria, to date it has been difficult to obtain successful results in real samples in a simple, reliable, and rapid manner. In this Article, we demonstrate that the label-free detection and identification of living bacteria in real samples can be carried out in a couple of minutes and in a direct, simple, and selective way at concentration levels as low as 6 colony forming units/mL (CFU) in complex matrices such as milk or 26 CFU/mL in apple juice where the pretreatment step of samples is extremely easy. We chose Escherichia coli (E. coli) CECT 675 cells as a model organism as a nonpathogenic surrogate for pathogenic E. coli O157:H7 to test the effectiveness of a potentiometric aptamer-based biosensor. This biosensor uses single-walled carbon nanotubes (SWCNT) as excellent ion-to-electron transducers and covalently immobilized aptamers as biorecognition elements. The selective aptamer−target interaction significantly changes the electrical potential, thus allowing for both interspecies and interstrain selectivity and enabling the direct detection of the target. This technique is therefore a powerful tool for the immediate identification and detection of microorganisms. We demonstrate the highly selective detection of living bacteria with an immediate linear response of up to 10^4 CFU/mL. The biosensor can be easily built and used, is regenerated without difficulty, and can be used at least five times with no loss in the minimum amount of detected bacteria.