title: Label-free detection of Staphylococcus aureus in skin using real-time potentiometric biosensors based on carbon nanotubes and aptamers.
abstract: 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 8×10(2)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 (10(7) 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.
authors.affiliation: Department of Analytical and Organic Chemistry, Universitat Rovira i Virgili, Campus Sescelades, C/Marcel·lí Domingo s/n, 43007 Tarragona, Spain. gustavozelada@gmail.com
authors.forename: Gustavo A
authors.initials: GA
authors.lastname: Zelada-Guillén
authors.forename: José Luis
authors.initials: JL
authors.lastname: Sebastián-Avila
authors.forename: Pascal
authors.initials: P
authors.lastname: Blondeau
authors.forename: Jordi
authors.initials: J
authors.lastname: Riu
authors.forename: F Xavier
authors.initials: FX
authors.lastname: Rius
mesh_terms: D000818:Animals; D052158:Aptamers, Peptide / Q000737:chemistry; D015374:Biosensing Techniques / Q000295:instrumentation*; D015169:Colony Count, Microbial / Q000295:instrumentation*; D003199:Computer Systems; D003217:Conductometry / Q000295:instrumentation*; D004566:Electrodes; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D036103:Nanotechnology / Q000295:instrumentation; D037742:Nanotubes, Carbon / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012867:Skin / Q000382:microbiology*; D013194:Staining and Labeling; D013207:Staphylococcal Skin Infections / Q000175:diagnosis / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000302:isolation & purification*; D013552:Swine
chemical_list: D052158:Aptamers, Peptide; D037742:Nanotubes, Carbon