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The development of a label-free impedimetric aptasensor is reported for rapid and sensitive detection of Escherichia coli O157:H7 employing boron-carbon nanorods decorated by nickel nanoparticles (BC-Ni) nanostructured platform. These highly electroactive BC-Ni nanorods were synthesized to increase the sensitivity of the sensor surface and subsequently functionalized with a specific anti-E. coli O157:H7 aptamer (Kd = 69 nM) as bio-recognition moiety. This fully characterized high-affinity DNA aptamer against the bacteria was selected using a facile microtiter plate-based cell-SELEX methodology. The fabricated electrochemical aptasensor is demonstrated to detect E. coli O157:H7 selectively with a detection limit of 10 cfu and a dynamic detection range of 100 to 105 cfu in water, juice, and fecal samples. [ABSTRACT FROM AUTHOR]

A nanohybrid mediated SERS substrate was prepared by in-situ synthesis and assembly of gold nanoparticles (AuNPs) on exfoliated nanosheets of tungsten disulfide (WS2) to form plasmonic hotspots. The nanohybrid surface was functionalized with specific aptamers which imparted high selectivity for the cardiac marker myoglobin (Mb). The fabricated aptasensor was read by SERS using a 532 nm laser and demonstrated significant signal enhancement, and this allowed Mb to be determined in the 10 f. mL−1 to 0.1 μg mL−1 concentration range. The study presents an approach to synergistically exploit the unique chemical and electromagnetic properties of both WS2 and AuNPs for many-fold enhancement of SERS signals.Schematic presentation of a nanohybrid-mediated SERS substrate prepared by in-situ assembly of gold nanoparticles (AuNPs) reduced on exfoliated nanosheets of tungsten disulfide (WS2) to form plasmonic hot spots. Specific aptamers immobilized on the SERS surface impart high sensitivity and selectivity for the cardiac marker myoglobin (Mb). [ABSTRACT FROM AUTHOR]