FIG. 4.

RNA detection using a ionic-membrane sensor. (a) I-V characteristic or a 3.5 mm² ionic-membrane sensor, functionalized with a Brucella capture probe before (blue line) and after the addition of Brucella RNA at 2 pg/μl (green line). Addition of a non-target RNA (Dengue virus) does not produce a shift in the I-V characteristics (red dotted line). (b) Detection of Dengue virus serotype 2 (DENV-2) RNA at 50 pg/μl in a sample with mixed serotypes 1 to 4. (c) Voltage shifts for miR550 concentrations 10 pM to 1 nM (corresponding to 10⁷–10⁹ miR550 copies) spiked in conditioned cell culture media. (d) Calibration curve of the voltage shift vs. miR550 concentration, averaged over 7 different sensors, along a 3-decade dynamic range starting at 1 pM (10⁶ copies). The Langmuir constant K ∼ 1/500pM indicates saturation at about 1 nM. Adapted with permission from Biomicrofluidics 60, 92–100 (2014). Copyright 2014 AIP Publishing LLC;¹¹⁸ and from Taller et al., Lab Chip 15, 1656–1666 (2015). Copyright 2015 Royal Society of Chemistry.¹¹⁹