Fig. 4. Phage-based magnetoresistive biochip for cell viability assessment. Phage-based magnetoresistive biochip measurements performed on an electronic reader. (A) Normalized differential voltage signal for Salmonella samples subjected to different treatments (dashed line and black dots). The acquired sensor signals are differential values (ΔVbinding), calculated from the difference between the sensor baseline (Vsensor) and the signal from the specifically bound MNPs over the sensor (Vparticles) as previously described (Martins et al., 2009). The shaded area in blue on the bottom refers to the average signal from the control sensors using an unspecific phage. Each point and shaded area represents the average value of at least 10 independent sensors with respective associated standard deviation (error bars). Bars represent the concentration of cells and respective cell state (viable, compromised (comp.) and dead) for each cell sample measured on the MR-chip. Cell concentrations were obtained by flow cytometry using the LIVE/DEAD counting Baclight kit, in which each data point results from the analysis of triplicate samples from one representative experiment out of three. (B) Schematic representation of the “sandwich” type biomolecular recognition strategy adopted in the MR-biochip measurements. (C) Picture of the MR-biochip PCB used for the detection of Salmonella cells, shown on a standard cell culture plate.
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