Measurements of Bio-EGOFET Sample Clauses

Measurements of Bio-EGOFET responses to model avidin solutions Sensors following the strategies described above were checked by analysing their response to (strep)avidin solutions and evaluating their analytical figures of merit. The measurements were made in (strept)avidin solutions of concentration ranging from 1 µg/ml (0.016 µM) to 100 µg/ml (1.6 µM). A decrease of the drain current was observed after the addition and incubation of streptavidin solutions on sensors fabricated with biotin directly bound to P3HT, while an increase of the drain current occurred on sensors with biotin embedded in a phospholipid layer. The difference in the biosensors response can be explained by assuming that a different mechanism is involved in the transduction mechanism of the bio-recognition process. However, in both cases, the current change (decrease or increase) follows the variation of the streptavidin concentrations. Importantly, the streptavidin detection limit was much lower than the micro-molar range targeted by the project. Control measurements with HSA (human serum albumin) or BSA (bovine serum albumin), which are proteins not recognized by biotin, also demonstrated a good specificity of the sensors. The main drawback of these sensors is a low reproducibility. This point is still under investigation. Reproducibility could be improved by employing a microfluidic system to perform the electrical measurements. The compatibility with a printing process is another important issue. While the strategy with biotin directly bound to P3HT can be easily implemented with a printing process, sensors with biotin embedded in a phospholipid layer are difficult to make by printing techniques because of the functionalization step with carboxyl groups and subsequent activation with NHS/EDC chemistry to allow a stable deposition of biotinylated phospholipids layers.