We present the design and implementation of a prototype complementary metal-oxide semiconductor (CMOS) conductometric integrated circuit (IC) for colony growth monitoring and specific sensing of Escherichia coli (E. coli) bacteria. The detection of E. coli is done by employing T4 bacteriophages as receptor organisms. The conductometric system operates by measuring the resistance of the test sample between the electrodes of a two-electrode electrochemical system (reference electrode and working electrode). The CMOS IC is fabricated in a TSMC 0.35-μm process and uses a current-to-frequency (I to F) conversion circuit to convert the test sample resistance into a digital output modulated in frequency. Pulsewidth control (one-shot circuit) is implemented on-chip to control the pulsewidth of the output digital signal. The novelty in the current work lies in the ability of the CMOS sensor system to monitor very low initial concentrations of bacteria (4×10(2) to 4×10(4) colony forming unit (CFU)/mL). The CMOS system is also used to record the interaction between E. coli and its specific receptor T4 bacteriophage. The prototype CMOS IC consumes an average power of 1.85 mW with a 3.3-V dc power supply.
We put forward an impedometric protein-based biosensor platform suitable for point-of-care diagnostics. A hand-held scale impedance reader system is described for the detection of corresponding physiochemical changes as the immobilized proteins bind to the analyte molecules in the proximity of the microfabricated electrodes. Specifically, we study the viability of this approach for glucose biosensing purposes using genetically engineered glucokinase as receptor proteins. The proposed reagent-less biosensor offers a high sensitivity of 0.5 mM glucose concentration level in the physiologically relevant range of 0.5 mM to 7.5 mM with less than 10 s response time.
In the original version of this article unfortunately two of the co-authors names were spelled incorrectly. They should be listed as "Rose Lumbroso" and "Lenore K. Beitel".The online version of the original article can be found at http://dx.doi.
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