CMOS-compatible biosensor for L-carnitine detection

A CMOS-compatible ISFET with a Ta2O5 sensitive surface was developed. The structure was optimized for achieving high sensitivity using a subthreshold operation mode and by reducing the influence of the capacitances on the value of subthreshold swing. The developed ISFET was used as a basis for a biosensor for L-carnitine detection. To this end, carnitine acetyltransferase was immobilized on the ISFET sensitive surface. The immobilized enzyme was active (0.082 U/g model plate). The complete microsystem, consisting of a packaged chip, an immobilized enzyme and a microfluidic channel, detected L-carnitine at a range of 0.2–100 μM with a LOD of 0.2 μM. The biosensor response was linear in the range of 0.2–50 μM of L-carnitine with sensitivity 18.0 ± 1.7 mV/μM. An experiment with artificial urine containing 1.3 μM L-carnitine showed that the proposed biosensor could be used on a real sample. Therefore, a new sensor specially optimized for biosensing CMOS-compatible ISFET structures and direct determination of L-carnitine with immobilized carnitine acetyltransferase was developed. •A novel CMOS-compatible ISFET was developed and specially optimized for use in subthreshold operation mode.•Carnitine acetyltransferase reaction was directly detected using an electrochemical method for the first time.•The fabricated biosensor allowed detection of L-carnitine in artificial urine.