A Phenylalanine Sensor Exploiting a Capacitive Readout Strategy Embedding a Selective Enzymatic Mechanism

This article introduces a cost-effective and fast-response capacitive sensor designed for quantifying phenylalanine (Phe) levels in PKU patients. The sensor comprises planar interdigitated electrodes (IDEs) on a substrate, with NH3-sensitive dielectric material, and exploits an enzymatic reaction to indirectly assess Phe levels. IDEs are created using aerosol jet printing (AJP), with two variants differing in the type of ink used. Experimental results achieved by exposing sensors to standard NH3 and Phe solutions have been reported. The proposed approach provides a capacitive readout strategy for low analyte concentrations, high specificity to NH3 using yttria-stabilized zirconia (YSZ), easy miniaturization, faster response times, and cost-effectiveness through rapid-prototyping technologies. A sensor limit of detection of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.52~\mu $ </tex-math></inline-formula>M has been estimated for Phe detection, along with an accuracy of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6.27~\mu $ </tex-math></inline-formula>M.