Abstract A low cost and rapid electrochemical immunosensor for direct screening of L-phenylalanine (L-Phe) using square wave voltammetry (SWV) is presented. Fern-like gold nanostructures were electro-deposited onto a screen-printed electrode (SPE) using chronoamperometry (CA), to enhance sensitivity and surface area. A novel light-driven surface functionalisation process was used to decorate the gold nanostructured SPE with target-specific antibody fragments and develop the L-Phe-specific immunosensor. The selectivity of the sensor was confirmed against tyrosine, tryptophan and D-phenylalanine, thus indicating the sensor’s potential for use at points of care (POC) without interference from structurally related biomolecules. The sensor demonstrated high sensitivity across the full clinical range (120 µM-1200 µM) and excellent linearity within the concentration range 1 µM to 2000 µM (R²= 0.99, LOD = 0.3 µM, LOQ = 1 µM). Quantification of L-Phe in human blood dry spots (DBS) by the new sensor and SWV were in excellent agreement with mass spectroscopy (MS) measurements by 2 independent pathology labs. The sensor was successfully integrated with an ultra-compact potentiostat in a Lab-on-a-Phone assembly for L-Phe screening in DBS, thus demonstrating its potential for use at POC and at home by phenylketonuria (PKU) patients in both remote and rural areas.
Houston et al. (Fri,) studied this question.