Copper/Nafion/PANI Nanocomposite as an electrochemical transducer for creatinine and urea enzymatic biosensing

• Chronic Kidney diseases (CKD) affect, to different degrees, ca. 25 million Americans and 19 million Europeans. Monitoring of creatinine and urea levels is of great importance for a correct evaluation of the status of patients and for their treatment. In this paper, we present the development of creatinine and urea enzymatic biosensors, based on a novel ammonium ion-specific Copper/Nafion/Polyanyline (PANI) nanocomposite electrode (Fig. 1A), and suitable for PoC and decentralised diagnostic applications. . Studies on the nanocomposite electrode revealed its high sensitivity and specificity towards ammonium, in respect to amino acids, creatinine and urea, with response range between 5 and 75 μM (Fig. 1B) and with a detection limit of 1 μM. To demonstrate its suitability as transducer in biosensors, creatinine and urea biosensors were fabricated by immobilising creatinine deiminase or urease, respectively, on the nanocomposite surface. Optimisation of the enzyme immobilisation demonstrated that the incorporation of lactitol markedly improved the stability of the biosensors. The response range of the creatinine biosensor was 2 to 100 μM, which fits well with the normal levels of creatinine in healthy people (30-150 µM).The urea biosensor had a response range of 5 to 100 µM. A limit of quantification of 1 µM was achieved for both the biosensors.Evaluation of the performance of the biosensors in real sample matrices and cross reactivity studies are currently on-going. We envisage that the proposed design will be particularly compatible with fully-printed systems thus offering a viable route to the mass production of inexpensive sensors for mobile health.  

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