Detecting age-related changes in faecal vasoactive intestinal polypeptide using a 3D-printed electrochemical immunosensor

Vasoactive intestinal polypeptide (VIP) is a 28-amino acid neuropeptide with a multitude of diverse physiological functions, including vasodilation, immune modulation, and most notable gastrointestinal regulation. At present, VIP is determined using biochemical assays, which are time-consuming and require complex multi-step sample preparation. Therefore, we focused on the development of the first electrochemical immunosensor for the detection of VIP in faecal pellets. Our VIP immunosensor was made by covalent immobilization of an anti-VIP antibody onto a thiophene-2-carboxylic acid conductive polymer layer, after deposition of gold nanostars onto a carbon black/polylactic acid 3D printed electrode. Scanning electron microscopy and electrochemical measurements confirmed layer-by-layer modification of the electrode to craft the VIP immunosensor. The immunosensor exhibited a linear range between 10 and 100 pM, with a limit of detection of 4.3 pM. The immunosensor was selective against electroactive compounds known to be present within the intestinal tract. We observed a reduction in VIP levels in faecal pellets from 24-month-old mice when compared to 12-month-old mice. This novel VIP electrochemical immunosensor can be an effective tool for diagnosis or prognosis of various diseases given the diverse physiological function of VIP. • Study crafts an electrochemical immunosensor for the detection of vasoactive intestinal polypeptide (VIP). •The VIP electrochemical immunosensor exhibits linear range and detection limits similar to ELISA assays. •The developed 3D printed VIP electrochemical immunosensor was able to detect VIP in faeces. •Age-related changes in VIP levels were observed when assessing faeces from 12- and 24-month-old animals.