Advanced label-free electrochemical immunosensor for a minimally invasive detection of proteins in paintings

In recent decades, scientific methodologies applied in theCultural Heritage field have been growing, due to their pivotal role in guiding informed decisions concerning conservation strategies and daily maintenance. To achieve this goal, minimally/non-invasive quantitative and qualitative analyses are needed. However, the non-invasive and selective identification of proteinaceous binders and coatings in artworks represent an open issue in Cultural Heritage science. Herein, a novel miniaturized system is introduced, which consists of a label-free electrochemical immunosensor integrated with biocompatible Gellan gel. This method is intended to selectively and minimally invasively identify ovalbumin (OVA) on-site in paintings. The label-free immunosensor is made up on screen-printed electrodes (SPEs) by functionalizing the working electrode (WE) with a primary antibody (anti-ovalbumin) for the specific recognition of OVA. The presence of OVA produces antigen-antibody reaction, which results in the development of a bulky immunocomplex on the WE. This complex is quantified using square wave voltammetry (SWV) and a reversible redox probe: the current measured is inversely proportional to the OVA concentrations. The developed immunosensors showed good analytical performances when applied directly to painted mock-ups, exhibiting a limit of detection (LOD) of 1.6 ng mL^-1, a limit of quantification (LOQ) equal to 16 ng mL^-1, a working range between 0.01 and 0.4 μg mL^-1 and selectivity for OVA over other protein components commonly present in painted artworks, including bovine serum albumin (BSA), collagen, and casein. The outcomes highlighted the dependability of the immunosensor in detecting OVA and the efficacy of Gellan gel as a streamlined method for extracting the target protein while preventing residue accumulation on the painting surface. This advancement suggests the potential of Gellan gel-coupled immunosensor systems as viable diagnostic alternatives for artwork management and preservation.