Single and multiplexed immunoassays for the chemiluminescent imaging detection of animal glues in historical paint cross-sections

Abstract

The characterization of the organic components in a complex, multilayered paint structure is fundamental for studying painting techniques and for authentication and restoration purposes. Proteinaceous materials, such as animal glue, are of particular importance since they are widely used as binders, adhesives and for gilding. Even though proteins are usually detected by chromatographic and proteomic techniques, immunological methods represent an alternative powerful approach to protein analysis thanks to the high specificity of antigen-antibody reactions. Our previous studies demonstrated that ovalbumin and casein could be localized in paint cross-sections with high sensitivity and good spatial resolution (i.e. within the single painting layers) by using chemiluminescent (CL) immunochemical microscope imaging. In the present research work, we describe for the first time the immunolocalization of collagen (the main protein of animal glue) in paint cross-sections by CL imaging microscopy. Two different analytical protocols have been developed, allowing either the detection of collagen or the simultaneous detection of collagen and ovalbumin in the same paint sample. The assays were used to detect collagen and ovalbumin in cross-sections from model samples and historical paintings (a wall painting dated to 1773-1774 and a painted wood panel of the Renaissance period) in order to achieve information on paint techniques and past restoration interventions.

Mapping of egg yolk and animal skin glue paint binders in Early Renaissance paintings using near infrared reflectance imaging spectroscopy

“…Tools developed for biomedical chemical imaging have also been applied to analysis of art, including immunouorescence imaging to localize proteins in paint cross-sections [2][3][4] and methods that use two-photon confocal microscopy. On the microscale, the eld has drawn from advances over the years in analytical chemistry and materials science.…”

Miniaturized Biosensors to Preserve and Monitor Cultural Heritage: from Medical to Conservation Diagnosis

“…[22,23] Thef irst sample was collected from aR enaissance wood painting dated to second half of the 15th century (Figure 5b). [22,23] Thef irst sample was collected from aR enaissance wood painting dated to second half of the 15th century (Figure 5b).…”

“…To assess the applicability of the CL-LFIA biosensor,w e analyzed historical samples in which ovalbumin and/or collagen had been previously located within the paint stratigraphies by microscopy immunochemical analyses. [22,23] Thef irst sample was collected from aR enaissance wood painting dated to second half of the 15th century (Figure 5b). Ad iagnostic campaign has been required to support the restoration and in particular,t he removal of an aged varnish layer.…”

“…Thesame results have been also obtained with other immunochemical procedures,based for instance on SERS Raman detection. [22] Animal glue has been identified in the gypsum ground, according to the dictates of ancient recipes.The present study confirmed these outcomes,s ince both ovalbumin (0.69 mgmL À1 )a nd collagen (1.22 mgmL À1 )w ere detected in the extract from this sample.Itisworth noting that the use of our portable device does not allow the localization of the target protein within ap aint stratigraphy.N evertheless, selective sampling and background information on painting technique may help in the evaluation of results.T he second sample was collected from am ural painting dated back to 1774, in the Abbey of S. Maria del Monte (Figure 5d). Preliminary stratigraphical analyses recognized the presence of collagen in the pigment layer.…”

Identification of Proteinaceous Binders in Ancient Tripitaka by the Use of an Enzyme-linked Immunosorbent Assay

“…20 These features make ELISA a promising technique for routine analysis of proteinaceous materials and biopolymers in the conservation of cultural heritage. [21][22][23][24] ELISA has been widely used in clinical and bioanalytical chemistry, in various branches of medicine, pharmaceutical and food industries, and in environmental monitoring. The identification of proteins by ELISA is feasible due to the high specificity of antibody-antigen binding, 25 through which one can detect the presence of protein at very low quantities.…”