Development of an analytical protocol for a fast, sensitive and specific protein recognition in paintings by enzyme-linked immunosorbent assay (ELISA)

A portable microfluidic device integrated with electrochemical sensing platform for detection of multiple binders in ancient wall paintings

The aging of the proteinaceous binders will cause the cultural relics to suffer from diseases such as flaking, cracks, and even peeling. Identifying the type of binders in a timely manner is conducive to restore diseased cultural relics. High-throughput and portable detection system are of great significance for researching cultural relic materials on the archaeological site. Therefore, in this work, a portable electrochemical microfluidic device for the simultaneous detection of casein, ovalbumin, and peach gum binders was developed. The proposed electrochemical immunosensor technology integrated with microfluidic device achieve the goals of miniaturization, portability and reagent-saving. For casein, ovalbumin and peach gum, excellent performance was obtained in terms of their limits of detection (LOD) at 0.237, 0.507, and 0.403 ng mL^-1 (S/N = 3), respectively. In addition, the microfluidic sensing platform exhibited acceptable anti-interference ability, stability, and storage capacity. In order to evaluate the practical application value, the proposed microfluidic sensing device was applied for detecting eight archaeological samples from different historic sites. This work demonstrates great potential for high-throughput, portable detection of cultural relic proteinaceous binder materials.

Development of an Enzyme-Linked Immunosorbent Assay and Gold-Labelled Immunochromatographic Strip Assay for the Detection of Ancient Wool

The identification of ancient wool is of great importance in archaeology. Despite lots of meaningful information can be achieved by conventional detection methods, that is, light and electron microscopy, spectroscopy, and chromatography, the efficacy is likely to be limited in the detection of ancient samples with contamination or severe degradation. In this work, an immunoassay was proposed and performed for the identification of ancient wool. First, a specific antibody, which has the benefits of low cost, easy operation, and extensive applicability, was developed directly through immunizing rabbits with complete antigen (keratin). Then, an enzyme-linked immunosorbent assay (ELISA) and a colloidal gold-labelled immunochromatographic strip (ICS) were developed to qualitatively identify the corresponding protein in ancient wool samples unearthed from Kazakhstan and China. The anti-keratin antibody exhibited high sensitivity and specificity for the identification of modern and ancient wool. The limit of detection (LOD) of the ELISA method was 10 ng/mL, and no cross-reactions with other interfering antigens have been noted. It is concluded that the immunoassays are reliable methods for the identification of ancient wool.

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

The point-of-care testing concept has been exploited to design and develop portable and cheap bioanalytical systems that can be used on-site by conservators. These systems employ lateral flow immunoassays to simultaneously detect two proteins (ovalbumin and collagen) in artworks. For an in-depth study on the application of these portable biosensors, both chemiluminescent and colorimetric detections were developed and compared in terms of sensitivity and feasibility. The chemiluminescent system displayed the best analytical performance (that is, two orders of magnitude lower limits of detection than the colorimetric system). To simplify its use, a disposable cartridge was designed ad hoc for this specific application. These results highlight the enormous potential of these inexpensive, easy-to-use, and minimally invasive diagnostic tools for conservators in the cultural heritage field.

Capabilities and limitations of handheld Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for the analysis of colourants and binders in 20th-century reverse paintings on glass

A non-invasive method has been carried out to show the capabilities and limitations of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for identifying of colourants and binders in modern reverse glass paintings. For this purpose, the reverse glass paintings "Zwei Frauen am Tisch" (1920-22), "Bäume" (1946) (both by Heinrich Campendonk), "Lofoten" (1933) (Edith Campendonk-van Leckwyck) and "Ohne Titel" (1954) (Marianne Uhlenhuth), were measured. In contrast to other techniques (e.g. panel and mural painting), the paint layers are applied in reverse succession. In multi-layered paint systems, the front paint layer may no longer be accessible. The work points out the different spectral appearance of a given substance (gypsum, basic lead white) in reverse glass paintings. However, inverted bands, band overlapping and derivative-shaped spectral features can be interpreted by comparing the spectra from the paintings with spectra from pure powders and pigment/linseed oil mock-ups. Moreover, the work focuses on this method's capabilities in identifying synthetic organic pigments (SOP). Reference spectra of three common SOP (PG7, PY1, PR83) were obtained from powders and historical colour charts. We identified PR83 and PY1 in two reverse glass paintings, using the measured reference spectra. The recorded DRIFTS spectra of pure linseed oil, gum Arabic, mastic, polyvinyl acetate resin and bees wax can be used to classify the binding media of the measured paintings.

Lanthanide-Labeled Immunochromatographic Strip Assay for the On-Site Identification of Ancient Silk

The on-site identification of ancient silks has long been a key challenge in archeology. Therefore, a rapid, cost-effective, sensitive analytical approach is highly desirable. In this paper, a lanthanide-labeled immunochromatographic strip which is suitable for the on-site identification of ancient silks is described. Compared with the conventional colloidal gold-based immunochromatographic strip, this strip shows much higher analytical sensitivity and better quantitative discrimination. The limit of detection (LOD) of the strip for silk fibroin (SF) was calculated as 8.09 ng/mL, approximately 185 times lower than that of the colloidal gold-based immunochromatographic strip. No cross-reactions with other possible interfering antigens were observed. Moreover, the strip also shows good reproducibility, with a mean recovery of 94.15-102.55% and coefficient of variation of 5.22-17.57% in the repeated tests. Based on the advantages of portability and cost-effectiveness, as well as sensitivity, specificity, and reproducibility, the lanthanide-labeled immunochromatographic strip is a promising tool for on-site detection of ancient relics in archeological fieldwork.

Immunochemical Methods Applied to Art-Historical Materials: Identification and Localization of Proteins by ELISA and IFM

Despite the large diffusion of natural organic substances in art-historical materials, their characterization presents many challenges due to the chemical complexity and instability with respect to degradation processes. Among natural products, proteins have been largely used in the past as binders but also as adhesives or additives in coating layers. Nevertheless, biological identification of proteins in art-historical objects is one of the most recent achievements obtained in heritage science thanks to the development of specifically tailored bio-analytical strategies. In the context of this active emerging discipline, immunological methods stand out for sensitivity, specificity and versatility for both protein recognition and localization in micro-samples. Furthermore, the growing use of immunological techniques for advanced diagnostics and clinical applications ensures continuous improvement in their analytical performance. Considering such, this review provides an overview of the most recent applications of enzyme linked immunosorbent assay and immunofluorescence microscopy techniques in the field of heritage materials. Specifically, the main strengths and potentials of the two techniques as well as their limits and drawbacks are presented and discussed herein.

Immunochemical Micro Imaging Analyses for the Detection of Proteins in Artworks

The present review is aimed at reporting on the most advanced and recent applications of immunochemical imaging techniques for the localization of proteins within complex and multilayered paint stratigraphies. Indeed, a paint sample is usually constituted by the superimposition of different layers whose characterization is fundamental in the evaluation of the state of conservation and for addressing proper restoration interventions. Immunochemical methods, which are based on the high selectivity of antigen-antibody reactions, were proposed some years ago in the field of cultural heritage. In addition to enzyme-linked immunosorbent assays for protein identification, immunochemical imaging methods have also been explored in the last decades, thanks to the possibility to localize the target analytes, thus increasing the amount of information obtained and thereby reducing the number of samples and/or analyses needed for a comprehensive characterization of the sample. In this review, chemiluminescent, spectroscopic and electrochemical imaging detection methods are discussed to illustrate potentialities and limits of advanced immunochemical imaging systems for the analysis of paint cross-sections.

Microchemical Study of Pigments and Binders in Polychrome Relics from Maiji Mountain Grottoes in Northwestern China

In this study, an integrated analytical method was developed to investigate the composition of both the inorganic pigments and organic binders of polychrome relics in Maiji Mountain Grottoes in northwestern China. Cross-sections of each sample were prepared at the beginning of the study, and all experiments were carried out on these cross-sections. Polychromic structures were revealed by optical microscopy and scanning electron microscopy-backscattered electron imaging. Inorganic materials were determined by using SEM coupled with an energy dispersive spectrometer and μ-Raman spectrometer, whereas organic materials were identified by staining techniques and highly sensitive and specific immunofluorescence microscopy. Data showed that the red colors are attributed to one or two pigments of red ochre, cinnabar, and minium; the blue pigment is natural lazurite; the green pigment is ascribed to atacamite; the white color is attributed to potassium feldspar; and the black surface is formed by the discoloration of minium to plattnerite under the influence of environmental factors. Regarding organic binders used in painting and preparation layers, mammalian animal glue and chicken egg white were both found alone or in mixture. Finally, the conclusion is made that the Secco technique is employed in polychrome relics from Maiji Mountain Grottoes.

Identification of Organic Binders in Ancient Chinese Paintings by Immunological Techniques

The identification and localization of organic binders in artworks are big challenges in archaeology and conservation science. Immunological techniques, such as enzyme-linked immunosorbent assay (ELISA) and immunofluorescence microscopy (IFM) have the potential to become powerful tools for the analysis of organic materials in ancient samples. In this study, ELISA and IFM techniques were combined to identify chicken ovalbumin, glue from several mammalian species, bovine milk, and fish glue in ancient Chinese painting samples. As binders, egg ovalbumin was found in two painting samples and animal glue was found in three samples, which were dated from the 4th to 8th centuries. The results clearly demonstrate that ELISA and IFM can be used to validate results from ancient samples.

Bone marrow-derived mesenchymal stem cells increase dopamine synthesis in the injured striatum

Previous studies showed that tyrosine hydroxylase or neurturin gene-modified cells transplanted into rats with Parkinson’s disease significantly improved behavior and increased striatal dopamine content. In the present study, we transplanted tyrosine hydroxylase and neurturin gene-modified bone marrow-derived mesenchymal stem cells into the damaged striatum of Parkinson’s disease model rats. Several weeks after cell transplantation, in addition to an improvement of motor function, tyrosine hydroxylase and neurturin proteins were up-regulated in the injured striatum, and importantly, levels of dopamine and its metabolite 3,4-dihydroxyphenylacetic acid increased significantly. Furthermore, the density of the D2 dopamine receptor in the postsynaptic membranes of dopaminergic neurons was decreased. These results indicate that transplantation of tyrosine hydroxylase and neurturin gene-modified bone marrow-derived mesenchymal stem cells increases dopamine synthesis and significantly improves the behavior of rats with Parkinson’s disease.