In situ detection of silk fibroin using a dual recognition strategy with a flexible pressure immunosensor

Silk is a symbol of ancient Chinese civilization that has made an indelible contribution to the development of world civilization. However, because ancient artifacts are often contaminated or degraded, it is difficult to detect the presence of silk therein, and the true origin of silk thus remains a mystery. Therefore, this work presents a flexible pressure immunosensor that was designed based on 3D polypyrrole (PPy) foams for the trace detection of silk fibroin at archaeological sites. Initially, silk fibroin (SF) was conjugated with antibody-functionalized copper oxide nanoparticles (CuO NPs) and carboxylated magnetic beads (MBs) to form a sandwich immune complex. Then, the sandwich immune complex was added to hydrogen peroxide (H2O2) by magnetic separation to catalyse the generation of oxygen (O2), which converted the antigen-antibody specific recognition signal to gas pressure. As the pressure within the device increases, the 3D PPy foam, as the sensing layer resistance was 150 Ω, undergoes extrusion and deformation. This deformation leads to alterations in the foam resistance. The flexible pressure immunosensor can sensitively monitor the change in electrical resistance in the system and quantitatively detect silk fibroin. With optimization, the flexible pressure immunosensor demonstrates a dynamic range of operation spanning from 10 ng mL-1 to 100 μg mL-1, exhibiting a remarkable detection limit of 10.58 ng mL-1 specifically for silk fibroin. Notably, this immunosensor surpasses enzyme-linked immunosorbent assay (ELISA) in terms of superior reproducibility, specificity, and accuracy. Therefore, this application provides a new method and technical support for silk detection.

Ancient fibrous biomaterials from silkworm protein fibroin and spider silk blends: Biomechanical patterns

Silkworm silk protein fibroin and spider silk spidroin are known biocompatible and natural biodegradable polymers in biomedical applications. The presence of β-sheets in silk fibroin and spider spidroin conformation improves their mechanical properties. The strength and toughness of pure recombinant silkworm fibroin and spidroin are relatively low due to reduced molecular weight. Hence, blending is the foremost approach of recent studies to optimize silk fibroin and spidroin's mechanical properties. As summarised in the present review, numerous research investigations evaluate the blending of natural and synthetic polymers. The effects of blending silk fibroin and spidroin with natural and synthetic polymers on the mechanical properties are discussed in this review article. Indeed, combining natural and synthetic polymers with silk fibroin and spidroin changes their conformation and structure, fine-tuning the blends' mechanical properties. STATEMENT OF SIGNIFICANCE: Silkworm and spider silk proteins (silk fibroin and spidroin) are biocompatible and biodegradable natural polymers having different types of biomedical applications. Their mechanical and biological properties may be tuned through various strategies such as blending, conjugating and cross-linking. Blending is the most common method to modify fibroin and spidroin properties on demand, this review article aims to categorize and evaluate the effects of blending fibroin and spidroin with different natural and synthetic polymers. Increased polarity and hydrophilicity end to hydrogen bonding triggered conformational change in fibroin and spidroin blends. The effect of polarity and hydrophilicity of the blending compound is discussed and categorized to a combinatorial, synergistic and indirect impacts. This outlook guides us to choose the blending compounds mindfully as this mixing affects the biochemical and biophysical characteristics of the biomaterials.

Art-omics: multi-omics meet archaeology and art conservation

Multi-omics can informally be described as the combined use of high-throughput techniques allowing the characterization of complete microbial communities by the sequencing/identification of total pools of biomolecules including DNA, proteins or metabolites. These techniques have allowed an unprecedented level of knowledge on complex microbial ecosystems, which is having key implications in land and marine ecology, industrial biotechnology or biomedicine. Multi-omics have recently been applied to artistic or archaeological objects, with the goal of either contributing to shedding light on the original context of the pieces and/or to inform conservation approaches. In this minireview, we discuss the application of -omic techniques to the study of prehistoric artworks and ancient man-made objects in three main technical blocks: metagenomics, proteomics and metabolomics. In particular, we will focus on how proteomics and metabolomics can provide paradigm-breaking results by unambiguously identifying peptides associated with a given, palaeo-cultural context; and we will discuss how metagenomics can be central for the identification of the microbial keyplayers on artworks surfaces, whose conservation can then be approached by a range of techniques, including using selected microorganisms as 'probiotics' because of their direct or indirect effect in the stabilization and preservation of valuable art objects.

Tailored monoclonal antibody as recognition probe of immunosensor for ultrasensitive detection of silk fibroin and use in the study of archaeological samples

The ultrasensitive detection of fibroin in unearthed silk relics has great significance for investigating the origin and transmission of silk. In this study, an anti-fibroin monoclonal antibody was successfully prepared through animal immunization. Next, a label-free electrochemical immunosensor was fabricated using layer-by-layer self-assembly technology, and an indirect enzyme-linked immunosorbent assay (ELISA) was proposed. The two methods exhibited excellent sensitivity and specificity in the detection of silk fibroin, while the immunosensor showed a wider quantitative detection range (0.1-100 ng mL^-1) and a lower detection limit (0.051 ng mL^-1) than ELISA (10-100 ng mL^-1 and 8.71 ng mL^-1). Furthermore, the performance of the immunosensor was superior in archaeological sample detection. Taking advantage of the well-prepared monoclonal antibody, the two proposed immunological assays demonstrate tremendous potential for the ultrasensitive detection of silk fibroin, which can make great contributions to exploring the origin and transmission routes of ancient silks.

Understanding the structural degradation of South American historical silk: A Focal Plane Array (FPA) FTIR and multivariate analysis

Silk artifacts constitute an invaluable heritage, and to preserve such patrimony it is necessary to correlate the degradation of silk fibroin with the presence of dyes, pollutants, manufacturing techniques, etc. Fourier Transform Infrared Spectroscopy with a Focal plane array detector (FPA FTIR) provides structural information at the micron scale. We characterized the distribution of secondary structures in silk fibers for a large set of South American historical textiles, coupling FTIR with multivariate statistical analysis to correlate the protein structure with the age of the samples and the presence of dyes. We found that the pressure applied during attenuated total reflectance (ATR) measurements might induce structural changes in the fibers, producing similar spectra for pristine and aged samples. Reflectance spectra were thus used for the rigorous characterization of secondary structures. Some correlation was highlighted between the age of the samples (spanning over five centuries) and specific changes in their secondary structure. A correlation was found between the color of the samples and structural alterations, in agreement with the chemical nature of the dyes. Overall, we demonstrated the efficacy of reflectance FPA µ-FTIR, combined with multivariate analysis, for the rigorous and non-invasive description of protein secondary structures on large sets of samples.

Immunological Methods for the Detection of Binders in Ancient Tibetan Murals

Tibetan mural samples from the Jiazhaer mountain cave were studied using enzyme-linked immunosorbent assays (ELISA) and immunofluorescence microscopy (IFM). Samples containing protein binders were first identified using ELISA, and then IFM was used to determine the location of protein binders. Using these methods, we discovered gelatin and casein in samples from wall murals, distributed in both red and black pigments. We excluded the possibility of contamination by conducting further experiments where simulated samples were spiked with milk. We conclude that both gelatin and casein were used as binders in the pigments of the Tibetan Buddhist murals in the Jiazhaer (Transliteration from Tibetan) mountain cave. This is the first evidence of casein being used as a binder in Chinese mural pigments.

Discerning Silk Produced by Bombyx mori from Those Produced by Wild Species Using an Enzyme-Linked Immunosorbent Assay Combined with Conventional Methods

Recently, much interest has been paid to the separation of silk produced by Bombyx mori from silk produced by other species and tracing the beginnings of silk cultivation from wild silk exploitation. In this paper, significant differences between silks from Bombyx mori and other species were found by microscopy and spectroscopy, such as morphology, secondary structure, and amino acid composition. For further accurate identification, a diagnostic antibody was designed by comparing the peptide sequences of silks produced by Bombyx mori and other species. The results of the noncompetitive indirect enzyme-linked immunosorbent assay (ELISA) indicated that the antibody that showed good sensitivity and high specificity can definitely discern silk produced by Bombyx mori from silk produced by wild species. Thus, the antibody-based immunoassay has the potential to be a powerful tool for tracing the beginnings of silk cultivation. In addition, combining the sensitive, specific, and convenient ELISA technology with other conventional methods can provide more in-depth and accurate information for species identification.

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.