A Rapid and Simple LC-MS Method Using Collagen Marker Peptides for Identification of the Animal Source of Leather

On-site rapid detection of ancient leather using a dual recognition strategy

Leather has been widely used since ancient times, and the discovery of ancient leather is of great value for studying the origin and development of costume culture. However, due to contamination and degradation of leather relics in the buried environment, traditional analytical methods face challenges in detecting microtraces of ancient leather. Therefore, an immunosensor based on a dual recognition strategy was proposed in this work for the detection of leather artifacts at archaeological sites. Anti-collagen antibodies type I (Anti-COL I) and type II (Anti-COL II) were prepared through animal immunization. Next, the antibodies on the surfaces of magnetic beads (MBs) and polystyrene microspheres (PMs) underwent a specific binding reaction with the antigens, which were magnetically separated and placed in sucrose solution, further catalyzed by sucrose invertase on functionalized polystyrene microspheres (FPMs). Finally, the collagen concentration was detected using a personal glucose meter (PGM). The prepared immunosensor exhibited excellent sensitivity, specificity, and stability, with a limit of detection (LOD) of 4.92 ng mL-1, a relative standard deviation (RSD) of 8.39% for sensitivity, and a linear detection range of 10 ng mL-1 to 100 μg mL-1. The coefficient of variation of specificity was less than 4.34%, and the sensor demonstrated a lifespan of up to three weeks. Moreover, the sensor outperforms enzyme-linked immunosorbent assay (ELISA) in terms of accuracy, specificity, and reproducibility. Therefore, this sensor provides a new strategy for the on-site detection of leather artifacts.

Identification of Marker Peptides in Gelatins from Sika Deer (Cervus nippon) Using Ultra-High-Performance Liquid Chromatography-Quadrupole-Exactive-Orbitrap Mass Spectrometry

Gelatin from deer has garnered attention as a high-value health-promoting resource given its history of usage as a traditional Chinese medicine and recent studies demonstrating its biological activities. Mass spectrometry-based methods have increasingly been employed for species identification in collagen-based materials, effectively addressing challenges in quality control and authenticity verification. This study aims to identify characteristic marker peptides in gelatins from sika deer (Cervus nippon) to support their effective use as a health-promoting resource. Gelatin samples were enzymatically digested, and the resulting peptide mixtures were analyzed using ultra-high-performance liquid chromatography coupled with quadrupole Q-Exactive-Orbitrap mass spectrometry (UHPLC-Q-Exactive-Orbitrap MS). Marker peptide candidates were selected based on their high detection intensity and a literature review. Among the 28 selected marker peptide candidates, four peptides (P11, R2, R3, and R4) were defined as characteristic of sika deer gelatin. Comparative analyses with gelatins derived from donkey hide, bovine, porcine, and fish samples further confirmed the specificity of these peptides. These findings establish a robust analytical method for verifying the authenticity of sika deer gelatin, contributing to its safe and effective use as a health-promoting resource.

LeaData a novel reference data of leather images for automatic species identification

In the leather industry, the mammalian skins of buffalo, cow, goat, and sheep are the permissible materials for leather-making. They serve the trade of quality leather products; hence, the knowledge of animal species in leather is inevitable. The traditional identification techniques are prone to ambiguous predictions due to insufficient reference studies. Indeed, leather image analysis with big data can pave the way for automatic and objective analysis with accurate prediction. This study focuses on creating novel and unique leather image data, LeaData. The objective is to automatically determine species from grain surface analysis. Hence, it employs a simple, cheaper, handheld digital microscope for leather image acquisition. The magnifying parameter 47× captures the species-unique grain patterns distributed over the leather surface. In total, the LeaData encloses 38,172 images of four species from 137 leather samples. This big data spans leather images with theoretically ideal and practically non-ideal grain patterns. It also includes images of grain patterns varying over different body parts. Thus, the novel LeaData is an adequately larger pool of leather images with diverse behavior. The motive is to establish a smart leather species identification technique that can be easily accessible by leather specialists, customs officials, and leather product manufacturers. Hence, this paper solely creates the bigger LeaData and presents its different versions to the digital image processing and computer vision research community. This digitized source of permissible leather species helps enable digitization in leather technology for species identification. In turn, in maintaining biodiversity preservation and consumer protection.

A comprehensive quantitative LC-MS/MS method for rapid gelatin source identification in food products: Comparison with PCR

Authentication of gelatin sources are required for cultural beliefs and food integrity. This paper describes a sensitive and rapid detection of gelatin sources using liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. The specific peptide markers were adopted to accurately identify bovine and porcine gelatin in pharmaceutical capsules and jellies. Multiple reaction monitoring (MRM) was employed to identify and quantify over five specific peptide markers, each characterized by its unique precursor and product ion transitions. The developed method was validated at three concentration levels in gelatin-containing products to assess its accuracy and precision. The recovery (accuracy) of the proposed method was between 80 % and 107 %, and relative standard deviation (precision) was in the range of 5.16-9.97 %. Linearity was obtained ≥ 0.99 (R2). To ensure the accuracy of ingredient labeling, the LC-MS/MS results were compared with those obtained from PCR assays. The LC-MS/MS method demonstrated exceptional sensitivity, reliably detecting gelatin adulteration at concentrations as low as 0.01 %. The developed LC-MS/MS method provides a rapid and accurate results for authenticating gelatin sources in various food products within 4 hours.

Rapid Identification of Ancient Leather Species Using an Enzyme-Linked Immunosorbent Assay Based on Proteomic and Evolutionary Analyses

The species identification of leather artifacts is of great significance for studying the use and spread of ancient leathers; however, the absence of effective detection methods remains an obstacle. Here, we performed a shotgun proteomic analysis to identify the protein composition of ancient leather artifacts. Based on the Swiss-Prot database, 154 proteins were identified. We investigated these proteins using molecular evolution, structural domain, and sequence alignment analyses to select suitable proteins. Two proteins, Kelch-like family member 17 (KLHL17) and Nance-Horan Syndrome actin remodeling regulator (NHS), were selected for antibody preparation. Their binding affinities were determined by antibody potency and surface plasmon resonance (SPR). Furthermore, we developed and optimized an enzyme-linked immunosorbent assay (ELISA) suitable for the species identification of ancient leather artifacts. Two antibodies specifically identified the species of leather samples from goats and cattle, respectively. We established a new method with the advantages of portability, cost-effectiveness, and high sensitivity that was applied to leather species identification. Our study provides an effective detection tool for archeological leather artifacts utilizing the classical proteomics approach and ELISA technique. In addition, this study provides insights into the development of new protein-based methods for the identification of cultural relics.

A portable colorimetric immunosensor for highly sensitive point-of-care testing of leather artifacts

A point-of-care testing (POCT) platform, i.e., a portable colorimetric immunosensor based on iron oxide magnetic beads and AuNPs, has been developed for detecting leather residues. The immunosensor demonstrates a linear detection range from 1 ng/mL to 10 µg/mL, with a limit of detection (LOD) of 0.985 ng/mL. The sensor exhibits high specificity and repeatability and performs effectively in detecting leather artifacts excavated from Inner Mongolia. Thus, the proposed colorimetric immunosensor not only enables the micro-detection of leather artifacts but also shows significant potential for on-site leather detection at archaeological sites.

Direct infusion-multiple reaction monitoring cubed (DI-MRM3) enables widely targeted bi-omics of Colla Corii Asini (Chinese name: Ejiao)

Food authenticity is extremely important and widely targeted bi-omics is a promising pipeline attributing to incorporating metabolomics and peptidomics. Colla Corii Asini (CCA, Ejiao) is one of the most popular tonic edible materials, with counterfeit and adulterated products being widespread. An attempt was devoted to develop a high-throughput and reliable DI-MRM3 program facilitating widely targeted bi-omics of CCA. Firstly, predictive MRM program captured metabolites and peptides in trypsin-digestive gelatins. After data alignment and structure annotation, primary parameters such as Q1 → Q3 → QLIT, CE, and EE were optimized for all 17 metabolites and 34 peptides by online ER-MS. Though a single run merely consumed 6.5 min, great selectivity was reached for each analyte. Statistical results showed that nine peptides contributed to distinguish CCA from other gelatins. After cross-validation with LC-MRM, DI-MRM3 was justified to be reproducible and high-throughput for widely targeted bi-omics of CCA, suggesting a meaningful tool for food authenticity.

The Efficient Extraction Method of Collagen from Deteriorated Leather Artifacts

Collagen is the most crucial component of leather artifacts and analyzing collagen can provide vital information for studying and conserving such artifacts. However, collagen in leather artifacts often faces challenges such as degradation, denaturation, and contamination, which make it difficult to achieve an ideal protein extract using traditional extraction methods. This study aimed to find an efficient collagen extraction strategy for aging leather by comparing and improving commonly used methods. The results of comparing different extraction methods indicated that a NaOH solution was highly effective in extracting collagen from aged leather. To determine the optimal conditions for collagen extraction from the NaOH solution, we conducted orthogonal experiments. The results revealed that a NaOH concentration of 0.05 mol/L, a dissolution temperature of 80 °C, and a dissolution time of 12 h were the most favorable conditions. To validate the effectiveness of this method, we performed SDS-PAGE and biological mass spectrometry tests on collagen extracts from leather samples with varying degrees of aging. All collagen extracts exhibited distinct bands in the gel, and the molecular weight of collagen in each sample exceeded 20 kDa. Furthermore, even with a reduced sample mass of 1 mg (micro-destructive sampling), biological mass spectrometry identified 124 peptides in the protein extract. Notably, four of these peptides were unique to cattle hide collagen and were not present in the collagen of pig, sheep, horse, deer, or human skins. These experimental findings confirm the efficacy of the NaOH solution for extracting collagen from aging leather, suggesting that it can serve as a significant method for collagen identification and analysis in leather artifacts.

Identification of Five Gelatins Based on Marker Peptides from Type I Collagen by Mass Spectrum in Multiple Reaction Monitoring Mode

In this study, a novel pseudo-targeted peptidomics strategy, integrating the transition list generated by an in-house software (Pep-MRMer) and the retention time transfer by high-abundance ion-based retention time calibration (HAI-RT-cal), was developed to screen marker peptides of gelatins from five closely related animal species, including porcine, bovine, horse, mule, and donkey. Five marker peptides were screened from the molecular phenotypic differences of type I collagen. Furthermore, a simple and robust 10 min multiple reaction monitoring (MRM) method was established and performed well in distinguishing different gelatins, particularly in discerning horse-hide gelatin (HHG) and mule-hide gelatin (MHG) from donkey-hide gelatin (DHG). The market investigation revealed the serious adulteration of DHG. Meantime, the pseudo-targeted peptidomics could be used to screen marker peptides of other gelatin foods.

Species-specific identification of donkey-hide gelatin and its adulterants using marker peptides

Donkey-hide gelatin is an important traditional Chinese medicine made from donkey skin. Despite decades of effort, identifying the animal materials (donkeys, horses, cattle and pigs) in donkey-hide gelatin remains challenging. In our study, we aimed to identify marker peptides of donkey-hide gelatin and its adulterants and develop a liquid chromatography–tandem mass spectrometry method to identify them. Theoretical marker peptides of four animals (donkeys, horses, cattle and pigs) were predicted and verified by proteomic experiments, and 12 species-specific marker peptides from donkey-hide gelatin and its adulterants were identified. One marker peptide for each gelatin was selected to develop the liquid chromatography–tandem mass spectrometry method. The applicability of the method was evaluated by investigating homemade mixed gelatin samples and commercial donkey-hide gelatin products. Using the liquid chromatography–tandem mass spectrometry method, the addition of cattle-hide gelatin and pig-hide gelatin to donkey-hide gelatin could be detected at a level of 0.1%. Horse-hide gelatin was detected when added at a level of 0.5%. Among 18 batches of donkey-hide gelatin products, nine were identified as authentic, and eight of the remaining samples were suspected to be adulterated with horse materials. These results provide both a practical method to control the quality of donkey-hide gelatin and a good reference for quality evaluations of other medicinal materials and foods containing protein components.

Fourier transform infrared spectroscopy and chemometrics for the discrimination of animal fur types

Rapid and reliable animal fur identification has remained a challenge for customs inspection. The accurate distinction between fur types has a significant meaning in implementing the correct tariff policy. A variety of analytical methods have been applied to work on distinguishing animal fur types, with tools of microscopy, molecular testing, mass spectrometry, Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. In this research, the capability of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) combined with pattern recognition methods was investigated for the discrimination of animal fur in six types. This work was to explore the non-destructive application of ATR-FTIR technique in discriminant analysis of animal fur. All spectra were collected by ATR-FTIR of the wavenumber ranging from 4000 to 650 cm^-1. Data pretreatments included moving average smoothing and multiplicative scatter correction (MSC). Four supervised classification algorithms were chosen to categorize the types of fur: soft independent modeling of class analogy (SIMCA), principal component analysis linear discriminant analysis (PCA-LDA), partial least squares discriminant analysis (PLS-DA), least squares support vector machine (LS-SVM). PLS-DA and LS-SVM were both effective approaches, with a 100% classification accuracy rate. The accuracy of PCA-LDA and SIMCA was 98.33% and 99.44%, respectively. Furthermore, LS-SVM model obtained using Monte-Carlo sampling method also obtained 100% prediction accuracy, while all other methods produced misclassification. LS-SVM corrected the non-linearities for the animal fur FTIR data but also remarkably improved the prediction performance level. The results of this study revealed that the combination of ATR-FTIR and chemometrics has a huge potential for animal fur discrimination.

A rapid and simple signature peptides-based method for species authentication of three main commercial Pheretima

Pheretima with various activities is a commonly used animal-derived traditional medicine in Asia countries. However, almost half of them are non-pharmacopoeia species in the market due to the similar morphological characteristics between medicinal and non-medicinal species. This study aims to establish an effective method based on signature peptides for species authentication of three main commercial Pheretima, including two major Pheretima species (Amynthas aspergillum, Metaphire vulgaris) and one main adulteration (Metaphire magna). Firstly, the species of 52 batches of commercial Pheretima were authenticated based on DNA barcodes. Secondly, proteomic analysis was performed for protein characterization of three main commercial Pheretima. Furthermore, their signature peptides were screened and validated using ultra-high performance liquid chromatography coupled with mass spectrometry (UPLC-MS/MS) in multiple reaction monitoring (MRM) mode. Moreover, a simplified sample processing method was developed. Finally, large quantities of commercial Pheretima samples were analyzed for further verifying the feasibility of the signature peptides-based method. The result showed that the established method had a great application potential for authenticity identification of commercial Pheretima. SIGNIFICANCE: The authenticity assessment of medicinal materials is a main issue in the quality control process as deceptive practices could imply severe health risks. In this study, a rapid and simple method based on signature peptides was established for species authentication of three main commercial Pheretima, which can be an effective alternative to complex DNA barcoding and difficult morphological identification, and provided a reference for improvement of Pheretima quality standards.

Rapid porcine detection in gelatin-based highly processed products using loop mediated isothermal amplification

Low DNA concentration recovered from highly processed products such as gelatin and gelatin-based products renders difficulty in detecting porcine contamination using conventional PCR techniques. We documented here a porcine-specific loop-mediated isothermal amplification (LAMP) to identify porcine traces in gelatin products. The porcine-specific primers were designed according to mitochondrial DNA of Cytochrome b gene sequence. Here we used two different reaction mixtures for LAMP assay (GENIE and MYRM) against the same DNA samples extracted from gelatin products and porcine-specific primers to detect the presence of porcine DNA. The porcine-specific primers were shown to be specific only to Sus scrofa against 14 DNA of other meat species. The analytical sensitivity of the LAMP assay for porcine DNA detection is 1 pg/µL using both GENIE (within 30 m) and MYRM (within 60 m) reaction mixtures. Analysis against 32 samples of gelatin products showed that five samples were found to contain porcine DNA; two samples out of six gelatin powder samples and three gelatin capsule samples out of nine. Out of these five positive samples, three were not labeled containing porcine gelatin. Overall, LAMP assay in this study showed an excellent specificity, sensitivity and rapidity in detection of porcine DNA in gelatin products.

Supplementary Information

The online version contains supplementary material available at (10.1007/s13197-020-04932-2).

Real-time authentication of animal species origin of leather products using rapid evaporative ionization mass spectrometry and chemometric analysis

Increasing accounts of fraud and persistent labeling problems have brought the authenticity of leather products into question. In this study, we developed an extremely simplified workflow for real-time, in situ, and unambiguous authentication of leather samples using rapid evaporative ionization mass spectrometry (REIMS) coupled with an electric soldering iron. Initially, authentic leather samples from cattle, sheep, pig, deer, ostrich, crocodile, and snake were used to create a chemometric model based on principal component analysis and linear discriminant analysis algorithms. The validated multivariate statistical model was then used to analyze and generate live classifications of commercial leather samples. In addition to REIMS analysis, the microstructures of leathers were characterized by scanning electron microscopy to provide complementary information. The current study is expected to provide a high-throughput tool with superior efficiency and accuracy for authenticating the identity of leathers and other consumer products of biogenic origin.

Collagen: quantification, biomechanics, and role of minor subtypes in cartilage

Collagen is a ubiquitous biomaterial in vertebrate animals. Although each of its 28 subtypes contributes to the functions of many different tissues in the body, most studies on collagen or collagenous tissues have focussed on only one or two subtypes. With recent developments in analytical chemistry, especially mass spectrometry, significant advances have been made toward quantifying the different collagen subtypes in various tissues; however, high-throughput and low-cost methods for collagen subtype quantification do not yet exist. In this Review, we introduce the roles of collagen subtypes and crosslinks, and describe modern assays that enable a deep understanding of tissue physiology and disease states. Using cartilage as a model tissue, we describe the roles of major and minor collagen subtypes in detail; discuss known and unknown structure-function relationships; and show how tissue engineers may harness the functional characteristics of collagen to engineer robust neotissues.

Quantitative mass spectrometry-based analysis of proteins related to cattle and their products - Focus on cows' milk beta-casein proteoforms

Modern mass spectrometers can accurately measure thousands of compounds in complex mixtures over a given liquid chromatograph method, depending on desired outcome and method duration. This stream of analytical chemistry has wide ranging application across food, pharma, environmental, forensics, clinical and research. With consistent pressure on both the ruminant production and product industries to face new and substantial challenges, liquid chromatography-mass spectrometry (LC-MS) is an ideal tool to identify, detect and quantify markers of breeding, production and adaption to support both research and industry to overcome these challenges. Herein, we provide a description of the theoretical basis and framework for LC-MS as a rapidly developing technique and highlight its application in measuring cattle and cattle product traits through protein quantitation with specific focus on beta-casein proteoforms.

Collagen analysis with mass spectrometry

Mass spectrometry-based techniques can be applied to investigate collagen with respect to identification, quantification, supramolecular organization, and various post-translational modifications. The continuous interest in collagen research has led to a shift from techniques to analyze the physical characteristics of collagen to methods to study collagen abundance and modifications. In this review, we illustrate the potential of mass spectrometry for in-depth analyses of collagen.

Semi-Nondestructive Certification of Crocodilian Leather by LC-MS Detection of Collagen Marker Peptides

Leather produced from crocodile, alligator, and caiman skin is widely used in the fashion industry. Crocodilian leather is generally more expensive than mammalian leather, and the value greatly differs even between the crocodilian species. However, inappropriate labeling of the animal source on leather products sometimes arises from accidental or fraudulent substitution, which is difficult to unambiguously detect by existing methods. In the present study, animal source identification of crocodilian leather was carried out using type I collagen-derived marker peptides generated after dechroming, heat denaturation, and trypsin digestion. Definitive discrimination between the three crocodilian species and also a related species, lizard, was achieved based on the detection patterns of selected six marker peptides, determined by LC-MS. Furthermore, powdering of the leather samples enabled a reduction in the sample amount required and allowed the elimination of the dechroming step. Approximately 100 μg of powder was taken from commercial leather watch straps by filing, resulting in only slight damage to the undersides of the straps. The animal sources of the crocodilian products and also a crocodile-embossed calf product were successfully identified using a combination of the crocodilian marker peptides and previously established mammalian marker peptides. This semi-nondestructive species identification method is not only useful for certification of leather products but also for monitoring of international trade of leather and skin.

Effect of Linear-Hyperbranched Amphiphilic Phosphate Esters on Collagen Fibers

The surfactants of the linear-hyperbranched phosphate esters (PAMAM_Gn-3-Ps) have been constructed through random multibranching esterification of lauroyl chloride and phosphate ester as a branching agent. Subsequently, a series of surfactant products were obtained. Benefiting from the amphiphilic structure with the hydrophilic core and many hydrophobic tails, PAMAM_Gn-3-Ps were able to self-assemble into nanomicelles in aqueous media. Importantly, the polymers show low critical micelle concentrations (CMCs) and small particle sizes. Here, PAMAM_G1-3-P was applied in the collagen fibers of leather to improve the fibers' distance and mechanical property of collagen fibers. Additionally, the polymers display significant flexibility, which could replace ordinary fatliquor in the future. The result provides a new application of using linear-hyperbranched amphiphilic phosphate esters into traditional leather materials to enhance the performance of collagen fibers.