Development and Validation of a Multiplex PCR-capillary Electrophoresis System for Identification of Frequently Encountered Species

<bold>Objective</bold> To address the challenge of identifying unknown animal-derived components in the fields of forensic evidence and food safety, we developed and validated a sensitive and efficient multiplex polymerase chain reaction-capillary electrophoresis (PCR-CE) detection system capable of simultaneously identifying DNA from 13 species—cattle (<italic>Bos taurus</italic>), mouse (<italic>Mus musculus</italic>), dog (<italic>Canis lupus familiaris</italic>), rat (<italic>Rattus norvegicus</italic>), pig (<italic>Sus scrofa</italic>), Chinese hamster (<italic>Cricetulus griseus</italic>), cat (<italic>Felis catus</italic>), horse (<italic>Equus caballus</italic>), human (<italic>Homo sapiens</italic>), chicken (<italic>Gallus gallus</italic>), duck (<italic>Anas platyrhynchos</italic>), donkey (<italic>Equus asinus</italic>), and sheep (<italic>Ovis aries</italic>)—within a single-tube reaction. <bold>Methods</bold> Species-specific primers were meticulously designed targeting hypervariable regions of the mitochondrial DNA (including <italic>Cytb</italic>,<italic> COI</italic>, <italic>16S rRNA</italic>, and <italic>ND2</italic> genes), with primer specificity rigorously verified in silico using BLAST analysis against non-target species. A multiplex PCR system was constructed, and critical reaction parameters, including primer concentrations and annealing temperature, were systematically optimized through gradient experiments to ensure balanced amplification of all 13 targets without non-specific products or primer-dimer formation. Amplification products were subsequently separated and detected based on their characteristic fragment lengths and distinct fluorescent labels (6-FAM, HEX) using a capillary electrophoresis platform. The established multiplex PCR-CE system was comprehensively evaluated across several parameters: specificity was tested against 17 species (13 target species and 4 non-target species); sensitivity was determined using serial dilutions of mixed DNA templates; the ability to detect adulteration was assessed using simulated mixed meat samples with known adulteration percentages (10% to 0.1%); and practical applicability was investigated by analyzing 27 commercially available meat products and authentic casework samples from a fatal dog attack incident. <bold>Results</bold> The optimized multiplex PCR-CE system successfully demonstrated specific and simultaneous amplification for all 13 target species, with zero cross-reactivity observed with 4 non-target species. The system exhibited high sensitivity, with detection limits ranging from 0.05 ng to 0.001 ng of DNA template depending on the species; ten species were detectable at the 0.001 ng level. In simulated adulteration studies, the system reliably detected duck DNA in sheep meat at 0.5%, pork in beef at 0.5%, and horse meat in donkey meat at a remarkably low level of 0.1%. Analysis of commercial meat products revealed an 18.52% (5/27) mislabeling rate. These findings were consistent with validation tests using national and industry standard methods. Furthermore, the system effectively identified human and dog DNA from real forensic case evidence (clothing fragments from bite marks), and even detected trace pig DNA, suggesting the dog’s prior pork consumption. <bold>Conclusion</bold> This study successfully established a highly specific, sensitive, and practical multiplex PCR-CE system for the simultaneous identification of 13 species. By combining the power of multiplex PCR with capillary electrophoresis, our approach delivers a significant advantage in terms of throughput, resolution, and automation over traditional gel-based methods. The system’s proven effectiveness in detecting low-level adulteration in complex mixtures and processed food products, along with its successful application to genuine forensic specimens, underscores its substantial value and broad potential for routine use in forensic laboratories for evidence analysis and in regulatory settings for ensuring food authenticity and safety monitoring.