Establishment of rapid identification methods of menstrual blood based on SHERLOCK technology

The accurate determination of the tissue origin of body fluid-like forensic samples at crime scenes holds significant value for crime scene reconstruction and case trials. mRNA is the most commonly used molecular marker for body fluid identification. In this study, short crRNA fragments targeting the menstrual blood-specific genes MMP10 and STC1 were designed and screened. A SHERLOCK detection method based on CRISPR/Cas technology was established. Two signal detection methods, SHERLOCK-Fluorescence and SHERLOCK-LFA, were evaluated using 86 samples from five body fluid types (semen, peripheral blood, menstrual blood, saliva, and vaginal secretions). The SHERLOCK-Fluorescence method showed a sensitivity of 10⁻³ ng and could detect trace menstrual blood in mixed stains, aged, and mock degraded (UV-irradiated) samples. Compared to traditional RNA detection methods, it offered higher sensitivity, specificity, and simplicity. The SHERLOCK-LFA method, with a sensitivity of 10⁻¹ ng, was also effective for detecting menstrual blood and is suitable for rapid, on-site forensic detection. Both methods provide new approaches for the rapid identification of menstrual blood in forensic science.