Anti-interference labeled SERS lateral flow immunoassay based on Prussian blue for ultra-sensitive quantitative detection of bloodstains in forensic field.

Abstract

In the field investigation of criminal cases, the tracking of blood evidence is very important. However, post-crime bloodstains are often cleaned up or covered up, making residual traces difficult to detect. Consequently, the creation of expeditious, exceptionally precise, and selective analytical techniques for human bloodstain recognition is imperative. Prussian blue (PB) served as a surface-enhanced Raman scattering (SERS) tag in this research, characterized by an intense monochromatic signal in the biological silent region (1800-2800 cm^-1), while endogenous biomolecules had no Raman signal in this region. This feature allows the PB signal to be completely separated from the biological background, without the need for complex spectral analysis, and perfectly adapts to complex forensic field requirements. Based on this, we constructed a Prussian blue-modified anti-interference SERS lateral flow immunoassay strip (SERS-LFIA) for highly sensitive and rapid detection of blood evidence. The visual detection Limit of the test strip for human hemoglobin was 100 ng/mL (equivalent to the commercially available colloidal gold test strip), showing a good Linear response in the range of 1.00 ng/mL to 100 μg/mL (R² = 0.950), and the SERS detection threshold was as low as 1.00 ng/mL. The results suggest that Au@PB nanoparticles (Au@PB NPs) SERS-LFIA can be used as an effective detection method for on-site bloodstains, and is suitable for long-term preservation and traceability analysis of physical evidence.