Modular PVDF-PEI membrane-based SERS sensor for rapid on-site detection of methamphetamine in complex matrices

Methamphetamine (METH), a highly addictive central nervous system stimulant, poses a serious threat to public health, highlighting the urgent need for rapid, sensitive, and reliable on-site detection strategies. Although traditional chromatographic-mass spectrometry techniques offer high accuracy, they are hindered by complex sample preparation, expensive equipment, and lengthy detection times, making them unsuitable for rapid field screening. Herein, we developed a surface-enhanced Raman scattering (SERS) sensor based on a polyvinylidene fluoride (PVDF)-polyethyleneimine (PEI) membrane, utilizing a competitive immunoassay mechanism. The sensor consists of two key components: antibody-functionalized SERS nanoprobes and antigen-immobilized PVDF-PEI membranes. By enabling competition between METH in the sample and membrane-bound antigens for probe binding, the sensor allows for highly selective detection of the target analyte. The proposed sensor exhibits excellent analytical performance in four complex matrices, including domestic sewage, lake water, saliva, and serum, providing high sensitivity and reliable quantification enabled by matrix-matched calibration. In standard solution systems, a limit of detection (LOD) of 9.8 fg mL^-1 was achieved for METH, which remains as low as 18 pg/mL in lake water matrices. In addition, a LOD of 82 pg/mL was obtained for Δ⁹-tetrahydrocannabinol (THC), demonstrating the versatility of the platform for small-molecule drug analysis. Benefiting from its modular design and membrane-based configuration, this SERS sensor exhibits strong potential for portability and on-site deployment. Overall, the proposed platform provides an efficient and robust analytical strategy for the rapid detection of illicit drugs and small-molecule pollutants in complex environmental and biological matrices, offering promising prospects for environmental monitoring, forensic analysis, and biomedical applications.