A wafer-scale, ultrasensitive, highly uniform, paper-based, portable SERS detection platform was developed. This system is well-suited for clinical applications such as therapeutic drug monitoring for individualized medication adjustment and ultra-early diagnosis of pesticide intoxication. Consequently, these ultrasensitive fibrous SERS substrates offer new opportunities for practical on-site detection in biofluid analysis, point-of-care diagnostics, and precision medicine.

The paper-based SERS substrate exhibited an extremely high Raman enhancement factor (3.9 x 10^11), detectability at sub-femtomolar concentrations (single-molecule level), and great signal reproductivity (relative standard deviation: 3.97%), even when operated with a portable 785-nm Raman spectrometer. The sensors enable ultrasensitive, label-free detection of a wide range of analytes, including adulterants, dyes, feed additives, illegal drugs, medicines, mycotoxins, and pesticide residues.

Our paper-based SERS platform offers label-free single-molecule detection, low cost, flexibility, and high stability. Applications span biomedicine, food safety, and precision medicine, detecting physiological samples like serum, urine, sweat, tears, and saliva. It can also integrate with microneedle patches for painless drug monitoring in interstitial fluid, aiding personalized medicine.