In-fiber optofluidic online SERS detection of trace uremia toxin

In this Letter, we propose a microstructured in-fiber optofluidic surface-enhanced Raman spectroscopy (SERS) sensor for the initial inspection of uremia through the detection of unlabeled urea and creatinine. As a natural microfluidic device, microstructured hollow fiber has a special structure inside. Through chemical bonds, the SERS substrate can be modified and grown on the surface of the suspended core. Here, the silver nanoparticles (Ag NPs) are embedded on the poly diallyl dimethyl ammonium chloride-modified graphene oxide sheet to achieve the self-assembled SERS substrate. The reduced distance between Ag NPs can increase the strong hot spots that generate enhanced Raman signals. Therefore, it can effectively detect the Raman signal of unlabeled trace uremic toxin analytes (urea, creatinine) inside the optical fiber. The results show that under simulated biophysical conditions, the limit detection (LOD) for urea is 10^-4M and the linearity is good, especially at the clinical conventional concentration range (2.5-6.5×10^-3M). In addition, the online Raman detection of creatinine aqueous solution LOD is 10^-6M, which also has good linearity. Significantly, this Letter provides a microstructured optofluidic in-fiber Raman sensor for the preliminary detection of uremia, which will have good development prospects in the field of clinical biomedicine.