A Simple Sensitive Solution-Based “Mix-and-Detect” SERS Platform Utilizing Highly Stable Multibranched Gold Nanostars for Bilirubin Detection in Urine

Bilirubin, a critical circulating metabolite, functions as a key biomarker for a range of health conditions, including jaundice, hepatitis, cirrhosis, and liver disorders. This highlights the need for a straightforward, rapid, sensitive, and cost-effective method for bilirubin monitoring to enable early diagnosis. In this study, we developed a simple and efficient solution-based SERS platform using highly stable gold nanostars (GNS) with tunable spike numbers (7-20) for direct bilirubin detection in urine without any sample pretreatment. Among the variants tested, GNS with the highest spike number (GNS-4) exhibited the strongest SERS enhancement, achieving a detection limit of 7.4 nM with methylene blue (Mb) as a model analyte. GNS-4 also enabled the direct detection of bilirubin spiked in artificial urine at a 20 nM detection limit. Furthermore, our "mix-and-detect" SERS platform effectively monitored bilirubin levels in urine samples from ten healthy volunteers without any pretreatment, highlighting its potential to differentiate healthy individuals from those at risk. Notably, GNS-4 maintained excellent SERS reproducibility and stability after six months of storage at room temperature. These results underscore the potential of solution-based SERS platforms for rapid, reliable, and cost-effective point-of-care diagnostics.