Preparation of carboxymethyl cellulose membrane flexible SERS substrate and its application in the detection of metabolites and pH in urine.

Uric acid, urea, and other metabolites in urine after exercise often reflect chronic injury syndrome in athletes. However, traditional urine detection methods have issues such as high costs and low detection sensitivity. SERS can rapidly, continuously, and sensitively monitor metabolites in human urine. In this research, a combined SERS substrate (CMBCM@Ag NPs@PGA) was developed based on the carboxymethyl modification of the bacterial cellulose membrane (BCM) surface. The numerous carboxyl groups on the CMBCM surface made it easier for silver ions to be adsorbed, leading to their conversion into silver nanoparticles (Ag NPs) when a reducing agent was introduced. This process allowed the nanoparticles to firmly adhere to the CMBCM surface, forming a uniform and stable "hot spot." "The CMBCM@Ag NPs@PGA substrate maintains excellent stability and sensitivity in the assay." It can detect very small amounts of urea and uric acid in urine with high sensitivity, with LOD of 1.05 μM for urea and 0.0075 μM for uric acid. Additionally, it exhibits good stability, antibacterial properties, and cell compatibility. In addition, the substrate can be used as a sensor to monitor pH in real-time. This expands the use of cellulose in flexible SERS sensing and detecting human exercise metabolic health.