Three-dimensional flexible SERS substrate based on bacterial cellulose membrane for detection of glutathione in serum

We developed a method for the fabrication of in-situ reduced bacterial cellulose membrane (BCM) for the simple synthesis of three-dimensional (3D) flexible SERS substrate. Ag NPs with high density were in-situ grown and uniformly distributed on the 3D BCM nanofibers through a controlled “silver mirror reaction” and “volume shrinkage” treatment, which created highly stable and uniform hot spots in the networked SERS substrate. “Hydrogel” BCM was formed by soaking in ammonia solution to hydrolyze the hemiacetal structure of cellulose, followed by in-situ reduction in silver trifluoroacetate (CF 3 COOAg) solution, the BCM enriched with silver nanospheres (Ag NPs-BCM) substrate was prepared. The results showed that the optimized Ag NPs-BCM substrate exhibited high SERS activity, and displayed an average EF of 5.3 × 10 8 and RSD of 11.0%, especially when protected from light for 45 days, the SERS performance kept steady. The Ag NPs-BCM substrate was used to detect glutathione (GSH). Interestingly, adding Ellman's reagent (DTNB) to serum, we clearly distinguished the amount of GSH content in cancer and normal using Ag NPs-BCM substrate. This has provided the opportunity to use flexible substrate in rapid biomedical assays.