Pretreatment-free SERS analysis of raw bile juice for identification of gall bladder disease using paper-coupled Au nanodendrite-encaged nickel foam

Abstract

For pretreatment-free SERS measurement of raw bile juice for the identification of gall bladder (GB) disease, a paper strip bridging Au nanodendrite-encaged nickel foam (PS-AuND@NF) was demonstrated. To build a medium for facile sample diffusion as well as SERS generation, Au nanodendrite (AuND) with a high SERS efficiency was constructed on the porous frame of the NF (AuND@NF). Then, the PS-AuND@NF was built by simply positioning AuND@NF on a paper strip, which functioned as a channel for sample introduction to AuND@NF and a subsequent sample drain. With the continuous elution of raw bile juice, non-specific adsorption of SERS-inactive constituents such as lipids on the Au surface could be minimized. Using the PS-AuND@NF, raw bile juice samples obtained from 6 GB polyp and 21 GB stone patients were measured. Since only a few components in bile juice are expected to be SERS-active such as bilirubin-containing metabolites, the information obtained from the SERS spectra is not descriptive enough for the discrimination of both GB diseases. Therefore, two-trace two-dimensional (2T2D) correlation analysis, which is able to effectively feature out asynchronous (dissimilar) spectral behaviors in the comparison of two spectra, was carried out in parallel. When the principal component (PC) scores obtained from the 2T2D slice spectra were used for the k-nearest neighbor (k-NN), the discrimination accuracy improved to 88.9 % from 81.5 % obtained when using the PC scores of the raw spectra. Overall, the PS-AuND@NF enabled simple pretreatment-free SERS analysis of complex and viscous bile juice without interference from other existing components.