XPS depth profiling of protein content in nanoporous silica thin film proteomic chips
C. Chiappini, E. Tasciotti, A. Bouamrani, Y. Hu, X. Liu, M. Ferrari
The University of Texas at Austin, US
Keywords: XPS, Depth profile, silica membrane, protein, proteomics
Abstract:Nanoporous silica thin films (NSF) can be manufactured via evaporation-induced-self-assembly and are employed for protein fractionation of complex biological samples. We were able to build a depth profile of the peptides concentration within the SNF by means of X-ray diffraction (XRD) analysis. Exploiting the presence of nitrogen in aminoacids, we quantifed the amount of peptides present within the silica matrix comparing the results with a control membrane showing complete absence of nitrogen. By means of surface XRD analysis, coupled with sequential removal of surfacial NSF layers through Ar sputtering, we built a complete depth profile of the NSF nitrogen and silicon content. We showed the presence of a thick protein layer on the NSF following serum spotting. The layer was removed by washings. We showed a decrease in the amount of protein content within the NSF after elution compared to that pre elution ranging from 9% to 74%. We have shown the ability to quantify the capture and reclaim of peptides from a proteomic chip as a function of depth with nanometric resolution. The information gathered from material science methods applied to this biologically relevant system could not be obtained through standard biometric assays.