Dendrogram produced by hierarchical cluster analysis (HCA) of the SERS spectra shown in Fig. 4 calculated using Ward’s method and label-coded as follows: (A) anti-vasopressin aptamer complex and influenza nucleoproteins from A/Uruguay, A/Brisbane, B/Brisbane, (B) anti-vasopressin aptamer (1000 nM) - spacer (100 nM) complex, along with blank buffer control, and (C) anti-vasopressin aptamer complex and vasopressin (1μg/mL). A total of 240 spectra were used to generate this dendrogram, corresponding to 40 spectra in each of the 6 sample categories.