RBP4 and influenza: SPR detection was employed in the selection of an RNA aptamer for human influenza [46], and aptamer-based SPR analyses were successfully applied in the detection of human IgE [47], C-reactive protein (CRP) [48] and the HIV-1-trans-activating (Tat) protein [49], and RBP4 (retinol binding protein 4), a diabetes biomarker [50].