Fig. 3
Simultaneous monitoring of multiple biological analytes. a Schematic of the experimental configuration. b Infrared reflectance spectrum of the multi-resonant sensor chip in PBS buffer solution. c Reflectance spectra before (R0) and after (R) lipid membrane formation in the CH2 band spectral region, magnified from marked area in (b). d Differential absorption spectrum calculated from the reflectance spectra in (c). The dashed line corresponds to the second-order polynomial used for baseline correction. e Color-coded time-dependent differential absorption spectra acquired during the lipid membrane formation and streptavidin-binding experiment. f Time trace of the integrated absorbance signal in the amide (red-shaded area) and CH2 (green-shaded area) bands from (e). The lipid and streptadivin injection steps are indicated by the blue- and orange-shaded areas, respectively. The integrated absorbance signals from the amide (red curve) and CH2 (green curve) bands exhibit pronounced signal modulations during the lipid membrane formation and streptavidin-binding steps, evidencing an inadequate discrimination of the two analytes. g Reference spectra for the lipid (blue-shaded area) and streptavidin (orange-shaded area) signal contributions. h Linear regression signals obtained from the spectral data in (e) with respect to the reference spectra in (g). Linear regression signals for lipid (blue curve) and streptadivin (orange curve) show a significant signal increase only during the corresponding lipid or streptavidin injection step, demonstrating effective chemical discrimination
