Characterization of micrometer thick layers of spin-coated chitin

Application Note #163

Full SPR curves registered in air at two wavelengths (670 nm – orange lines, 785 nm – blue lines) of chitin layer on polystyrene and gold. Dashed lines are the fitted curves from LayerSolver™ analysis.

Multi-Parametric Surface Plasmon Resonance (MP-SPR) instruments can measure optical properties and address surface interactions from very thin films (down to Ångstroms) up to micrometer thick layers. The measurement of thicker sensor coatings is based on a SPR waveguide mode. Micrometer thick chitin layers were spin-coated onto gold (Au) and polystyrene (PS) substrates and subsequently assessed through MP-SPR waveguide signal. Thickness and refractive index (RI) of chitin layer were determined in dry and liquid conditions using the same instrument set-up (Figure 1). The polymer thickness was almost 2 μm in air but less than 200 nm in buffer and in addition it was thicker on gold when compared to polystyrene. The affinity constant of a chitin binding domain of Bacillus circulans (CBD-INN) was determined and evidenced to be higher on chitin deposited on the polystyrene-coated sensor when compared to chitin on gold. Additionally, split-intein protein (INC-eGFP) affinity on CBD-INN was determined.

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