Fig. 3

a Kinetics of formation of the enzymatic product for different concentrations of antibodies used for the covalent immobilization (ppm = parts per million, i.e. µg/mL in water). Rates are expressed in units of cm⁻¹ s⁻¹. The dotted line represents the unspecific signal for particles modified with 100 µg/mL IgG anti-PCB169 and exhibiting R = 6.2e⁻⁶ cm⁻¹ s⁻¹. The case of PEGylated GNRs without any antibody corresponds to R = 2.1e⁻⁷ cm⁻¹ s⁻¹. b Rate of enzymatic reaction as a function of the concentration of antibodies used for the covalent immobilization. The unspecific signal relates to particles modified with IgG anti-PCB169. c Optical absorbance from particles modified with 100 µg/mL IgG anti-PCB28 or anti-PCB169, in a window covering both the fingerprint of the enzymatic product around 400 nm and the transverse SPR peak of the GNRs around 520 nm