2.2.3. Quantification of Amine Groups Present at the Functionalized NFMs

Quantification of amine groups present in each NFM was performed as described elsewhere [50,51]. For that, SH groups were inserted at the surface of the aminolysis-treated NFMs through the reaction of the amine groups with a 20 mM 2IT solution (0.1 mM PBS at pH8) and with a 20 mM DMAP solution during 1 h at 37 ◦C. Ellman's reagent method was used to quantify the amino groups. For that, samples were immersed in 0.1 mM DTNB solution (in PBS 0.1 mM at pH 7.27) and incubated during 1 h at 37 ◦C. The absorbance of supernatants was measured in triplicate at 412 nm in a quartz plate, using the DTNB solution as blank. For the calculation of the 2-nitro-5-thiobenzoate (NTB<sup>−</sup>2) molar absorption coefficient, the value of 14,151 M−<sup>1</sup> cm−<sup>1</sup> was used [50,51].
