Spectrum 100 optica ft ir spectrometer

The synthesis of HA-Rfv was carried out according to the procedure described by Di Meo et al. [20 (link)] 2’3’4’5’-tetrabutyryl-3-(6-bromohexyl) riboflavin (Rfv-Br) was first obtained from 2’3’4’5’-tetrabutyl-riboflavin and 1,6-dibromohexane in dry N,N-dimethylformamide; then, in a typical reaction, the derivatization of HA-TBA with Rfv-Br was achieved by dissolving 300 mg of the polymer in 30 mL of NMP, followed by the addition of 119 mg of Rfv-Br previously solubilized in 3 mL of NMP to obtain a theoretical derivatization degree of 30% mol_Rfv/mol_HA (mol of Rfv per mol of HA repeating units). The reaction was left under vigorous magnetic stirring for 48 h at room temperature in the dark; the mixture was then diluted with distilled water, transferred into a dialysis tube (cut-off 12,000–14,000) and dialyzed until water conductibity was about 1.5 μS. The final solution was frozen in liquid nitrogen and freeze-dried (yield > 80%). The obtained product was analyzed by FT-IR ATR (PerkinElmer Spectrum 100 Optica FT-IR spectrometer, Waltham, MA, USA) using a spectral resolution of 4 cm⁻¹ with 64 co-added scans over a spectral range of 4000–600 cm⁻¹. The derivatization degree of hyaluronan was assessed by UV-Vis spectroscopy (PerkinElmer LAMBDA 25 UV/Vis system, Waltham, MA, USA) using a calibration curve of Rfv at λ = 445 nm in the concentration range of 3.125–50 μg/mL in DMSO.