Aviii300

Reagents and solvents were purchased from commercial suppliers and used without further purification, unless otherwise stated. 5′-O-(4,4′-dimethoxytrityl)-5-iodo-2′-deoxyuridine 2 was synthesised following an established procedure.^{20 (link)} Column chromatography was carried out using open columns packed with Merck grade 60 silica gel topped with 0.5 cm of sand. TLC analysis was performed on Merck silica gel 60 silica sheets. ¹H, ¹³C, and ³¹P NMR spectra were obtained on Bruker AVIII300 or AVIII400 spectrometers. Chemical shifts (δ) are given in ppm and are relative to the residual solvent peak. Electrospray mass (ESI-MS) spectra were measured by either Waters micromass LCT electrospray time-of-flight (ES-TOF), Waters Xevo G2-XS, or Synapt G2S mass spectrometers. Milli-Q water purified with a Millipore Elix-Gradient A10 system (resistivity > 18 μΩ cm, TOC ≤ 5 ppb, Millipore, France) was used for DNA sample preparation.

The chemical structure of starting materials, functionalised polymers and hydrogels were determined using FTIR in reflection mode (ThermoFisher (Waltham, MA, USA), Nicolet iN10 MX, USA) and 1H NMR (Bruker, AVIII300, USA). Hydrogels were air dried and the FTIR spectra recorded from 400–4000 cm⁻¹, at a resolution of 8 cm⁻¹ and three scans were performed [101 (link)]. 1H NMR measurements were performed in D₂O solution by dissolving 11 mg chitosan in 650 µL D₂O and 6.5 µL acetic acid and thiolated chitosan in 650 µL D₂O. GPTMS was added dropwise to the solutions to produce a chitosan monomer to 6 mg/mL GPTMS ratio of 4:1 and reacted for 24 h at room temperature before performing 1H NMR measurements. Unreacted starting materials including acetic acid, GPTMS, chitosan in acetic acid and thiolated chitosan dissolved in D₂O were also analysed. Mnova V.14 software was used to analyse NMR spectra.

The 300 MHz ¹H and the 75 MHz ¹³C-{¹H} NMR spectra were measured on a Bruker AVIII 300 and the 600 MHz ¹H NMR spectra were performed using a Bruker Advance III 600. The 500 MHz ¹H NMR spectra were obtained using a Bruker AV DRX 500. MALDI–TOF spectra were performed on a Bruker Ultraflex TOF mass spectrometer, the molecular masses being recorded in linear mode. Dithranol was used as a matrix and sodium trifluoroacetate (NaTFA) as ionization reagent. The samples were dissolved in DMF. DSC measurements were performed using a Mettler Toledo DSC 822. The GC–MS analyses were carried out on Thermo Finnigan Trace DSQ GC/MS-System with THF as solvent. HPLC analyses were performed on BioTek Konton 525 equipped with UV detector (at 260 nm, diode array detector HPLC 540) at room temperature (column: Chiralcel OD-H, eluent: methanol/water 8:2, flow rate: 0,4 mL/min). Optical rotations were measured with a Perkin-Elmer 341 polarimeter in THF as solvent, with a concentration of 10 mg ml⁻¹. GPC analysis were carried out at 60 °C with N,N-dimethylformamide as eluent with a flow rate of 1 mL/min using a ViscotekGPCmax VE2001 system and a Viscotek VE 3500 RI detector. The system was calibrated with polystyrene standards with a molecular range from 1,280 g/mol to 1,373,000 g/mol.