Arx 300 nmr spectrometer

8.7 mg of 1,1’-carbonyldiimidazole (CDI) dissolved in 0.7 mL dry chloroform was mixed with 15.8 mg LCA in 2 mL dry chloroform under stirring. After 1 h, the reaction mixture was slowly added into 10 mL of 5 mg/mL PEI base form (2.5 kDa) chloroform solution at 60 °C and reacted for 24 h under stirring. LCA-PEI (lp) was purified by dialysis (MWCO: 1000 Da) against ethanol (containing 0.4 mL of 1N HCl per 200 mL ethanol), followed by DI water and then acidified DI water (5 mL of 1N HCl per 200 mL DI water). The resulting product was dissolved in DMSO and analyzed by a Bruker ARX-300 NMR spectrometer equipped with a 5 mm QNP probe.

LCA-LPEI conjugate (3 molar equivalent LCA to 1 mole LPEI, or 3E) was synthesized using carbodiimide chemistry. Forty micromolar LPEI (base form, Polysciences) and 120 μmol LCA were dissolved in 25 mL of dichloromethane (DCM). Dicyclohexyl carbodiimide (DCC) 120 μmol and N,N-diisopropyl-ethylamine (DIPEA) 120 μL were added to the mixture and reacted over 15 h. 3E was purified by dialysis against 95% ethanol followed by dialysis against acidified DI water. The resulting product was dissolved in D₂O and analyzed with a Bruker ARX-300 NMR spectrometer equipped with a 5 mm QNP probe.