Carbonyl diimidazole cdi

Triblock copolymers Pluronic^® F127 (EO 200, PO 65), L35 (EO 22, PO 16), and L81 (EO 6, PO 43) were purchased form Sigma-Aldrich (USA) in powder form and dried by azeotropic distillation from benzene before use. Other reagents such as N,N-dimethylethylenediamine (DMEDA), 2-Hydroxypropyl-β-cyclodextrin (with average degree of hydroxypropyl substitution = 6.8), triethylamine (TEA), tris(2-aminoethyl)amine (TAEA), cholesteryl chloroformate, and carbonyldiimidazole (CDI), were also purchased from Sigma-Aldrich (USA) and used without further processing. Except DCM and DMF, all the solvents were used without further purification; DMF and DCM were dried over CaH₂, filtered, distilled at low pressure and stored under Ar environment prior to use. Cellulose dialysis membranes (Spectrum Labs, USA) were rinsed thrice followed by immersion in deionized water for at least 30 min at room temperature prior to use. Ultra-pure H₂O (resistivity ≈ 18.0 MΩ/cm⁻¹) was used for all the experiments and was obtained from a NANOpure water purification system.

The Pluronic triblock copolymers F127 (EO 200, PO 65, MW = 12600), F68 (EO 153, PO 29, MW = 8350), L35 (EO 22, PO 16, MW = 1900), L64 (EO 26, PO 30, MW = 2900), and L81 (EO 6, PO 43, MW = 2800) were purchased from Sigma-Aldrich and dried by azeotropic distillation from benzene under vacuum before use. 2-Hydroxypropyl-β-cyclodextrin, with an average degree of hydroxypropyl substitution of 6.8, carbonyldiimidazole (CDI), triethylamine (TEA), tris(2-aminoethyl)amine (TAEA), and cholesteryl chloroformate were also purchased from Sigma-Aldrich and used received. 4-Sulfobutylether-β-cyclodextrin (SBEβCD, a.k.a. Captisol) with an average degree of SBE substitution of 7 was generously supplied by Cydex Pharmaceuticals (Lawrence, KS) and was used without further purification. S-2-(4-Isothiocyanatobenzyl)-1,4,7,10-tetraazacyclododecane tetraacetic acid (p-SCN-Bn-DOTA) was obtained from Macrocyclics (Dallas, TX). All solvents were reagent grade, purchased from commercial sources, and were dried over CaH₂, filtered, and distilled at reduced pressure before storing under Ar prior to use. Cellulose dialysis membranes were obtained from Spectrum Labs and immersed in deionized water for at least 30 min prior to use. A Barnstead MicroPure water purification system was used to produce ultrapure water (resistivity ≈ 18.2 MΩ/cm⁻¹).