Synthesis Dextran-Agmatine

Reagents

Pharmacia: Dextran T-40 (M w 1⁄4 40,000)

Sigma: 4-Aminobutylg-uanidine sulfate (agmatine, 97%), p-toluenesulfonyl chloride (TsCl, 99%), lauric acid (98%), triethanolamine

1,1′-Carbonyldiimidazole (CDI, 98%):  Alfa Aesar, http://www.sigmaaldrich.com/catalog/product/aldrich/115533, 115533-5G, $28.50, 115533-10G, $43.60

Synthesis of tosylated dextran

The synthesis procedures of tosylated dextran were depicted in Scheme 1. The detailed preparation of tosylated dextran at anhydroglucose units (AGU)/tosyl chloride 1⁄4 1:3(mol/mol) (Dex-Ts3) was described as a typical example. Dextran (2 g, 12.4 mmol) was dispersed in 20 mL of water, and the pH was adjusted to 13 with NaOH. The solution was stirred vigorously and placed on ice. Tosyl chloride (7.2 g, 37.2 mmol) in 20 mL of acetonitrile was added dropwise with stirring over 30 min, causing immediate formation of a white precipitate. After 3 h of stirring at the room temperature, the precipitate was removed by suction filtration and the filtrate was dialyzed in ultrapure water for 5 days and the Dex-Ts3 was collected by lyophilization.

Synthesis of lauryl tosylated dextran

The Dex-Ts3 was selected to prepare lauryl tosylated dextran. Briefly, to 3 mL
solution of lauric acid (1.8 mmol) in DMSO, was added 3 mL solution CDI
(1.8 mmol) in DMSO. After stirring for 3 h at 80 � C, the solution of dextran
(6 mmol) in 5 mL DMSO was added. The mixture was allowed to react for 6 h at
80 � C under stirring. The raw product was isolated by precipitation in 100 mL
ethanol and washed several times with ethanol. The product was dialyzed in
ultrapure water for 5 days and the resultant lauryl tosylated dextran was collected
by lyophilization.

Synthesis of dextran-agmatine (Dex-Agm) and lauryl dextran-agmatine (Dex-L-Agm) conjugates

The synthesis of dextran-agmatine and lauryl dextran-agmatine conjugates was based on previous method [25,26] with a slight modification. Agmatine (25 mmol)

and tosylated dextran or lauryl tosylated dextran (5 mmol) were dissolved in water (30 mL) containing triethanolamine (20 mL) at 85 � C with stirring for 24 h under N 2 .
The resulting solution was adjusted to pH 7 and dialyzed against ultrapure water for 5 days, followed by lyophilization to obtain the Dex-Agm and the Dex- L -Agm conjugates. The preparation of Dex-Agm with different substitution degrees of agmatine was carried out by varying the molar ratio of dextran/tosyl chloride.