Dextran is one of the FDA-approved natural polymers employed in medicines.In this study,we prepared dextran based polymer networks crosslinked by disulfide bonds,which are reduced in response to the relatively high level of cytoplasmic glutathione.miR-145,a tumor suppressor micro RNA [1] was conjugated to the hydrogel by glutathione responsive disulfide bonds (Fig.1).Thiolated dextran was prepared according to the Shahnaz et al.reported method [2].Calcium and zinc ions were used as templates and temporary ionic crosslinkers between cysteine conjugated carboxymethyl dextran chains and double stranded mimic of miR-145 with thiol modification at 3end of antisense.