Hydrogel is a non-soluble polymer but swelling and reach equilibrium in water. Hydrogel is compatible with body-fluid, blood, and tissue. Synthesis of hydrogel has been carried out from 5%; 7,5%; and 10 % polyvynilpyrollidon, using gamma irradiation with doses of 10, 20 ,30, and 40 kGy at dose rate of 5 kGy/hour. Hydrogel fraction values were determined. The effect of pH, temperature, and immersion in water, on the hydrogel swelling ratio were investigated; the hydrogel then was tested for its ability to immobilize and to release drug, propranolol HCl as a model. Result showed that the gel fraction value increasing with the increase of PVP concentration and gamma irradiation dose, while the swelling ratio decreasing. Hydrogel swelling ratio was not sensitive to pH, nor to temperature. Immersion of hydrogel in water showed that swelling has reached maximum in 24 hours. Immobilization test showed that the quantity of propranolol HCl absorbed into hydrogel was not influenced by the initial drug concentration, but by the swelling ability of hydrogel. The average amount of drug absorbed by the hydrogel was 86,51%. Different tests showed that the release of propranolol HCl from hydrogel into 0,1N hydrochloric acid solution (±80% in 8 hours) was influenced by the hydrogel swelling ability. It can be concluded that PVP-hydrogel can be best synthesized from 10% PVP by 40 kGy gamma irradiation. The PVP-hydrogel is promising to be used for drug immobilization and controlled-released matrix.Key words: hydrogel, polyvynilpyrollidon, gamma irradiation, immobilization, propranolol HCl
