A novel thermo-responsive drug delivery system with positive controlled release.

The model drug, 5-fluorouracil (5-FU) was loaded into the poly(N-isopropylacrylamide) (PNIPA) hydrogel at 25 degrees C, then the drug-loaded, swollen hydrogel sample was carefully enveloped in the dialysis bag to form a novel thermo-responsive drug delivery system (DDS). The concentration of released 5-FU was monitored at 266 nm on the UV spectrophotometer. We found that this novel DDS provides a positive drug release pattern and the drug, 5-FU, was released faster at the increased temperature (37 degrees C, >25 degrees C) than the one at the decreased temperature (10 degrees C, <25 degrees C). This was attributed to the double control of the thermo-sensitivity of the hydrogel matrix and the dialysis membrane. By employing the fast response PNIPA hydrogel instead of the conventional hydrogel in this novel DDS, we can further control the drug release rate and/or drug release amount etc., without changing the positive, thermo-responsive drug release pattern.