Effect of porous silica on sustained release behaviors of pH sensitive pluronic F127/poly(acrylic acid) hydrogels containing tulobuterol.

pH sensitive Pluronic F127 (PF127)/poly(acrylic acid) (PAAc) hydrogels containing tulobuterol-loaded silica were prepared with PF127 content. The effects of the PF127 content and silica on the sustained release behaviors of the PAAc hydrogels were investigated. The results showed that the swelling ratio and rate of the hydrogels were decreased with increasing PF127 content compared with pure PAAc hydrogel, whereas the stability of the hydrogels was enhanced by the addition of PF127 after swelling. The release behaviors of the PAAc hydrogels showed that the release rate of the pure PAAc hydrogels increased as the pH value of the release medium was increased, whereas it decreased with the addition of PF127 due to a decrease in the swelling rate. Also, the hydrogels containing tulobuterol-loaded silica showed more sustained release behaviors, which was attributed to the delayed diffusion rate of the drugs by physical interaction between the drugs and porous silica.