BRIEF COMMUNICATIONS pH-Sensitive Hydrogels for Colon Specifi c Delivery *

A novel fl uid loss additive (FLA) was synthesized using 2-acrylamido-2-methyl-propane sulphonic acid, acrylic acid, N,N-dimethyl acrylamide and N-vinyl-2-pyrrolidone by aqueous solution polymerization. TGA spectrum indicated that the decomposition temperature of FLA was higher than 330°C. The fl uid loss testing showed that the FLA had an outstanding property of reducing fl uid loss at 203°C in salt water cement slurry and the amount of fl uid loss was controlled about 100 mL when FLA dosage was 1.0%. Cement slurry with 0.1-1.5% FLA kept stable thickening time. A better performance of FLA was found in fresh water cement slurry than in salt water cement slurry. pH-sensitive hydrogels based on chitosan-sodium alginate (CS-SA) was synthesized by using glutaraldehyde as cross-link agent. The effects of the degree of the dosage of crosslinking, and pH on the swelling behaviors of the hydrogel have been studied, and the swelling ratio (SR) of this hydrogel in acide solution is much larger than that in alkaline solution. The release behavior of bovine serum albumin entrapped in the hydrogels was of distinctly difference with the changes of pH value of loading medium. The release of bovine serum albumin in those two kinds of hydrogels in the medium of pH = 1.0 was much quicker in pH = 7.4 and 9.18. The amount of bovine serum albumin (BSA) released from the fi lms at different time intervals was estimated by UV spectrophotometric method at 279 nm. The dissolution profi le and in vitro release kinetics showed that chitosan− sodium alginate (CS-SA) hydrogels were promising for controlled delivery of the drug. Formulation containing chitosan and sodium alginate may be suitable as a coating formulation for colon targeted drug delivery.