Preparation of Chondroitin Sulfate-Glycyl-Prednisolone Conjugate Nanogel and Its Efficacy in Rats with Ulcerative Colitis.

A conjugate between chondroitin sulfate (CS) and glycyl-prednisolone (GP), named CS-GP, was produced by carbodiimide coupling at a high GP/CS ratio. CS-GP was not water-soluble and gave a nanogel (NG) in aqueous solution. Two types of nanogels, NG(I) and NG(II), with prednisolone (PD) contents of 5.5 and 21.1% (w/w), respectively, were obtained. They had particle sizes of approximately 280 and 570 nm, respectively, and showed negative ζ-potentials of approximately -40 mV. The PD release rate was slower in the nanogels than in a solution of CS-GP with a PD content of 1.4% (w/w). The PD release rate was slower in NG(II) than in NG(I), and was elevated at pH 7.4 than at pH 6.8. NG(II) was applied in vivo to rats with trinitrobenzene sulfonic acid (TNBS)-induced colitis, and its therapeutic efficacy and pharmacokinetic features were investigated. The therapeutic efficacy of NG(II) was slightly better than that of PD alone. Drug delivery to the lower intestines was enhanced with NG(II). The CS-GP nanogel has potential as a potent DDS for the treatment of ulcerative colitis.