Oral delivery of pH-sensitive nanoparticles loaded Celastrol targeting the inflammatory colons to treat ulcerative colitis oleh Yue Zhao, Yinlian Yao, Shilong Fan, Xin Shen, Xingxing Chai, Zimin Li, Jiachun Zeng, Jiang Pi, Zhikun Zhou, Gonghua Huang, Hua Jin