title: Preparation and characterization of pH-sensitive anionic hydrogel microparticles for oral protein-delivery applications.
abstract: pH-sensitive P(MAA-g-EG) anionic hydrogel microparticles having an average diameter of approx. 4 microm were prepared by suspension photopolymerization. The pH-sensitive swelling and release behaviors of the P(MAA-g-EG) hydrogel microparticles were investigated as a biological on-off switch for the design of an oral protein delivery system triggered by external pH changes in the human GI tract. There was a drastic change of the equilibrium weight swelling ratio of P(MAA-g-EG) particles at a pH of around 5, which is the pK(a) of PMAA. At pH < 5, the particles were in a relatively collapsed state, while at a pH > 5 the particles swelled to a high degree. When the concentration of the cross-linker of the hydrogel increased, the swelling ratio of the P(MAA-g-EG) hydrogel microparticles decreased at a pH higher than 5 and the pK(a) of all the microparticles was in the pH range 4.0-6.0. In release experiments using Rhodamine B (Rh-B) as a model solute, the P(MAA-g-EG) hydrogel microparticles showed a pH-responsive release behavior. At low pH (pH 4.0) only a small amount of Rh-B was released while at high pH (pH 6.0) a relatively large amount of Rh-B was released from the hydrogel particles.
authors.affiliation: Department of Chemical Engineering, Hongik University, Mapo-gu, Sangsu-dong, Seoul 121-791, South Korea. bskim@hongik.ac.kr
authors.forename: Bumsang
authors.initials: B
authors.lastname: Kim
authors.forename: Sang Hoon
authors.initials: SH
authors.lastname: Lim
authors.forename: Won
authors.initials: W
authors.lastname: Ryoo
mesh_terms: D000284:Administration, Oral; D003432:Cross-Linking Reagents / Q000737:chemistry; D004337:Drug Carriers / Q000138:chemical synthesis* / Q000378:metabolism*; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000138:chemical synthesis / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D010777:Photochemistry; D011092:Polyethylene Glycols / Q000138:chemical synthesis* / Q000378:metabolism*; D011109:Polymethacrylic Acids / Q000138:chemical synthesis* / Q000378:metabolism*; D012235:Rhodamines / Q000378:metabolism*
chemical_list: D003432:Cross-Linking Reagents; D004337:Drug Carriers; D011109:Polymethacrylic Acids; D012235:Rhodamines; C099679:poly(methacrylic acid-ethylene glycol); D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D011092:Polyethylene Glycols; C029773:rhodamine B