title: pH-triggered injectable hydrogels prepared from aqueous N-palmitoyl chitosan: in vitro characteristics and in vivo biocompatibility.
abstract: In-situ forming hydrogels triggered by environmental stimuli have emerged as a promising injectable strategy targeted for various biomedical applications. However, several drawbacks associated with temperature-stimulated hydrogels have been reported. Employing a hydrophobically-modified chitosan (N-palmitoyl chitosan, NPCS), we developed a pH-triggered hydrogel system which showed a rapid nanostructure transformation within a narrow pH range (pH 6.5-7.0). NPCS in an aqueous environment was found to be a shear-thinning fluid and exhibited an instant recovery of its elastic properties after shear thinning, thereby making it an injectable material. Additionally, aqueous NPCS, an associating polyelectrolyte, can be rapidly transformed into hydrogel triggered simply by its environmental pH through a proper balance between charge repulsion and hydrophobic interaction. This in-situ hydrogel system was shown to be nontoxic. Subcutaneous injection of aqueous NPCS (pH 6.5) into a rat model resulted in rapid formation of a massive hydrogel at the location of injection. The implanted hydrogel was found to be degradable and was associated with an initial macrophage response which decreased with time as the degradation proceeded. These results suggested that the developed NPCS hydrogel may be used as an injectable drug/cell delivery system.
authors.affiliation: Department of Chemical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan, ROC.
authors.forename: Ya-Ling
authors.initials: YL
authors.lastname: Chiu
authors.forename: Sung-Ching
authors.initials: SC
authors.lastname: Chen
authors.forename: Chun-Jen
authors.initials: CJ
authors.lastname: Su
authors.forename: Chun-Wen
authors.initials: CW
authors.lastname: Hsiao
authors.forename: Yu-Ming
authors.initials: YM
authors.lastname: Chen
authors.forename: Hsin-Lung
authors.initials: HL
authors.lastname: Chen
authors.forename: Hsing-Wen
authors.initials: HW
authors.lastname: Sung
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry* / Q000633:toxicity*; D002470:Cell Survival / Q000187:drug effects; D048271:Chitosan / Q000031:analogs & derivatives* / Q000737:chemistry / Q000633:toxicity; D055119:Elastic Modulus; D020100:Hydrogels / Q000737:chemistry* / Q000633:toxicity*; D006863:Hydrogen-Ion Concentration; D007279:Injections, Subcutaneous; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D051379:Mice; D051381:Rats; D017208:Rats, Wistar; D053838:Scattering, Small Angle; D014783:Viscosity; D014961:X-Ray Diffraction
chemical_list: D001672:Biocompatible Materials; D020100:Hydrogels; C510699:N-palmitoyl chitosan; D048271:Chitosan