INJECTABLE COLLAGEN AS A PH-SENSITIVE HYDROGEL

Injectable collagen is a concentrated dispersion of phase-separated co llagen fibres in aqueous solution. The structure and properties of col lagen fibres are defined by the magnitudes of electrostatic and hydrop hobic attractive forces between neighbouring collagen molecules within collagen fibres. The structure and mechanical properties of collagen fibre dispersions were studied by dynamic theological measurements and by polarized microscopy. Rheological measurements were performed over pHs ranging from 6 to 9 and over temperatures ranging from 283 to 298 K. At higher pHs, the fibre dispersions were found to possess more ri gid fibres and stronger inter-fibre attractive forces. This response i s argued to result from changes in the ionization of amino acid side c hains, which result in larger net-electrostatic attractive forces. Rai sing the temperature caused fibres to rigidify through enhanced hydrop hobic attractive forces. Gels formed by lower pH-higher temperature fi bre dispersions possess different properties than gels formed at highe r pHs and lower temperatures.