Aj. Kuijpers et al., Combined gelatin-chondroitin sulfate hydrogels for controlled release of cationic antibacterial proteins, MACROMOLEC, 33(10), 2000, pp. 3705-3713
Chemically cross-linked gelatin-chondroitin sulfate (ChS) hydrogels were pr
epared for the controlled release of small cationic proteins. The amount of
chondroitin sulfate in the gelatin gels varied between 0 and 20 wt %. The
chemical cross-link density, the degree of swelling, and the rheological be
havior were determined to characterize the cross-linked hydrogels. Chemical
ly cross-linked gelatin-ChS hydrogels were loaded with lysozyme, and the re
lease was measured using phosphate-buffered saline. The lysozyme loading ca
pacity of the hydrogels significantly increased with increasing chondroitin
sulfate content of the gels. Compared to plain gelatin gels, the release r
ate of lysozyme slowed for the hydrogels containing 5 and 10 wt % of chondr
oitin sulfate, while the release was faster for hydrogels containing 20 wt
% of chondroitin sulfate. The permeation of lysozyme through gelatin-ChS ge
ls was measured using a two-compartment diffusion cell, and the effective d
iffusion coefficient was calculated. The effective diffusion of lysozyme in
the gels was also qualitatively studied using fluorescence recovery after
photobleaching. The Langmuir isotherms of lysozyme adsorption to gelatin-Ch
S gels and the lysozyme diffusion in the gels in the absence of electrostat
ic interactions were determined to evaluate the contributions of unspecific
interaction between lysozyme and chondroitin sulfate and diffusion to the
release. Both the interaction and the diffusion increase with increasing ch
ondroitin sulfate content of the hydrogels, which resulted in a minimum val
ue of the effective release rate for gels containing 5 wt % chondroitin sul
fate.