On the release of proteins from degrading dextran methacrylate hydrogels and the correlation with the rheologic properties of the hydrogels.
OBJECTIVE
To study the release of macromolecules of different sizes (bovine serum albumin, immunoglobulin G) from degrading (addition of dextranase) dextran methacrylate (dex-MA) hydrogels and to correlate the release with the evolution of the rehologic properties of the hydrogels during degradation.


METHODS
The size of the macromolecules, the degree of substitution (i.e., number of methacrylates per 100 glycopyranose residues) of the dex-MA and the dextranase concentration in the hydrogels was varied. The rheologic properties were measured with a controlled stress rheometer.


RESULTS
The release from dex-MA hydrogels without dextranase was very small [7-20% (time frame up to 180 days)] showing that most of the molecules were entrapped within the hydrogel network. The release from degrading dex-MA hydrogels followed zero-order kinetics for all molecules during a substantial period of the release. This was explained by a liberation and an increasing diffusivity of the proteins in the course of the degradation. The total amount released and the release rates could be well correlated with the rheologically observed degradation rates.


CONCLUSIONS
It was shown that rheology can be a useful tool to help explain the release from degrading hydrogels.
Meyvis
T
T
Laboratory of General Biochemistry and Physical Pharmacy, Ghent University, Belgium.
De Smedt
S
S
Stubbe
B
B
Hennink
W
W
Demeester
J
J
D003910:Dextranase / Q000737:chemistry; D003911:Dextrans / Q000737:chemistry*; D020100:Hydrogels; D007074:Immunoglobulin G / Q000737:chemistry; D008689:Methacrylates / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*; D012212:Rheology; D012710:Serum Albumin, Bovine / Q000737:chemistry
D003911:Dextrans; D020100:Hydrogels; D007074:Immunoglobulin G; D008689:Methacrylates; D011506:Proteins; D012710:Serum Albumin, Bovine; D003910:Dextranase