Biomaterials Modelling
Characterization of the rhEGF-collagen sponges
[1]Determination of the degree of crosslinking
The crosslinking degree could then be obtained from the
differences between the absorbance values before and after
the crosslinking. The equation is as follows:
where s is the sample and ncl is non-crosslinked.
[2]Water-binding capacity
The water uptake of the collagen sponges was calculated using
the following equation:
where Wd is the weight of the dry sponge and Ws is the
weight of the swollen sponge.
[3]Release kinetics
To determine the possible release mechanism, drug release
from collagen sponges was fitted to the following power
model:
where Mt/M is the fractional drug release percentage at
time t, and k is a constant related to the properties of the
drug delivery system and n is the diffusional exponent
which characterizes the drug transport mechanism.
Recombinant hEGF release from collagen sponges
Figure 1 shows the release profiles of rhEGF from collagen
sponge at 37 �C in PBS with/without collagenase solution.
Chih-Hui Yang in his study supposed that
under the in vitro non-degradation conditions, rhEGF was
initially released by diffusion. Generally speaking, since
collagen is enzymatically degraded, low final release values
are expected in the absence of any enzymes. Therefore,
collagenase was employed for the model of the in vitro
rhEGF release study.
In project, this case is also valuable.
Therefore, the influence of the types and the
concentrations of the crosslinking agents and the preparation
conditions on the structures and characteristics of
collagen sponges, and the rhEGF release from collagen sponges were compared in his study.
Three different
types of crosslinking agents, GTA, genipin and ECD were
used to prepare crosslinked collagen sponges. The rhEGF
release patterns from collagen sponges are shown in Figure 2.
The drug release rate from crosslinked collagen sponges
treated with EDC was the fastest, followed by collagen
sponges treated with genipin and GTA, respectively. The
EDC crosslinked collagen showed no release control effect,
which was probably due to the fact that EDC increased the
water-solubility and lowered the viscosity of collagen (data
not shown). GTA crosslinked collagen showed the most
potent release control effect than the other two (EDC and
genipin). However, since we want controlled and orderly release system which will be improved our transgenic bacteria, we used genipin for formation our cellulose Wound Dressing layer in three different types of crosslinking agents, GTA, genipin and ECD.
Conclusion