Team:METU-Gene/Collagen Sponge

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The release rate of bioactive hEGF from crosslinking collagen sponges


The purpose of this study was to prepare recombinant human epidermal growth factor (rhEGF) collagen sponges for topical applications and investigate the effects of different types of crosslinked collagen sponges as platforms for the controlled release of rhEGF.


The microstructure and the drug release rates of collagen sponges were modified through treatment with different types (glutaraldehyde (GTA), genipin and 1-ethyl-3- (3-dimethylaminopropyl)carbodiimide (EDC)), different concentrations of crosslinking agents and various preparation conditions.


A good correlation was obtained for in vitro release rates of rhEGF using the power model. The crosslinked rhEGF collagen sponges showed a successful delivery of rhEGF in bioactive form to stimulate cell proliferation.


In addition, EGF can inhibit gastric acid secretions in the stomach, enhance the proliferation and keratinization of epithelial tissues and accelerate wound healing. Due to its wound healing properties, EGF is an attractive candidate for a therapeutic drug. Studies have demonstrated that topical applications of EGF promote wound healing in healthy and impaired healing animals.


Since Carpenter and co-workers first reported that for a mitogenic effect of EGF, a continuous exposure of the target cells to EGF was required for a minimum of 6–12 h, maintaining an effective topical concentration at the wound site for a certain period of time has become vital in the application of EGF. Indeed, we increased this continuous exposures by using Quaroum Sensing Mechanism of E.coli.



Collagen is a major constituent of the connective tissue and is potentially a highly useful biomaterial. It has characteristics that are suitable in medical application, such as biodegradability and weak antigenicity, and it has been used in resorbable surgical sutures, hemostatic agents, and wound dressings for many years.


An in vitro controlled release study was conducted to investigate the mechanism of recombinant human epidermal growth factor (rhEGF) release from the different degree of crosslinked collagen sponges.


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:

Formul1.jpg

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:

Formul2.jpg

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:

Formul3.jpg

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.

Figure1.jpg

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.