Production
To evaluate an ideal hydrogel, various compositions were tested, like pure chitosan or chitosan in combination with agarose, agar or alginate.
The hydrogels we wanted to create are due to their compounds not toxic, biodegradable, biocompatible, while at the same time having low-cost and easy to manufacturing processes. They are easy to produce in different sizes and thicknesses. While being flexible they keep their stability, which makes it comfortable for patients to wear, as well easy to manufacture, handle and apply on patients.
The pH-level of our hydrogels are easy to regulate.
We were focused to work with basic laboratory equipment. For the preparation of chitosan hydrogels, an acidic environment is usually required to dissolve chitosan. We manufactured our chitosan containing hydrogel in aqueous acetic acid.
A long time continuous mechanical stirring (6 hours) is required to dissolve the chitosan in the acetic acid-deionized water solution. Under continuous pH measurement it needs mechanically stirring for 12 hours. This solution needs to rest for at least 12 hours for further processing.
Chitosan Hydrogel solidified in Alginate-Quercetin solution
Chitosan Hydrogel solidified in Alginate-Quercetin solution
The alginate/quercetin solution was poured into a mold and then liquid-frozen. The 2,2% chitosan solution was then poured onto it and streaked out to the certain thickness, covered with the alginate/quercetin solution, placed into the 37° incubator for 24 hours.
After the solidification process the arisen solid hydrogel was rinsed with ultrapure water.
Placed into an aqueous solution it will swell massively after time.
The swelling degree of the hydrogel was calculated by
The hydrogel were saturated with the liquid in which it was immersed. Our manufactured hydrogel has a degree of swelling of almost 600 %.
Chitosan Hydrogel with high pH-level
Manufacturing process of our chitosan hydrogel with a high pH-level was performed by rinsing the 2% chitosan solution with a defined NaOH solution with the desired pH-level.
A hydrogel composed of chitosan and agarose fulfils most of the required criteria for an “ideal” wound dressing.
Agarose is a biocompatible, linear polysaccharide which is extracted from marine algae. It consists of 1,4-linked 3,6-anhydro-α-L-galactose and 1,3-linked β-D-galactose derivatives.
The mixture of chitosan with agar forms hydrogels with enhanced swelling compared to pure chitosan ones.
Agar is a hydrophilic cell-wall polysaccharide extracted from the family of seaweeds. It composes of alternating (1-4)-D-galactose and (1-3)-3,6-anhydro-L-galactose repeating units and forms reversible gels even with a low concentration because of the formation of hydrogen bonds[2][10]. It is soluble in hot water and forms a gel during cooling. The polymer is biodegradable, low-cost, environmentally friendly and easy to extract. It is already used in pharmaceutical industry as a gelling, stabilizing and encapsulating agent [11]. It forms a stable, elastic gel which allows easy handling.
During the work with chitosan hydrogels various compositions were tested and promising hydrogels were produced. Hydrogels were manufactured with pure chitosan or chitosan in combination with agarose, agar or alginate. Depending on the concentration of chitosan and the respective gelling agent (agarose, agar, alginate) the gels were more or less solid. We manufactured stable and elastic gels which allows easy handling. According to the field of application a solid or smooth hydrogel is advisable.
Chitosan-Agarose Hydrogel
When the agarose is dissolved in water, it forms a gel with a three-dimensional scaffold and a porous structure providing a good environment for cell adhesion, spreading and proliferation. It is capable of gelling within the desired site because of the polymer interaction. By varying the concentration of agarose in the hydrogel, the mechanical properties, which are similar to those of tissues, can easily be adjusted [8]. The simplicity of preparing the hydrogel and its multifunctionality allows many future applications of agarose-based hydrogels
[9].
Chitosan-Agar Hydrogel
Outlook
The pH-level of the hydrogels is easy to regulate by rinsing it with the proper defined pH-level solution or using a higher or lower acetic acid concentration to dissolve the chitosan in a aqueous solution. This is beneficial for an adjustment to the respective wound and the pH of the affected wound.
Another advantage is the application for moist wound healing, as well as the factor that our hydrogels could airtight the wounds. Here the hydrogel prevents the formation of crusts and provides moisture. Both are important wound healing factors. The nutrient transport and release of signaling molecules is improved and scarring is massivly reduced with chitosan as wound toping layer. Our hydrogels can additionally deliver a monitoring bandage for affected patients without the need to disrupt the healing process. The hydrogel should help to prevent or treat wound infections for example at any degree of burns. We thanks the iGEM Team diagnost-X from Berlin for their expertise and informations which they provided us regarding these medical problems.
The chitosan with itself or in combination other natural polymers is an ideal scaffold material to manufacture different types of hydrogels as salves, pastes or solid bandages. Due to its wound healing effects and in combination with the medical benefits of a hydrogel it means an optimal wound healing dressing.
References
[1]
Tsou, Y. H., Khoneisser, J., Huang, P. C., and Xu, X. (2016) Hydrogel as a bioactive material to regulate stem cell fate. Bioactive Materials, 1, 29 – 55
DOI: 10.1016/j.bioactmat.2016.05.001
[2]
El-Hefian, E. A., Nasef, M. M., and Yahaya, A. H. (2012) Preparation and Characterization of Chitosan/Agar Blended Films: Part 1. Chemical Structure and Morphology. E-Journal of Chemistry, 9, 1431 - 1439
DOI: 10.1155/2012/781206
[3]
Chen, S.-C., Wu, Y.-C., Mi, F.-L., Lin, Y.-H., Yu, L.-C., and Sung, H.-W. (2004) A novel pH-sensitive hydrogel composed of N,O-carboxymethyl chitosan and alginate cross-linked by genipin for protein drug delivery. Journal of Controlled Release, 96, 285 – 300
DOI: 10.1016/j.jconrel.2004.02.002
[4]
Kharkar, P., Kiick, K., and Kloxin, A. M. (2013) Desining degradable hydrogels for orthogonal control of cell microenviroments. Chem Soc Rev, 42, 7335 – 7372
DOI: 10.1039/c3cs60040h
[5]
Dissemond, J. (2006) Modern wound dressing for the therapy of chronic wounds. Hautarzt, 57, 881 – 887
DOI: 10.1007/s00105-005-1054-y
[6]
Kurita, K. (2006) Chitin and Chitosan: Functional Biopolymers from Marine Crustaceans. Marine Biotechnology, 8, 203 – 226
DOI: 10.1007/s10126-005-0097-5
[7]
Ahsan, S. M., Thomas, M., Reddy, K. K., Sooraparaju, S. G., Asthana, A., and Bhatnagar, I. (2017) Chitosan as biomaterial in drug delivery and tissue engineering. International Journal of Biological Macromolecules, In Press
DOI: 10.1016/j.ijbiomac.2017.08.140
[8]
Miguel, S. P., Ribeiro, M. P., Brancal, H., Coutinho, P., and Correia, I. J. (2014) Thermoresponsive chitosan-agarose hydrogel for skin regeneration. Carbohydrate Polymers, 111, 366 – 373
DOI: 10.1016/j.carbpol.2014.04.093
[9]
Cao, Z., Gilbert, R. J., and He, W. (2009) Simple Agarose-Chitosan Gel Composite System for Enhanced Neuronal Growth in Three Dimensions. Biomacromolecules, 10, 2954 – 2959
DOI: 10.1021/bm900670n
[10]
El-Hefian, E. A., Nasef, M. M., and Yahaya, A. H. (2012) Preparation and Characterization of Chitosan/Agar Blended Films: Part 2. Thermal, Mechanical, and Surface Properties. E-Journal of Chemistry, 9, 510 – 516
DOI: 10.1155/2012/285318
[11]
Sousa, A. M. M., Sereno, A. M., Hilliou, L., and Goncalves, M. P. (2010) Biodegradable Agar extracted from Gracilaria Vermiculophylla: Film Properties and Application to Edible Coating. Materials Science Forum, 636-637, 739 – 744
DOI: 10.4028/www.scientific.net/MSF.636-637.739
