The process of wound healing is very complex. It is often supported by the use of dressings, which keep the wound moist and can help to actively repair damaged tissue. Biopolymer hydrogels are attractive wound dressing materials as they contain a lot of water and have a high biocompatibility. In this study, a mechanically enforced hydrogel made of Alginate and Chitosan, two biopolymers, is presented. By exchanging Ca2+ ions partially with chitosan or polyimine as a cross-linker for Alginate, the Young’s modulus could be improved.[1,2] This hydrogel allows to encapsulate stems cells, without affecting their viability. In addition, the chitosan supported gels show bactericidal effects on p. aeruginosa and s. aureus, which are two wound isolated bacterial strains. Therefore, a bactericidal, cell laden hydrogel wound dressing was created. This wound dressing can also be used to fit larger more complicated wounds, as it can be formed inside the wound by simple two component mixing.
Alginate-Chitosan hydrogels were prepared by mixing Alginate solution (2wt%, pH 7.0) with the gelation solution in a 1:1 ratio. The gelation solution consisted of CaCl2 (50mM, pH 8.0) and Chitosan (1.5wt%, pH 6.0) in different volume ratios. Changing the ratio of Ca2+/Chitosan in a regular fashion going from 100/0 Ca2+/Chitosan gelation solution to 0/100 Ca2+/Chitosan solution affected the stiffness in a non-linear fashion displaying a maximum achievable stiffness of 26kPa at a 60/40 Ca2+/Chitosan charge ratio. The developed Alginate-Chitosan system displays a dual functionality important for the purpose of wound healing. It enables encapsulation BM-hMSCs in an efficient way without reducing their viability and additionally the Chitosan functions as an anti-microbial agent tested against two major strains involved in wound infections. The two component system offers the possibility of using it either as a preformed dressing or as a wound filling model. The wound filling model offers two advantages: 1) using two liquid components allows sufficient contact with the whole wound before setting as a gel, 2) it has a higher bactericidal effect. Particularly in wounds which remain non-healing e.g. diabetic ulcers in need of debridement, would potentially benefit from this system as it is known that stem cells enhance wound healing and infection is often a major complication.
 P.T. Kühn, et al., Polymers, 2017, 9, 149.
 P.T. Kühn, et al., Macromol. Biosci. 2016, 16, 11, 1696.