Printable biodegradable hydrogel for skin wound dressing using inkjet printing technology

Chronic wounds are becoming more frequent. Foot ulcers affect approximately 10% - 15% of patients with diabetes throughout their lifetimes, and by 2025, it is estimated the prevalence of diabetes will be 250 million people in the worldwide. There is increased potential for patients with peripheral neuropathy and peripheral vascular disease to suffer more foot injuries. These conditions reduce the normal pain sensations and healing of minor traumas, allowing the development of chronic non-healing ulcers, often preceding lower-extremity amputation. These types of wounds are very difficult to treat and sometimes take months or even years to heal because of many possible complications during the process. The treatments of wounds and its complications represent more than $20 billion in United States, in part because non-healing wound need repetitive treatments. Close to 10% of patients admitted to hospitals will receive skin grafting treatments for various reasons, thus bringing the skin grafting market to $1 billion yearly. Skin graft materials have been used trying to improve wound healing. The majority of them are allogeneic and they do not survive several days when are implanted. Several studies exist where commercially available dermal substitutes have been augmented with autologous cells and these studies suggested that autologous cells still may not survive due to the lack of vascularization in these constructs. Recognizing this, we have been studying the behavior of fibroblasts and keratinocytes in engineered capillary-like endothelial networks. A dermo-epidermal graft has been implanted in athymic nude mouse model to assess the integration with the host tissue as well as the wound healing process. To build these networks into skin graft, a modified inkjet printer was used, which allowed to deposit human microvascular endothelial cells. Neonatal human dermal fibroblast cells and neonatal human epidermal keratinocytes were manually mixed in the collagen matrix while endothelial cells printed. A full thickness wound was created at the top of the back of athymic nude mice and the area was covered by the bilayer skin graft. The mice of the different groups (experimental; printable skin graft, comparative; comertial available skin graft-Apligraf®, and control group; without any type of skin graft) were followed until completion of the specified experimental time line, at which time the animals were humanely euthanized and tissue samples were collected. The tissue was fixed in 10% buffer formalin, and process for histological and immunohestochemical analysis. In conclusion, wound contraction improved by up to 10% when compared with the control groups. Histological analysis showed the neoskin having similar appearance than normal skin. Both layers dermis and epidermis were present with thicknesses resembling normal skin. Immunohistochemistry analysis showed favorable results proving survival of the implanted cells, and confocal images showed the human cells location in the samples that were collocated with the bilayer printed skin graft