Abstract
Full-thickness skin wounds are common and could be a heavy physical and economic burden. With the development of three dimensional (3D) printing technology, skin-like constructs have been fabricated for skin wound healing and regeneration. Although the 3D printed skin has great potential and enormous advantages before vascular networks can be well-constructed, living cells are not recommended for 3D skin printing for in vivo applications. Herein, we designed and printed a bilayer membrane (BLM) scaffold consisting of an outer poly (lactic-co-glycolic acid) (PLGA) membrane and a lower alginate hydrogel layer, which respectively mimicked the skin epidermis and dermis. The multi-porous alginate hydrogel of the BLM scaffolds promoted cell adhesion and proliferation in vitro, while the PLGA membrane prevented bacterial invasion and maintained the moisture content of the hydrogel. Skin regeneration using the bilayer scaffold was compared with that of PLGA, alginate hydrogel and the untreated defect in vivo. Tissue samples were analyzed using histopathological and immunohistochemical staining of CD31. In addition, mRNA expression levels of collagen markers [collagen type 1 alpha 1 (COL1a1) and collagen type 3 alpha 1 (COL3a1)] and inflammatory markers [interleukin-1β (IL-1β), as well as tumor necrosis factor (TNF-α)] were measured. Conclusively, the application of BLM scaffold resulted in highest levels of best skin regeneration by increasing neovascularization and boosting collagen I/III deposition. Taken together, the 3D-printed BLM scaffolds can promote wound healing, and are highly suitable for a wide range of applications as wound dressings or skin substitutes.
Highlights
Skin is the largest organ and the outermost protective sheath of the human body (Iii et al, 2000; Sun and Mao, 2012)
While only 20% of the PLGA nanofiber degraded within 4 weeks, 3D-Printed Scaffold Promotes Wound Healing the degradation rate of alginate was slow in the first 2 weeks, and accelerated to 80% thereafter (Figure 3C), which is consistent with previous reports (Danhier et al, 2012; Lee and Mooney, 2012)
The porous alginate hydrogel promoted cell adhesion and proliferation, compared with PLGA, whereas the bilayer membrane (BLM) scaffold with a PLGA layer was able to prevent bacterial invasion and retain the humidity of the underlying hydrogel in vitro
Summary
Skin is the largest organ and the outermost protective sheath of the human body (Iii et al, 2000; Sun and Mao, 2012). The multiporous structure of these hydrogels promote cell invasion and neovascularization (Sun et al, 2018), and provide a physiologically moist microenvironment for wound healing (Boateng et al, 2014) Another major advantage of alginate hydrogel in the context of tissue reconstruction is the ease of 3D printing (Jahangir et al, 2018). Studies show that alginate wound dressings maintain a physiologically moist microenvironment, reduce bacterial infection at the wound site, and promote wound healing (Lee and Mooney, 2012) To this end, we used the 3D printing technology to create an BLM scaffold, with PLGA membrane as the superior layer and alginate membrane as inferior layer that, respectively, mimic the epidermis and dermis. The BLM scaffold provided an isolated and moist micro-environment that promoted inflammation, facilitated rapid vascularization and collagen deposition, and accelerated wound healing
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