Skin tissue engineering scaffolds should possess key properties such as porosity, degradability, durability, and biocompatibility to effectively facilitate skin cell adhesion and growth. In this study, recombinant human collagen (RHC) was used to fabricate porous scaffolds via freeze-drying, offering an alternative to animal-derived collagen where bovine collagen (BC)-based scaffolds were also prepared for comparison. The internal morphology of the RHC scaffolds were characterized by scanning electron microscopy (SEM) and the pore size ranged from 68.39 to 117.52 µm. The results from compression and fatigue tests showed that the mechanical strength and durability of RHC scaffolds could be tailored by adjusting the RHC concentration, and the maximum compressive modulus reached to 0.003 MPa, which is comparable to that of BC scaffolds. The degradation test illustrated that the RHC scaffolds had a slower degradation rate compared to BC scaffolds. Finally, the biocompatibilities of the porous scaffolds were studied by seeding and culturing the human foreskin fibroblasts (HFFs) and human umbilical vein endothelial cells (HUVECs) in samples. The fluorescent images and Cell Counting Kit-8 (CCK-8) assay revealed RHC porous scaffolds were non-cytotoxic and supported the attachment as well as the proliferation of the seeded cells. Overall, the results demonstrated that RHC-based scaffolds exhibited adequate mechanical strength, ideal biodegradability, and exceptional biocompatibility, making them highly suitable for skin-tissue-engineering applications.

Collagen types I and III are primary structural proteins that maintain human skin integrity, and their ratio is disrupted during aging. In this study, we developed a biomimetic 3D skin model with vascularization potential to evaluate the effects of nano-zinc oxide (nano-ZnO) in a physiologically relevant context. The model used methacrylated recombinant human collagen (RHC-MA) bioinks with tunable collagen I/III ratios that mimic the skin of children and adults. The bioinks exhibited excellent printability and mechanical properties that enabled the 3D bioprinting of full-thickness skin products, including dermal layers with human skin fibroblasts (HSFs) and human umbilical vein endothelial cells (HUVECs), as well as epidermal layers with keratinocytes (KCs). The model recapitulated native skin architecture, and key markers such as keratin 10 (K10), keratin 14 (K14), and cluster of differentiation 31 (CD31) were determined. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis showed that nano-ZnO significantly modulated genes associated with apoptosis, inflammation, and oxidative stress in skin cells.