Tissue engineered skin substitutes for wound healing have evolved tremendously over the last couple of years. New advances have been made toward developing skin substitutes made up of artificial and natural materials. Engineered skin substitutes are developed from acellular materials or can be synthesized from autologous, allograft, xenogenic, or synthetic sources. Each of these engineered skin substitutes has their advantages and disadvantages. However, to this date, a complete functional skin substitute is not available, and research is continuing to develop a competent full thickness skin substitute product that can vascularize rapidly. There is also a need to redesign the currently available substitutes to make them user friendly, commercially affordable, and viable with longer shelf life. The present review focuses on providing an overview of advances in the field of tissue engineered skin substitute development, the availability of various types, and their application.

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Over centuries, the field of regenerative skin tissue engineering has had several advancements to facilitate faster wound healing and thereby restoration of skin. Skin tissue regeneration is mainly based on the use of suitable scaffold matrices. There are several scaffold types, such as porous, fibrous, microsphere, hydrogel, composite and acellular, etc., with discrete advantages and disadvantages. These scaffolds are either made up of highly biocompatible natural biomaterials, such as collagen, chitosan, etc., or synthetic materials, such as polycaprolactone (PCL), and poly-ethylene-glycol (PEG), etc. Composite scaffolds, which are a combination of natural or synthetic biomaterials, are highly biocompatible with improved tensile strength for effective skin tissue regeneration. Appropriate knowledge of the properties, advantages and disadvantages of various biomaterials and scaffolds will accelerate the production of suitable scaffolds for skin tissue regeneration applications. At the same time, emphasis on some of the leading challenges in the field of skin tissue engineering, such as cell interaction with scaffolds, faster cellular proliferation/differentiation, and vascularization of engineered tissues, is inevitable. In this review, we discuss various types of scaffolding approaches and biomaterials used in the field of skin tissue engineering and more importantly their future prospects in skin tissue regeneration efforts.

Anti‐microbial activity is a commonly suggested but rarely tested property of avian uropygial oil. Birds may defend themselves against feather‐degrading and other potentially harmful bacteria using this oil. We preliminarily identified 13 bacterial isolates taken from the plumage of wild house finches Carpodacus mexicanus, measured bacterial production of the enzyme keratinase as an index of feather‐degrading activity, and used the disc‐diffusion method to test bacterial response to uropygial oil of house finches. For comparison, we performed the same tests on a type strain of the known feather‐degrading bacterium Bacillus licheniformis. Uropygial oil inhibited the growth of three strongly feather‐degrading isolates (including Bacillus licheniformis), as well as one weakly feather‐degrading isolate and one non‐feather‐degrading isolate. Uropygial oil appeared to enhance the growth of one weakly feather‐degrading isolate. Growth of the remaining isolates was unaffected by uropygial oil. These results suggest that birds may defend themselves against some feather‐degrading bacteria using uropygial oil.

Recent studies have documented that a diverse assemblage of bacteria is present on the feathers of wild birds and that uropygial oil affects these bacteria in diverse ways. These findings suggest that birds may regulate the microbial flora on their feathers. Birds may directly inhibit the growth of harmful microbes or promote the growth of other harmless microbes that competitively exclude them. If keratinolytic (i.e., feather-degrading) bacteria degrade colored feathers, then plumage coloration could reveal the ability of individual birds to regulate microbial flora. We used field- and lab-based methods to test whether male eastern bluebirds (Sialia sialis) with brighter blue structural plumage coloration were better able to regulate their microbial flora than duller males. When we sampled bluebirds in the field, individuals with brighter color had higher bacterial loads than duller individuals. In the lab, we tested whether bacteria could directly alter feather color. We found that keratinolytic bacteria increased the brightness and purity, decreased the ultraviolet chroma, and did not affect the hue of structural color. This change in spectral properties of feathers may occur through degradation of the cortex and spongy layer of structurally colored barbs. These data suggest that bacteria can alter structural plumage color through degradation.