A suspended layer additive manufacturing approach to the bioprinting of tri-layered skin equivalents

Abstract

Skin exhibits a complex structure consisting of three predominant layers (epidermis, dermis, and hypodermis). Extensive trauma may result in the loss of these structures and poor repair, in the longer term, forming scarred tissue and associated reduction in function. Although a number of skin replacements exist, there have been no solutions that recapitulate the chemical, mechanical, and biological roles that exist within native skin. This study reports the use of suspended layer additive manufacturing to produce a continuous tri-layered implant, which closely resembles human skin. Through careful control of the bioink composition, gradients (chemical and cellular) were formed throughout the printed construct. Culture of the model demonstrated that over 21 days, the cellular components played a key role in remodeling the supporting matrix into architectures comparable with those of healthy skin. Indeed, it has been demonstrated that even at seven days post-implantation, the integration of the implant had occurred, with mobilization of the adipose tissue from the surrounding tissue into the construct itself. As such, it is believed that these implants can facilitate healing, commencing from the fascia, up toward the skin surface—a mechanism recently shown to be key within deep wounds.

Developing a bioink for single-step deposition and maturation of human epidermis

“…Different biomaterial mixtures have been explored in the literature for epidermis bioink[ 10 , 15 , 16 , 20 , 21 , 25 , 41 ]. The formulations typically contain natural polymers like fibrinogen[ 10 , 15 , 16 , 21 ] and collagen[ 16 , 20 ] which provide cell adhesion moieties necessary for cell viability.…”

“…This typically involves a multi-step process, where different components are printed at different times, and matured under different conditions over several days. While most bioprinted skin constructs are intended for in vitro testing purposes[ 17 - 19 , 24 ], some have taken it a step further, and implanted the constructs onto animal models[ 20 - 23 ]. Although these implants have shown promise, they also share the challenges associated with CEA, such as poor conformance to body contours, and long and costly culture before use.…”

Evolution of nanostructured skin patches towards multifunctional wearable platforms for biomedical applications

“…Moakes et al developed a continuous tri-layered implant using suspended layer additive manufacturing. 115 By controlling the bio-ink composition, the authors could form chemical and cellular gradients throughout the printed construct. The first epidermis layer was pectin mixed with collagen (2 : 1) gel and contained 2 × 106 keratinocytes.…”

Novel Electrospun Polycaprolactone/Calcium Alginate Scaffolds for Skin Tissue Engineering

“…Scaffolds have played a critical role in tissue regeneration, with past research leading to potential success in various tissue applications such as cardiac muscle [12], bone [13], liver [14], and skin [15,16]. Scaffolds are three-dimensional (3D) networks made of different materials by various fabrication processes including decellularized extracellular membranes [17,18], freeze drying [19], electrospinning [20], and 3D printing [16].…”

“…Scaffolds have played a critical role in tissue regeneration, with past research leading to potential success in various tissue applications such as cardiac muscle [12], bone [13], liver [14], and skin [15,16]. Scaffolds are three-dimensional (3D) networks made of different materials by various fabrication processes including decellularized extracellular membranes [17,18], freeze drying [19], electrospinning [20], and 3D printing [16]. Particularly, electrospinning is a widely used fabrication method that uses electrostatic force to generate a charged stream of a polymeric solution from a liquid droplet, which stretches and elongates to generate fibers.…”