Page 551 - IJB-10-5

International Journal of Bioprinting 3D bioprinting of collagen hydrogels

clinical applications face challenges, including infection collagen scaffold exhibited micron-scale resolution,
risks, potential harm to soft tissues, and the possibility of substantial mechanical strength, and robust resistance to
immune rejection. Tissue engineering for skin repair is swelling and degradation. Demonstrating commendable
7–9
an emerging technology that aims to establish personalized biocompatibility, these collagen scaffolds supported the
microenvironments for wound healing, offering promising proliferation, adhesion, migration, and differentiation
solutions to the complexities associated with full-thickness of human foreskin fibroblasts (HFF-1 cells). In a rat full-
skin injuries. 10–12 thickness skin injury model, the collagen scaffold exhibited

Collagen, the primary component of the dermal layer outstanding biological activity, significantly enhancing the
of the skin, is widely utilized as a scaffold in skin tissue regeneration of full-thickness skin injuries. This innovative
engineering due to its excellent biocompatibility, low in situ 3D bioprinting method for collagen-based
immunogenicity, flexibility, and biodegradability. 13–16 biomaterial ink holds immense potential for applications
Collagen is utilized in various forms (e.g., sponges, in tissue regenerative engineering and clinical medicine.
films, and hydrogels) for skin repair. Its pivotal roles in
hemostasis, inflammation, proliferation, and maturation 2. Materials and methods
during wound healing contribute to its effectiveness 2.1. Materials
in promoting skin regeneration. 17–23 Initially, collagen Methacrylic anhydride (MA) was procured from Hebei
hydrogels provide temporary structural support and create Bailingwei Hyperfine Material Co., Ltd. (China). LAP
a 3D environment for dermal fibroblasts and keratinocytes, was obtained from Shanghai Aladdin Biochemical
promoting tissue formation and integration. 24,25 As skin Technology Co., Ltd. (China). Other reagents used were
regeneration progresses, the hydrogels gradually degrade analytically pure.
into biocompatible products. Ideally, the degradation rate
should match the tissue regeneration rate for optimal 2.2. Preparation of collagen-based biomaterial ink
healing. However, traditional tissue engineering techniques Yak tendons are an excellent collagen source due to their
face challenges in precisely fabricating highly conformable high collagen content, constituting 65–80% of their dry
hydrogels tailored to wound demands. 26 weight, predominantly as collagen type I (Col-I). Their
superior quality (healthier, purer collagen with fewer
As a cutting-edge technology in biomanufacturing, contaminants) is attributed to the yaks’ high-altitude,
3D bioprinting can produce personalized biomimetic pollution-free environments. Additionally, sourcing
scaffolds tailored to specific wound shapes. 27–29 Extrusion- collagen from yaks is more sustainable and ethical
based 3D printing, the most widely used technique in compared to industrial farming, as yaks are often raised
3D bioprinting, has been employed to fabricate various in traditional, extensive farming systems that have a lower
tissues such as skin, bone, heart valves, corneas, and environmental impact and are more aligned with natural
more. 30,31 However, current strategies in extrusion-based animal behaviors.
bioprinting, including support bath, 32,33 temperature 34,35
and pH regulation, 36,37 and post-extrusion crosslinking The yak tendons were washed with ultra-pure water to
agents, 38–41 encounter several issues. These include residual remove surface impurities and then cut into small pieces
support baths, rapid temperature and pH changes causing of tendon tissue. These small tissue pieces were soaked
collagen denaturation, toxic side effects from crosslinking overnight in a 20% (w/v) NaCl solution, followed by
agents, and complex operational procedures, limiting treatment with a 0.1% (w/v) chlorhexidine solution and
their effectiveness for in situ printing directly applicable a 5% (w/v) hydrogen peroxide solution. Subsequently,
to wound repair. 42–45 Consequently, there is an urgent need they were successively immersed in a 10% (w/v) n-butyl
to develop a new, simple, and efficient method for the 3D alcohol solution, a 0.1 M NaOH solution, and a 0.5 M HCl
46
printing of active collagen with enhanced efficacy. solution with shaking. Finally, collagen was extracted
from the treated tendon tissue using an acetic acid solution
Herein, we introduce, for the first time, an approach 47
employing methacrylic anhydride (MA)-assisted one- containing pepsin. The extracted yak collagen underwent
purification through salting out, redissolving, and dialysis.
step in situ extrusion 3D bioprinting of collagen, which It was then freeze-dried and stored at −20 °C.
significantly enhances full-thickness skin regeneration
(Figure 1). The stable extrusion collagen-based The 100 mg freeze-dried yak collagen was dissolved in
biomaterial ink, consisting of collagen, trace amounts 10 mL acetic acid solution (1 M). The solution was stirred
of MA, and the photoinitiator lithium phenyl-2,4,6- until fully dissolved before being transferred to a dialysis
trimethylbenzoylphosphinate (LAP), was obtained bag with a molecular weight cutoff range of 8000–14000 Da.
and efficiently facilitated in situ 3D bioprinting of the Dialysis was carried out first in a 0.5 M acetic acid solution
biomaterial ink through a one-step method. The resulting for 12 hrs, followed by dialysis in a 0.1 M acetic acid solution

Volume 10 Issue 5 (2024) 543 doi: 10.36922/ijb.4069