Page 67 - IJB-9-2

International Journal of Bioprinting Bioprinting in wound dressing and healing

soluble collagen fibrillates at neutral pH and 37°C, thus Fibroblasts are found in the dermis of the skin and are
limiting its use in wound dressing and healing. Hartwell responsible for the production of extracellular matrix and
et al. proposed the addition of polyvinyl alcohol:borate non-fibrous components. Shi et al. fabricated a novel
[67]
[59]
hydrogels to overcome this challenge. The results showed dermal replacement scaffold using sodium alginate/gelatin
that adding this hydrogel to the collagen solution improved composites and fibroblasts through extrusion molding,
stability. Cultured cells also exhibited more organized which has similar physical and chemical properties to
f-actin and reduced abundance of pro-collagen and human skin tissue. Won et al. used skin-decellularized
[68]
α-smooth actin. extracellular matrix powders and fibroblasts as bioinks
3.2. Polysaccharide. The content of this cluster and found that gene expression in cells was similar to skin
[69]
also focuses on the preparation of different hydrogels. morphologic biology. Ng et al. used three different types
However, polysaccharides were focused on in this cluster. of skin cells (keratinocytes, melanocytes, and fibroblasts)
In particular, two articles focus on the value of carrageenan to produce pigmented human skin structures and showed
in bioprinting [60,61] . Xu et al. summarized the hydrogels light pigmentation similar to that of the skin donor.
[62]
synthesized with Schiff bases and polysaccharides and their 3.4. Healing process. Skin trauma healing includes
applications. Graham et al. investigated the properties interaction of multiple cells, growth factors, and cytokines.
[63]
of a range of thermosensitive polysaccharides and how The articles and reviews in this cluster focus on the
these properties can be applied to bioprinting. Rastin functions of growth factors and bioactive molecules in
et al. wanted to improve the antimicrobial properties of bioprinted skin. For example, Huang et al. created a
[64]
[70]
polysaccharide hydrogels. They chose to use Ga in the functional in vitro cell-loaded 3D extracellular matrix
3+
bioink formulation design. The Ga cross-linked bioink mimic. This biological 3D structure effectively creates
3+
exhibited potent antimicrobial activity against Gram- local ecological niches for epidermal progenitor cells,
positive (Staphylococcus aureus) and Gram-negative ensuring unilateral differentiation into sweat cells. Schmitt
bacteria (Pseudomonas aeruginosa). et al. reported a closed-loop fat-processing system that
[71]
3.3. Skin. This cluster focuses on the interaction processes fat aspirates into microfat clusters. The microfat
between bioink and skin cells. Bioprinting inks govern can be mixed with methacrylic acid collagen bioink to
the print resolution and the quality of bioprinted tissue. generate microfat-rich collagen structures by bioprinting.
Bioprinted ink materials provide physical and biochemical This collagen structure remains viable and metabolically
microenvironmental signals to seed cells that can active in vitro for 10 days.
influence cell polarity and control cell migration. Skin heat 3.5. Human skin This cluster contains 13 papers, but it
dissipation accounts for 90% of the total heat dissipation has a silhouette value of only 0.861, which represents not
in the body. The critical role of the skin cooling system is very excellent clustering. This cluster contains papers on
played by the sweat glands, located in the lower dermis, the effectiveness of different bioprinted dressings in wound
which secrete sweat, excrete waste, and regulate body healing [6,72-75] and a series of investigations on bioprinting
temperature. Bioprinted skin requires the construction of using stem cells [47,76,77] .
interconnected ducts between the basal epidermal layers
to uniformly excrete waste to achieve the sweat gland 3.6. Keratinocyte. Keratinocyte is a high-frequency
function of the skin. The hair follicles are connected to the keyword in this cluster. Keratinocytes and fibroblasts of
sebaceous ducts that carry the secretions produced by the the skin can be accumulated using an extrusion technique
body to the surface of the skin for discharge. No studies and cultured over time to form tissue cells with epithelium
[78]
have successfully induced the production of new human and dermis. Michael et al. placed fibroblasts and
hair follicles due to the lack of hair papilla cells with dermal keratinocytes on a stable matrix, and found that printed
sensing properties. In order to more realistically simulate keratinocytes formed a multi-layered epidermis with
the physiological functions of the skin, hair papilla cells beginning differentiation and stratum corneum.
should be added to the dermal papilla and epidermal 3.7. In situ bioprinting. In situ bioprinting and
layers. The bioprinted 3D spatial structure can partially handheld instruments are the focus of attention in this
restore the hair induction properties and eventually achieve cluster. The in situ skin-printing procedure is generally
hair regeneration . This cluster contains melanocytes- divided into two phases [79,80] . In phase I, fibroblasts
[65]
and fibroblasts-related bioprinting. Melanin secreted by and keratinocytes are isolated from the discarded skin
melanocytes can be used to regulate skin color and protect fragments. The cells are proliferated and mixed with
against ultraviolet rays. Min et al. printed melanocytes biopolymers, i.e., fibrin and collagen type I, to prepare
[66]
and keratinocytes on the top of the dermis and observed the bioink. In phase II, the area to be repaired is placed
freckle-like pigmentation at the dermo-epidermal junction. underneath the portable bioprinter, and the bioink is

Volume 9 Issue 2 (2023) 59 http://doi.org/10.18063/ijb.v9i2.653