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3D Printed Dressings for Burn Wound Treatment
USA). The weight change was considered as the total Non-printed hydrogels were mixed with 10 cells/mL
5
water content (n = 3) . and consequently bioprinted under aseptic conditions.
[30]
To predict the hydration activity of the samples The bioprinted cell-laden scaffolds were placed in 6-well
on burn wounds, ethylcellulose super absorbent foam plates and maintained in 5 mL DMEM fortified with 5%
(Shield Line LLC, NJ, USA) was used as a model of the FBS and 1% Pen/Strep. Blank wells cultured with HDFs
dehydrated burn wound. The 3D-printed dressings were with no further treatment were considered as the control
mounted on the foam surface at 32°C, and hydration samples. After 3 days of incubation at 37°C, the cell-
activity was calculated by weight change after 24 h. laden scaffolds were exposed to the Live/Dead staining
It is highly important to provide continuous hydration kit (Abcam, MA, USA) for 10 min according to the
in the first 24 h after injury, because the systemic manufacturer’s manual. The viable and dead cells within
capillary leak, intravascular fluid loss, and large fluid the samples were observed using a confocal microscope
shifts will mostly occur within the first 24 h, peaking at (Nikon, Japan) in green and red channel, respectively. The
around 6 – 8 h after injury [31,32] . The total water content live and dead cell counts were measured using ImageJ
and moisturizing activity were calculated using the software v1.53s (National Institute of Health, MD, USA).
following equations:
W − W 2.8. Animal test
Totalwater content % () = 0 H ×100 (3) 2.8.1. In vivo burn wound model
W 0
All in vivo experiments were approved by the Institutional
( W − W ) Animal Care and Use Committee at the Missouri
Moisturizing activity = 0 24 (4)
W − W University of Science and Technology (Reference
0 H
No. 177-20). The ability of the 3D-printed wound
where W is the initial weight, W is the weight after dressings for the treatment of deep PTB wound healing
H
0
heating at 250°C, and W is the weight after placing on was evaluated by creating a circular burn wound using a
24
dry surfaces for 24 h. hot metal bar on the lumbar area of 18 Sprague Dawley
rats, in three groups of six rats in each group (n=6), as
2.7. In vitro biological evaluation follows:
2.7.1 MTT assay i. Control: Wounds covered with petrolatum gauze as
the current standard of care
MTT assay was used to test and compare the viability ii. Non-printed hydrogel: Wounds covered with non-
and proliferation of dermal cells after exposure to the printed hydrogel
3D-printed acellular dressings. In this research, the iii. 3D-printed hydrogel: Wounds covered with
sample extracts were used to indirectly evaluate the cell 3D-printed hydrogel dressings.
viability in accordance with the ISO-10993 standard. The After shaving the animal’s back area, the skin was
extracts were collected and filtered after 3, 7, and 14 days cleaned with iodine and then sterilized with alcohol
of immersion of the 3D-printed dressing in DMEM swabs. The animals were anesthetized using inhaled
(3 replications). The DMEM culture media with no isoflurane through a nose cone. The deep partial‐
further treatment were considered as the control sample. thickness defect was made by placing a 100°C metal bar
First, HDF cells were cultured in 100 μL DMEM plus of 20 mm diameter on the lumbar area of the rat for 10
10% FBS and 1% pen/strep (10 cells/well) and incubated s. After implementation, the wounds were disinfected by
4
at 37°C with 5% carbon dioxide (CO ). After 24 h, the Dermoplast antiseptic spray (Advantice Health LLC, NJ,
2
initial culture media were replaced by 90 μL sample USA). After applying the treatment, the wounds were
extract fortified with 9% FBS plus 1% pen/strep. After covered with Petrolatum Gauze and Elastikon bandage
24 h, the media were replaced by 100 μL MTT 0.5 M (3M, MN, USA). Figure 3 shows the application of
solution. After 4 h, the MTT solution was replaced by dressing on the wounds in the three groups. All animals
100 μL isopropanol. After 30 min, the optical density were monitored for post‐operative recovery on a daily
(OD) of formazan crystals was read at 545 nm using an basis, and the wounds were inspected under isoflurane
ELISA reader (Stat Fax 2100, USA). anesthesia every week to record the change in wound
size and formation of necrotic tissue formation. Sharp
2.7.2. Live/dead assay
debridement was performed and recorded if needed. The
Live/Dead assay was used to assess the direct cell experiment was terminated after 4 weeks by euthanizing
viability of the 3D-bioprinted dressings using HDFs. the animals using a lethal dose of CO . Wound tissue
2
Therefore, the 3D-bioprinted cell-laden dressings were explants were incised and fixed in formalin solution
evaluated in direct contact with HDF cells (n = 3). overnight for further histology investigation.

278 International Journal of Bioprinting (2022)–Volume 8, Issue 4