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International Journal of Bioprinting Bioprinted skin scaffolds with GNP exposure

studies, effective treatment is crucial to prevent morbidity or developed. The overall schematic of the 3D bioprinting
mortality in patients with skin injuries resulting from burns, hardware is displayed in Figure S1, Supplementary File.
infections, cancer surgery, and other genetic and somatic This system is capable of accurately positioning cells,
diseases. To address these challenges, three-dimensional extracellular matrix (ECM), and growth factors in any
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(3D) bioprinting, as an additive manufacturing technology to desired 3D configuration. Each dispenser operates
fabricate biological constructs with hierarchical architecture independently with electromechanical valves and is
similar to their native counterparts, offers significant mounted on a high-precision XYZ robotic stage with three
advantages in fabricating artificial skin substitutes. 3D axes. The liquid materials are dispensed using pneumatic
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bioprinting has adopted various techniques, including inkjet- pressure during the micro-valves’ gate-opening phase.
based bioprinting, laser-assisted bioprinting, extrusion- Moreover, the volume of the dispensed droplets (drop size)
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based bioprinting, and stereolithography bioprinting, can be adjusted by controlling the valve opening time and
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to improve the viability of cells and biomaterials. Using a air pressure. The non-contact dispensers can dispense cells
pneumatic micro-extrusion-based 3D freeform fabrication in volumes of 769.5 nL, maintaining high cell viability. The
technology, artificial scaffolds can be fabricated by precisely dispensed volume is regulated by digitally controlling the
positioning various types of matrix materials and cells in pressure and pulse duration (3 ms). The system allows for
a layer-by-layer assembly, with appropriate structures and continuous dispensing at an actuation frequency of 200 Hz,
cell compositions in different sizes, high throughput, and ensuring high-throughput printing. The minimum printing
reproducible fashion. Artificial skin scaffolds are mainly resolution varies with material viscosity: 400 μm for aqueous
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fabricated using cell lines and stem cells with adequate materials (e.g., water and cell culture media), and higher
structures and viability. Recently, organoid engineering resolution for viscous substances (e.g., collagen and matrix
holds significant promise for fabricating skin substitutes, proteins). The bioprinting resolution can be systematically
leveraging the self-renewal and differentiation capabilities adjusted by controlling the dispensed droplet volume. Both
to create complex structures that mimic the morphology the syringe and building plate were maintained at 4°C.
and function of native tissues. 9–11 Thus, with these significant
improvements in the areas of bioinks, printing techniques, 2.2. Optimization of bioprinting parameters
and various cell types, 3D bioprinting has become a reliable Before cell-laden scaffold bioprinting, we conducted
and promising approach to fabricating artificial tissue for experiments on the optimization of bioprinting parameters
skin transplantation. with ultrapure water and different types of cells, such as
human epidermal keratinocytes (HEK; 2110; ScienCell,
Besides grafts, 3D-bioprinted scaffolds can also be used United States of America [USA]) and human dermal
as implants for drug delivery, serving as physical protection fibroblasts (HDF; 2320; ScienCell, USA). Different air
for wounds and a depot to release therapeutic drugs. pressures (2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 psi) and
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Notably, nanoparticles, including gold nanoparticles internal needle diameters (0.18, 0.23, 0.26, 0.3, 0.34, and
(GNPs), are increasingly utilized as carriers for the delivery 0.41 mm) were investigated with ultrapure water to test the
of drugs, genetic materials, and antigens. 15,16 For skin performance and sensitivity of the machine. Furthermore,
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wound healing, GNPs have been widely used as delivery the required pulses of 1 mL ultrapure water were examined
devices for drugs and antimicrobial agents. 17,18 Most studies as a reference for comparison.
employ GNPs for transdermal drug delivery. 19,20 In this
regard, employing GNP delivery systems in artificial skin Cell viability was tested at different bioprinting air
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grafts raises concerns about potential risks. However, the pressures, internal needle diameters, and cell suspension
retention, deposition, and biodistribution of GNPs in the densities to determine the optimum conditions for each
fabricated scaffold still require detailed investigation. cell type. Combinations of various bioprinting air pressures
(2, 4, 6, 8, and 10 psi), internal needle diameters (0.2, 0.25,
For this purpose, cell-laden scaffolds were bioprinted 0.3, 0.35, and 0.4 mm), and cell suspension densities (0.5,
and transplanted on the dorsal back of nude mice for 11 0.75, 1, 2, and 3 × 10 cells/mL for HDF; 0.5, 1, 2, 3, and 5
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days along with GNP exposure. Importantly, the retention × 10 cells/mL for HEK) were tested. Various bioprinting
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and biodistribution of GNPs in skin scaffolds and other air pressures were examined with 0.2 mm internal needle
tissues were investigated in transplanted mice after diameter and cell suspension densities of 2 × 10 cells/
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tail-vein injection. mL (Figure 1G and J). Additionally, various internal
needle diameters were examined with an air pressure of
2. Methods 0.2 psi and cell suspension densities of 2 million cells/mL
2.1. Development of a 3D bioprinter (Figure 1H and K), as cell suspension densities were
A robotic bioprinting system utilizing pneumatic micro- examined with 0.2 mm internal needle diameter and an air
extrusion-based 3D freeform fabrication technology was pressure of 0.2 psi (Figure 1I and L).

Volume 10 Issue 6 (2024) 431 doi: 10.36922/ijb.4692