Page 367 - IJB-10-1

International Journal of Bioprinting Transdermal vitamin C delivery by MNPs

drug molecules at a smaller concentration of particles. MNPs. A single projection of three-armed MNP was placed
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Taken together, we used the MNPs prepared by a micro- vertically on the test bench, and the metal probe was gently
printing process for transdermal delivery of vitamin C to moved to contact the tip of the projection. The metal probe
alleviate skin photodamage, so as to reduce physical pain was then set to move vertically downward with a velocity
and mental suffering. of 0.05 mm/s. The compression process and morphologies
of the microneedle were captured by a camera. TA software
2. Materials and methods recorded the relationship between compression displacement

2.1. Materials and force. The data were subsequently processed in Prism
Photosensitive resin was purchased from SUMAOPAI 8.2.0 (GraphPad Software), and the fracture (failure) force
(Shenzhen, China). Hair removing cream VEET was was the turning point of static force on the curve.
obtained from Reckitt Benckiser Plc. (Wuhan, China). 2.4. Investigation of puncture performance and skin
Agarose gel was purchased from Biowest (Spain). Vitamin healing
C was purchased from Shanghai Sigma Co., Ltd. Abrasive Puncture experiments were performed on the agarose gel
gel was purchased from Cofoe Medical Technology Co., and skin of mice to assess the skin insertion ability of the
Ltd. Rhodamine B was purchased from Tianjin Guangfu MNPs. According to the literature, agarose powder was
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Fine Chemical Research Institute. Gentian violet was added to distilled water (0.0265 g/mL), heated to 100°C
purchased from Shanghai Sigma Co., Ltd. All chemical until completely dissolved, and poured into the mold for
reagents were of analytical grade. Male Balb/C mice cooling and molding for later use. Gentian violet staining
(8 weeks old) were provided by the Sichuan Dashuo was performed following treatment with the 1.2 wt%, 2.4
Bioscience Co. Inc. Animal experiments were conducted wt%, 4.8 wt%, and 9.6 wt% MNPs in 40 mg abrasive gel
in compliance with the guidelines for the ethical use of applied to 4 cm of agarose gel. Each application was made
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animals and were conducted at State Key Laboratory of by placing the agarose gel on a flat surface under slight
Biotherapy, Sichuan University, China. tension. For the topical treatments, a cotton swab was used

2.2. Preparation of MNPs to gently smear each formulation on the surface of agarose
The MNPs were fabricated by DLP-based micro-printing gel with light pressure, typically in circular motions for 5 s.
process. The printing device consisted of a light source, Immediately after that, gentian violet (Sigma) was applied
digital micromirror device (DMD) chip, optical lens, to the treated sample for 30 s. Excess gentian violet was
and reservoir. For the printing of customized MNPs, we then wiped from the skin with alcohol wipe until the
first designed the structure of MNPs by using Adobe residual, non-adherent dye on the surface was removed.
Photoshop CC 2019 software. Next, the pattern was Subsequently, pictures of the stained skin were taken with
imported into the DLP Light Crafter 4500 control software, a camera. In the same manner, puncture experiments
and the DMD modulated the light beam into a customized were performed by using depilated dorsal skin of mice.
light pattern according to the printing picture. Then, the Moreover, the proportion of staining-covered skin area
digital light projected from the DMD was adjusted by a was calculated by ImageJ, and data analysis was performed.
high-magnification micro-lens to improve the printing Next, mice were anesthetized using 1.5% pentobarbital,
resolution. The patterned light was projected into the shaved and depilated of dorsal hair, and then wiped clean
reservoir, inducing the polymerization of monomer with saline. The 4.8 wt% formulation (20 mg gel containing
solutions (resin) to form the MNPs. 120 MNPs) was topically applied to the circular area of
the dorsal skin followed by smearing using a cotton swab
MNPs were printed on a glass slide, followed by removal
of the residual resin on the surface of MNPs. Then, they for seconds. Then, the treated skin was harvested for
hematoxylin–eosin (H&E) staining.
were exposed to UV-visible radiation at 405 nm for 5 min.
Next, they were washed with 75% ethanol and phosphate- Moreover, the formulation was applied to the mouse
buffered saline (PBS). Finally, the MNPs were removed skin for 5 s and then wiped off to verify whether the skin
from the glass slide and stored at room temperature for would heal rapidly after the MNPs treatment. At 0 and
later use. The morphologies of the customized MNP were 30 min after the MNPs application, the mice’s skin was
observed with camera and scanning electron microscope observed, and pictures were taken with a camera.
(SEM; JSM-7500F) at 15 kV.
2.5. Evaluation of skin permeability after MNPs
2.3. Evaluation of mechanical properties treatment ex vivo
A compression test (Texture Analyzer, TA.XTC-18, Bosin After formulations treatment (4.8 wt% MNPs, applied
Tech) was used to evaluate the mechanical properties of for 5 s or control treatment), fresh mouse dorsal skin

Volume 10 Issue 1 (2024) 359 https://doi.org/10.36922/ijb.1285