Anti-Nociceptive Effect of Sufentanil Polymeric Dissolving Microneedle on Male Mice by Hot Plate Technique

Abstract

Background: Despite the widespread use of opioids to manage severe pain, its systemic administration results in side effects. Among the subcutaneous and transdermal drug delivery systems developed to deal with adverse effects, microneedles have drawn attention due to their rapid action, high drug bioavailability, and improved permeability. Sufentanil (SUF) is an effective injectable opioid for treating severe pain. In this study, we investigated the analgesic effects of SUF using dissolvable microneedles.

Methods: SUF polymeric dissolvable microneedles were constructed through the mold casting method and characterized by SEM and FTIR analysis. Its mechanical strength was also investigated using a texture analyzer. Fluorescence microscopy was applied in vitro to measure the penetration depth of microneedle arrays. Irritation and microchannel closure time, drug release profile, and hemocompatibility test were conducted for the validation of microneedle efficiency. Hot plate test was also used to investigate the analgesic effect of microneedle in an animal model.

Results: Local administration of SUF via dissolving microneedles had an effective analgesic impact. One hour after administration, there was no significant difference between the subcutaneous and the microneedle groups, and the mechanical properties were within acceptable limits.

Conclusion: Microneedling is an effective strategy in immediate pain relief compared to the traditional methods.

Keywords: Mice; Pain management; Sufentanil.

Fig. 1

Mechanical performance of PVP and SUF DMNs, and SEM micrographs of microneedle patches at different forces. The breaking force of the DMNs is 73 N/patch.

Fig. 2

Penetration test with DMNs. (A) Light microscopic images (1-5 layers) of DMN infiltration into PF layers. PVP DMNs penetrated the fourth layer of PF and SUF DMNs completely pierced the third layer (the thickness of each layer is 127 μm, with a dimension of 3 × 3 cm). (B) Percentage of each DMN penetration versus the number of PF layers and penetration depth. The total insertion depth is approximately 508 µm for PVP DMN and 381 μm for Suf DMN. The experiment was conducted in triplicates. (C) Insertion of trypan blue DMN and trypan blue/SUF DMN into mouse skin using H&E staining. (D) Transdermal administration of FITC DMN. Two-dimensional confocal microphotographs of FITC emission at different times after insertion (1, 4, and 8 h; for normalization of images, all images were taken at a depth of 2400 µm), the diffusion depth was (i) ~700 µm at 1 h, (ii) 1200 µm at 4 h, and (iii) ~2000 µm at 8 h after insertion.

Fig. 3

Inflammatory and histological examination of the skin. (A) Mild and transient skin irritation immediately after the removal of the DMN patch. (B) H&E images of the process of skin healing. As shown in the image, the depth of micropores decreases over time. Arrows indicate the perforated ducts and their closing process (Olympus BX61, Japan). SC: subcutaneous

Fig. 4

Cumulative release percentage of SUF. Up to 60% of SUF is released within 15 min, which may be due to the suitable water solubility of PVP. About 84% is released within 25 min, and the cumulative percentage remains almost unchanged 45 min after initiation. The experiment was carried out in triplicates.

Fig. 5

Hemocompatibility test of DMNs. (A) Hemolysis percentage graph of the study groups vs. the negative control (PBS). As shown in all tested concentrations of both PVP DMNs and SUF DMNs, the results for non-hemolyzed erythrocytes were ˃99%, in contrast to the positive control with 100% erythrocyte lysis. (B) The transparency of supernatants in the tubes. Water was used as a positive control. The experiment was performed in four replicates.

Fig. 6

In vivo toxicity assay. (A) Graph of hematological parameter assay in the studied groups. No statistical difference was observed between the control group (N/S SC) and the treated groups (SUF SC, SUF DMN, and PVP DMN) for each of the parameters (data reported as mean ± SD; one-way ANOVA, Tukey post hoc (p ˃ 0.05). The experiment was performed in triplicates. (B) H&E staining of the kidney, liver, and spleen of mice 14 days after treatment. No noticeable histopathological abnormalities or damage were detected in the experimental groups compared to the control group. SC: subcutaneous

Fig. 7

In vivo transdermal dissolution test. The (A) image and (B) graph of microneedle dissolution in different experimental groups. The DMNs exhibit different results in the presence or absence of supporter. The difference in the thickness of the animal's skin also significantly affected the dissolution (p ˂ 0.05); the experiment was performed in triplicates. On the other hand, in each group, there was no significant difference between the microneedles containing the drug and those without the drug (p ˃ 0.05).

Fig. 8

The graph of hot plate test. Jumping times of mice on the surface of the hot plate (55 °C ± 0.1) were recorded. Test was performed on four different groups of male mice (n = 6 in each group, weighing 18-22 g). The cut-off time was 20 s. The percentage of MPA was calculated for each group. There was no significant difference in hot plate response between the SUF DMN group and the group received subcutaneous SUF within 1 h of injection. However, a significant difference was observed between these two groups and the control groups (p ˂ 0.05). From 6 h, the SUF DMN group also lost its efficacy in pain control, with a notable difference from the subcutaneous SUF group (p < 0.05).