Preparation and In Vitro/In Vivo Characterization of Mixed-Micelles-Loaded Dissolving Microneedles for Sustained Release of Indomethacin

Abstract

Background/Objectives: Indomethacin (IDM) is commonly used to treat chronic inflammatory diseases such as rheumatoid arthritis and osteoarthritis. However, long-term oral IDM treatment can harm the gastrointestinal tract. This study presents a design for encapsulating IDM within mixed micelles (MMs)-loaded dissolving microneedles (DMNs) to improve and sustain transdermal drug delivery. Methods: Indomethacin-loaded mixed micelles (IDM-MMs) were prepared from Soluplus^® and Poloxamer F127 by means of a thin-film hydration method. The MMs-loaded DMNs were fabricated using a two-step molding method and evaluated for storage stability, insertion ability, in vitro release, in vitro transdermal penetration, and in vivo PK/PD studies. Results: The obtained MMs were stable at 4 °C and 30 °C for 60 days. The in vitro IDM transdermal penetration was remarkably improved by the MMs-loaded DMNs compared to a commercial patch. A pharmacokinetic study demonstrated that the MMs-loaded DMNs had a relative bioavailability of 4.1 in comparison with the commercial patch. Furthermore, the MMs-loaded DMNs showed a significantly shorter lag time than the commercial patch, as well as a more stable plasma concentration than the DMNs without MMs. The therapeutic efficacy of the IDM DMNs was examined in Complete Freund's Adjuvant-induced arthritis mice. The IDM DMN treatment effectively reduced arthritis severity, resulting in decreased paw swelling, arthritis index, spleen hyperplasia, and serum IL-1β and TNF-α levels. Conclusions: Our findings demonstrated that the novel MMs-loaded DMNs were an effective strategy for sustained IDM release, providing an alternate route of anti-inflammatory drug delivery.

Keywords: adjuvant induced arthritis; dissolving microneedles; indomethacin; mixed micelles; sustained release.

Figure 1

Schematic illustration of the fabrication of IDM-MMs-loaded DMNs.

Figure 2

TEM image of IDM-MMs (A). TEM image of IDM-MMs (close-up) (B).

Figure 3

The morphology of IDM-MMs-loaded DMNs. Photograph of IDM-MMs-loaded DMNs (A); microscope image of the tips of IDM-MMs-loaded DMNs (B); SEM image of IDM-MMs-loaded DMNs (close-up) (C); SEM image of IDM-MMs-loaded DMNs (D).

Figure 4

The storage stability of IDM-MMs and IDM-MMs-loaded DMNs. Changes in particle size and PDI of IDM-MMs (A); changes in EE% of IDM-MMs (B); changes in particle size of IDM-MMs redissolved from the IDM-MMs-loaded DMNs (C) (mean ± SD, n = 3) (** p < 0.01 compared with day 0, *** p < 0.001 compared with day 0).

Figure 5

The micrographs of different layers of parafilm^® M after insertion by IDM-MMs-loaded DMNs (A). The first layer (a). The second layer (b). The third layer (c). The fourth layer (d). The fifth layer (e). The sixth layer (f); percentage of holes created in each parafilm layer by the IDM or IDM-MMs-loaded DMNs (mean ± SD, n = 3) (B); H&E-staining image after insertion of IDM-MMs-loaded DMNs into rat skin (C).

Figure 5

The micrographs of different layers of parafilm^® M after insertion by IDM-MMs-loaded DMNs (A). The first layer (a). The second layer (b). The third layer (c). The fourth layer (d). The fifth layer (e). The sixth layer (f); percentage of holes created in each parafilm layer by the IDM or IDM-MMs-loaded DMNs (mean ± SD, n = 3) (B); H&E-staining image after insertion of IDM-MMs-loaded DMNs into rat skin (C).

Figure 6

In vitro release profile of IDM-MMs (A); in vitro release profiles of IDM DMNs and IDM-MMs-loaded DMNs (B) (mean ± SD, n = 3).

Figure 7

In vitro penetration results of IDM across full-thickness porcine skin (A); skin retention of IDM after transdermal penetration (B) (mean ± SD, n = 3. ** p < 0.01 compared with the IDM-MMs-loaded DMNs.

Figure 8

The mean plasma concentrations and time profiles of IDM DMNs, IDM MMs-loaded DMNs, and commercial patch (mean ± SD, n = 5).

Figure 9

Representative photographs of mouse paw and joint before CFA induction (the picture above) and on day 7 after CFA induction (the picture below) (A); effect of IDM treatment on swelling ratio in AIA mice (B); arthritis index (C); spleen index (D); serum IL-1β level (E); serum TNF-α levels (F) (mean ± SD, n = 6. ** p < 0.01 compared with the AIA model group. *** p < 0.001 compared to the AIA. model group).

Figure 9

Representative photographs of mouse paw and joint before CFA induction (the picture above) and on day 7 after CFA induction (the picture below) (A); effect of IDM treatment on swelling ratio in AIA mice (B); arthritis index (C); spleen index (D); serum IL-1β level (E); serum TNF-α levels (F) (mean ± SD, n = 6. ** p < 0.01 compared with the AIA model group. *** p < 0.001 compared to the AIA. model group).