pH- and Matrix Metalloproteinase-Responsive Multifunctional Bilayer Microneedles Platform for Treatment of Tinea Pedis

Abstract

Persistent foot odor and itchiness are common symptoms of tinea pedis, significantly disrupting the daily life of those affected. The cuticular barrier at the site of the tinea pedis is thickened, which impedes the effective penetration of antifungal agents. Additionally, fungi can migrate from the skin surface to deeper tissues, posing challenges in the current clinical treatment for tinea pedis. To effectively treat tinea pedis, we developed a platform of bilayer gelatin methacrylate (GelMA) microneedles (MNs) loaded with salicylic acid (SA) and FK13-a1 (SA/FK13-a1@GelMA MNs). SA/FK13-a1@GelMA MNs exhibit pH- and matrix metalloproteinase (MMP)-responsive properties for efficient drug delivery. The MNs are designed to deliver salicylic acid (SA) deep into the stratum corneum, softening the cuticle and creating microchannels. This process enables the antibacterial peptide FK13-a1 to penetrate through the stratum corneum barrier, facilitating intradermal diffusion and exerting antifungal and anti-inflammatory effects. In severe cases of tinea pedis, heightened local pH levels and MMP activity further accelerate drug release. Our research demonstrates that SA/FK13-a1@GelMA MNs are highly effective against Trichophyton mentagrophytes, Trichophyton rubrum, and Candida albicans. They also reduced stratum corneum thickness, fungal burden, and inflammation in a guinea pig model of tinea pedis induced by T. mentagrophytes. Furthermore, it was discovered that SA/FK13-a1@GelMA MNs exhibit excellent biocompatibility. These findings suggest that SA/FK13-a1@GelMA MNs have significant potential for the clinical treatment of tinea pedis as well as other fungal skin disorders.

Keywords: FK13-a1; bilayer microneedles; pH- and MMP-responsive; salicylic acid; tinea pedis.

Figure 1

Schematic representation of SA/FK13-a1@GelMA MNs application in treating tinea pedis.

Figure 2

Characterization of SA/FK13-a1@GelMA MNs. (A–C) Fluorescence microscopy image of bilayer MNs loaded with rhodamine B and FITC-FK13-a1. (D) Single-needle tip force–displacement curve of SA/FK13-a1@GelMA MNs. (E) After inserting the SA/FK13-a1@GelMA MNs into the skin of the mouse, images of the pinholes were captured using a camera.

Figure 3

In vitro swelling degradation and drug release of SA/FK13-a1@GelMA MNs. (A, B) Characterization of SA/FK13-a1@GelMA MNs swelling and degradation in different pH solutions. (C, F) Cumulative release ratio of SA/FK13-a1@GelMA MNs in solutions with different gelatinase concentrations. All data are represented as mean ± standard deviation (n = 3).

Figure 4

Antifungal activity of SA/FK13-a1@GelMA MNs in vitro. (A, B) The antifungal ratio of SA/FK13-a1@GelMA MNs. The inhibitory zone of SA/FK13-a1@GelMA MNs. All data are represented as mean ± standard deviation (n = 3). *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001.

Figure 5

Anti-inflammatory activity of SA/FK13-a1@GelMA MNs in vitro. (A) Evaluation of RAW264.7 cell viability (n = 6). (B) Determination of NO content (n = 3). (C–F) Quantification of TNF-α, IL-1β, IL-6, and IL-10 levels using ELISA (n = 4). All data are represented as mean ± standard deviation. *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001.

Figure 6

Cytotoxicity of SA/FK13-a1@GelMA MNs in vitro. (A–F) Cytotoxicity assay against NIH-3T3, HaCaT, and L929 cells (n = 6). All data are represented as mean ± standard deviation.

Figure 7

Representative images of tinea pedis treated with different drugs on days 0 and 14.

Figure 8

Antifungal efficacy and oxidative stress level in vivo. (A, B) Intensity of fungal infection score. (C, F) Local oxidative stress detection. All data are represented as mean ± standard deviation (n = 3). *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001.

Figure 9

Histological features of skin sections. (A) H&E staining used for general morphology assessment. Blue arrows indicate the thickness of the stratum corneum. (B) Periodic acid-schiff (PAS) staining employed to evaluate specific fungal components. The red arrow points to fungi.

Figure 10

Anti-inflammatory activity of SA/FK13-a1@GelMA MNs in vivo. (A–D) ELISA results of TNF-α, IL-1β, IL-6, and IL-10 contents in skin homogenates. All data are represented as mean ± standard deviation (n = 3). *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001.

Figure 11

Biocompatibility assessment of SA/FK13-a1@GelMA MNs in vivo. (A–D) Determination of CRE, BUN, AST, and ALT. All data are represented as mean ± standard deviation (n = 3).