Protium spruceanum Extract Enhances Mupirocin Activity When Combined with Nanoemulsion-Based Hydrogel: A Multi-Target Strategy for Treating Skin and Soft Tissue Infections

Abstract

The treatment of skin and soft tissue infections (SSTIs) can be challenging due to bacterial resistance, particularly from strains like MRSA and biofilm formation. However, combining conventional antibiotics with natural products shows promise in treating SSTIs. The objective of this study is to develop a nanoemulsion-based hydrogel containing Protium spruceanum extract and mupirocin and evaluate its potential for the treatment of SSTIs. The nanoemulsion was obtained by phase inversion and subsequently characterized. The antibacterial activity was evaluated in vitro against S. aureus MRSA, including the synergism of the combination, changes in membrane permeability using flow cytometry, and the anti-biofilm effect. In addition, the irritative potential was evaluated by the HET-CAM assay. The combination exhibited synergistic antibacterial activity against S. aureus and MRSA due to the extract enhancing membrane permeability. The hydrogel demonstrated suitable physicochemical properties, inhibited biofilm formation, and exhibited low irritation. The formulation was nanometric (176.0 ± 1.656 nm) and monodisperse (polydispersity index 0.286 ± 0.011). It exhibited a controlled release profile at 48 h and high encapsulation efficacy (94.29 ± 4.54% for quercitrin and 94.20 ± 5.44% for mupirocin). Therefore, these findings suggest that the hydrogel developed could be a safe and effective option for treating SSTIs.

Keywords: Protium spruceanum; SSTIs; antibacterial; nanoemulsion-based hydrogel; synergistic activity.

Figure 1

Flow cytometry analysis of Staphylococcus aureus (A,C) and MRSA (B,D) membrane permeability for the control (untreated cells) and after treatment with Protium spruceanum extract and/or mupirocin. (A,B) Histograms; (C,D) Percentage of damaged cells stained by propidium iodide (PI). (*) denotes a significant difference compared to the untreated cells (p ≤ 0.05), as determined by one-way ANOVA followed by Dunnett’s post-test.

Figure 2

Schematic representation of the mechanism of antibacterial (A), antioxidant (B), and anti-inflammatory (C) actions of the hydromethanolic extract of Protium spruceanum.

Figure 3

Stability of the nanoemulsion-based hydrogel containing Protium spruceanum extract and mupirocin stored at room temperature for 28 days. Different lowercase letters indicate a significant statistical difference between the same sample in different periods (p < 0.05), as determined by the t test.

Figure 4

Steady shear flow curve (A) and rheogram (B) of the nanoemulsion-based hydrogel containing Protium spruceanum extract and mupirocin.

Figure 5

Release profile of nanoemulsion-based hydrogel containing Protium spruceanum extract and mupirocin.

Figure 6

FTIR spectra for mupirocin, extract and nanoemulsion-based hydrogel with and without mupirocin and extract.

Figure 7

Efficiency of the nanoemulsion-based hydrogel containing Protium spruceanum extract and mupirocin in inhibiting biofilm formation. Percentage of biofilm inhibition related to untreated Staphylococcus aureus (A) and MRSA (B). Microscopy images with DAPI (C), Gram (D) stains, and scanning electron microscope (E). (*) denotes a significant difference compared to the untreated cells (p ≤ 0.05), as determined by one-way ANOVA, followed by Dunnett’s post-test.

Figure 8

Macroscopic evaluation of the irritating potential of nanoemulsion-based hydrogel using the HET-CAM methodology. CN: Negative control; CP: positive Control; NG: nanoemulsion-based hydrogel.