Keywords
silver nanoparticles
hydrogel
Citrus limon
Curcuma longa
Hymenocardia acida
antibacterial
anti-inflammatory
antioxidant
wound healing.
How to Cite
Abstract
Introduction
Chronic skin wounds, characterized by impaired healing exceeding six weeks, create a significant global socio-economic burden driven by reactive oxygen species (ROS) overproduction, persistent microbial infection, and sustained pro-inflammatory signaling. Although plant-derived biogenic silver nanoparticles (AgNPs) exhibit multifunctional biological properties, hydrogels incorporating AgNPs synthesized simultaneously from multiple Congolese plant species remain largely underinvestigated.
Purpose
This study aimed to formulate, physically characterize, and biologically evaluate a Carbopol 940–based hydrogel incorporating biogenic AgNPs synthesized from Citrus limon, Curcuma longa, and Hymenocardia acida extracts in a 1:1:1 mass ratio for chronic wound management.
Methods
Biogenic AgNPs were synthesized via optimized green protocols and characterized using UV-Vis spectrophotometry (200–800 nm) and dynamic light scattering (DLS) for particle size, polydispersity index (PDI), and zeta potential (ZP). Six Carbopol 940 hydrogel formulations (F1–F6) incorporating varying AgNP concentrations (0–1000 µg/mL per plant) were evaluated for viscosity, pH, thermal gel transition, and 14-day pH stability. Antibacterial activity was assessed via liquid microdilution (ISO 20776-1) against Staphylococcus aureus (ATCC 29213), Escherichia coli (ATCC 25922), and Pseudomonas aeruginosa (ATCC 27853) and confirmed by disk diffusion. Anti-inflammatory activity was evaluated using the heat-induced egg albumin denaturation assay (IC₅₀), while free-radical scavenging was quantified using ABTS and DPPH assays. Non-parametric Kruskal–Wallis tests and Dunn’s post-hoc comparisons (α= 0.05) were performed.
Results
UV-Vis spectra confirmed AgNP formation with surface plasmon resonance peaks at 422 nm (C. limon), 448 nm (C. longa), and 426 nm (H. acida). DLS showed hydrodynamic diameters of 50 ± 23 nm (PDI = 0.39, ZP = -32.23 mV) for C. limon, 47 ± 4.04 nm (PDI = 0.29, ZP = -35.59 mV) for C. longa, and 54.66 ± 15.94 nm (PDI = 0.26, ZP = -30.22 mV) for H. acida. The optimized hydrogel (1.5% Carbopol 940, 1000 µg/mL AgNPs) exhibited a stable pH (5.83 ± 0.12) and consistent viscosity (197.9 mPa·s; 98.9% stability over 14 days). It demonstrated a broad-spectrum minimum inhibitory concentration (MIC) of 125 µg/mL across all strains, with inhibition zones of 20.0 mm (S. aureus), 22.0 mm (E. coli), and 24.0 mm (P. aeruginosa). Significant anti-inflammatory (IC₅₀= 17.55 µg/mL) and antioxidant activities (ABTS IC₅₀= 155.50 µg/mL; DPPH IC₅₀= 126.70 µg/mL) were observed (p < 0.05).
Conclusion
A stable biogenic AgNP-loaded hydrogel combining extracts from three Congolese medicinal plants was successfully developed. The formulation demonstrated potent in vitro antibacterial, anti-inflammatory, and radical-scavenging properties, supporting its potential as an advanced topical dressing for chronic wound healing.
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