Development and Characterization of Fusidic Acid-Loaded Alginate-Aloe vera Based Hydrogel Film

Summary

A formulation of fusidic acid-loaded hydrogel film was developed with different Aloe vera ratios and characterized in this study.

Abstract

A new fusidic acid-loaded hydrogel film was prepared via the solvent casting technique using alginate and Aloe vera. The hydrogel films were optimized using different ratios of sodium alginate, Aloe vera, and glycerin. The films containing 10% glycerin (w/w of alginate) exhibited the best appearance. Incorporating Aloe vera influenced the thickness, swelling behavior, water vapor permeability, and drug release profile of the hydrogel films. Higher Aloe vera content resulted in thicker films (up to a certain ratio), increased swelling, reduced water vapor permeability, and a prolonged drug release of up to 93% over 12 h. Fourier-transform infrared spectroscopy (FTIR) analysis confirmed the presence of key functional groups and the interaction between the hydrogel components. The study suggests that the combination of sodium alginate, Aloe vera, and glycerin can improve the mechanical properties and drug release profiles of hydrogel films, making them a promising option for enhanced topical drug delivery and wound healing applications.

Introduction

Fusidic acid is a potent steroidal antibiotic derived from Fusidium coccineum. It is widely used to treat staphylococcal skin infections and impetigo. This drug has high efficacy, even against antibiotic-resistant strains, and low toxicity, making it a suitable option for managing skin infections¹. Unlike other topical antibiotics, fusidic acid penetrates deeply into the skin, enhancing its antimicrobial effects, especially in areas where the skin's protective barrier is damaged. Its structure allows for versatile solubility characteristics, enabling widespread distribution throughout body tissues, which is further enhanced in its sodium fusidate form for better water solubility and penetration rates^2,3. Fusidic acid can be administered in various ways, including orally, intravenously, and topically, adapting to different treatment needs and making it a flexible choice for various infections⁴.

Hydrogels, with their high water content and biocompatibility, have emerged as innovative carriers for antibiotics in wound treatment, providing moisture retention, controlled drug release, and improved patient outcomes. They are made from natural or synthetic polymers like alginate, which is favored for its strong biocompatibility, affordability, and gelation properties that mimic natural tissue extracellular matrices⁵. Alginate-based hydrogels, in particular, offer a moist environment conducive to wound healing, do not adhere to the wound, and allow for easy removal, making them ideal for delivering bioactive substances and supporting tissue regeneration. The development of hydrogels encapsulating antibiotics represents a significant advancement in wound care, ensuring targeted drug delivery and sustained therapeutic effects^6,7.

The proposed fusidic acid-loaded alginate/Aloe vera hydrogel aims to overcome fusidic acid's solubility challenges and enhance its dermal penetration. Aloe vera, known for its skin-friendly, moisturizing, and antibacterial properties, also serves as a chemical penetration enhancer, potentially improving the efficacy of fusidic acid in treating skin infections^8,9. This innovative formulation leverages the synergistic effects of Aloe vera and alginate hydrogel to create a conducive healing environment, optimize drug delivery, and offer a promising solution for enhanced treatment of skin infections, making the most of fusidic acid's potent antimicrobial activity with improved delivery and healing outcomes¹⁰.

Protocol

The details of the reagents and equipment used in this study are listed in the Table of Materials.

1. Preparation of fusidic acid hydrogel films

1. Prepare solutions of sodium alginate (2.0% w/v) and Aloe vera (1.0% w/v) by dissolving them in distilled water.
2. Add 200 mg of fusidic acid to the sodium alginate solution and stir for 1 h.
3. Add glycerol to the alginate solution at concentrations of 10%, 12%, and 14% (w/w, based on the alginate mass).
4. Combine the alginate and Aloe vera solutions to achieve final alginate/Aloe vera ratios (v/v) of 100:0, 90:10, 80:20, and 75:25.
5. Cast 25 mL of each mixture into glass Petri dishes (100 mm x 20 mm) and leave to dry at room temperature (25 °C) and controlled humidity (50%) for 2 days.
6. Immerse the dried films into a calcium chloride (CaCl₂) aqueous solution (5.0% w/v) for 5 min to obtain the hydrogel films.
7. Wash the resulting films with distilled water and dry them at room temperature before use.

2. Determining the film thickness

1. Use a digital micrometer to measure the thickness of the film¹¹.
2. Take measurements at five distinct points across the film.
3. Record the measurements obtained from each point.
4. Calculate the average film thickness based on the measurements taken.

3. Determining the swelling index

1. Cut the film samples into 2 cm x 2 cm squares using a lab knife.
2. Weigh each sample accurately.
3. Soak the samples in PBS buffer (pH 6.8) at room temperature for 24 h.
4. Absorb any excess water on the film surface using filter paper.
5. Weigh the samples again.
6. Weigh the films at different time intervals. Calculate the swelling capacity using the following equation:
   
   NOTE: Wh represents the hydrated weight of the sample, and Wd corresponds to the dry weight of the sample.

4. Water vapor permeability or occlusion test

1. Cover the opening of a glass beaker containing 50 mL of water with filter paper¹¹.
2. Apply a film-forming solution to one of the papers and permit it to develop a film.
3. Store the beaker at room temperature and humidity.
4. Assess the film's permeability to water based on the decrease in water weight within the beaker.
5. To determine the evaluation of water vapor permeability for the prepared hydrogel film, use the following formula:
   
   NOTE: The occlusivity factor, F, measures the permeability of a film. It is determined by calculating the difference in water weight between a glass beaker covered with filter paper without a film and a glass beaker covered with filter paper coated with the film. A smaller occlusivity factor value indicates greater film permeability.

5. Fourier transform infrared spectroscopy (FTIR)

1. Place the hydrogel sample onto the ATR crystal of the FTIR spectroscopy machine.
2. Set the wavenumber range to 4000-400 cm⁻¹.
3. Set the scan rate to 60 scans per sample.
4. Set the resolution to 4 cm⁻¹.
5. Record an air background before each sample run.
6. Run the analysis for each hydrogel sample individually.
7. Analyze the FTIR spectra for each hydrogel sample to confirm functional groups and examine interactions among all components¹².
8. Repeat the analysis for raw Aloe vera, sodium alginate, glycerin, and fusidic acid separately.

6. Differential Scanning Calorimetry (DSC)

1. Use a commercially available thermal analysis instrument to acquire thermal profiles.
2. Craft the measurement samples from multiple circular pieces cut from the polymer film.
3. Investigate the temperature range from 25-230 °C.
4. Set the heating/cooling rate at 20 °C/min.
5. Carry out temperature and enthalpy calibration using standard indium with compatible software.

7. Drug release test

1. Prepare a solution of 50 mL PBS (pH = 7.4) as the dissolution medium.
2. Immerse the hydrogel films in PBS at 37 °C for 24 h while stirring at a rate of 50 rpm.
3. At predetermined intervals, collect 2 mL of the samples.
4. Dilute and filter the collected samples through a syringe filter.
5. Promptly replenish an equivalent volume of PBS.
6. Assess the concentrations of fusidic acid released using a UV spectrophotometer, measuring absorption at 285 nm.
7. Evaluate the release kinetics of fusidic acid using zero-order, first-order, Higuchi, and Korsmeyer-Peppas models⁴.

Results

Preparation of alginate/Aloe vera hydrogel film
Different ratios of sodium alginate, Aloe vera, and glycerin were used to prepare the formulation of hydrogel film. The final preparation and assessment of the formulations were carried out only with 10% glycerin (w/w of alginate). Figure 1 shows the hydrogel film with different Aloe vera ratios. This selection was made because other glycerin ratios did not provide the necessary adhesiveness and...

Discussion

Fusidic acid was incorporated in alginate hydrogel films with various ratios of Aloe vera and glycerin. The presence of Aloe vera did not affect the appearance, but a decrease in viscosity was observed in the solutions containing Aloe vera during preparation. The findings from thickness testing suggest that the inclusion of Aloe vera may have some impact on film thickness to a certain extent, but it is not considered significant. In general, there is not a single ideal thickness that s...

Materials

Name	Company	Catalog Number	Comments
Aloe vera	Local supplier, Kuala Lumpur, Malaysia		It was raw aloe vera bark and prepared the materials in our lab
Calcium Chloride	R&M Chemicals
Differential Scanning Calorimetry	Netzsch-Gruppe	DSC 300 Caliris
FTIR spectroscopy	Perkin Elmer	107914
Fusidic Acid	Sigma-Aldrich, St. Louis, MO, USA	PHR2810	certified reference material, pharmaceutical secondary standard
Glycerin	Sigma-Aldrich, St. Louis, MO, USA	PHR1020	United States Pharmacopeia (USP) Reference Standard
Micrometer Screw Gauge	Blomker Industries, Malaysia
NETZSCH proteus software	Netzsch-Gruppe	DSC 300 Caliris
Phosphate Buffer Saline	Sigma-Aldrich, St. Louis, MO, USA	P4417	Tablets
Sodium alginate	Sigma-Aldrich, St. Louis, MO, USA	W201502
thermal analysis instrument	NETZSCH	DSC Caliris
UV-SPECTROPHOTOMETER / UV LINE-9400	SECOMAM	/ 8512047