A formulation of fusidic acid-loaded hydrogel film was developed with different Aloe vera ratios and characterized in this study.
Method Article
A formulation of fusidic acid-loaded hydrogel film was developed with different Aloe vera ratios and characterized in this study.
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.
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 rates2,3. 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 effects6,7.
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 infections8,9. 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.
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
2. Determining the film thickness
3. Determining the swelling index

4. Water vapor permeability or occlusion test

5. Fourier transform infrared spectroscopy (FTIR)
6. Differential Scanning Calorimetry (DSC)
7. Drug release test
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 flexibility, leading to improperly formed films. The strong adhesion and elasticity of the films were due to the presence of sodium alginate and glycerin. The addition of Aloe vera did not alter the appearance but affected the viscosity of the solutions during preparation.
Thickness
The thickness results are presented in Table 1. The control sample A, which contained only alginate, had a thickness of 0.11 mm. As the proportion of Aloe vera increased in samples B and C, the film thickness increased, measuring 0.13 mm and 0.12 mm, respectively. However, sample D, which had the highest proportion of Aloe vera, had the thinnest film at 0.09 mm. Based on these results, it appears that the addition of Aloe vera may have some effect on the film thickness to a certain extent.
Swelling index
Assessing the capacity of hydrogels to absorb various liquids is a key aspect of this research. The focus is on understanding the ability of polymers to swell under different conditions. As illustrated in Figure 2, the swelling index results over time reveal the influence of varying Aloe vera concentrations on the water absorption capacity of alginate-based films. The film with 0% Aloe vera (A) exhibited the lowest swelling index after 24 h (364.8%). In contrast, samples with increasing Aloe vera content showed progressively higher swelling indices, with the 25:75 film (D) reaching the highest value of approximately 549%. These results indicate that the hydrophilic properties of Aloe vera play a significant role in enhancing the swelling behavior of the films. Figure 3 shows the hydrogel film before and after swelling.
Water vapor permeability or occlusion test
The water vapor permeability of the films was assessed by comparing the amount of water in a beaker with and without the films. According to the results shown in Table 2, the control sample with no Aloe vera showed no occlusion effect, while the other samples exhibited an increase in the occlusivity factor upon the addition of Aloe vera. Sample B had an occlusivity factor of 13.2, while samples C and D had the highest occlusivity factor of 20. This indicates that the addition of Aloe vera helped decrease the water vapor permeability (WVP) of the alginate films.
Structural analysis by FTIR
Figure 4 demonstrates the FTIR spectra of hydrogel formulations containing fusidic acid, along with the spectra of raw materials, including sodium alginate, Aloe vera, glycerin, and fusidic acid. The spectra of the hydrogel formulation show a broad absorption band around 3200-3400 cm−1 and a band at approximately 1636 cm−1, which correspond to the stretching of O-H groups attributed to sodium alginate, Aloe vera, and glycerin, as well as the asymmetric stretching vibration of alginate COO groups, respectively13. Additionally, the absorption peak at around 1330-1340 cm−1 reflects the bending vibration of the C-H group, while the peak at 1171 cm−1 is related to the C-O stretching vibration of sodium alginate.
Differential Scanning Calorimetry (DSC)
Differential Scanning Calorimetry (DSC) was used to analyze the thermal behavior of sodium alginate, Aloe vera, pure fusidic acid, and drug-loaded hydrogel film. The thermogram of sodium alginate showed an endothermic peak at approximately 132 °C (as demonstrated in Figure 5). On the other hand, the Aloe vera thermogram displayed multiple peaks. The DSC analysis of pure fusidic acid showed a sharp and well-defined endothermic peak at 184.5 °C. For the drug-loaded hydrogel film, only a broad peak was detected between 103 °C and 170 °C, lacking any melting peaks for the components or the drug.
Drug release
The in vitro drug release was examined for all samples over 24 h using PBS solution at pH 7.4. The film samples showed a gradual release of the drug, likely due to the compact hydrogel structure. The samples containing Aloe vera displayed 89.7% to 93% of fusidic acid release within 12 h, while the control film with no Aloe vera released all of the drugs after 12 h, as shown in Figure 6. Different release kinetic models were evaluated for the fusidic acid. The results are presented in Table 3. The drug release results were best fitted with the zero-order release model, which exhibited the highest R2 values.

Figure 1: Physical appearance of fusidic acid-loaded hydrogel films. Photographs of fusidic acid-loaded alginate/Aloe vera hydrogel films at various ratios: (A) 100:0, (B) 90:10, (C) 80:20, and (D) 75:25, observed under 4x magnification. Please click here to view a larger version of this figure.

Figure 2: Swelling index of hydrogel films. The swelling index percentage of fusidic acid-loaded alginate/Aloe vera hydrogel films at different ratios: (A) 100:0, (B) 90:10, (C) 80:20, and (D) 75:25. The error bars represent standard deviation (SD), n = 3. Please click here to view a larger version of this figure.

Figure 3: Hydrogel film before and after swelling. Comparison of a hydrogel film (A) before and (B) after swelling, illustrating the changes in physical appearance due to the swelling process. Please click here to view a larger version of this figure.

Figure 4: FTIR spectrum analysis. FTIR spectra of various components and formulations: (A) fusidic acid, (B) sodium alginate, (C) Aloe vera, (D) glycerin, (E) formulation 100:0, (F) formulation 90:10, (G) formulation 80:20, and (H) formulation 75:25. Please click here to view a larger version of this figure.

Figure 5: DSC Thermogram of hydrogel formulations. Differential scanning calorimetry (DSC) thermograms of the hydrogel formulation, fusidic acid, alginate, and Aloe vera, showing thermal properties and transitions. Please click here to view a larger version of this figure.

Figure 6: Cumulative drug release from hydrogel films. Cumulative drug release from fusidic acid-loaded alginate/Aloe vera hydrogel films at different ratios: (A) 100:0, (B) 90:10, (C) 80:20, and (D) 75:25. The error bars represent standard deviation (SD), with n = 3. Please click here to view a larger version of this figure.
| Film samples | Thickness (mm) |
| A (100:0) | 0.11 ± 0.01 |
| B (90:10) | 0.13 ± 0.01 |
| C (80:20) | 0.12 ± 0.01 |
| D (75:25) | 0.09 ± 0.01 |
Table 1: Thickness of hydrogel film formulations. Measurements of the thickness of various alginate/Aloe vera hydrogel film formulations, with n = 3.
| Samples | Reduction in water volume (mL) | Occlusivity factor |
| Control | 2.50 ± 0.00 | - |
| A (100:0) | 2.50 ± 0.41 | 0 |
| B (90:10) | 2.17 ± 0.24 | 13.2 ± 0.5 |
| C (80:20) | 2.00 ± 0.11 | 20.0 ± 0.3* |
| D (75:25) | 2.00 ± 0.02 | 20.0 ± 0.21* |
Table 2: Reduction in water volume and occlusivity factor. Data on the reduction in water volume (mL) and occlusivity factor of the alginate/Aloe vera hydrogel film formulations, with n = 3. *p≤ 0.005.
| Zero Order | First Order | Korsmeyer-Peppas | Higuchi | ||
| F1 (100:0) | R2 | 0.995 | 0.6607 | 0.9925 | 0.9142 |
| F2 (90:10) | R2 | 0.995 | 0.667 | 0.9917 | 0.9141 |
| F3 (80:20) | R2 | 0.995 | 0.6674 | 0.9917 | 0.9141 |
| F4 (75:25) | R2 | 0.995 | 0.6674 | 0.9917 | 0.9141 |
Table 3: Release kinetics of fusidic acid. Correlation coefficients and release kinetics of fusidic acid from the hydrogel formulations, demonstrating the mathematical models used in the analysis.
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 suits all applications. However, research indicated that the adhesive and mechanical properties of films are influenced by thickness, with thinner films potentially leading to faster water vapor transition rates and better maintenance of a moist environment for wound healing14.
The study on the swelling capacity of hydrogels is a key focus of research, as it aims to assess the ability of polymers to absorb different liquids. Findings show that the hydrophilic characteristics of Aloe vera significantly contribute to improving the films' swelling behavior. The increased swelling indices indicate that Aloe vera facilitated greater water absorption, possibly by retaining moisture and creating a hydrated gel-like structure within the film matrix15. The observed swelling behavior of the hydrogel films may be due to the polysaccharide content of Aloe vera. At low levels, polysaccharides may hinder the connection between alginate chains, resulting in a less compact structure and potentially less initial swelling. However, at higher concentrations, these polysaccharides can aid in cross-linking, creating a denser network capable of retaining more water and increasing the swelling index16.
An edible film's water vapor permeability (WVP) is determined by the proportion of hydrophilic and non-hydrophilic groups contained in the film. This ratio plays a major role in how the film matrix interacts with the molecules of water17. The incorporation of Aloe vera reduced the WVP of the alginate films. Similar results were obtained in another study investigating the effect of chitosan and Aloe vera extract concentrations on the physicochemical properties of chitosan biofilms, where a decrease in water vapor permeability was reported with the addition of Aloe vera18. The reduction of WVP may result from the interaction between the large-molecular-size polysaccharides found in Aloe vera and alginate, which minimizes the total intermolecular space available for water movement19. As a result, although the effect is insignificant, the hydrogel films incorporating Aloe vera demonstrated an enhanced occlusive effect compared to the control film. This can create a warmer and moist environment within the wound site, potentially aiding wound healing by reducing tissue necrosis and facilitating cell communication20.
All hydrogel film samples showed a gradual drug release, likely attributed to the compact structure of the hydrogels21. The results demonstrate that an increase in Aloe vera content leads to a minor slowing in drug release, promoting a prolonged drug release effect. This aligns with the findings of Mahmood et al., indicating that utilizing Aloe vera-based polymeric networks offers an effective method for achieving sustained drug delivery22. FTIR analysis is essential for rapidly and efficiently identifying encapsulated chemical molecules. It is particularly valuable for examining chemical alterations within polymers, such as changes in stretching or bending bands resulting from drug incorporation23. All peaks associated with fusidic acid were found to be absent in all fusidic acid-loaded hydrogels, indicating the successful incorporation of the fusidic acid into the hydrogels. According to the findings shown in Figure 4, the hydrogel film loaded with fusidic acid displayed a broad peak between 103 °C to 170 °C, with no evident components or drug melting peaks. This indicates that the drug and components were evenly distributed within the hydrogel at a molecular level, which suggests that the hydrogel system was successfully formed and that the ingredients were well incorporated into the cross-linked rigid polymer network of the hydrogel22. The release kinetic of fusidic acid was determined based on the highest regression coefficient (R2) values23. The findings of R2 values suggest that the zero-order model most accurately describes the release of fusidic acid from the polymer, indicating a consistent release rate independent of the remaining drug quantity. This is consistent with the known applications of zero-order kinetics in modified release systems, such as transdermal patches, where the drug diffuses through a polymer membrane at a constant rate. Zero-order drug delivery systems have the potential to improve patient compliance and reduce adverse side effects due to frequent dosing24,25. Cross-linked alginate/chitosan hydrogel films with 0.5 M of CaCl2 were reported to show zero-order release kinetic previously. Lowering the CaCl2 cross-linking resulted in shifting from zero order to the Korsmeyer-Peppas model26.
Limitations
While solvent casting and cross-linking with CaCl2 offer a simple approach to hydrogel film preparation, they have limitations. Factors such as CaCl2 concentration, alginate composition, and casting conditions can influence cross-linking while achieving precise control can be challenging. Excessive cross-linking with CaCl2 was reported to lead to brittle films prone to cracking or breaking. The mechanical properties (strength, elasticity) of the films might vary depending on the degree of cross-linking achieved, leading to inconsistency27,28. In conclusion, there are a number of limitations related to mechanical strength, water sensitivity, uniformity, processing conditions, adhesion, barrier properties, and environmental impact that should be carefully evaluated depending on the intended application of the films, even though solvent casting with alginate and Aloe vera offers advantages like biocompatibility and potential bioactivity. Furthermore, the solvent casting method's simplicity makes it a good choice for production on a lab scale. Therefore, in order to guarantee appropriate solvent evaporation and film formation over a greater surface area, scaling up can necessitate certain tools and adjustments.
The authors have nothing to disclose.
This study was supported by Princess Nourah bint Abdulrahman University Researchers Supporting Project number (PNURSP2024R30), Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia. This research was funded by the Researchers Supporting Project number (RSPD2024R811), King Saud University, Riyadh, Saudi Arabia.
| 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 |
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