*Article* **Gellan Gum Hydrogels Filled Edible Oil Microemulsion for Biomedical Materials: Phase Diagram, Mechanical Behavior, and In Vivo Studies**

**Muhammad Zulhelmi Muktar <sup>1</sup> , Muhammad Ameerul Amin Bakar <sup>2</sup> , Khairul Anuar Mat Amin 1,\* , Laili Che Rose <sup>1</sup> , Wan Iryani Wan Ismail <sup>1</sup> , Mohd Hasmizam Razali <sup>1</sup> , Saiful Izwan Abd Razak <sup>3</sup> and Marc in het Panhuis 4,\***


**Abstract:** The demand for wound care products, especially advanced and active wound care products is huge. In this study, gellan gum (GG) and virgin coconut oil (VCO) were utilized to develop microemulsion-based hydrogel for wound dressing materials. A ternary phase diagram was constructed to obtain an optimized ratio of VCO, water, and surfactant to produce VCO microemulsion. The VCO microemulsion was incorporated into gellan gum (GG) hydrogel (GVCO) and their chemical interaction, mechanical performance, physical properties, and thermal behavior were examined. The stress-at-break (σ) and Young's modulus (YM) of GVCO hydrogel films were increased along with thermal behavior with the inclusion of VCO microemulsion. The swelling degree of GVCO hydrogel decreased as the VCO microemulsion increased and the water vapor transmission rate of GVCO hydrogels was comparable to commercial dressing in the range of 332–391 g m−<sup>2</sup> d −1 . The qualitative antibacterial activities do not show any inhibition against Gram-negative (*Escherichia coli* and *Klebsiella pneumoniae*) and Gram-positive (*Staphylococcus aureus* and *Bacillus subtilis*) bacteria. In vivo studies on Sprague–Dawley rats show the wound contraction of GVCO hydrogel is best (95 ± 2%) after the 14th day compared to a commercial dressing of Smith and Nephew Opsite post-op waterproof dressing, and this result is supported by the ultrasound images of wound skin and histological evaluation of the wound. The findings suggest that GVCO hydrogel has the potential to be developed as a biomedical material.

**Keywords:** gellan gum; virgin coconut oil; hydrogels; biomaterials; wound dressing
