PSI - Issue 52

Dita Puspitasari et al. / Procedia Structural Integrity 52 (2024) 410–417 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

411

2

1. Introduction Diabetes mellitus (DM) has emerged as a global epidemic and is the fastest-growing disease of the 21 st century, and patients with DM have a 25% risk of developing diabetic foot ulcers (DFU) and/or foot soft tissue injuries as reported by International Diabetes Federation (2021) and Cardoso et al. (2019). Diabetic and biochemical disturbances lead to slow wound healing processes and the risk of foot amputation therefore early treatment is very important. One possible treatment for DFU that is in the early stage of development is the use of wound dressings or scaffolds as it will relieve symptoms, protects wounds, and promotes healing (Hilton et al. (2004)). Appropriate dressings such as hydrogels should be selected to protect against bacterial infection, maintain a moist environment, facilitate epidermal transitions, allow gas exchange, are non-toxic, non-allergenic, and have good mechanical properties. The high-water content makes hydrogels biocompatible and a good candidate for DFU treatment. A sericin-based hydrogel is a potential material for the DFU scaffold as sericin is reported by Kunz et. al (2016) to have promising biological activities and can be isolated from silkworm cocoons. Sericin has antioxidant properties, promotes collagen formation, anti-inflammatory and antimicrobial properties, excellent swelling, high porosity, pH-responsive rupture, excellent adhesion, and cytocompatibility (Zhang et al. (2019)). Pure sericin has to be composited with other polymers (such as polyvinyl alcohol/PVA) to increase stability as hydrogel tends to have poor hydrogel shape retention and relatively poor mechanical properties (Ekasurya et. al (2023)). Therapeutic reagents, which are moringa leaf extract ( Moringa oleifera/ MOL) are encapsulated to improve the effectiveness of wound healing. MOL has been reported to increase the proliferation, survival, and migration of human skin fibroblasts. One of the components of MOL is vicenin-2, which can induce the wound-healing process. MOL also contains multiple antioxidants, anticancer, anti-inflammatory, and most importantly antidiabetic activities (Muhammad et al. (2013), Kasolo et al. (2010), Marrufo et al. (2013)). Pore sizes and interconnectivity, for example, can either directly or indirectly influence the mechanical and biological properties of scaffold, making the physical architecture of the scaffold just as significant as its chemical composition (Bai et al. (2010)). However, the mechanical properties of the hydrogel are crucial, especially for applications where motion and bending regularly occur, due to mechanical failure that would result in nutrient loss and wound exposure that would result in infection. Mechanical properties including stiffness, stretchability, and compressibility should be considered based on the types and locations of the wounds. Porosity, low material content, and swelling properties can all result in mechanical deformation. Therefore, compositing hydrogel will consequently create hydrogels with excellent mechanical tolerance (Fan et al. (2021)). Previous research has indicated that wound healing scaffolds with a porosity range of 60-90% are appropriate due to their ability to allow for cell activity, oxygen and nutrient exchange, and the production of a new extracellular matrix (ECM) in the wound area (Nosrati et al. (2021) and (Annabi, et al. (2010)). Hence it is important the resulted sericin PVA hydrogel has such high degree of porosity. However, it is challenging to maintain the mechanical stability of hydrogels while achieving high porosity (Annabi, et al. (2010)). One way to address this issue is to develop hyperelastic hydrogels that can withstand large deformations without undergoing plastic deformation. Therefore, a compression test was performed in this research. The computed tomography (CT) based test, the micro-CT test, was also done to provide the 3D architecture of the scaffold (Cengiz et al. (2018)). Hyperelastic hydrogels can provide the desired combination of high porosity and mechanical stability that is attractive for tissue engineering applications (Fray et al. (2021)). In this study, we investigated the hyperelasticity of sericin/PVA hydrogels using a combination of volumetric compression and tensile tests. The material model constants were determined from the experimental data, and finite element analysis (FEA) was used to confirm the validity of the hyperelastic behavior of the hydrogel. The results of this study provide valuable insights into the mechanical properties of PVA/sericin hydrogels, which could be used to design effective and safe scaffolds for tissue engineering applications. 2. Methods 2.1. Hydrogel Preparation The first stage of the hydrogel preparation is to extract sericin from the fibroin which is called the degumming process. The cocoon was washed and cut to smaller sizes and autoclaved for 30 minutes at 121  C. The liquid sericin is then stored in the freezer for the freeze-drying step to acquire the sericin powder. Next, MOL is extracted by using