The extracellular matrix (ECM) is a three-dimensional network that is found in all tissues and organs and is made up of macromolecules, primarily collagen, glycosaminoglycans, glycoproteins, growth factors, and other bioactive molecules that can affect the various functions of cells, like cell growth, survival, proliferation, morphological features, and migration [[1], [2], [3], [4]]. Due to these suitable features, there is a significant interest in employing tissue decellularization to generate ECM-based scaffolds [5,6]. Decellularized extracellular matrix is created by eliminating cells and other antigenic components, while retaining the majority of the extracellular matrix components and structure of native tissue [7]. Decellularized materials are made from natural tissues and organs using a variety of decellularization methods, primarily chemical, physical, biological, and combination methods [8,9]. Scaffolds made from the extracellular matrix (ECM) of different organs have become particularly appealing options among the other biomaterials because of their natural bioactivity and structural similarity to in vivo tissue, complex natural composition, three-dimensional structure, retention of growth factors, and bioactive properties, including stimulation of angiogenesis [10]. ECM-based materials are now being developed for different tissue engineering applications, like cartilage tissue engineering [11], corneal [12], and skin tissue engineering applications [13], in a variety of forms, such as patches [14,15], organoids [16], sponges [17], matrix powder [18] and hydrogels [10,19]. Recent work by Majedi et al., 2025 has reported a bilayer film made from decellularized amniotic membrane and a polymeric emulsion of polycarbonate urethane and silk for skin tissue engineering applications [13].

Umbilical cord (UC), taken from prenatal tissue, is often discarded as medical waste, making it a readily available human tissue source [20]. The umbilical cord serves as a nutritional bridge connecting maternal and newborn tissues and also has less ECM crosslinking and more immature collagen than adult tissues. Additionally, the unfavorable effects of age can be removed [21]. Notably, the umbilical cord is frequently utilized in regenerative medicine to isolate endothelial cells and mesenchymal stem cells. It can also be employed in the isolation of hyaluronic acid. Its remaining worth can be utilized by producing hydrogels from decellularized ECM. The motivation for the development of umbilical cord-based hydrogels for application in tissue engineering is due to the abundance of growth factors and young ECM.

Among the various natural and synthetic materials that can be mixed with solubilized ECM, chitosan has been selected in this work because of its biocompatibility and biodegradability [22,23]. Chitosan, a linear polysaccharide, is a type of polymer material formed as a result of the deacetylation of natural chitin [24]. Due to the abundance of -NH2 and -OH active groups in chitosan molecules [25,26], it is easy to combine them with ECM. Chitosan is very critical in tissue engineering applications because of its high hemostasis capability [27], biocompatibility, degradability, and wide range of antibacterial activity [28].

Hydrogels are 3D scaffolds with customizable stiffness and composition, enabling attachment and proliferation of many cell types [29]. Hydrogels are made up of at least 30 % water by weight, which guarantees that all cells receive enough nutrients and the elimination of waste products from cells [30,31]. Their unique qualities, like their absorbency and flexibility, make them perfect for using as scaffolds to support tissues and cells during regeneration [32]. ECM-based hydrogels from decellularized tissues have been shown to improve the retention and delivery of growth factors, along with supporting the viability and function of cells.

Human-derived ECM-based hydrogels could be used as an allograft to avoid immune reactions. Fabrication of hydrogels from different human tissues, like the lung [33], liver [34], and adipose [35] have been reported. Allografts of human origin are mostly prepared from cadavers [36]. But the donor tissue's age is uncontrollable in case of a cadaveric donor, due to which the ECM properties are affected, resulting in increased ECM-crosslinking with age [10]. Fetal or neonatal tissue has an extracellular matrix (ECM) made up of more immature collagen with fewer crosslinking than adult tissue, which allows for more effective tissue remodeling [37,38].

In this work, human umbilical cord tissue was decellularized using a newly established decellularization protocol. Agarose Gel electrophoresis experiment, DNA quantification by Nano-Drop Spectrophotometer, and various staining techniques and quantification assays were performed to confirm the efficiency of the decellularization procedure. Furthermore, ECM was solubilized using an acid-pepsin digestion approach to prepare DUC hydrogels. Then, ECM and chitosan solutions were prepared by mixing ECM with different percentages of chitosan solutions to fabricate DUC-CS hybrid hydrogels. These hydrogels were characterized by using various physical, chemical, and biological characterizations. The results showed that these hydrogels possessed good biocompatibility and could be used as a potential candidate for tissue engineering applications.