Efficient Recovery of Collagen from Tannery Waste Materials and Its Integration into Functional Hydrogel Systems

The development of multifunctional, mechanically robust, and sustainable hydrogels from renewable biomaterials has attracted increasing attention for advanced biomedical applications; however, achieving an optimal balance between mechanical stability, biofunctionality, and infection control remains challenging. In this work, collagen (COL) extracted from raw trimming wastes from a tannery is used to fabricate COL/PAA/Fe composite hydrogels via the ammonium persulfate (APS)-initiated polymerization of acrylic acid (AA) coupled with Fe³⁺-mediated coordination cross-linking. The resulting hydrogel network is stabilized by synergistic COL-poly(acrylic acid) (PAA) hydrogen bonding and dynamic Fe³⁺-carboxylate coordination, imparting enhanced mechanical strength and elasticity. The optimized hydrogel exhibited maximum tensile and compressive strengths of ~0.176 MPa at 751% elongation and ~1.945 MPa at a strain of 80%, respectively. In addition, a high ionic conductivity of 4.11 S·m^-1 is achieved, enabling structural integrity under deformation and suitability for flexible electronic interfaces. The prepared hydrogel also displayed rapid autonomous self-healing behavior and substantial antibacterial properties against both Gram-positive and Gram-negative bacteria. Overall, COL is employed herein as a sustainable precursor, highlighting an eco-conscious approach to biomaterial design. This work presents a versatile strategy for producing mechanically stable and biofunctional hydrogels with strong potential for wound dressing, tissue engineering, and injectable biomedical applications.