Injectable gelatin/modified starch waste hydrogels containing metal-phenolic network derived from phenol-rich spent...

Injectable hydrogels hold promise for drug delivery and biomedical applications but often lack multifunctional properties such as antibacterial activity, self-adhesion, and controlled drug release. This study developed a multifunctional gelatin-based hydrogel using modified cassava starch waste (CSW) and a metal-phenolic complex from spent coffee grounds (ex-SCG). The CSW was used to prepare aldehyde starch (DAS), while ferric ions formed metal-ligand bonds with phenolic compounds extracted from ex-SCG. The injectable hydrogel's properties were evaluated based on metal coordination complex with Fe³⁺ (ex-SCG-Fe³⁺) content. The presence of 1 % ex-SCG-Fe³⁺ in the gelatin/DAS hydrogel exhibited a minimum inhibitory concentration against both gram-positive and gram-negative bacteria. The adhesive strength of the samples increased from 1.44 ± 0.45 kPa to 6.50 ± 0.12 kPa with the addition of ex-SCG-Fe³⁺ ranging from 0 to 3 %. The gelatin/DAS hydrogel containing ex-SCG-Fe³⁺ exhibited better pH-responsive control of drug release compared to the neat gelatin/DAS hydrogel. Additionally, it demonstrated self-healing ability. The presence of metronidazole (MTZ) as a model drug in the gelatin/DAS hydrogel containing ex-SCG-Fe³⁺ enhanced antibacterial activities but slightly decreased mechanical properties. The obtained injectable hydrogel presents a promising approach, utilizing food by-products as a beneficial material for medical applications.