From Coffee Waste to Bioactive Hydrogels: In Situ Antioxidant Functionalization of Bacterial Cellulose During Biosynthesis

Bacterial cellulose (BC) is a highly biocompatible nanofibrillar hydrogel widely explored for wound healing and tissue engineering; however, its intrinsic lack of bioactivity limits its use in advanced regenerative applications. Here, we report a one-step biosynthetic strategy that employs spent coffee grounds (SCG) extract as a dual-function cultivation medium, enabling simultaneous BC production and in situ biofunctionalization. The SCG extract fully replaced glucose in Hestrin-Schramm medium, providing fermentable sugars together with naturally occurring bioactive compounds that support cellulose biosynthesis by Komagataeibacter xylinus at a level comparable to that achieved with glucose-based cultivation. The resulting SCG-modified BC (SCG-BC) maintained a continuous nanofibrillar network while exhibiting altered supramolecular organization, including changes in molecular weight, swelling behavior, and hydrogel mechanics. Importantly, SCG-BC displayed strong and sustained antioxidant activity (200.23 ± 59.14 mg TE g-1), indicating stable incorporation of redox-active SCG-derived constituents and limited leaching under aqueous conditions. Biological evaluation demonstrated enhanced metabolic activity of human Wharton's jelly-derived mesenchymal stromal cells and dermal fibroblasts on SCG-BC compared with native BC, while supporting cell viability under direct-contact conditions. An in vivo-like assessment using the quail chorioallantoic membrane model revealed a modulated angiogenic response characterized by altered vessel density and branching without suppression of overall vascular development. Collectively, these results demonstrate that SCG-derived components can be integrated during bacterial cellulose biosynthesis to generate structurally intact, antioxidant-active, and biofunctional hydrogels while enabling sustainable utilization of an agro-industrial waste stream. This approach establishes a structure-bioactivity framework for engineering multifunctional BC-based biomaterials for skin-contact and wound-healing applications.