Electroactive collagen nanofibrous scaffolds stabilized with polyphenols, dopamine, and reduced graphene oxide for...

Electrospun scaffolds intended for post-resection bone reconstruction in osteosarcoma must combine ECM-mimetic architecture with sustained resistance to infection, oxidative stress, and premature functional depletion. Here, collagen/poly(ε-caprolactone) (COL/PCL) nanofibrous mats were functionalized with condensed tannins (10-20 wt%) and dopamine-functionalized reduced graphene oxide (rGO) to generate antioxidant, antibacterial, and electroactive interfaces. All formulations produced continuous bead-free fibers, while tannins modestly increased diameter and polydispersity and rGO induced a larger diameter shift and broader distributions. Dope rheology revealed enhanced shear-thinning behavior and increased consistency upon tannin addition, further reinforced by rGO, consistent with supramolecular structuring and nanofiller-mediated network formation. Tannins markedly improved wettability (water contact angle down to 59 °) and boosted antioxidant capacity (ORAC/ABTS/DPPH), whereas dopamine-rGO further increased ORAC/DPPH while suppressing tannin burst release and lowering cumulative polyphenol release, supporting interfacial immobilization and barrier-controlled transport. Degradation in PBS and collagenase was significantly slowed by tannins and further stabilized by dopamine-rGO, with kinetic fitting indicating multi-regime behavior and reduced early/late-stage erosion rates. Electrochemical impedance spectroscopy showed reduced impedance with rGO, and apparent conductivity was recovered to near-control levels. Biological validation demonstrated near-complete antibacterial activity against E. coli and S. aureus (up to 99%), low hemolysis (1-1.6%), and selective reduction of U2OS osteosarcoma viability in dopamine-rGO scaffolds while maintaining high viability in Jurkat, U937, and HeLa cells. These results position dopamine-rGO/tannin-functionalized COL/PCL scaffolds as promising multifunctional platforms for infection-resistant, electroactive, and structurally stable bone regeneration in orthopedic oncology applications.