Graphene-Modified Polycaprolactone Nanofibers for Biomedical Applications: Enhancing Mechanical Strength and...

Electrospun nanofiber scaffolds met a pressing need for degradable matrices that matched the architecture and mechanics of soft tissues, yet neat poly(ε-caprolactone) (PCL) fibers often exhibited low surface energy, modest stiffness, and a loss of strength after sterilization and hydration. Graphene additives were expected to provide interfacial reinforcement and wettability improvements, but the effects of specific functional groups at low loading and under clinically relevant conditioning conditions had not been clarified. This study aimed to engineer sterilization-resistant, water-stable PCL scaffolds by comparing carboxyl- and hydroxyl-functionalized graphene (CFG and HFG) and defining an operating window via response surface methodology. PCL was electrospun with 0.5-2.0 wt% CFG or HFG while varying voltage; dispersion and chemistry were verified by FTIR and Raman mapping, thermal behavior by DSC/TGA, mechanics by tensile and DMA including cyclic loading, stability by EtO and γ sterilization with wet testing, surface energetics by contact angles and Owens-Wendt analysis, protein adsorption by BSA/fibronectin assays, cytocompatibility by human dermal fibroblasts, and aging by PBS degradation with GPC. The 1 wt% composites increased ultimate tensile strength by ~45%-55% and modulus by ~40%-55% relative to neat PCL, with modest reductions in elongation; storage modulus increased across -20°C to 60°C, and the composite retained ~98% stiffness after 50 cycles compared with ~90% for PCL. After γ-sterilization, strength retention was ~90%-92% for composites versus ~80% for PCL; wet-state modulus retention approached ~95%. Tc shifted upward by 2°C-3°C and crystallinity increase by ~5%-8%, while TGA showed a ~10°C onset increase; Raman maps confirmed uniform dispersion with $I_D/I_G$  ≈ 1.1 (CFG) and ≈1.0 (HFG). Contact angle fell from ~130° (PCL) to ~90°-95°, fibronectin adsorption increased and correlated with Day-7 viability (R ≈ 0.95), hemolysis stayed near 1%-2%, and bacterial attachment decreased to ~70%-80% of PCL. Response-surface analysis identified a practical region around 1.2-1.3 wt% graphene and 16-18 kV that balanced strength and sterilization retention. These findings supported use in soft-tissue scaffolds requiring robust handling and rapid cell coverage, and suggested extension to scale-up studies and in vivo validation, including sterilization dose mapping and sustained-release add-ons.