Surface engineering of 3D-printed PLA scaffolds via γ-ray-induced acrylic acid grafting: pH-responsiveness and antimicrobial properties

Additive manufacturing is enabling unprecedented control over scaffold architecture for biomedical applications, yet the limited chemical functionality and surface responsiveness of commonly printed thermoplastics remain a major bottleneck. Here, we present a hybrid strategy that combines extrusion-based 3D printing of poly(lactic acid) (PLA) scaffolds with γ-ray–induced graft polymerization of acrylic acid (AAc) to obtain pH-responsive and antibacterial 4D scaffolds. 3D patterned PLA scaffolds were functionalized via γ-irradiation using pre-irradiation and direct grafting protocols within sterilization-relevant dose ranges. PolyAAc nanobrushes were successfully grafted onto the scaffold strands while preserving the original 3D architecture when grafting conditions were optimized. Direct γ-ray grafting in ethanol at 10 kGy provided superior reproducibility, scaffold stability, and process sustainability compared with pre-irradiation methods. The grafting degree was a key parameter controlling performance: grafting levels of ≈10% conferred reversible pH-triggered swelling and a hydrogel-like surface while maintaining mechanical integrity and excellent compatibility with human cells, whereas higher grafting levels induced excessive swelling and scaffold delamination. PolyAAc grafting further enabled the incorporation of benzalkonium chloride and chlorhexidine, imparting strong antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa . Overall, this work demonstrates a scalable route to engineer multifunctional, stimuli-responsive hybrid scaffolds by integrating 3D printing with radiation chemistry.