Lignin-Based Fluorescent Polymers: From Aggregation-Induced Emission Mechanism to Intelligent Bone Regeneration.

Lignin's intrinsic fluorescence and bioactivities (antioxidant, antibacterial, photoprotective) arise directly from its polyphenolic macromolecular architecture. This review critically integrates lignin-based fluorescent polymers for intelligent bone regeneration, bridging lignin photophysics and tissue engineering. We dissect the macromolecular origins of lignin's biological modalities and its aggregation-induced emission (AIE) behavior, where clustering of phenylpropanoid units transforms concentration quenching into a luminescent design advantage. Synthetic strategies that employ lignin as macromonomers, initiators, and crosslinkers to fabricate fluorescent polymers with tunable optics and preserved bioactivity are surveyed. We highlight two emerging applications: non-invasive, real-time tracing of scaffold degradation via intrinsic fluorescence, and integrated theranostics that synergize antibacterial defense, oxidative stress modulation, and pro-osteogenic induction within a single macromolecular system. Critically, we identify five translational bottlenecks-heterogeneity-driven photophysical variability, insufficient quantum yield, long-term chromophore biosafety, multifunctionality‑processability trade-offs, and batch‑to‑batch fluorescence inconsistency-and propose chemical and processing strategies to overcome them. By merging lignin macromolecular chemistry, fluorescence photophysics, and bone biology, we position lignin-based fluorescent polymers as a distinct bioactive class where therapeutic function is programmed into the polymer backbone, offering a promising paradigm for macromolecular design.