Multifunctional Vitamin B₁-Derived Fluorescent Copper Nanoclusters for Efficient Maize Protoplast Transformation

Fluorescent copper nanoclusters are promising functional nanomaterials; however, controlling their redox behavior through ligand engineering remains challenging. Herein, a multifunctional Vitamin B₁-derived fluorescent copper nanohybrid system was synthesized by a simple one-pot method, where Vitamin B₁ served as both a reducing and stabilizing agent. Spectroscopic and structural characterization supported the formation of ligand-stabilized fluorescent ultrasmall copper species exhibiting blue emission at 465 nm with a quantum yield of 5.7%. The B₁-Cu nanohybrid system displayed pronounced environment-dependent dual redox activity. ORAC analysis revealed a Trolox-equivalent antioxidant capacity of 229.2 ± 5.8 µM TE, compared with 28.1 ± 4.3 µM TE for pure Vitamin B₁, while the ABTS assay yielded an IC₅₀ value of 14.4 ± 0.4 µM, representing an approximately fivefold improvement over Vitamin B₁ (73.7 ± 1.9 µM). In addition, the material exhibited pH-dependent peroxidase-like activity, demonstrating its nanozyme functionality. Biological validation in maize protoplasts showed concentration-dependent intracellular ROS regulation, a pronounced hormetic response, and up to 83% higher GFP-mediated transformation efficiency than the untreated control. These findings demonstrate that ligand-directed modulation of fluorescent copper nanoclusters provides an effective strategy for engineering multifunctional redox-active nanohybrid systems for plant biotechnology and other redox-regulated biointerface applications.