Target-Responsive Lanthanide Coordination Nanoparticles for Time-Resolved Photoluminescence and SERS Dual-Mode Biosensing

Lanthanide coordination nanoparticles (Ln-CNPs) have shown significant potential in optical biosensing. However, the conventional self-assembly of lanthanides and ligands generally produces large cross-linked coordination networks with uncontrollable morphologies and poor dispersibility. In this work, we developed a facile coordination-driven self-assembly strategy for preparing Ln-CNPs with tunable properties, demonstrating their exceptional utility in the dual-mode time-resolved photoluminescence (TRPL)/surface-enhanced Raman spectroscopy (SERS) detection of analytes in complex matrices. Specifically, a series of Ln-CNPs were prepared by the coordination-driven self-assembly of adenosine diphosphate (ADP) with Ln³⁺. The resulting Ln-CNPs exhibited a controllable morphology, excellent monodispersity, long-lived luminescence, and other functionalities. Notably, the luminescence of ADP-Eu and ADP-Tb CNPs remained detectable even at a delay time of 1 ms, making them ideal for TRPL biosensing; while ADP-Gd CNPs showed potential for magnetic resonance imaging. As a proof-of-concept for optical biosensing applications, we engineered a TRPL/SERS dual-mode platform leveraging the specific response of ADP-Eu CNPs to tetracycline (TC). TC binding to ADP-Eu CNPs induced up to 13-fold TRPL enhancement through the antenna effect, while unbound TC molecules enabled 10^-9 M-level SERS detection via plasmonic coupling. Quantitative cross-verification between TRPL and SERS significantly enhanced the determination accuracy. This dual-mode platform achieved 97.64-108.90% recoveries for TC detection in serum samples with <3.2% RSD. Our methodology establishes a generalizable paradigm for engineering multifunctional Ln-CNPs and further opens exciting avenues for the accurate detection of analytes in complex biological systems.