Phenylboronic acid-functionalized copper nanoclusters with sensitivity and selectivity for the ratiometric detection of luteolin.

A desirable ratiometric fluorescent probe was designed by using 3-carboxyphenylboronic acid functionalized polyethyleneimine ethoxylated modified copper nanoclusters (CPBA@PEI-CuNCs) for detecting luteolin (LTL, cis-diols structure) with sensitivity and selectivity. Characterization techniques were carried out with the TEM, PSD, FT-IR, XPS and XRD, confirming its successful formation with a quantum yield of 40.49 %. As the optimal excitation wavelength at 386 nm, the fluorescence intensity was detected by fluorophotometer. Meanwhile, the nanoprobe has two emission wavelengths 396 and 473 nm. According to the fluorescence quenching intensity ratio (F₄₇₃/F₃₉₆), the LOD reached as low as 1.22 nM within the range from 0.11 to 600 μM. The CPBA@PEI-CuNCs exhibited pH-controlled, covalent, and reversible binding properties. Using PEI capped by CuNCs, cytotoxicity is reduced for potential treatment purposes. Additionally, the developed probe was used for LTL detection, HepG2 cell imaging and pH-responsive drug delivery in real samples with carrot leaves, peanut shells, and perilla leaves samples. CPBA@PEI-CuNCs demonstrated repeatability and reproducibility, making it a cost-effective and practical tool for fluorescence analysis in detection.