Ratiometric fluorescence detection of amikacin and neomycin in biological samples using Eu(III)-functionalized hydrogen-bonded organic frameworks

Individualized dosing of amikacin (AMK) and neomycin (NEO) guided by therapeutic drug monitoring (TDM) is critical for minimizing toxicity and optimizing clinical efficacy. Herein, a novel europium-functionalized hydrogen-bonded organic framework (Eu@HOF) was fabricated from 5-boronoisophthalic acid (5-bop) and melamine (MA), followed by post-synthetic doping of Eu³⁺. Benefiting from the antenna-sensitized luminescence of Eu³⁺, Eu@HOF displays dual emission at 422 nm (ligand-centered MA emission) and 617 nm (⁵D₀→⁷F₂ transition of Eu³⁺), enabling a self-calibrating ratiometric strategy. Upon the addition of AMK or NEO, the fluorescence intensity ratio (F₄₂₂/F₆₁₇) increased markedly. Mechanistic analysis suggested that binding of the antibiotics to the boronic acid sites of 5-bop partially interrupts the antenna-mediated energy transfer to Eu³⁺ and redistributes the excitation energy toward the 422 nm emission, whereas a reductive photoinduced electron transfer from the bound antibiotics shortens the 422 nm lifetime. Among 15 antibiotics tested, only AMK and NEO increased the ratio, whereas kanamycin and nitrofurazone markedly decreased it. The sensor was largely unaffected by common inorganic ions, biological small molecules and amino acids, and discriminated binary AMK/NEO mixtures at a fixed total concentration. Linear ranges of 5-200 µmol·L^-1 for AMK and 5-140 µmol·L^-1 for NEO were achieved. Eu@HOF was applied to quantify AMK and NEO in spiked human plasma and urine with satisfactory recoveries, indicating its potential for TDM-oriented detection of aminoglycosides, subject to further validation at clinically relevant concentrations.