Comparative fluorimetric strategies for determination of landiolol hydrochloride using native fluorescence and green synthesized silver nanoparticles

Abstract This study introduces the first reported stepwise fluorimetric strategy for the sensitive and rapid determination of the ultra-short-acting β₁-blocker, landiolol hydrochloride. Initially, an environmentally benign method was developed by exploiting the drug’s native fluorescence in water (λ ex /λ em = 217/298 nm). While this cost-effective approach successfully utilized water as a green solvent, it demonstrated limited LOD of 32.57 ng/mL. To enhance fluorescence performance, various organic solvents were investigated, with acetonitrile providing the highest signal at λ ex /λ em = 222/300 nm and improving the LOD to 16.31 ng/mL. To enable ultra-trace clinical monitoring, a third “turn-on” method was developed using silver nanoparticles (AgNPs). By measuring fluorescence enhancement at λ ex /λ em = 260/524.6 nm upon interaction with landiolol, this platform amplifies the signal, achieving an outstanding LOD of 3.10 ng/mL. AgNPs were prepared using a green synthesis approach employing Aloe vera extract as a natural reducing and stabilizing agent in an aqueous medium avoiding using hazardous chemicals. Water was used throughout both nanoparticle preparation and the AgNP-enhanced determination, reinforcing the eco-friendly profile of the method. Unlike native fluorescence, the AgNP-assisted method enhances sensitivity through nanoparticle-mediated surface passivation, with a possible auxiliary contribution from resonance energy transfer (RET)-like processes. Selectivity is improved through preferential adsorption of landiolol on the AgNP surface and a large Stokes shift that minimizes interference from UV-absorbing matrix components. The resulting enhanced sensitivity and reduced matrix interference make this method a powerful tool for ultra-trace, selective, and sustainable determination of landiolol in pharmaceutical formulations and human plasma, demonstrating its suitability for routine quality control and bioanalytical applications.