Transferrin-stabilized bimetallic nanoclusters: Design of a new fluorescent biosensor to identify tryptophan metabolites

Turcsányi, Árpád and Juhász, Ádám and Csapó, Edit (2025) Transferrin-stabilized bimetallic nanoclusters: Design of a new fluorescent biosensor to identify tryptophan metabolites. MATERIALS TODAY CHEMISTRY, 47. No. 102835. ISSN 2468-5194

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Abstract

The determination of neuroactive molecules is an important task in the monitoring of patient health. In this work, a one-step, green preparation protocol has been newly developed to synthesize highly reddish-orangeemitting gold-silver bimetallic nanoclusters reduced and stabilized by transferrin protein (Tf-AuAg NCs). The fabrication route of these bimetallic NCs was optimized first based on different parameters (gold:silver ratio, transferrin and metal concentrations, temperature and synthesis time). The properties of the nanoclusters (NCs) having a controlled gold/silver ratio were thoroughly analyzed using multiple methods, focusing on their optical characteristics. The source and various characteristics (excitation, emission maximum, lifetime) of the emitting species were also determined. Additional quenching studies were performed using iodide, a well-known quencher of tryptophan, to check the effect on different emission peaks. This newly fabricated NCs can play an important role as a sensing agent. Thus, sensing measurements were conducted on tryptophan metabolites (kynurenine and serotonin pathway, a total of 15 molecules) in three different media (phosphate buffered saline (PBS), artificial cerebrospinal fluid (aCSF) and diluted human serum), determining the limit of detection for 3- hydroxyanthranilic acid at 0.55 and 0.32 μM in PBS and aCSF. This molecule is a fluorophore itself whose detection is problematic due to many interfering substances (for example anthranilic acid), while its selective enhancement distinct from other kynurenine pathway molecules can be used for determination at the NCs emission wavelength centered around 610 nm. Additional calorimetric studies were also performed to identify the interaction between the sensed molecule and the Tf-AuAg NCs.

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