Ryza I, Granata C, Ribeiro N, Nalewajko-Sieliwoniuk E, Kießling A, Hryniewicka M, Plass W, Godlewska-Żyłkiewicz B, Cabo Verde S, Milea D, and Gama S
The binding ability of 8-hydroxyquinoline-2-carboxylic acid (8-HQA) towards Ga 3+ has been investigated by ISEH + (Ion Selective Electrode, glass electrode) potentiometric and UV/Vis spectrophotometric titrations in KCl (aq) at I = 0.2 mol dm -3 and at T = 298.15 K. Further experiments were also performed adopting both the metal (with Fe 3+ as competing cation) and ligand-competition approaches (with EDTA as competing ligand). Results gave evidence of the formation of the [Ga(8-HQA)] + , [Ga(8-HQA)(OH)], [Ga(8-HQA)(OH) 2 ] - and [Ga(8-HQA) 2 ] - species, the latter being so far the most stable, as also confirmed by ESI-MS analysis. Experiments were also designed to determine the stability constants of the [Ga(EDTA)] - and [Ga(EDTA)(OH)] 2- in the above conditions. Due to the relevance of Ga 3+ hydrolysis in aqueous systems, literature data on this topic were collected and critically analyzed, providing equations for the calculation of mononuclear Ga 3+ hydrolysis constants at T = 298.15 K, in different ionic media, in the ionic strength range 0 < I / mol dm -3 ≤ 1.0. The synthesis and characterization (by ElectroSpray Ionization - Mass Spectrometry (ESI-MS), Attenuated Total Reflectance - Fourier-Transform Infrared Spectroscopy (ATR-FTIR) and ThermoGravimetric Analysis (TGA)) of Ga 3+ /8-HQA complexes were also performed, identifying [Ga(8-HQA) 2 ] - as the main isolated species, even in the solid state. Finally, the potential effects of 8-HQA and Ga 3+ /8-HQA complex towards human microbiota exposed to ionizing radiation were evaluated (namely Actinomyces viscosus, Streptococcus mutans, Streptococcus sobrinus, Pseudomonas putida, Pseudomonas fluorescens and Escherichia coli), as well as their anti-proliferative and anti-inflammatory properties. A radioprotective effect of Ga 3+ /8-HQA complex was observed on Actinomyces viscosus, while showing a potential radiosensitizing effect against Streptococcus mutans and Streptococcus sobrinus. No cytotoxicity on RAW264.7 murine macrophage cells was observed, neither for the free ligand or Ga 3+ /8-HQA complex. Nevertheless, Ga 3+ /8-HQA complex highlighted potential anti-inflammatory properties., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Sofia Gama reports financial support was provided by National Science Centre Poland. Demetrio Milea reports financial support was provided by Italian Ministry of University and Research. Sandra Cabo Verde reports financial support was provided by Foundation for Science and Technology. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)