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Abstract INTRODUCTION: Ruthenium metallocomplexes are promising candidates for anti-tumour therapy, which can be efficient even against tumours that are resistant to cisplatin. Cyclopentadienylbis(triphenylphosphine)ruthenium(II) chloride ([Ru(η5-C5H5)(PPh3)2Cl], RuCp in the text), as reported previously by us, presented in vitro significant cytotoxicity properties against several types of cancer cell lines.
OBJECTIVES: To study the possibility for detection of metabolized ruthenium-based metallodrug in patient´s urine and other body fluids by matrix-assisted laser desorption and ionization mass spectrometry (MALDI MS) without purification.
METHODS: RuCp was synthesized and characterized by common spectroscopic techniques. Mass spectra were acquired on the Bruker Autoflex Max MALDI TOF/TOF device in the positive and negative ion mode. Various concentrations of RuCp dissolved in 1.5 M NaCl were applied on the stainless steel MALDI target without matrix, or with either α-cyano-hydroxycinnamic acid (CHCA) or 2,5-dihydroxybenzoic acid (DHB), both at 10 mg/mL in 50 % acetonitrile and 0.05 % trifluoroacetic acid. In additional experiments, urine samples were analyzed when spiked with various concentrations of RuCp.
RESULTS: In the presence of 1.5 M NaCl, i.e. under physiological solutions, RuCp yields various signals in the MALDI TOF mass spectra, both in the positive and in the negative ion mode. Ions related to the Ru-complex were generated by the loss of ligands (or ligand fragments), followed by hydrolysis. Since photoactive, RuCp can be detected even without organic matrix (LDI mass spectra), but in this case, the extent of fragmentation was increased when compared to the spectra acquired with the matrix. In positive ion mode and in all spectra, the fragment at the position m/z 429.3 was detectable, which corresponds to the species generated by the loss of a triphenylphosphine group and a chloride ion. Additionally, in the presence of NaCl, these species were detected below 4.7 nM concentration.
CONCLUSION: We have shown that very low concentrations of RuCp potential metabolites can be detected in the presence of physiologically relevant concentrations of NaCl, without the necessity of further separation. Also, structural analysis of a metabolite is possible, which makes this approach potentially useful in clinics as the method for monitoring the effect of patient´s therapy with metallodrugs.
Acknowledgements: We acknowledge FCT for funding through the CQM PEst-OE/QUI/UI0674/2019, IDR and Madeira 14-20 Program through the project PROEQUIPRAM – Reforço do Investimento em Equipamentos e Infraestruturas Científicas na RAM – (M1420-01-0145-FEDER-000008) and ARDITI – Agência Regional para o Desenvolvimento da Investigação Tecnologia e Inovação – through the project M1420-01-0145-FEDER-000005 – CQM+ (Madeira 14-20 Program). |
= Discovery stage.
= Translation stage.
= Clinically available.
