Abstract

The synthesis and chemical characterization of two trans platinum complexes, (1) trans-[PtCl₂NH₃(2-hydroxymethylpyridine)] and (2) trans-[PtCl₂NH₃(3-hydroxymethylpyridine)], are described. The structures and chemical behaviour of these compounds have been compared to those of their isomer (3) trans-[PtCl₂NH₃(4-hydroxymethylpyridine)] previously studied. X-ray structures of all of them were solved and some interesting differences were found. The values of the dihedral angle (85°, 57° and 42° for 1, 2 and 3, respectively) demonstrate how important is the position of substituent from a structural point of view. Studies of circular dichroism (CD), electrophoretic mobility (EM) in agarose gel and atomic force microscopy (AFM) showed differences in the modifications caused by the three complexes on DNA. Studies of antiproliferative activity of complexes 1 and 2 against cell tumour lines (HL-60) and apoptosis assays have also been carried out, showing that 1 as well as 2 are far less active than the previously described complex 3 (IC₅₀ = 19; 19 and 3 μM, respectively). This fact probes that slight modifications on the drug’s design may generate significant differences in the final antitumour activity by modifying the DNA–drug adducts, performance of resistance mechanisms and all the factors that play a fundamental role in Pt complexes’ cytotoxicity.

Graphical abstract

The synthesis, chemical characterization, interaction with DNA and cytotoxic activity of two trans platinum complexes, (Complex-1) trans-[PtCl₂NH₃(3-hydroxymethylpyridine)] and (Complex-2) trans-[PtCl₂NH₃(2-hydroxymethylpyridine)], are described. We have probed that the different position of the hydroxymethyl substituent is crucial in their activity.

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Keywords: Anticancer agents; Apoptosis induction of Pt(II)2-,3-, and 4-hydroxymethylpyridine complexes; Pt(II) drugs; Pt(II) 4-hydroxymethylpyridine derivatives; Pt complexes-DNA interactions

Article Outline

1. Introduction

2. Results and discussion

2.1. Results

2.1.1. Chemistry

2.1.2. Crystal and molecular structure determination

2.1.3. Biochemical studies

2.1.3.1. Circular dichroism

2.1.3.2. Electrophoretic mobility

2.1.3.3. Atomic force microscopy (AFM)

2.1.4. Pt cell uptake

2.1.5. Cytotoxicity of the platinum complexes against HL-60 cells

2.1.6. Quantification of apoptosis by annexin V binding and flow cytometry

2.2. Discussion

3. Experimental

3.1. Chemistry

3.2. X-ray diffraction

3.3. Biological assays

3.3.1. Formation of drug–DNA complexes

3.3.2. Circular dichroism (CD) spectroscopy

3.3.3. Electrophoretic mobility in agarose gel

3.3.4. Atomic force microscopy (TMAFM)

3.4. Determination of platinum binding to DNA in Culture Cells

3.5. Tumour cell lines and culture conditions

3.5.1. Cytotoxicity assay

3.5.2. In vitro apoptosis assay

Acknowledgements

References