Synthesis of gamma radiation-induced PEGylated cisplatin for cancer treatment

Abstract

The use of poly(ethylene glycol) (PEG) for the development of novel PEGylated biomolecules is playing an increasingly meaningful role in cancer treatment. Cisplatin (CDDP), is a useful chemotherapy drug. However, it is unclear whether PEGylated cisplatin (CDDPPEG) has potential as an alternative therapeutic agent. Here we prepared a PEGylated cisplatin by gamma radiation-induced synthesis, for the first time. PEGylated drugs were characterized using Raman and Fourier transform infrared spectroscopy (FTIR), as well as scanning electron microscopy coupled with Energy Dispersive X-ray (SEM/EDX). The results show that the cisplatin can be successfully PEGylated by this method. Furthermore, we show a proposal for the mechanism of the PEGylation reaction. The novel product exhibits in vitro therapeutic potential comparable to cisplatin at concentrations lower than 23 μM (Pt), causing differences in cell cycle checkpoints, which suggest changes in the signaling pathways that control growth arrest and cause apoptosis of A549 cells.

Fig. 1. (A) Raman spectrum of pure solid cisplatin in the region 3500–50 cm⁻¹. (B) Raman spectrum of aqueous cisplatin in distilled water (1 mg mL⁻¹). (C) Raman spectrum of aqueous polyethylene glycol (400 Da). (D) Raman spectrum of radiation-induced PEGylated cisplatin (M1G1D1). (E) Raman spectra of the effect of different doses on the synthesis of PEGylated cisplatin (F) Raman spectra of the effect of different PEG molecular weights (G1, G2, G3, G4 and G5) on the synthesis of PEGylated cisplatin.

Fig. 2. Proposed mechanism of gamma radiation-induced PEGylated cisplatin/adduct formation (G = guanine).

Fig. 3. CDDPPEG does not reduce cell proliferation rates over 30 μM (or 23 μM (Pt)). A549 cells (4000 cells per cm²; seeded 24 h before the treatment starting point) were treated as indicated: NT-non-treated, (a) CDDP from 10 to 80 μM (or 62 μM (Pt)). and (b) CDDPPEG, same concentration range. Cell viability was determined by a MTT assay. Absorbance values from non-treated cells at time zero (NT) were set as 100% for comparison purposes. Proliferation rates were measured after 24, 48, and 72 h. Mean values and standard error (±S.E.) from at least three independent experiments performed in triplicates are shown. *P > 0.05 between non-treated and treated cells.

Fig. 4. Cell viability profile obtained by treating A549 cells with CDDP and CDDPPEG at different concentrations (30, 50 and 80 μM) (or 23, 39 and 62 μM (Pt)) for 48 h.

Fig. 5. Cell cycle analysis obtained by treating A549 cells with CDDP and CDDPPEG at different concentrations (30, 50 and 80 μM) (23, 39 and 62 μM (Pt)) for 48 h.