Cytotoxic potentials of biologically fabricated platinum nanoparticles from Streptomyces sp. on MCF-7 breast cancer cells

Abstract

Biosynthesis of novel therapeutic nano-scale materials for biomedical and pharmaceutical applications has been enormously developed, since last decade. Herein, the authors report an ecological way of synthesising the platinum nanoparticles (PtNPs) using Streptomyces sp. for the first time. The produced PtNPs exhibited the face centred cubic system. The fourier transform infrared spectrum revealed the existence of amino acids in proteins which serves as an essential reductant for the formation of PtNPs. The spherical morphology of the PtNPs with an average size of 20-50 nm was observed from topographical images of atomic force microscopy and field emission scanning electron microscopy. The X-ray fluorescence spectrum confirms the presence of PtNPs with higher purity. The PtNPs size was further confirmed with transmission electron microscopy analysis and the particles were found to exist in the same size regime. Additionally, PtNPs showed the characteristic surface plasmon resonance peak at 262 nm. Dynamic light scattering studies report that 97.2% of particles were <100 nm, with an average particle diameter of about 45 nm. Furthermore, 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-tetrazolium assay based in vitro cytotoxicity analysis was conducted for the PtNPs, which showed the inhibitory concentration (IC₅₀) at 31.2 µg/ml against Michigan Cancer Foundation-7 breast cancer cells.

Fig. 1

Spectrum obtained for the PtNPs (a) UV absorbance spectrum of biologically synthesised PtNPs, inset: UV absorbance spectrum of Streptomyces sp. CFS, (b) FTIR spectroscopy spectrum of biologically synthesised PtNPs

Fig. 2

Formation mechanism of biologically synthesised PtNPs

Fig. 3

X‐ray diffraction pattern of crystalline PtNPs

Fig. 4

Topographical images of biologically synthesised PtNPs

Fig. 5

Morphological analysis of PtNPs (a) Surface morphology analysis using FESEM, (b) Size distribution of PtNPs, (c) Energy dispersive X‐ray spectrum of PtNPs

Fig. 6

Morphology and the size analysis of the PtNPs (a) Transmission electron microscopic analysis for biologically synthesised PtNPs, (b) Particle size distribution graphs measured using DLS for PtNPs, (c) Surface zeta potential graph showing negative zeta potential value for PtNPs synthesised by CFS of Streptomyces sp.

Fig. 7

Schematic mechanism to illustrate the anticancer activity of PtNPs

Fig. 8

Phase contrast photomicrographs and graphical representation of MCF‐7 cell line (a) Morphological changes in MCF‐7 cells treated with PtNPs. The changes in the cell morphology due to toxicity of PtNPs were determined by phase contrast microscopical analysis: (i) normal breast cancer cell line, (ii) Toxicity‐1000 µg/ml, (iii) Toxicity‐125 µg/ml, (iv) Toxicity‐62.5 µg/ml and (v) Toxicity‐31.2 µg/ml, (b) Assessment of PtNPs induced cell death in MCF‐7 breast cancer. The cells were treated with a range of concentration of PtNPs and incubated for 24 h, the per cent of cell viability and cell death was determined by MTT assay, (c) Absorbance analysis for MCF‐7 cell line with various concentrations of biological synthesised PtNPs