Facile synthesis and characterization of W-doped TiO2 nanoparticles: Promising ancticancer activity with high selectivity

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Highlights

  • Pure and W doped TiO2 nanoparticles have been successfully synthesized.

  • The average crystallite size of W doped TiO2 nanoparticles is ~ 40 nm.

  • Due to W doping, lowering the band gap of TiO2 nanoparticles.

  • W doped TiO2 nanoparticles induced toxicity in human cervical cancer (HeLa) cells.

  • W doped TiO2 nanoparticles benign with the human normal cells.

Abstract

In this research work, the effect of tungsten (W) doping on the crystal structure, morphology and anticancer activity of titanium dioxide (TiO2) nanoparticles were studied. The synthesized W doped TiO2 nanoparticles have been characterized by spectroscopic and microscopic techniques. XRD pattern of pure TiO2 and 1 wt% W-doped TiO2 nanoparticles confirms the anatase structure and increase in the W-doping changes the phase of TiO2 to rutile. The images of HRTEM clearly confirm that size of 5 wt% W-doped TiO2 nanoparticles are in the range of ~ 40 nm. The FESEM images show the agglomerated spherical-like morphology for pure TiO2, 1 wt%, 3 wt% W-doped TiO2 nanoparticles and flower like morphology for 5 wt% W-doped TiO2 nanoparticles. Both pure TiO2 and W-doped TiO2 nanoparticles did not show any notable cytotoxicity against human normal embryonic kidney cell line (HEK 293), but showed effective cytotoxicity against HeLa cancer cell lines evaluated by MTT assay.

Graphical abstract

The effect of tungsten (W) doping on the crystal structure, morphology, cytotoxicity and anticancer activity of titanium dioxide (TiO2) nanoparticles were studied.

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Introduction

Titanium dioxide (TiO2) nanoparticles are an inexpensive, easily available, nontoxicity and chemically stable material [1]. In past decades, it is mostly used in the field of photocatalyst, drug delivery, photodynamic therapy and cell imaging, etc [2], [3], [4], [5]. When, the TiO2 nanoparticles calcinated to above 450 °C, the crystal phase has been changed from anatase to rutile structure [6], [7]. Anatase and rutile phases of TiO2 nanoparticles are the two important photoactive polymorphic phases with the band-gap energy of 3.20 and 3.02 eV respectively [8]. Band gap value of the anatase phase is larger than that of the rutile phase, so the rutile phase properties are slightly better than the anatase phase properties in semiconducting performance [9]. Many researches have been reported for the improvement of TiO2 nanoparticles optical properties by doping with transition metals, transition metal ions, nonmetal atoms, MWNCTs, polymers and organic materials [10], [11], [12]. M. M. Abutalib et al. reported the enhancement of mechanical, electrical and biological properties of TiO2, ferrite and gold nanoparticles by doping with the gold, silver, MWNCTs and polymers [13], [14], [15], [16], [17]. Nevertheless, using tungsten (W) as a dopant will increase the possibility as to release of up to two electrons for each one dopant atom, it permits the utilization of low dopant levels that lessen defect concentrations and consequently diminish scattering of charge carriers [18]. Moreover, W doping of TiO2 has different points of advantages, as it is known to enhance the photocatalytic activity by decreasing charge carrier recombination and by expanding light absorption by absorbing in the visible portion of the spectrum [19], [20], [21]. On the other hand, the scientists are focuses in the biological impacts of TiO2 nanoparticles due to its rapid recombination of photo activated electrons and positive holes [22]. In recent decades, researcher’s shows interest on the antimicrobial activity and anticancer activity of transition metal doped TiO2 nanoparticles due to their reactive oxygen species (ROS) generating potential [23], [24], [25], [26]. Manipulating intracellular ROS level by redox modulators is a possible way to harm cancer cells selectively without affecting the normal cells [27], [28]. However they did not explain clearly the effect of doped percentage of metals on the ROS generating efficacy of TiO2 nanoparticles. Moreover there is no reports on the chemotherapeautic effects of W doped of TiO2 nanoparticles against human cancer cells.

Therefore in the present study, we tried to evaluate the cytotoxicity (anticancer property) of TiO2 nanoparticles against human cervical cancer cell line (HeLa), when it is doped with different weight percentage of W. Along with, their cytotoxicity on human normal embryonic kidney cell line (HEK 293) was also analyzed.

Section snippets

Experimental

Pure TiO2 nanoparticles were prepared by mixing titanium isopropoxide (3 ml) with ethanol (24 ml) in the molar ratio of 1:8 respectively, via sol gel method. The aforesaid mixture is dissolved in 1 L of DD water and kept at room temperature to obtain titanium isopropoxide sol. The hydroxylamine hydrochloride solution (0.694 g in 100 ml of DD water) was added gradually to the titanium isopropoxide sol and stirred for 3 h. The obtained aqueous solution was centrifuged and the precipitate was

Results and discussion

Fig. 1 (a-d) depicts the XRD patterns of the crystalline structure and phase of the synthesised pure and W doped TiO2 nanoparticles. The characteristics peaks at corresponding 2θ values confirms the rutile phase of pure TiO2 nanoparticles(Fig. 1a). The XRD pattern of 1 wt% W-doped TiO2 nanoparticles calcinated at 600 °C shows the most of peaks correspond to anatase phase confirmed by the existence of strong diffraction peaks at 2θ values of 25.3°, 38.44°, 48°, 54°, 55.07°, 63°, 69.23°, 70.89°

Conclusion

In summary, pure and 1 wt%, 3 wt%, 5 wt% W doped TiO2 nanoparticles were successfully synthesized by facile sol–gel route. The XRD analysis represents, when TiO2 nanoparticles doped with different wt% of W, does not affect their crystalline phase. FETEM and FESEM analysis showed that the significant morphology and average crystallite size of 5 wt% W doped TiO2 nanoparticles is ~ 40 nm. Interestingly, we found that W doped TiO2 nanoparticles induced toxicity in human cervical cancer (HeLa) cells

CRediT authorship contribution statement

K. Manikandan: Investigation, Writing – original draft, Writing – review & editing, Validation. Mookkandi Palsamy Kesavan: Investigation, Writing – original draft. A. Thirugnanasundar: Writing – review & editing, Writing – original draft, Conceptualization. N.M. Abdul Khader Jailani: Writing – review & editing, Conceptualization, Methodology. A. Jafar Ahamed: Writing – review & editing, Methodology.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors honestly acknowledge to the management of Velalar College of Engineering and Technology, Erode for their lab and instrumental facilities.

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