44 Ti diffusion labelling of commercially available, engineered TiO2 and SiO2 nanoparticles
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RESEARCH PAPER
44
Ti diffusion labelling of commercially available, engineered TiO2 and SiO2 nanoparticles
Uwe Holzwarth
&
Jessica Ponti
Received: 17 February 2020 / Accepted: 6 August 2020 # The Author(s) 2020
Abstract In realistic exposure scenarios, the detection and quantification of engineered nanoparticles in complex environmental or biological matrixes is a challenge since nanoparticle concentrations are frequently low and have to be discerned from a background that may contain the same elements in various chemical forms in much higher concentrations. The use of radiolabelled nanoparticles may overcome these difficulties offering high detection sensitivity without the necessity of complex sample preparation procedures. However, the labelling procedure must not alter the physicochemical and biological properties of the nanoparticles. In the present work, the radiolabelling of three different types of TiO2 nanoparticles with primary particle sizes between 5 nm and 26 nm with commercially available 44 Ti has been investigated applying a simple diffusion heat treatment at 180 °C for 2.5 h on nanoparticles impregnated with a solution containing the 44Ti radiolabel. The same treatment has been investigated to radiolabel amorphous SiO2 nanoparticles with 44Ti. The radiolabels are stably integrated in the nanoparticle matrix, and the release is less than 0.1% in aqueous suspension at neutral pH for at least 4 weeks. The method appears to be fast and reliable. By transmission electron microscopy, dynamic light scattering and ζ-potential measurements, only minor alterations of the nanoparticle size could be detected in the range of 1 to 2 nm.
U. Holzwarth (*) : J. Ponti European Commission, Joint Research Centre, Ispra, Italy e-mail: [email protected]
Keywords Radiolabelled nanoparticles . TiO2 nanoparticles . SiO2 nanoparticles . Diffusion labelling . Leaching . Radiolabel release . Radiolabel stability
Introduction Investigations of the fate of nanoparticles in biological systems and environmental matrices frequently encounter the challenge to detect the applied nanoparticles on a chemically identical natural background (Gibson et al. 2011) and in very low concentrations in experimental settings mimicking realistically low exposure scenarios. It is a drawback of many investigations that they compensate for insufficient detection sensitivity by unrealistically high dosage or exposure (e.g. Krug 2014). Radiolabelled nanoparticles have been applied in in vitro (e.g. Marmorato et al. 2011; Simonelli et al. 2011; Ponti et al. 2009) and in in vivo toxicological (e.g. Schleh et al. 2013; Kreyling et al. 2017a, b, c; Xie et al. 2010; Zhang et al. 2009) and environmental studies (e.g. Kleiven et al. 2018; Chekli et al. 2016; Vitorge et al. 2014; Coutris et al. 2012; Oughton et al. 2008) where they demonstrated the advantage of very high detection sensitivity and easy quantification, usually without special specimen preparation procedures (Bello and Warheit 2017; Llop et al. 2013; Weiss and Diabate 2011). H
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