Université de Fribourg

Lock‐in thermography to analyze plasmonic nanoparticle dispersions

Steinmetz, Lukas ; Taladriz‐Blanco, Patricia ; Geers, Christoph ; Spuch‐Calvar, Miguel ; Bonmarin, Mathias ; Balog, Sandor ; Rothen‐Rutishauser, Barbara ; Petri‐Fink, Alke

In: Particle & Particle Systems Characterization, 2019, p. 1900224

The physicochemical properties of nanoparticles (NPs) strongly rely on their colloidal stability, and any given dispersion can display remarkably different features, depending on whether it contains single particles or clusters. Thus, developing efficient experimental methods that are able to provide accurate and reproducible measures of the NP properties is a considerable challenge for both...

Université de Fribourg

Heating behavior of magnetic iron oxide nanoparticles at clinically relevant concentration

Lemal, Philipp ; Balog, Sandor ; Geers, Christoph ; Taladriz-Blanco, Patricia ; Palumbo, Andrea ; M.Hirt, Ann ; Rothen-Rutishauser, Barbara ; Petri-Fink, Alke

In: Journal of Magnetism and Magnetic Materials, 2019, vol. 474, p. 637–642

Magnetic hyperthermia for cancer treatment has gained significant attention in recent years, due to its biocompatibility of applied nanoparticles and the possibility for spatially localized heating in deep tissues. Clinical treatments use nanoparticle concentrations of 112 mg Fe/mL, while the concentrations experimental studies have addressed are considerably smaller, usually between 0.1...

Université de Fribourg

Taylor dispersion of inorganic nanoparticles and comparison to dynamic light scattering and transmission electron microscopy

A.Urban, Dominic ; M.Milosevic, Ana ; Bossert, David ; Crippa, Federica ; L.Moore, Thomas ; Geers, Christoph ; Balog, Sandor ; Rothen-Rutishauser, Barbara ; Petri-Fink, Alke

In: Colloid and Interface Science Communications, 2018, vol. 22, p. 29–33

Taylor dispersion analysis (TDA) is an analytical method that has so far mainly been utilized to determine the diffusion coefficient of small molecules, and proteins. Due to increasing interest in nanoscience, some research has been done on the applicability of TDA towards characterizing nanoparticles. This work aims to expand this knowledge and give insight into the range for which TDA can...

Université de Fribourg

Lock-in thermography as an analytical tool for magnetic nanoparticles: measuring heating power and magnetic fields

Monnier, Christophe A. ; Crippa, Federica ; Geers, Christoph ; Knapp, Evelyne ; Rothen-Rutishauser, Barbara ; Bonmarin, Mathias ; Lattuada, Marco ; Petri-Fink, Alke

In: The Journal of Physical Chemistry C, 2017, vol. 121, no. 48, p. 27164–27175

Magnetic nanoparticles and their ability to convert electromagnetic energy into heat are of explicit interest for various applications. However, precise quantification of their heating efficiency is not always upfront, and several parameters render comparative studies challenging. This paper describes the theory behind lock-in thermography, a new technique for quantifying the heating...

Université de Fribourg

Dynamic and biocompatible thermo-responsive magnetic hydrogels that respond to an alternating magnetic field

Crippa, Federica ; Moore, Thomas L. ; Mortato, Mariangela ; Geers, Christoph ; Haeni, Laetitia ; Hirt, Ann M. ; Rothen-Rutishauser, Barbara ; Petri-Fink, Alke

In: Journal of Magnetism and Magnetic Materials, 2017, vol. 427, p. 212–219

Magnetic thermo-responsive hydrogels are a new class of materials that have recently attracted interest in biomedicine due to their ability to change phase upon magnetic stimulation. They have been used for drug release, magnetic hyperthermia treatment, and can potentially be engineered as stimuli-responsive substrates for cell mechanobiology. In this regard, we propose a series of magnetic...

Université de Fribourg

Lock-in thermography as a rapid and reproducible thermal characterization method for magnetic nanoparticles

Lemal, Philipp ; Geers, Christoph ; Monnier, Christophe A. ; Crippa, Federica ; Daum, Leopold ; Urban, Dominic A. ; Rothen-Rutishauser, Barbara ; Bonmarin, Mathias ; Petri-Fink, Alke

In: Journal of Magnetism and Magnetic Materials, 2017, vol. 427, p. 206–211

Lock-in thermography (LIT) is a sensitive imaging technique generally used in engineering and materials science (e.g. detecting defects in composite materials). However, it has recently been expanded for investigating the heating power of nanomaterials, such as superparamagnetic iron oxide nanoparticles (SPIONs). Here we implement LIT as a rapid and reproducible method that can evaluate the...

Université de Fribourg

Combined exposure of diesel exhaust particles and respirable Soufrière Hills volcanic ash causes a (pro-)inflammatory response in an in vitro multicellular epithelial tissue barrier model

Tomašek, Ines ; Horwell, Claire J. ; Damby, David E. ; Barošová, Hana ; Geers, Christoph ; Petri-Fink, Alke ; Rothen-Rutishauser, Barbara ; Clift, Martin J. D.

In: Particle and Fibre Toxicology, 2016, vol. 13, p. 67

There are justifiable health concerns regarding the potential adverse effects associated with human exposure to volcanic ash (VA) particles, especially when considering communities living in urban areas already exposed to heightened air pollution. The aim of this study was, therefore, to gain an imperative, first understanding of the biological impacts of respirable VA when exposed...

Université de Fribourg

A new angle on dynamic depolarized light scattering: number-averaged size distribution of nanoparticles in focus

Geers, Christoph ; Rodriguez-Lorenzo, Laura ; Urban, Dominic Andreas ; Kinnear, Calum ; Petri-Finka, Alke ; Balog, Sandor

In: Nanoscale, 2016, vol. 8, no. 34, p. 15813–15821

Size polydispersity is a common phenomenon that strongly influences the physicochemical properties of nanoparticles (NPs). We present an analytical approach that is universally applicable to characterizing optically anisotropic round NPs and determines directly the number-averaged size distribution and polydispersity via depolarized dynamic light scattering (DDLS). To demonstrate, we use...

Université de Fribourg

Distribution of silica-coated silver/gold nanostars in soft- and hardwood applying SERS-based imaging

Geers, Christoph ; Rodríguez-Lorenzo, Laura ; Placencia Peña, M. I. ; Brodard, Pierre ; Volkmer, T. ; Rothen-Rutishauser, Barbara ; Petri-Fink, Alke

In: Langmuir, 2016, vol. 32, no. 1, p. 274–283

Nanoparticles (NPs) in aqueous suspension have just begun to be exploited for the preservative treatment of wood. However, at present, there is very little information available on the distribution of NPs in wood after impregnation, due to associated analytical challenges. In this study, we present the detection of model NPs in softwood and hardwood by surface-enhanced Raman spectroscopy (SERS)....

Université de Fribourg

Avoiding drying-artifacts in transmission electron microscopy: Characterizing the size and colloidal state of nanoparticles

Michen, Benjamin ; Geers, Christoph ; Vanhecke, Dimitri ; Endes, Carola ; Rothen-Rutishauser, Barbara ; Balog, Sandor ; Petri-Fink, Alke

In: Scientific Reports, 2015, vol. 5, p. 9793

Standard transmission electron microscopy nanoparticle sample preparation generally requires the complete removal of the suspending liquid. Drying often introduces artifacts, which can obscure the state of the dispersion prior to drying and preclude automated image analysis typically used to obtain number-weighted particle size distribution. Here we present a straightforward protocol for...