Engineered nanomaterials (ENMs) have the ability to revolutionize many industries and are already used in e.g., cosmetics, electronics, batteries, fuels, fuel cells, solar cells, automobile components, etc. In medicine, they are used for the detection of biological molecules, imaging of diseased tissues and innovative therapeutics as well as drug delivery systems. Safety and targeting ability are important factors in developing sustainable nanomaterials. Designing safe and efficient ENMs for different applications requires an understanding of how ENMs behave in organisms’ bodies and humans and how they interact with the surrounding cells and tissues.
Metal-bearing ENMs (M-ENMs) of different shapes and sizes are taken up by organisms through, e.g., gills/lungs and stomach, or via attachment to the outer membranes. When entering the biological medium, e.g., in the blood, M-ENM are prone to dissolution and agglomeration. It is also possible that the M-ENMs acquire an evolving layer of proteins and other biomolecules.
Tracking and analysing ENMs in cells and tissues is difficult. This difficulty arises because there is a limitation in analytics for characterization and quantification of ENMs in bio- and physiological matrices due to their presence at trace levels, and because of the presence of different background materials which interfere with the measurement of ENMs. Thus, researchers must apply an approach that is not only capable of measuring ENMs at trace levels but also of measuring the form of the particles at a specific moment in time. There are no standard and straightforward methods and analytical techniques available that are able to comprehensively characterize and quantify ENMs in situ in (micro)organisms.
We developed the first protocol, which combines different methods and fit-for-purpose techniques, for characterizing and quantifying metal-bearing ENMs (M-ENMs) in biological samples including cells, microorganisms, and higher organisms. The protocol is applicable to measurement of M-ENMs in tissues from both laboratory and field experiments. We have used this protocol previously to understand the bioaccumulation and biodistribution of M-ENMs in organisms (e.g., fish), which are important factors for understanding the toxicity of ENMs. The method was also used to quantify the cellular uptake of M-ENMs on a cell-by-cell basis in microorganisms (algae). The workflow is optimized to cover cells and microorganisms such as bacteria as well as tissues and organs of different organisms including plants.
For example, we have applied the protocol to understand whether silver (Ag) ENMs transform and transport into and through the human blood-brain barrier (BBB) cell layer. The optical density images show the shape of the cells. The results suggest the silver ENMs are transformed following uptake into the human BBB cells.
Unlike previous methods, the protocol uses no fluorescent dyes or radiolabels to trace M-ENMs in biota and enables analysis of most M-ENMs at cellular, tissue and organism levels. Method development and validation should continue in order to optimize the workflows for different M-ENMs and also for carbon-based ENMs such as nanoplastics and carbon nanotubes and to facilitate direct analysis of these materials in organisms collected from the field. The protocols can be applied by a wide variety of users e.g., to correlate toxicity with a specific particle form, or to understand the ADME (Absorption, Distribution, Metabolism, and Excretion) of M-ENMs, which will open a new horizon for medical applications and risk assessment of ENMs as well as adaptation of safe by-design strategies for ENMs. In conclusion, this protocol can provide comprehensive information about the dynamic behavior and biological fate of M-ENMs in laboratory or field-based studies.
I did my PhD at the Department of Environmental Geoscience, University of Vienna, Austria, where I focused on developing methods for extraction, characterization, and quantification of nanomaterials (NMs) in complex matrices e.g. consumer products and environmental samples. Nanomaterials are considered as emerging contaminants with many challenges yet to be tackled to assess their risk. I am interested in synthesizing safe nanomaterials and tracking and characterizing them (metal-based and carbon-based nanomaterials) in biological matrices to understand their biological fate (e.g., biodistribution, localization, bioaccumulation, and clearance). During my Postdoc, I could merge my skills in nano-analytical chemistry with environmental science and toxicology to use different techniques to develop a suited-for-purpose workflow for tracing and characterizing nanomaterials in organisms. I am thankful to the European Commission that supported my ideas through the Marie Skłodowska-Curie IF (Horizon 2020) funding scheme and offered me a great opportunity to test the idea.
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