Give examples of materials which have different properties at the nanoscale.
Gold is yellow, while gold nanoparticles in solution have a colour ranging from red to purple. TiO2 is white while TiO2 NPs are transparent. The melting temperature of Ag is much lower than of bulk Ag.
Why do nanomaterials generally have a higher reactivity than bulk materials?
the surface area per mass is much larger than for bulk material, and consequently number of surface molecules increases (exponentially with reduced particle size).
Describe ways of accidental and deliberate exposure to NPs.
accidental: occupational exposure, consumer exposure, and environmental exposure (waste). deliberate: medical / pharmaceutical applications (oral, topical, via injection).
What happens when a NP enters the bloodstream?
serum proteins and opsonins (IgG and complement factors) bind to NP opsonisation results in transfer of NP to spleen and liver (mononuclear phagocyte system)
How can you design a NP with reduced clearance by opsonisation?
What happens with a NP after inhalation?
disposition in a part of the respiratory tract, interaction with lung fliud/surfactant, clearance (physical dislocation or chemical clearance)
What happens with a NP after oral exposure
passes GI tract. no intestinal absorption
In which circumstances do you get systemic toxicity , after dermal exposure?
When the NP crosses the epidermis and reaches the dermis which has blood vessels.
What happens with a NP after absorption, and biodistribution occurs?
Interaction with plasma proteins (corona formation), with the immune system, with blood cells, and distribution to organs where it may interact with cells.
Describe what a protein corona is and how it evolves over time.
3 types of proteins (green, blue and yellow :)). soft corona and hard corona (several days) composition is determined by NP properties and by biological milieu. influential role biological fate: cellular uptake (endocytosis), biodistribution, toxicity
Describe the intracellular fate and biotransformation
How are NPs generally eliminated?
endosomal/lysosomal degradation, phagocytocis.
Which signs can you expect when NPs accumulate in the body?
frustrated phagocystosis and inflammation
Describe 6 mechanisms of NP toxicity
disruption of the cell membrane, disruption of transport processes, altered protein folding, protein aggregation, ROS, dissolution and release of toxic ions.
How can NPs result in the generation of reactive oxygen species?
- on NP surface: compounds which release ROS (pro-oxidant functioncal groups), or metal ions or quinones on the NP surface which catalyse OH radical or O2-radical formation. - in the cell, interaction with redox processes: membrane NADHP enzyme interaction, mitochondria interaction, ER interaction.
What happens when a NP gets into contact with blood?
- monocytes/phagocytes eat the NP, interaction with red blood cells gives hemolysis, interaction with coagulation system, interaction with immune system gives complement activation.
Mention physiochemical properties of NPs that influence their toxicity
- size and size distribution, shape, agglomeration and aggregation, surface properties (porosity, charge, reactivity, chemistry (coating etc), crystal structure, solubility
What are the key elements in the toxicity testing of NPs?
characterisation of physicochemical properties of the NPs, in vitro testing, in vivo testing.
mention different types of in vitro testing.
subcellular systems (macromolecules, organelles), cellular systems, whole tissues
give advantages and disadvantages of in vitro testing
what do indirect toxicity tests measure, and how do they work in principle?
- if there us a toxic substance leaking from the NP (material of which the NP is made or a contamination)
What are the steps in a direct in vitro tox test?
NP + cell model, exposure of certain duration and at certain dose, evaluation of tox.
What is the difference between primary cells and transformed cells?
- primary cells come from donor tissue, divide maybe 1-2 times and then die. - transformed cells continue to divide.
How do you think the cell response to NPs can be evaluated?
- metabolic activity (Alamar blue, MTT) , membrane integrity (LDH test) , ROS (DCFH), inflammation, DNA damage (Comet), apoptose/necrosis (Annexin V binds phophatidyl serine (early apoptosis) and propidium iodide binds to nuclei acids (membrane integrety), cell number and morphology, expression of specific markers, uptake of NP (microscopy)
How can you account for NPs which interfer with the read.out system of the assasy?
- use multiple assays and adequate controls.
NPs in contact with blood results in activation. Which systems?
- immune system (white blood cells, complement system) - inflammation; coagulation system (platelets, coagulation cascade) - clots; red blood cells - hemolysis.
Why are both the fluid phase and the material surface of the NP analysed in blood compability tests?
Describe 4 pathways of endocytosis
1) phagocytocis (>500 nm): immune-mediated, ends up with lysosome, inflammation 2) clathrin-medicated ( smaller than 100 nm): encapsulated with clathrin, endosome, lysosome 3) caveolin-medicated: caveosome ends up in ER and Golgi 4) pinocytosis (few to x100 nm) : endosomal compartment to lysosome
Why is it importang to charcterise the physicochemical properties of NPs before toxicity testing?
Case study: which experiments would you do to evaluate whether there is an effect of shape on cell toxicity?
- CBNs lead to cell proliferation inhibition and cell death
- A clear shape dependence was found for Cell toxicity: carbon black nanoparticles > carbon nanofibers> carbon nanotubes