Biomedical Engineering Reference
In-Depth Information
energies (power, duration). Otherwise, reproducible dosing and testing will
be impossible. Nanomaterial suspensions generally exhibit highly dynamic
properties that must be studied in detail. It is therefore mandatory to study
and report the following properties:
• Particle surface charge under testing conditions
• Agglomeration or deagglomeration propensity under testing conditions
• Stability and sedimentation propensity of suspensions used for dosing
• Applied nanomaterial dose in units of surface area and mass
Any study published without providing such crucial data will be of little
value for the scientific community. A number of additional nanomaterial
characteristics may be relevant for toxic properties and should be studied
whenever possible, including
• Apparent density
• Solubility in cytosol for cell toxicological studies
• Surface wettability and surface free energy
• Molecule adsorption dynamics in test medium
• Radical concentration and photocatalytic properties
2.5.2 Example: Characterization of Carbon Nanotubes
Carbon nanotubes exhibit fascinating and exceptional material proper-
ties. With various applications under development, they are at the brink of
becoming ubiquitous nanomaterials. CNT will therefore serve as an example
for the following brief presentation of a possible approach to nanoparticle
characterization for a toxicological assessment.
To begin with, a literature study should be performed focusing on char-
acterization methods, synthesis and purification methods, as well as mate-
rial particularities such as chirality and defects of CNT. With the gained
insights, a material choice with respect to the synthesis method has to be
made between more facile characterizable samples of high purity, structural
regularity and ensemble homogeneity, and “real-world” material samples
that are used in applications. All material data should be made available,
including material supplier, production process, batch number, storing con-
ditions and sample age (see Section 2.2.7). A fraction of the sample should be
stored under dark and inert conditions for possible future studies.
For tests of CNT specific toxicity, additional purification steps might be
required and should be adapted to the purity requirements of the sample and
the test with respect to remaining metal catalysts, amorphous carbon, chemi-
cal functionalization, etc. Generally, a multistep purification protocol might
be required using both physical and chemical methods. The most important
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