Biomedical Engineering Reference
In-Depth Information
dielectric parameters such as membrane capacitance and conductivity that can change rapidly
after exposure to toxic substances [223]. Tight cell layers grown on top of an electrode form an
electrical resistance, which is altered after drug-induced cell morphology alteration such as cell
rounding or cell-cell contact dissociation [224]. The online monitoring of cellular resistance can
be integrated in conventional high-throughput plate formats [225]. Compared with a conventional
MTT assay for cytotoxicity screening, electrochemical impedance spectroscopy was shown to be
more sensitive [226].
After evaluation and validation, these new marker-free and live measurement technologies
may define a new standard for a general
in vitro
toxicity testing of NPs unaffected by specific NP
properties.
In conclusion, NPs exhibit size-specific properties limiting the application of established
in vitro
assays. NP
in vitro
toxicity testing therefore requires a careful characterization of particle prop-
erties and an extensive validation of assay systems when applying established methods for risk
assessment. Future studies should only present data obtained with well-characterized particles and
include reference materials when available. A major deficiency considering a wide range of NPs to
be assessed is the current lack of nationally or internationally agreed reference NPs or nanomateri-
als and standardized test protocols.
Since the current
in vitro
test methods are likely to be influenced by NP-specific properties, NP
risk assessment needs an adaptation of the existing cytotoxicity methods or the development of new
test systems. Technologies based on marker-free detection of cellular endpoints have the potential
to overcome nanomaterial-dependent assay limitations and will provide new standards for NP risk
assessment.
19.14 EUROPEAN UNION APPROACH TO NANOMATERIAL RISK ASSESSMENT
The current risk assessment tools in regard to nanomaterial and nanotechnologies most likely, in
many cases, lag behind the current understanding on nanomaterial and nanotechnologies [227],
and this gap tends to increase. For this reason, intelligent and affordable testing strategies address-
ing the specific features of nanomaterial are required. Thus, there is an urgent need to update the
REACH legislation to meet the challenges provided by the rapidly emerging novel nanomaterial
and nanotechnologies.
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