Biomedical Engineering Reference
In-Depth Information
biofilm survival and metabolism
[35]
. It was concluded that TMP, alone or combined to antimicro-
bials, had no direct action on biofilm. In addition, a pilot study compared the effect of treatment
(during 5 min) of bovine enamel blocks with commercial TMP and TMP with smaller particles in
different concentrations (3% and 5%) on the adhesion of C. albicans and C. glabrata. It was possi-
ble to observe that, regardless of the concentration, the treatment with TMP with different particle
sizes did not reduce the number of CFUs on the enamel blocks after a period of 2 h (initial adhe-
sion) for Candida species tested.
9.4
Pros and cons of nanoparticles toward biological-dental application
9.4.1
Toxicity
Profile toxicity of nanomaterials can be considered different from larger particles mainly because
of their small size and high reactivity
[37
39]
. Toxicology associated to nanostructures, in general,
is affected by different physical and chemical properties of each nanomaterial
[37,38]
. Precisely,
because of the number of variables interfering on the toxicity of nanomaterials, it is difficult to gen-
eralize their effects on the biological systems
[40]
.
Composition is clearly a key factor in determining the toxicity of nanomaterials. Actually, tak-
ing into consideration the chemical composition, there are an enormous number of different nano-
materials
[40,41]
. One of the most widely studied categories of nanomaterials are metal
nanoparticles; among them silver nanoparticles are those that generate more interest in nanotoxico-
logical
research, precisely because of
their use as antimicrobial agent
in the medical area
[17,21,42]
.
In general, shape and size of the nanomaterials directly influence on the toxicity
[39,43]
. It has
been stated that cubic nanoparticles induce lower level of toxicity compared to those that are cylin-
drical, spherical, and rod shaped
[44]
. Usually, smaller particles are considered more toxic since
they occupy less volume in a greater surface area per unit of mass increasing the availability for
the biological interactions
[37,38]
. Furthermore, it has been amply exposed that the internalization
of nanomaterials is a size-dependent process; smaller particles are much more easily internalized
into the cells and therefore more available for interaction with cellular components
[43,45]
.
The main objectives of surface treatment or functionalization of nanoparticles are ensuring
stability and promote favorable characteristics to a specific proposal
[46,47]
. Nanoparticles can be
superficially modified with polymers, drugs, peptides, proteins, oligonucleotides, and biological
molecules
[46,47]
and show different cytotoxic characteristics depending on the coating material
[47,48]
. Thus, surface treatment or functionalization can be considered one of the most relevant
factors of cytotoxicity
[43,49]
since the process modifies chemical properties inherent to the nano-
materials and determines their toxicity profile
[43,49]
.
Considering the agglomeration state of the nanomaterials and their related cytotoxicity, it has
been suggested that the process of agglomeration makes the particles become larger or even exceed
the nanoscale
[50]
. As discussed above, size is considered to be a relevant factor in determining the
toxicity profile. Recently, it was confirmed that large agglomerates are not effectively cell internal-
ized; therefore, agglomerated particles can be considered lower cytotoxic, once that the agglomera-
tion state of the particles significantly reduces surface area availability and access into the cells
[50]
.
