Chemistry Reference
In-Depth Information
Fig. 28 Sketch of the opening process of a polymer container filled with the drug and additionally
containing AuNPs for photoinduced heating process. Figure adapted from [
90
]
5.3 Drug Delivery
If AuNPs shall be used as therapeutic agents based on their cytotoxicity in the
future, a fundamental challenge has to be faced. One of the most common
drawbacks of the present treatment of tumors is the small specificity of the
respective drugs that means that the number of damaged tumor cells compared
with the number of damaged healthy cells is far too small. Therefore, worldwide
efforts are being made to improve the situation, among others by using the so-called
drug delivery (drug release) systems. The goal is to transport a drug specifically into
a tumor in order to avoid damage of healthy cells as far as possible. One promising
attempt is the use of micro- or nano-sized hollow containers which are filled with
chemotherapeutics or cytotoxins. The advantage of this technique is the possibility
to modify the surface of the capsules by tumor-specific antibodies without the need
to modify the drug itself. Accumulated in the tumor, the containers open themselves
or by stimuli from outside, for instance, by photoinduced heating of AuNPs, also
present in the containers [
163
,
166
,
214
-
216
]. The capsules usually consist of
polymers which can easily be modified by tumor-specific antibodies. Poly
(alkylcyanoacrylate) even degrades rapidly in vivo without any photoinduction of
AuNPs [
217
]. Figure
28
elucidates the artificial opening process using AuNPs.
The use of AuNPs for photoinduced heating is only of importance for the
opening of the polymer containers. Another chance is the direct use of AuNPs as
a drug. The cell toxicity of Au
55
with its ultrasmall 1.4 nm diameter has already
been discussed in Sect.
3
. Experiments to transport 1.4 nm Au particles in polymer
spheres are presently under
investigation (Simon U, Mayer C, private
communication).
Though not yet tested for the use of AuNPs, mesoporous silica nanoparticles are
a promising alternative to hollow nanospheres. They are intensively under investi-
gation, especially to study single particle tracking to living cells by fluorescence
microscopy allowing the discrimination between active transport and random
motion [
218
-
220
].
