There is a plethora of SERS substrates: hydrosols (colloids) easily synthesized
by wet chemistry methods, roughened electrodes, metal islands or periodic
nanostructures (Fig. 6.3c). Advances in nanoscience and nanotechnology allow
designing of various sizes and shapes of nanoparticles, from common nanospheres
to nanoflowers or nanopillars, and composed of single metals or their alloys. The
aim is engineering of LSPRs providing stable, reproducing, and high EF as *10
10
[48].
6.1.5 Applications of SERS in Structural Studies—A Case
of Pharmaceuticals
The fundamental information gathered from SERS spectra gives an insight into
interactions between the adsorbate and enhancing metallic nanoparticles, including
spatial orientation and polarization of the local electric field. This fact has opened
new perspectives in studies on behavior of molecules of a pharmaceutical interest
under different physiological conditions (e.g., pH, concentration) located close to a
surface. Quantum-chemical calculations support the interpretation of SERS spectra
of drugs, however, they can be reliably applied when the chemical mechanism
strongly contributes to surface enhancement of the adsorbate and must include a
model of metal clusters [50].
SERS studies have been carried out on a wide diversity of pharmaceutical
compounds, e.g., analgesics, antidepressants, antibiotics, vitamins as well as on
potential drugs whose SERS characteristics are compared with their precursors [47–
49]. Here, we present briefly two groups of pharmaceuticals.
A series of tricyclic antidepressants TCA (imipramine, desipramine, clomipramine, amitriptyline, nortriptyline, and doxepine) known as surface-active drugs has
been used as a model for evaluation of their adsorption mechanism on the metal
substrate and its relationship to mechanism of interaction with receptors, cf. Fig. 6.4
[51, 52]. SERS spectra clearly showed that the main site of interaction of all the
drugs is the p-electron system and the methyl-aminopropyl side chain, similarly to
docking of these ligands in serotonin and leucine transporters, where the ring
system is located almost perpendicularly in the outer vestibule of the receptor.
However, orientations of each drug are slightly different, so specific for each of
them (Fig. 6.4). Integral intensity ratios of bands assigned to the breathing mode of
the dibenzazepine ring and the 8a mode of the phenyl ring were found to be
different for particular groups of the drugs indicating changes in the orientation of
the tricyclic ring. For instance, the comparison of SERS features of clomipramine
(Clo) with imipramine (Imi) and desipramine (Des) indicated that the ring of Clo is
less tilted than for Imi and Des due to the substitution of the tricyclic ring by the
chlorine atom (Fig. 6.4). Živanovic et al. [53] continued SERS study on selected
TCAs observing them in vitro after the delivery by a nanoparticles-drug system.
Another example of the application of SERS in the examination of drug-target
168
K. Czamara et al.
by wet chemistry methods, roughened electrodes, metal islands or periodic
nanostructures (Fig. 6.3c). Advances in nanoscience and nanotechnology allow
designing of various sizes and shapes of nanoparticles, from common nanospheres
to nanoflowers or nanopillars, and composed of single metals or their alloys. The
aim is engineering of LSPRs providing stable, reproducing, and high EF as *10
10
[48].
6.1.5 Applications of SERS in Structural Studies—A Case
of Pharmaceuticals
The fundamental information gathered from SERS spectra gives an insight into
interactions between the adsorbate and enhancing metallic nanoparticles, including
spatial orientation and polarization of the local electric field. This fact has opened
new perspectives in studies on behavior of molecules of a pharmaceutical interest
under different physiological conditions (e.g., pH, concentration) located close to a
surface. Quantum-chemical calculations support the interpretation of SERS spectra
of drugs, however, they can be reliably applied when the chemical mechanism
strongly contributes to surface enhancement of the adsorbate and must include a
model of metal clusters [50].
SERS studies have been carried out on a wide diversity of pharmaceutical
compounds, e.g., analgesics, antidepressants, antibiotics, vitamins as well as on
potential drugs whose SERS characteristics are compared with their precursors [47–
49]. Here, we present briefly two groups of pharmaceuticals.
A series of tricyclic antidepressants TCA (imipramine, desipramine, clomipramine, amitriptyline, nortriptyline, and doxepine) known as surface-active drugs has
been used as a model for evaluation of their adsorption mechanism on the metal
substrate and its relationship to mechanism of interaction with receptors, cf. Fig. 6.4
[51, 52]. SERS spectra clearly showed that the main site of interaction of all the
drugs is the p-electron system and the methyl-aminopropyl side chain, similarly to
docking of these ligands in serotonin and leucine transporters, where the ring
system is located almost perpendicularly in the outer vestibule of the receptor.
However, orientations of each drug are slightly different, so specific for each of
them (Fig. 6.4). Integral intensity ratios of bands assigned to the breathing mode of
the dibenzazepine ring and the 8a mode of the phenyl ring were found to be
different for particular groups of the drugs indicating changes in the orientation of
the tricyclic ring. For instance, the comparison of SERS features of clomipramine
(Clo) with imipramine (Imi) and desipramine (Des) indicated that the ring of Clo is
less tilted than for Imi and Des due to the substitution of the tricyclic ring by the
chlorine atom (Fig. 6.4). Živanovic et al. [53] continued SERS study on selected
TCAs observing them in vitro after the delivery by a nanoparticles-drug system.
Another example of the application of SERS in the examination of drug-target
168
K. Czamara et al.