with 4-MBA and ICAM-1 antibody indicated an increased level of inflammatory
proteins after short-time (1–5 h) treatment of cells with lipopolysaccharides [138].
An important issue in designing SERS sensors is to construct organelle-specific
nanoprobes which recognize particular compartments of cells as nuclei or mitochondria. Three different subcellular organelle-targeting SERS nanotags have been
employed by Kang et al. [139] for multiplex cell imaging and monitor cell morphologies during cell death. They attached cell-penetrating, mitochondria-targeting,
and nucleus-targeting peptides as recognizing sensors to NPs functionalized with
three different Raman reporters. This experiment has also showed that SERS-based
imaging of cells significantly improves spectral quality and temporal resolution of
Raman images [139]. Using SERS tags not only provides information about
organelles but also enables detecting specific molecules inside cells, e.g., telomerase. Telomerase ribonucleoprotein complex is an important biomarker in the early
clinical diagnostic, but its activity is difficult to recognize by conventional methods.
Xu et al. [140] have designed a DNA-driven NP self-assembling pyramid encoding
a Raman reporter (Cy5) which is specific for the recognition of telomerase at the
intracellular level [140]. These examples clearly show that SERS biosensing of
cellular environment requires the advanced development of nanotechnology combined with new techniques of molecular conjugation.
6.3 Examination of Primary and Cultured Cells
Cell culture studies provide a valuable complement to in vivo experiments,
allowing for a more controlled manipulation of cellular functions and processes.
In contrast to cell lines, primary cells which are isolated directly from tissues have
a finite lifespan and limited expansion capacity. On the other hand, primary cells
have normal cell morphology and maintain many of the important markers and
functions seen in vivo [65, 141]. Therefore, in many cases the use of a cell line is
desirable, e.g., in cell biological studies on basic mechanisms or in drug development; however, in other cases such as research on complex metabolic processes, the use of primary cells becomes essential [142]. A particular example are
medical conditions involving alterations in cross talk between few cell types
constituting the tissue. Such situation takes place in, e.g., the liver during
development of fatty liver disease and its progression into more advanced stages
[143] or development of heart failure [144]. In both cases, pathogenic mechanism
involves disruption of homeostatic signaling between cells such as hepatocytes,
hepatic stellate cells, and liver sinusoidal endothelial cells (LSECs)—in the liver
or between cardiomyocytes—and cardiac microvascular endothelial cells
(CMECs)—in the heart. In both cases, the pathogenic mechanism can be induced
and studied with the use of in vitro models; however, it cannot fully replicate the
processes occurring in living organisms [145].
6 Small and Large Molecules Investigated by Raman Spectroscopy
179
proteins after short-time (1–5 h) treatment of cells with lipopolysaccharides [138].
An important issue in designing SERS sensors is to construct organelle-specific
nanoprobes which recognize particular compartments of cells as nuclei or mitochondria. Three different subcellular organelle-targeting SERS nanotags have been
employed by Kang et al. [139] for multiplex cell imaging and monitor cell morphologies during cell death. They attached cell-penetrating, mitochondria-targeting,
and nucleus-targeting peptides as recognizing sensors to NPs functionalized with
three different Raman reporters. This experiment has also showed that SERS-based
imaging of cells significantly improves spectral quality and temporal resolution of
Raman images [139]. Using SERS tags not only provides information about
organelles but also enables detecting specific molecules inside cells, e.g., telomerase. Telomerase ribonucleoprotein complex is an important biomarker in the early
clinical diagnostic, but its activity is difficult to recognize by conventional methods.
Xu et al. [140] have designed a DNA-driven NP self-assembling pyramid encoding
a Raman reporter (Cy5) which is specific for the recognition of telomerase at the
intracellular level [140]. These examples clearly show that SERS biosensing of
cellular environment requires the advanced development of nanotechnology combined with new techniques of molecular conjugation.
6.3 Examination of Primary and Cultured Cells
Cell culture studies provide a valuable complement to in vivo experiments,
allowing for a more controlled manipulation of cellular functions and processes.
In contrast to cell lines, primary cells which are isolated directly from tissues have
a finite lifespan and limited expansion capacity. On the other hand, primary cells
have normal cell morphology and maintain many of the important markers and
functions seen in vivo [65, 141]. Therefore, in many cases the use of a cell line is
desirable, e.g., in cell biological studies on basic mechanisms or in drug development; however, in other cases such as research on complex metabolic processes, the use of primary cells becomes essential [142]. A particular example are
medical conditions involving alterations in cross talk between few cell types
constituting the tissue. Such situation takes place in, e.g., the liver during
development of fatty liver disease and its progression into more advanced stages
[143] or development of heart failure [144]. In both cases, pathogenic mechanism
involves disruption of homeostatic signaling between cells such as hepatocytes,
hepatic stellate cells, and liver sinusoidal endothelial cells (LSECs)—in the liver
or between cardiomyocytes—and cardiac microvascular endothelial cells
(CMECs)—in the heart. In both cases, the pathogenic mechanism can be induced
and studied with the use of in vitro models; however, it cannot fully replicate the
processes occurring in living organisms [145].
6 Small and Large Molecules Investigated by Raman Spectroscopy
179