J. Bukowska and P. Piotrowski
44
3.4.2 SERS Biosensors
term “biosensor” has no clear definition. therefore, it might be applied to many
different systems. generally, biosensors provide data about the biological analyte
they are exposed to, monitoring a change in their physicochemical response. If we
monitor a SERS spectrum coming from the sensor in varying conditions, we deal
with a SERS sensor. there is a whole range of tasks which biosensors may be
employed to: monitoring a chosen kind of molecules, identification of the analyte
composition, or determination of the environment parameters. Previous section of
this review describes SERS experiments used for detection of certain biomolecules
such as proteins or enzymes. those examples perfectly fit in what we call a biosensor—they give information about the presence of a chosen biochemical compound
in the sample. those SERS sensors make use of various types of metallic substrates
to enhance Raman scattering. however, lots of opportunities in the cell analysis
open if metallic nanoparticles are engaged: thanks to their size, they can be successfully introduced into the cell in order to report the intracellular conditions from a
precisely defined place.
3.4.2.1 Specific Sensing of Biomolecules
Previously described experiments intended to detect biomolecules were carried out
in the following manner: object of the study needs to be found in the close proximity of the Raman enhancing substrate and then its characteristic SERS spectrum is
collected. there are cases, however, when such a direct approach cannot be applied.
Problem of glucose sensing illustrates such situation perfectly. glucose is a molecule of great importance in human body, especially due to its relation to diabetes
which has been considered a disease of civilization in the Western World for years
while its incidence in developing countries has been increasing rapidly. monitoring
a concentration of glucose with SERS is hindered by its small Raman cross section and minimal adsorption on SERS-active metals. van duyne et al. performed
a series of experiments to improve and optimize sensing parameters of glucose
[127–130]. they increased its affinity to the SERS substrate by adsorbing a SAm
of decanethiol on the AgFoN surface [127]. It let them detect glucose over a clinically interesting concentration range. Further investigations focused both on the
composition of the partition layer and the substrate. Researches showed that the
sensor with (1-mercaptoundeca-11-yl)tri(ethylene glycol) as a partition layer works
also in presence of interfering specimens, such as bovine serum albumin [128].
Real-time sensing was possible with a mixed SAm consisting of decanethiol and
mercaptohexanol [129]. Such a device exhibited stability for 10 days and was used
to determine concentration of glucose in the environment of bovine plasma. on the
other hand, it was proved that replacing AgFoN with AuFoN and 1-mercaptoundeca-11-yl)tri(ethylene glycol) with 1-mercaptoocta-8-yltri(ethylene glycol) resulted
in red-shift of plasmonic resonance which could be a step forward towards apply-
44
3.4.2 SERS Biosensors
term “biosensor” has no clear definition. therefore, it might be applied to many
different systems. generally, biosensors provide data about the biological analyte
they are exposed to, monitoring a change in their physicochemical response. If we
monitor a SERS spectrum coming from the sensor in varying conditions, we deal
with a SERS sensor. there is a whole range of tasks which biosensors may be
employed to: monitoring a chosen kind of molecules, identification of the analyte
composition, or determination of the environment parameters. Previous section of
this review describes SERS experiments used for detection of certain biomolecules
such as proteins or enzymes. those examples perfectly fit in what we call a biosensor—they give information about the presence of a chosen biochemical compound
in the sample. those SERS sensors make use of various types of metallic substrates
to enhance Raman scattering. however, lots of opportunities in the cell analysis
open if metallic nanoparticles are engaged: thanks to their size, they can be successfully introduced into the cell in order to report the intracellular conditions from a
precisely defined place.
3.4.2.1 Specific Sensing of Biomolecules
Previously described experiments intended to detect biomolecules were carried out
in the following manner: object of the study needs to be found in the close proximity of the Raman enhancing substrate and then its characteristic SERS spectrum is
collected. there are cases, however, when such a direct approach cannot be applied.
Problem of glucose sensing illustrates such situation perfectly. glucose is a molecule of great importance in human body, especially due to its relation to diabetes
which has been considered a disease of civilization in the Western World for years
while its incidence in developing countries has been increasing rapidly. monitoring
a concentration of glucose with SERS is hindered by its small Raman cross section and minimal adsorption on SERS-active metals. van duyne et al. performed
a series of experiments to improve and optimize sensing parameters of glucose
[127–130]. they increased its affinity to the SERS substrate by adsorbing a SAm
of decanethiol on the AgFoN surface [127]. It let them detect glucose over a clinically interesting concentration range. Further investigations focused both on the
composition of the partition layer and the substrate. Researches showed that the
sensor with (1-mercaptoundeca-11-yl)tri(ethylene glycol) as a partition layer works
also in presence of interfering specimens, such as bovine serum albumin [128].
Real-time sensing was possible with a mixed SAm consisting of decanethiol and
mercaptohexanol [129]. Such a device exhibited stability for 10 days and was used
to determine concentration of glucose in the environment of bovine plasma. on the
other hand, it was proved that replacing AgFoN with AuFoN and 1-mercaptoundeca-11-yl)tri(ethylene glycol) with 1-mercaptoocta-8-yltri(ethylene glycol) resulted
in red-shift of plasmonic resonance which could be a step forward towards apply-