J. Bukowska and P. Piotrowski
50
Finding out the composition of the analyte is not always the main goal of the
research. Sometimes it is more interesting to determine intracellular variables. Concept of the biosensor remains the same: surface of the nanoparticle yielding Raman enhancement is modified with reporter molecules whose SERS spectra are
recorded. So that the sensor could monitor the environment, spectrum of the reporter should change with the studied parameter, such as intracellular redox potential.
It plays an important role in protein interactions, apoptosis and signalling. In this
approach, SERS spectra of the nanoprobe-attached molecules that exhibit SERS
spectrum sensitive to oxidation state are recorded. Auchinvole et al. constructed
a biosensor based on the SERS effect of two separate molecules, quinone derivatives: 1,8-diaza-4,5-dithia-1,8-di(2-chloro-[1,4]-naphthoquinone-3-yl)octane (NQ)
and 2-mercaptobenzene-1,4-diol (hQ), deposited on the surface of gold nanoshells
[162]. they undergo reversible two-electron redox reactions. the nanoprobes were
introduced into single fibroblast cell and the SERS spectra were collected from the
cytoplasm, where nanoprobes have been located. Plots of the marker band intensity
changes show sigmoidal shape for both of the sensors. Based on the intensities of
the respective SERS bands, relative content of the reduced/oxidized form of probe
molecules was estimated, enabling determination of the value of resting cellular
potential. What is important, it was proved that the introduction of the device into
the cell does not change the redox potential inside. In separate experiments, the
authors also demonstrated the capability of SERS to monitor the localized response
to reductive and oxidative stress.
Another essential variable of the intracellular environment is the ph value. different compartments are characterized by different ph ranges which additionally
change over time. Anomalies in the ph value might be associated with several diseases, such as kidney failure or certain cancers. Importance of acidity inside the cell
led to a big collection of ph biosensors throughout the literature. determination of
ph value inside the living cell may be an interesting illustration of possible applications of labeled SERS nanoprobes [163–170]. In these experiments, gold nanoparticles are functionalized with reporter molecules that demonstrate strong SERS
spectrum sensitive to ph, such as 4-mercaptobenzoic acid (PmBA), 4-mercaptopyridine [165] or 4-aminothiophenol [167]. Next, the nanosensors are introduced
into the cells and the SERS spectra of a reporter molecule are collected at many
points of the sample, thus probing and imaging ph values inside the individual living cells. due to changes in their chemical structure in varying ph, intensities of the
chosen marker band vary as well. Kneipp et al. employed PmBA based sensor to
perform SERS mapping of the ph-value in the cell [163]. they also broadened the
working range of the sensor by exploiting SEhRS (surface-enhanced hyper-Raman
scattering). A mobile SERS nanosensor made of aggregates of Au nanoparticles,
functionalized with PmBA enabled monitoring changes in local ph value over time
and observing some metabolic changes in living NIh/3t3 cells [166]. Local ph
value was also monitored inside individual cancer cells after treatment by the photodynamic therapy drug emodine [168]. In this report, a micrometer-sized silica
beads covered with Ag nanoparticles functionalized with PmBA were passively
embedded into the cells. the ph changes over time revealed ability of the cell to
50
Finding out the composition of the analyte is not always the main goal of the
research. Sometimes it is more interesting to determine intracellular variables. Concept of the biosensor remains the same: surface of the nanoparticle yielding Raman enhancement is modified with reporter molecules whose SERS spectra are
recorded. So that the sensor could monitor the environment, spectrum of the reporter should change with the studied parameter, such as intracellular redox potential.
It plays an important role in protein interactions, apoptosis and signalling. In this
approach, SERS spectra of the nanoprobe-attached molecules that exhibit SERS
spectrum sensitive to oxidation state are recorded. Auchinvole et al. constructed
a biosensor based on the SERS effect of two separate molecules, quinone derivatives: 1,8-diaza-4,5-dithia-1,8-di(2-chloro-[1,4]-naphthoquinone-3-yl)octane (NQ)
and 2-mercaptobenzene-1,4-diol (hQ), deposited on the surface of gold nanoshells
[162]. they undergo reversible two-electron redox reactions. the nanoprobes were
introduced into single fibroblast cell and the SERS spectra were collected from the
cytoplasm, where nanoprobes have been located. Plots of the marker band intensity
changes show sigmoidal shape for both of the sensors. Based on the intensities of
the respective SERS bands, relative content of the reduced/oxidized form of probe
molecules was estimated, enabling determination of the value of resting cellular
potential. What is important, it was proved that the introduction of the device into
the cell does not change the redox potential inside. In separate experiments, the
authors also demonstrated the capability of SERS to monitor the localized response
to reductive and oxidative stress.
Another essential variable of the intracellular environment is the ph value. different compartments are characterized by different ph ranges which additionally
change over time. Anomalies in the ph value might be associated with several diseases, such as kidney failure or certain cancers. Importance of acidity inside the cell
led to a big collection of ph biosensors throughout the literature. determination of
ph value inside the living cell may be an interesting illustration of possible applications of labeled SERS nanoprobes [163–170]. In these experiments, gold nanoparticles are functionalized with reporter molecules that demonstrate strong SERS
spectrum sensitive to ph, such as 4-mercaptobenzoic acid (PmBA), 4-mercaptopyridine [165] or 4-aminothiophenol [167]. Next, the nanosensors are introduced
into the cells and the SERS spectra of a reporter molecule are collected at many
points of the sample, thus probing and imaging ph values inside the individual living cells. due to changes in their chemical structure in varying ph, intensities of the
chosen marker band vary as well. Kneipp et al. employed PmBA based sensor to
perform SERS mapping of the ph-value in the cell [163]. they also broadened the
working range of the sensor by exploiting SEhRS (surface-enhanced hyper-Raman
scattering). A mobile SERS nanosensor made of aggregates of Au nanoparticles,
functionalized with PmBA enabled monitoring changes in local ph value over time
and observing some metabolic changes in living NIh/3t3 cells [166]. Local ph
value was also monitored inside individual cancer cells after treatment by the photodynamic therapy drug emodine [168]. In this report, a micrometer-sized silica
beads covered with Ag nanoparticles functionalized with PmBA were passively
embedded into the cells. the ph changes over time revealed ability of the cell to