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Recent advances in intracellular and in vivo ROS sensing: focus on nanoparticle and nanotube applications.

Uusitalo LM, Hempel N - Int J Mol Sci (2012)

Bottom Line: However, there is a great need to improve on current methods to address the above issues.Recently, the field of molecular sensing and imaging has begun to take advantage of the unique physico-chemical properties of nanoparticles and nanotubes.Here we discuss the recent advances in the use of these nanostructures as alternative platforms for ROS sensing, with particular emphasis on intracellular and in vivo ROS detection and quantification.

View Article: PubMed Central - PubMed

Affiliation: Nanobioscience Constellation, College of Nanoscale Sciences & Engineering, University at Albany, SUNY, 257 Fuller Rd., Albany, NY 12203, USA; E-Mail: luusitalo@albany.edu.

ABSTRACT
Reactive oxygen species (ROS) are increasingly being implicated in the regulation of cellular signaling cascades. Intracellular ROS fluxes are associated with cellular function ranging from proliferation to cell death. Moreover, the importance of subtle, spatio-temporal shifts in ROS during localized cellular signaling events is being realized. Understanding the biochemical nature of the ROS involved will enhance our knowledge of redox-signaling. An ideal intracellular sensor should therefore resolve real-time, localized ROS changes, be highly sensitive to physiologically relevant shifts in ROS and provide specificity towards a particular molecule. For in vivo applications issues such as bioavailability of the probe, tissue penetrance of the signal and signal-to-noise ratio also need to be considered. In the past researchers have heavily relied on the use of ROS-sensitive fluorescent probes and, more recently, genetically engineered ROS sensors. However, there is a great need to improve on current methods to address the above issues. Recently, the field of molecular sensing and imaging has begun to take advantage of the unique physico-chemical properties of nanoparticles and nanotubes. Here we discuss the recent advances in the use of these nanostructures as alternative platforms for ROS sensing, with particular emphasis on intracellular and in vivo ROS detection and quantification.

No MeSH data available.


Related in: MedlinePlus

Examples of Nanoparticles (NPs) adapted for ROS sensing (A) Polymer-based NPs embedded with ROS-sensing and reference fluorescent dyes; (B) Chemiluminescent NPs; (C) Metallic NP fluorescence quenching upon oxidation of functionalized ROS sensitive molecules (blue).
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f1-ijms-13-10660: Examples of Nanoparticles (NPs) adapted for ROS sensing (A) Polymer-based NPs embedded with ROS-sensing and reference fluorescent dyes; (B) Chemiluminescent NPs; (C) Metallic NP fluorescence quenching upon oxidation of functionalized ROS sensitive molecules (blue).

Mentions: As mentioned above, fluorescence sensors have the advantage of providing a high signal-to-noise ratio with high sensitivity and relative ease of detection. Embedding ROS-sensing dyes in polymeric NPs provide advantages, such as inhibiting interaction of the dye with intracellular proteins, protecting the dye somewhat from degradation and inhibiting undesired sequestration into subcellular compartments. In addition, loading of a reference dye allows for accurate ratiometric calculations of the ROS signal (Figure 1A). Kim et al. recently reasoned that specificity of DCFH-DA for H2O2 can be achieved by encapsulating the dye in organically modified silicate (ORMOSIL) NPs [34]. The authors describe cellular targeting of NPs to macrophages using a TAT-peptide to enhance membrane penetration and potentially prevent phagocytosis, as the probe is pH sensitive, a common feature of ROS-sensing probes. With this probe the authors reported sensing of low nM H2O2 levels and intracellular H2O2 bursts following macrophage stimulation. The authors argue that short-lived ROS such as ·OH cannot penetrate into the center of the NP due to time constraints, and that other ROS and RNS are excluded due to the hydrophobic energy barrier of the NP. Furthermore, size exclusion prevents access of alkylperoxyl radical and proteins such as esterase and HRP to the dye. The problem that remains with this proposed concept is the fact that H2O2 does not directly interact with DCFH-DA, but rather its hydrophilic derivative, which requires esterases for DCFH-DA hydrolysis. Since esterases presumably will not have access to the NP matrix this will present a fundamental problem to use of this NP in H2O2/ROS sensing. While the authors argue that DCFH-DA fluorescence can directly be induced by H2O2 in their system this is generally not considered to be an accurate assumption and questions the validity of their NP design [34]. ORMOSIL NPs have also been used to sense singlet oxygen using 9,10-dimethyl anthracene, again providing improved selectivity due to the hydrophobic nature of the matrix, inhibiting access to short lived and polar ROS [35]. Variations of NPs containing ROS-sensitive fluorescent dyes have also been used to detect other intracellular ROS and RNS, such as peroxinitrite and ·OH, and often contain a reference dye embedded in the matrix for ratiometric quantification [36–38]. An alternative to direct interaction of ROS with the sensor dye has been explored by encapsulating horseradish peroxidase (HRP) into NPs. In one study, H2O2 was used as a substrate by HRP to oxidize the target dye Amplex Red and shown to sense exogenously applied H2O2 and LPS induced ROS changes within macrophage cells [39].


Recent advances in intracellular and in vivo ROS sensing: focus on nanoparticle and nanotube applications.

Uusitalo LM, Hempel N - Int J Mol Sci (2012)

Examples of Nanoparticles (NPs) adapted for ROS sensing (A) Polymer-based NPs embedded with ROS-sensing and reference fluorescent dyes; (B) Chemiluminescent NPs; (C) Metallic NP fluorescence quenching upon oxidation of functionalized ROS sensitive molecules (blue).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3472707&req=5

f1-ijms-13-10660: Examples of Nanoparticles (NPs) adapted for ROS sensing (A) Polymer-based NPs embedded with ROS-sensing and reference fluorescent dyes; (B) Chemiluminescent NPs; (C) Metallic NP fluorescence quenching upon oxidation of functionalized ROS sensitive molecules (blue).
Mentions: As mentioned above, fluorescence sensors have the advantage of providing a high signal-to-noise ratio with high sensitivity and relative ease of detection. Embedding ROS-sensing dyes in polymeric NPs provide advantages, such as inhibiting interaction of the dye with intracellular proteins, protecting the dye somewhat from degradation and inhibiting undesired sequestration into subcellular compartments. In addition, loading of a reference dye allows for accurate ratiometric calculations of the ROS signal (Figure 1A). Kim et al. recently reasoned that specificity of DCFH-DA for H2O2 can be achieved by encapsulating the dye in organically modified silicate (ORMOSIL) NPs [34]. The authors describe cellular targeting of NPs to macrophages using a TAT-peptide to enhance membrane penetration and potentially prevent phagocytosis, as the probe is pH sensitive, a common feature of ROS-sensing probes. With this probe the authors reported sensing of low nM H2O2 levels and intracellular H2O2 bursts following macrophage stimulation. The authors argue that short-lived ROS such as ·OH cannot penetrate into the center of the NP due to time constraints, and that other ROS and RNS are excluded due to the hydrophobic energy barrier of the NP. Furthermore, size exclusion prevents access of alkylperoxyl radical and proteins such as esterase and HRP to the dye. The problem that remains with this proposed concept is the fact that H2O2 does not directly interact with DCFH-DA, but rather its hydrophilic derivative, which requires esterases for DCFH-DA hydrolysis. Since esterases presumably will not have access to the NP matrix this will present a fundamental problem to use of this NP in H2O2/ROS sensing. While the authors argue that DCFH-DA fluorescence can directly be induced by H2O2 in their system this is generally not considered to be an accurate assumption and questions the validity of their NP design [34]. ORMOSIL NPs have also been used to sense singlet oxygen using 9,10-dimethyl anthracene, again providing improved selectivity due to the hydrophobic nature of the matrix, inhibiting access to short lived and polar ROS [35]. Variations of NPs containing ROS-sensitive fluorescent dyes have also been used to detect other intracellular ROS and RNS, such as peroxinitrite and ·OH, and often contain a reference dye embedded in the matrix for ratiometric quantification [36–38]. An alternative to direct interaction of ROS with the sensor dye has been explored by encapsulating horseradish peroxidase (HRP) into NPs. In one study, H2O2 was used as a substrate by HRP to oxidize the target dye Amplex Red and shown to sense exogenously applied H2O2 and LPS induced ROS changes within macrophage cells [39].

Bottom Line: However, there is a great need to improve on current methods to address the above issues.Recently, the field of molecular sensing and imaging has begun to take advantage of the unique physico-chemical properties of nanoparticles and nanotubes.Here we discuss the recent advances in the use of these nanostructures as alternative platforms for ROS sensing, with particular emphasis on intracellular and in vivo ROS detection and quantification.

View Article: PubMed Central - PubMed

Affiliation: Nanobioscience Constellation, College of Nanoscale Sciences & Engineering, University at Albany, SUNY, 257 Fuller Rd., Albany, NY 12203, USA; E-Mail: luusitalo@albany.edu.

ABSTRACT
Reactive oxygen species (ROS) are increasingly being implicated in the regulation of cellular signaling cascades. Intracellular ROS fluxes are associated with cellular function ranging from proliferation to cell death. Moreover, the importance of subtle, spatio-temporal shifts in ROS during localized cellular signaling events is being realized. Understanding the biochemical nature of the ROS involved will enhance our knowledge of redox-signaling. An ideal intracellular sensor should therefore resolve real-time, localized ROS changes, be highly sensitive to physiologically relevant shifts in ROS and provide specificity towards a particular molecule. For in vivo applications issues such as bioavailability of the probe, tissue penetrance of the signal and signal-to-noise ratio also need to be considered. In the past researchers have heavily relied on the use of ROS-sensitive fluorescent probes and, more recently, genetically engineered ROS sensors. However, there is a great need to improve on current methods to address the above issues. Recently, the field of molecular sensing and imaging has begun to take advantage of the unique physico-chemical properties of nanoparticles and nanotubes. Here we discuss the recent advances in the use of these nanostructures as alternative platforms for ROS sensing, with particular emphasis on intracellular and in vivo ROS detection and quantification.

No MeSH data available.


Related in: MedlinePlus