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Multifunctional photosensitizer-based contrast agents for photoacoustic imaging.

Ho CJ, Balasundaram G, Driessen W, McLaren R, Wong CL, Dinish US, Attia AB, Ntziachristos V, Olivo M - Sci Rep (2014)

Bottom Line: Photoacoustic imaging is a novel hybrid imaging modality combining the high spatial resolution of optical imaging with the high penetration depth of ultrasound imaging.Photoacoustic imaging of photosensitizers exhibits advantages over fluorescence imaging, which is prone to photobleaching and autofluorescence interference.In this work, we examined the photoacoustic activity of 5 photosensitizers: zinc phthalocyanine, protoporphyrin IX, 2,4-bis [4-(N,N-dibenzylamino)-2,6-dihydroxyphenyl] squaraine, chlorin e6 and methylene blue in phantoms, among which zinc phthalocyanine showed the highest photoacoustic activity.

View Article: PubMed Central - PubMed

Affiliation: Singapore Bioimaging Consortium, Agency for Science, Technology and Research, Singapore.

ABSTRACT
Photoacoustic imaging is a novel hybrid imaging modality combining the high spatial resolution of optical imaging with the high penetration depth of ultrasound imaging. Here, for the first time, we evaluate the efficacy of various photosensitizers that are widely used as photodynamic therapeutic (PDT) agents as photoacoustic contrast agents. Photoacoustic imaging of photosensitizers exhibits advantages over fluorescence imaging, which is prone to photobleaching and autofluorescence interference. In this work, we examined the photoacoustic activity of 5 photosensitizers: zinc phthalocyanine, protoporphyrin IX, 2,4-bis [4-(N,N-dibenzylamino)-2,6-dihydroxyphenyl] squaraine, chlorin e6 and methylene blue in phantoms, among which zinc phthalocyanine showed the highest photoacoustic activity. Subsequently, we evaluated its tumor localization efficiency and biodistribution at multiple time points in a murine model using photoacoustic imaging. We observed that the probe localized at the tumor within 10 minutes post injection, reaching peak accumulation around 1 hour and was cleared within 24 hours, thus, demonstrating the potential of photosensitizers as photoacoustic imaging contrast agents in vivo. This means that the known advantages of photosensitizers such as preferential tumor uptake and PDT efficacy can be combined with photoacoustic imaging capabilities to achieve longitudinal monitoring of cancer progression and therapy in vivo.

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Related in: MedlinePlus

Normalized absorbance as a function of wavelength for the five photosensitizers in the NIR region from 680 to 900 nm.ZnPc shows the highest overall absorbance, followed by MB, Sq, PpIX and Ce6, in decreasing order.
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f1: Normalized absorbance as a function of wavelength for the five photosensitizers in the NIR region from 680 to 900 nm.ZnPc shows the highest overall absorbance, followed by MB, Sq, PpIX and Ce6, in decreasing order.

Mentions: In order to obtain information about the optical absorption properties of the contrast agents, their wavelength-dependent absorption spectra at known concentrations were measured using a spectrophotometer, which in turn were normalized to obtain the concentration-independent normalized absorbance (directly proportional to extinction coefficient) as a function of wavelength for each contrast agent (Figure 1), based on Beer-Lambert law: where A(λ) is the measured wavelength-dependent absorbance, I0 is the incident light intensity, I is the transmitted light intensity, ε(λ) is the wavelength-dependent extinction coefficient of the contrast agent, c is the concentration of the contrast agent and l is the path length of the quartz cuvette (1 cm).


Multifunctional photosensitizer-based contrast agents for photoacoustic imaging.

Ho CJ, Balasundaram G, Driessen W, McLaren R, Wong CL, Dinish US, Attia AB, Ntziachristos V, Olivo M - Sci Rep (2014)

Normalized absorbance as a function of wavelength for the five photosensitizers in the NIR region from 680 to 900 nm.ZnPc shows the highest overall absorbance, followed by MB, Sq, PpIX and Ce6, in decreasing order.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4061552&req=5

f1: Normalized absorbance as a function of wavelength for the five photosensitizers in the NIR region from 680 to 900 nm.ZnPc shows the highest overall absorbance, followed by MB, Sq, PpIX and Ce6, in decreasing order.
Mentions: In order to obtain information about the optical absorption properties of the contrast agents, their wavelength-dependent absorption spectra at known concentrations were measured using a spectrophotometer, which in turn were normalized to obtain the concentration-independent normalized absorbance (directly proportional to extinction coefficient) as a function of wavelength for each contrast agent (Figure 1), based on Beer-Lambert law: where A(λ) is the measured wavelength-dependent absorbance, I0 is the incident light intensity, I is the transmitted light intensity, ε(λ) is the wavelength-dependent extinction coefficient of the contrast agent, c is the concentration of the contrast agent and l is the path length of the quartz cuvette (1 cm).

Bottom Line: Photoacoustic imaging is a novel hybrid imaging modality combining the high spatial resolution of optical imaging with the high penetration depth of ultrasound imaging.Photoacoustic imaging of photosensitizers exhibits advantages over fluorescence imaging, which is prone to photobleaching and autofluorescence interference.In this work, we examined the photoacoustic activity of 5 photosensitizers: zinc phthalocyanine, protoporphyrin IX, 2,4-bis [4-(N,N-dibenzylamino)-2,6-dihydroxyphenyl] squaraine, chlorin e6 and methylene blue in phantoms, among which zinc phthalocyanine showed the highest photoacoustic activity.

View Article: PubMed Central - PubMed

Affiliation: Singapore Bioimaging Consortium, Agency for Science, Technology and Research, Singapore.

ABSTRACT
Photoacoustic imaging is a novel hybrid imaging modality combining the high spatial resolution of optical imaging with the high penetration depth of ultrasound imaging. Here, for the first time, we evaluate the efficacy of various photosensitizers that are widely used as photodynamic therapeutic (PDT) agents as photoacoustic contrast agents. Photoacoustic imaging of photosensitizers exhibits advantages over fluorescence imaging, which is prone to photobleaching and autofluorescence interference. In this work, we examined the photoacoustic activity of 5 photosensitizers: zinc phthalocyanine, protoporphyrin IX, 2,4-bis [4-(N,N-dibenzylamino)-2,6-dihydroxyphenyl] squaraine, chlorin e6 and methylene blue in phantoms, among which zinc phthalocyanine showed the highest photoacoustic activity. Subsequently, we evaluated its tumor localization efficiency and biodistribution at multiple time points in a murine model using photoacoustic imaging. We observed that the probe localized at the tumor within 10 minutes post injection, reaching peak accumulation around 1 hour and was cleared within 24 hours, thus, demonstrating the potential of photosensitizers as photoacoustic imaging contrast agents in vivo. This means that the known advantages of photosensitizers such as preferential tumor uptake and PDT efficacy can be combined with photoacoustic imaging capabilities to achieve longitudinal monitoring of cancer progression and therapy in vivo.

Show MeSH
Related in: MedlinePlus