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Department of Dermatology and AllergyCharité - Universitätsmedizin Berlin
Overview of noninvasive methods for determination of carotenoid concentrations in
mammalian skin
M.E. Darvin, J. Lademann
Charité-Universitätsmedizin Berlin, Center of Experimental and Applied Cutaneous Physiology, Department of Dermatology, Venerology and Allergology, Berlin,
Germany
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Carotenoids are known to be powerful antioxidants acting effectively against reactive oxygen species. The ability of carotenoids to quench oxygen radicals (including singlet oxygen) is related to the conjugated carbon double-bond system, and maximum protection is provided by those having nine or more double bonds.
Most prominent carotenoids being accumulated in human skin are beta-carotene (9 double bonds) and lycopene (11 double bonds) and their isomers.
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High-performance liquid chromatography (HPLC) is a widely used „gold standard“ method for determination of carotenoids. This method is highly invasive, time-consuming and expansive.Moreover, the oxidation of carotenoids during the sample preparation cannot be excluded.
For analyzing the kinetics of carotenoids in the skin noninvasive methods are irreplaceable and should be performed.
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Carotenoids cannot be detected in the skin using fluorescence analyses because their fluorescence efficiency is very low (10-
4-10-5).
Optical methods for noninvasive determination of carotenoids in mammalian skin:
1. resonance Raman spectroscopy2. Raman microscopy
3. reflection spectroscopy4. skin color measurements
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Resonance Raman spectroscopy
1 – Ar+ laser; 2 – lens system; 3 – filter (488nm/514.5nm);4, 9 – optical fiber; 5 – excitation channel; 6 – optical imaging system; 7 – skin; 8 – receiving channel; 10 – spectrometer; 11 – CCD; 2 – computer; 13 – photo detector
Darvin et al. J. Biomed. Opt. 18(6), 061230, 2013
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Brandon et al. Cancer Prev. Res. 3(4): 529-538, 2010
Excitation wavelength 488 nm
Fiber optic-based resonance Raman spectroscopy
for endoscopic measurement of carotenoid oxidative breakdown in living tissue
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Advantages:
- measurement quickness- high sensitivity- selectivity between beta-carotene and lycopene- increasing the measurement accuracy using photobleaching effect- measurement stability- transportability
Limitations:
- influence of other carotenoids- reabsorption of Raman signal at 527.2 nm by lycopene
Darvin et al. J. Biomed. Opt. 18(6), 061230, 2013
Resonance Raman spectroscopy
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Raman microscopy
1 – laser (NIR or VIS); 2 – short-pass filter; 3 – objective; 4 – mirrors;5 – skin; 6 – laser rejection filter; 7 – lens; 8 – optical fiber; 9 – spectrometer; 10 – CCD; 11 – computer
Darvin et al. J. Biomed. Opt. 18(6), 061230, 2013
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Advantages:
- measurement of axial distribution of carotenoids in the skin
Limitations:
- low and very low carotenoid concentrations are not detectable under non-resonant excitation
- bulky size- high price
Darvin et al. J. Biomed. Opt. 18(6), 061230, 2013
Raman microscopy
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Reflectance spectroscopy
1 – LED (440 - 490 nm); 2 – skin; 3 – focusing system;4 – replicated holographic grating spectrometer; 5 – Bluetooth
Darvin et al. J. Biophotonics 5(7): 550-558, 2012
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„Scanner“ in use
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Advantages:
- low price- measurement stability- compact size (easy to transport)- independence from electric mains
Limitations:
- low carotenoid concentrations are not detectable
- could be applied only on thenal and plantar skin areas where the epidermis is thick enough and influence of melanin and blood
chromophores is less pronounced
Darvin et al. J. Biomed. Opt. 18(6), 061230, 2013
Reflectance spectroscopy
Darvin et al. J. Biophotonics 5(7): 550-558, 2012
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Skin color measurements
Bersha. Master Thesis, University of Eastern Finland, 21 June 2010
b*-value characterizing yellowness of the skin serves as a measuring parameter for epidermal carotenoids
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Alaluf et al. Journal of Nutrition 132(3), 399-403, 2002
b*-value was found to correlatewith concentration of carotenoids in human epidermis
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Advantages:
- low price- compact size (easy to transport)- independence from electric mains
Limitations:
- low carotenoid concentrations are not detectable
- could be applied only on thenal and plantar skin areas where the epidermis is thick enough and influence of melanin and blood
chromophores is less pronounced- measurement stability is not high enough
Darvin et al. J. Biomed. Opt. 18(6), 061230, 2013
Skin color measurements
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Resonance Raman spectroscopy
Raman microscopy Skin color measurements Reflection spectroscopy
Size/weight compact to bulky bulky compact compact
Transportability yes no yes yes
Price middle to high high low low to middle
Measurement time 3 to 90 sec
around 60 seconds
around 30 sec
around 60 sec
Measurement stability better than 10%
better than 10%
no data
better than 10%
Light source laser, LED laser lamp, LED LED
Measurement depth up to 200 µm
up to 40 µm
up to 200 µm
up to 200 µm
Selectivity to lycopene no no no
Electric mains needed needed don’t needed don’t needed
Personal rating
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ConclusionsComparison of optical methods
for measurement of carotenoids in human skin
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Thank you for your attention