AGE-RELATED CHANGES IN THE FLUORESCENCE OF MELANIN and LIPOFUSCIN GRANULES OF THE RETINAL PIGMENT EPITHELIUM: A TIME-RESOLVED FLUORESCENCE SPECTROSCOPY STUDY

Authors

  • Franco Docchio,

    1. Centro di Elettronica Quantistica e Strumentazione Elettronica del CNR, Istituto di Fisica, Politecnico di Milano, P.za L. da Vinci, 32, 20133 Milano, Italia
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    • *Dipartimento di Automazione Industri-ale, Facolta' di Ingegneria, Universita' degli Studi di Brescia, v. D. Valotti, 9, 25060 Mompiano (BS), Italia.

  • Mike Boulton,

    1. Centro di Elettronica Quantistica e Strumentazione Elettronica del CNR, Istituto di Fisica, Politecnico di Milano, P.za L. da Vinci, 32, 20133 Milano, Italia
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    • †Department of Cell and Structural Biology, University of Manchester, Oxford Road, Manchester, UK.

  • Rinaldo Cubeddu,

    1. Centro di Elettronica Quantistica e Strumentazione Elettronica del CNR, Istituto di Fisica, Politecnico di Milano, P.za L. da Vinci, 32, 20133 Milano, Italia
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  • Roberta Ramponi,

    1. Centro di Elettronica Quantistica e Strumentazione Elettronica del CNR, Istituto di Fisica, Politecnico di Milano, P.za L. da Vinci, 32, 20133 Milano, Italia
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  • Pierrette Dayhaw Barker

    1. Centro di Elettronica Quantistica e Strumentazione Elettronica del CNR, Istituto di Fisica, Politecnico di Milano, P.za L. da Vinci, 32, 20133 Milano, Italia
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    • †Pennsylvania College of Optometry, 1200 West Godfrey Ave., Philadelphia, PA 19141, USA.


Abstract

The photophysical properties of purified populations of melanin and lipofuscin granules from human retinal pigment epithelium, and their changes with donor age, have been investigated using high-sensitivity time-resolved fluorescence spectroscopy techniques with picosecond gating capabilities. The overall fluorescence intensity of both melanin and lipofuscin granules clearly increased with increasing donor age, the increase being most marked for melanin. In all granule populations the fluorescence decays were multiexponential with subnanosecond and nanosecond decay components. The resultant time-integrated and time-gated spectra also exhibited marked age-variations for each type of granule. Young melanin showed spectral patterns similar to those of bovine melanin, while a yellow-orange fluorescence band appeared in melanin samples from older age groups. Lipofuscin granules exhibited a blue, a yellow and an orange band whose relative amounts were age-related. The results demonstrate the potential of time-resolved techniques for discriminating fluorophores in vitro and in situ, and have confirmed results previously obtained using extraction techniques. Furthermore, the ability of this technique to identify and quantify individual fluorophores within granules may provide an important insight into the origin and development of lipofuscin within the retinal pigment epithelium and ultimately into the mechanisms of age-related retinal diseases.

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