In situ estimation of the entire color and spectra of age pigment-like materials: Application of a front-surface 3D-fluorescence technique

Fluorescent characteristics of age pigment-related materials were re-examined with improved techniques. A series of fluorescent colors, from blue to yellow-red were observed in artificial ceroid/lipofuscin. A front-surface accessory attached to a spectrofluorometer was found very useful in studying the age pigment-like aggregates directly in its solid state. With a three-dimensional (3D)-fluorescence measurement, in addition to the front-surface application, entire fluorescence spectra of artificial ceroid/lipofuscin both in extractions and in non-extractable tissues were obtained. When the front-surface 3D-scan technique was applied to estimate collagen-related age pigments of rat-tails in situ, a dynamic process of age-related protein deterioration accompanied with age pigment development was recorded. The front-surface 3D-fluorescence technique introduced in this study may be used as a practical and effective tool in studying in situ pigment alterations during aging process.