Evidence for excitation of fluorescence in RPE melanin by multiphoton absorption

Randolph D. Glickman; Benjamin A. Rockwell; Gary D. Noojin; David J. Stolarski; Michael L. Denton

doi:10.1117/12.472521

27 June 2002 Evidence for excitation of fluorescence in RPE melanin by multiphoton absorption

Randolph D. Glickman, Benjamin A. Rockwell, Gary D. Noojin, David J. Stolarski, Michael L. Denton

Author Affiliations +

Proceedings Volume 4617, Laser Tissue Interaction XIII: Photochemical, Photothermal, and Photomechanical; (2002) https://doi.org/10.1117/12.472521
Event: International Symposium on Biomedical Optics, 2002, San Jose, CA, United States

Abstract

Previously, we reported that ultrashort, near infrared (NIR) laser pulses caused more DNA breakage in cultured retinal pigment epithelial (RPE) cells than did CW, NIR laser radiation delivering a similar radiant exposure. We hypothesized that this difference was due to multiphoton absorption in an intracellular chromophore such as the RPE melanin. We investigated two-photon excitation of fluorescence in a suspension of isolated bovine RPE melanosomes exposed to a 1-KHz train of approximately 50- fsec laser pulses at 810 nm from a Ti:Sapphire laser, and compared this to the fluorescence excited by CW exposures at 406 nm from a Krypton ion laser. Fluorescence was measured with a PC-based spectrometer. The CW sources excited fluorescence with a peak at 525 nm. The fluorescence intensity depended on the irradiance of the sample, as well as the melanosome concentration. Peak fluorescence was obtained with a suspension of ~2 x 10⁷ melanin granules/ml. The 810-nm, ultrashort pulses also excited fluorescence, but with a broader, lower-amplitude peak. The weaker fluorescence signal excited by the 810-nm ultrashort pulse laser for a given melanosome concentration, compared to 406-nm CW excitation, is possibly due to the smaller two- photon absorption cross-section. These results indicate the involvement of multiphoton absorption in DNA damage.

Citation Download Citation

Randolph D. Glickman, Benjamin A. Rockwell, Gary D. Noojin, David J. Stolarski, and Michael L. Denton "Evidence for excitation of fluorescence in RPE melanin by multiphoton absorption", Proc. SPIE 4617, Laser Tissue Interaction XIII: Photochemical, Photothermal, and Photomechanical, (27 June 2002); https://doi.org/10.1117/12.472521

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

;

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE