Short Laser Pulse-Induced Irreversible Photothermal Effects in Red Blood Cells

Background and Objectives: Photothermal (PT) responses of individual red blood cells (RBC) to short laser pulses may depend upon PT interactions at microscale. Study Design/Materials and Methods: A sequence of identical short laser pulses (0.5 and 10 nanoseconds, 532 nm) was applied to individual RBCs, and their PT properties were analyzed at microscale in real time after each single pulse. Results: PT interactions in RBC were found to be localized to sub-micrometer zones associated with Hb that may be responsible for overheating and evaporation at higher optical energies. At sub-ablative energies, a single short laser pulse induced irreversible changes in the optical properties of RBC that stimulated the transition from a heating-cooling response to ablative evaporation in individual erythrocytes during their exposure to subsequent, but identical pulses. Conclusion: The PT response of RBCs to short laser pulses of specific energy includes localized irreversible modifications of cell structure, resulting in three different effects: thermal non-ablative response, ablative evaporation, and residual thermal response. Lasers Surg. Med. 43:249-260, 2011. (C) 2011 Wiley-Liss, Inc.