Photothermal time-resolved imaging of living cells

Background and Objectives: Thermal effects of laser radiation at cell level play very important role in cell functioning and in many laser applications. The aim of this study was to evaluate a new method of photothermal imaging (PTI) for monitoring short-time nano-scale thermal effects in individual living cells. Study Design/Materials and Methods: PTI is based on the irradiation of a cell with a short laser pump pulse (8 nanoseconds, 532 nm) and on registration of the laser-induced local thermal effects using time-resolved phase-contrast imaging with a pulsed probe laser. Results: PT images of lymphocytes, lympholeukemia cells in vitro were obtained at different laser energies. PTI in time-resolved mode allowed visualizing the structures with size less than diffraction limit (90-nm liposomes). The photodamage process was visualized for a single human leukocyte in suspension. Conclusions: PTI in non-invasive mode offered better contrast of living cell image than conventional optical phase-contrast microscopy. The data obtained showed that PTI is in perspective for studies of live non-fluorescent cells. (C) 2002 Wiley-Liss, Inc.