Photothermal images of live cells in presence of drug

Abstract

A new method for the study of drug-cell interaction is suggested. It is based on optical monitoring of cell response to drug impact. To detect this response, a high sensitive photothermal imaging technique has been developed. This technique is based on irradiation of the cells with a focused short pulse double-frequency pump laser (532 nm, 8 ns) and monitoring the laser-induced local thermal effects. This is realized with a second collinear dye laser pulse (630 nm, 6 ns) that probes the heated cell absorbing zones. The temperature-dependent variations of the refractive index in the absorbing zones in cross section of probe beam are recorded with phase-contrast technique. The photothermal (PT) image represents a two-dimensional depth-integrated temperature distribution in the irradiated volume and correlates with the conventional optical absorption images. It was experimentally shown that the introduction of NaN(3) or anti-tumor drug in the cell suspension led to a change in the structure of PT images of human lymphocytes and human lympholeukemia cells, respectively. It was hypothesized that the observed effects could be associated with the change of redox state of respiratory chain component.

Spectral evaluation of laser-induced cell damage with photothermal microscopy

“…The general principles of the PT technique have already been reported [24][25][26][27][28][29]. Thermal-lens (thermolens) mode permitted the recording of a whole-cell's time-resolved integrated PT response via focusing/defocusing effects (depending on the polarity of refractive index changes and the optical scheme) of a collinear, intensity-stabilized, continuous-wave helium-neon (He-Ne) probe laser beam (wavelength, 633 nm; diameter, 15 mm; energy, 1.4 mW; model 117A, Spectra-Physics, Inc.) detected by a photodiode (C5658; Hamamatsu Corp.) (Fig.…”

“…The entire PT-image-acquisition procedure included illumination of the cell with three pulses: an initial probe pulse followed by a 0.1-second delay to the pump pulse, and then a second probe pulse with a tunable delay (0-5,000 nanoseconds) to the pump pulse. The PT image was calculated as the difference between the two probe images [28] and depended only on absorption contrast transformed by the pump laser pulse into refractive contrast, rather than on possible phase distortion of the probe beam itself, natural refractive intracellular heterogeneities, and especially, scattered light. The chosen energy of the probe laser pulse ($10 nJ) was much lower than the pump-pulse energy permitted, thus minimizing the influence of probe-beam absorption by objects.…”

Thermooptical detection in microchips: From macro‐ to micro‐scale with enhanced analytical parameters

“…However, a question arises for the analyst as to which variant of thermal lensing best suits chemical analysis, and which apparatus design should be selected. If we consider the vast material on optical-scheme optimization in continuous-wave thermal lensing [1,2,5,13,15,18,19,29,35,36], several conclusions can be drawn: a) Optimization of the optical schemes in TLS, CB-TLS, and TLM are considered separate tasks, due to differences in apparatuses.…”

“…Thirdly, if we use the same diffraction theory of thermal lensing [2,18,19,29,35] and work under the same conditions, the experimental optimum geometry parameters, V and B (Eq. 4), differ significantly for various setups (Table 1, see also [17-19, 23, 25, 27]).…”

Monitoring of apoptosis in intact single cells with photothermal microscope

“…The ability to detect thermal effects produced by cellular structures allows more direct diagnostics of the cell state. This method was applied for quantitative studies of cell metabolic activity (18), drug toxicity at cell level (19), and has been realized in three PT cytometric techniques: 1) measurement of cell integrated time-response to laser pulse-thermal lens method (20); 2) time-resolved phase-contrast photothermal microscopy-imaging method (21); and 3) laser-induced cell damage analysis-laser viability test (22).…”