Toward Controlled Photothermal Treatment of Single Cell: Optically Induced Heating and Remote Temperature Monitoring In Vitro through Double Wavelength Optical Tweezers

Sławomir Drobczyński, Katarzyna Prorok, Konstantin Tamarov, Kamila Duś-Szachniewicz, Vesa-Pekka Lehto, and Artur Bednarkiewicz
Cancer treatment based on hyperthermia (HT) relies on exposing the malignant cells to elevated local temperature. Although the procedure has been successfully applied in clinics, the fundamental aspects of HT are not yet fully understood. In order to verify the susceptibility of single cells in vitro to raised temperature, we have developed novel nano- and microtools. In particular, an optical double-trap system utilizing combined galvano-mirror scanning and spatial light phase modulator was devised to manipulate several micron-sized objects simultaneously. The manipulation comprised both optical trapping and translocating, on demand photoactivated heating, and simultaneous remote temperature readout of living cells, infrared activated heaters and optical thermometers, respectively. Mesoporous silicon microparticles were used as an infrared absorber to generate an increased temperature of about 100 °C with 0.4 W laser power. The optical micron-sized thermometer was based on up-converting Yb–Er codoped nanocrystalline particles encapsulated in amorphous silica shells produced with yeast cells as the templates. These hybrid particles displayed a relative sensitivity of 0.28%/K, an accuracy of 0.1 °C (at 32 °C), spatial resolution of <10 μm, and a temporal response of 50 ms/acquisition to record the temperature changes in specified areas in real time. The system was utilized in monitoring the stepwise cell death of individual diffuse large B-cell lymphoma (DLBCL) cells due to locally induced excessive heating induced by the absorber localized in the vicinity of the cell.

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