Quantum dot based thermal spectroscopy and imaging of optically trapped micro-spheres and single cells

Laser-induced thermal effects in optically trapped micro-spheres and single cells have been investigated by Quantum Dot Luminescence Thermometry. Thermal spectroscopy has revealed a non-localized temperature distribution around the trap that extends over tens of microns, in agreement with previous theoretical models besides identifying water absorption as the most important heating source. Our experimental results of thermal loading at a variety of wavelengths reveal that an optimum trapping wavelength exists for biological applications close to 820 nm. This has been corroborated by a simultaneous analysis of the spectral dependence of cellular heating and damage in human lymphocytes during optical trapping. Quantum Dot Luminescence Thermometry has demonstrated that optical trapping with 820 nm laser radiation produces minimum intracellular heating, well below the cytotoxic level (43ºC), thus, avoiding cell damage.