Numerical Investigation of a Novel Method to Vitrify Biological Tissues Using Pulsed Lasers and Cryogenic Temperatures

The ability to eliminate freezing damage using “vitrification” (or the formation of glass) has long been an area of intense interest in cryobiology. Typically vitrification is achieved when biological systems are cooled at rates ranging from ∼8,000 °C/min to ∼10,000 °C/min [1–5]. Using traditional cooling methods (immersion in liquid nitrogen), such high cooling rates are currently not achievable, in large tissue sections (∼cm’s). In the present study we investigate a novel method to achieve high cooling rates in large tissue sections by pulsed laser heating in conjunction with cryogenic temperatures, i.e. high cooling rates are achieved by the localized difference in temperature between the laser heated tissue (∼1000’s of °C) and the surrounding liquid nitrogen (∼−160 °C). Additionally, the use of pulsed lasers allows localized heating of the tissue coupled with small time scales of energy deposition (0.1 to 1 pico seconds) such that the heating/thermal damage in tissues is minimized. To amplify this idea further, we developed a numerical model to predict the temperature transients in tissues exposed to laser heating and cryogenic temperatures. Analysis of our numerical simulations suggest that a perturbation of ∼3500 °C in a 5mm thick tissue leads to cooling rates in excess of ∼8000 °C/min throughout the tissue slice. These results indicate the possibility of vitrifying large tissue sections of cryobiological relevance using a combination of laser heating and liquid nitrogen cooling.