Arteries with 1-mm thick walls can be successfully vitrified by loading cryoprotective agents (CPAs) such as VS55 (8.4 M) or less concentrated DP6 (6 M) and cooling at or beyond their critical cooling rates of 2.5 and 40 °C/min, respectively. Successful warming from this vitrified state, however, can be challenging. For example, convective warming by simple warm-bath immersion achieves 70 °C/min, which is faster than VS55’s critical warming rate of 55 °C/min, but remains far below that of DP6 (185 °C/min). Here we present a new method that can dramatically increase the warming rates within either a solution or tissue by inductively warming commercially available metal components placed within solutions or in proximity to tissues with non-invasive radiofrequency fields (360 kHz, 20 kA/m). Directly measured warming rates within solutions exceeded 1000 °C/min with specific absorption rates (W/g) of 100, 450 and 1000 for copper foam, aluminum foil, and nitinol mesh, respectively. As proof of principle, a carotid artery diffusively loaded with VS55 and DP6 CPA was successfully warmed with high viability using aluminum foil, while standard convection failed for the DP6 loaded tissue. Modeling suggests this approach can improve warming in tissues up to 4-mm thick where diffusive loading of CPA may be incomplete. Finally, this technology is not dependent on the size of the system and should therefore scale up where convection cannot.
Bibliographical noteFunding Information:
This work was supported by NSF CBET #1336659 and the Kuhrmeyer Chair to J.C.B. We are also grateful for the financial support provided by the National Natural Science Foundation of China (11532009) and the National 111 Project of China (B06024). Author contributions: N.M. and M.S. conceived of and carried out experiments with analysis and support from J.C.B. N.M. performed tissue viability work. N.M. and P.R. performed and/or analyzed the heating experiments and thermal and mechanical modeling. N.M. wrote the manuscript with support and input from all the authors.
- RF heating
- Skin depth
- Tissue preservation
- Ultrarapid warming