Amphiphilic phospholipid polymers as a cryoprotectant for vitrification and nanowarming of rat livers

Liver biobanking is a promising approach that saves the lives of patients with end-stage liver disease. Cryopreservation based on vitrification enables semi-permanent organ preservation, contributing to overcome the shortage of donors for liver transplants. A technical challenge in cryopreservation of transplantable organs lies in thawing methodology, and conventional convective warming cannot maintain the glassy state during thawing because of the large temperature gradient between the inner and outer parts of the organs, leading to ice formation and damage of cells in the organ. Nanowarming, in which magnetic nanoparticles are dispersed in a vitrification solution and heated by exposure of alternating magnetic field, can achieve uniform and rapid heating of organs. Herein, we report that amphiphilic phospholipid polymers composed of 2-methacryloyloxyethyl phosphorylcholine and n-butyl methacrylate can function as a cryoprotectant for nanowarming. The amphiphilic phospholipid polymers enhanced the viability of primary rat hepatocytes after vitrification. Moreover, the polymers enhanced the dispersion stability of magnetic nanoparticles in vitrification solution, and the perfusion of the vitrification solution with magnetic nanoparticles into rat livers through portal vein provided uniform distribution of the nanoparticles in the liver. After perfusion, the vitrified liver was successfully thawed rapidly and uniformly by nanowarming, which maintained tissue integrity and cell viability.