55. Remote control CPAs delivery via cryonanoliposomes

Abstract

Whole organ preservation remains one of the greatest challenges in cryobiology. The main approaches to organ preservation such as hypothermic storage, supercooling, and vitrification each suffer from limitations including short timescales for preservation, ice crystal formation, mechanical and thermal stresses, cryoprotectant toxicity, etc. Liposomes are non-toxic, biodegradable and non-immunogenic drug delivery vehicles that are approved by the US FDA (1995). Liposomes are still among the most widely used nanoparticles as drug delivery systems and they are suitable for delivering both hydrophilic and lipophilic agents. Despite their widespread use in diverse fields, this technology has not been widely applied in the field of cryopreservation. We propose a CPA delivery system which can achieve targeted delivery of cryoprotectant agents (CPAs) to the intracellular or extracellular environment, while also serving as a means to deliver CPAs to a specific cell type within complex tissues. Furthermore, our proposed CPA delivery system will utilize controlled and timed release of CPAs which will allow delivery at specific time points throughout the freezing and thawing process. Ultrasonic and electromagnetic waves can be used to manipulate the release profile of CPA-loaded liposomes and their release profile can be fine-tuned based on liposomal characteristics such as phospholipid type and saturation. We anticipate several applications for controlled, timed release of CPAs. For example, vitrification involves high concentrations of toxic CPAs which must be loaded at low temperatures and be washed from the system after preservation in order to reduce toxicity. Our system will allow liposomes to be perfused at relatively higher temperatures and the release of their contents would be activated at relatively lower temperatures, improving uniform distribution and reducing toxicity. Other examples include the timed release of enzymes during rewarming which would degrade toxic CPAs such as DMSO thereby reducing CPA toxicity, or endothermic reactants, which could help with temperature uniformity during cooling. Finally, encapsulation of vital energy substrates (e.g. glucose) and their timed release during the earlier phases of thawing process may aid in meeting challenges associated with rewarming.