There are huge markets for research, diagnostic and clinical applications of naturally occurring and engineered cells, tissues and organs. Strategic assessment of the field has identified the need for better preservation methods because freezing methods of cryopreservation have been shown to damage tissues and organs due to ice formation. Vitrification, sub-zero storage below the glass transition temperature in a 'glassy'rather than a crystalline frozen phase, is a form of cryopreservation that avoids ice formation. Itis an important enabling approach for cellular and regenerative medicine, offering the ability to store and transport cells, tissues and organs for a great variety of biomedical uses. Unfortunately, practical application of vitrification has been limited to smaller systems such as cells and thin tissues due to diffusive (heat and mass transfer) and phase change limitations that preclude use in organs and larger tissues. To circumvent this problem we propose using radiofrequency excited magnetic nanoparticles around and within biomaterials. This approach has the potential to dramatically improve vitrification through faster and more uniform thawing rates, thereby reducing or eliminating devitrification and thermal stress associated cracking to improve viability and structural integrity upon rewarming. In addition more rapid warming rates will also permit use of lower concentrations of cryoprotectants that will reduce the risks of cytotoxicity. Preliminary experiments have demonstrated that this innovative rewarming technique can increase heating rates by at least an order of magnitude over conventional boundary heating and that it does not depend on sample size. We propose using animal-derived blood vessel tissue models for development of a new approach for rapidly and uniformly heating vitrified biospecimens in two specific aims. The magnetic nanoparticles will be surrounding the vessel and within the vessel lumen.
In Aim 1 the magnetic nanoparticles will be coated with polyethylene glycol functionalized biocompatible mesoporous silica and the effects of coated magnetic nanoparticle concentration with and without ice-free vitrification and radiofrequency on a thin walled (<100 m) animal artery model will be assessed.
In Aim 2 finite element modeling of heat transfer will be performed followed by experimental evaluation of samples from 3- 100mL, total volume, containing animal blood vessels varying in wall thickness (<100 - >1,000 m) in order to determine the impact of variable non-uniform magnetic nanoparticle biodistribution. In both aims cell viability and tissue functions will be demonstrated using established viability and physiology assays. Effective vitrification will be evaluated using computed tomography and cryosubstitution methods to detect ice formation. These studies will combine to test the feasibility of our working hypothesis that 'radiofrequency excited biocompatible magnetic nanoparticles can be utilized to rewarm large volume samples without devitrification, associated ice damage, or cryoprotectant toxicity'. Provided that these studies employing vascular tissue models demonstrate feasibility of our technology, we will be assessed vitrification and magnetic rewarming of organs in a future Phase II SBIR proposal.
This proposal focuses on warming technology development for cryopreservation by vitrification of large volume samples. This technology is required for viable; functional preservation of many tissues and most organs. The technology involves the use of biocompatible coated magnetic nanoparticles and radiofrequency-induced warming of vitrified banked living biological materials. This technology could eventually impact hundreds of thousands of patients in North America annually if applied to allograft tissues; tissue engineered cellular constructs and organs.