Dextran Based Polyampholyte Having Cryoprotective Properties
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Dextran Based Polyampholyte Having Cryoprotective Properties Minkle Jain1, 2 and Kazuaki Matsumura1 1
School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 Japan
2
M. Tech (CSPT), Department of Chemistry, University of Delhi, Delhi-110007, India
ABSTRACT Dimethyl sulfoxide (DMSO) has been used for several decades as the most efficient cryoprotective agent (CPA) for many types of cells in spite of its cytotoxicity and its effect on differentiation. Recently we showed that carboxylated poly-L-lysine, which is classified as a polyampholyte, has a cryoprotective effect on cells in solution without any other cryoprotectant. Here we developed high molecular weight polyampholytes with an appropriate ratio of amino and carboxyl groups and evaluated their cryopreservation efficiency. A novel polyampholyte based on naturally available polymer dextran, in which we introduced both amino and carboxyl groups shows an excellent post thaw-survival efficiency of more than 90% of murine L929 cells. It can serve as the sole high molecular weight CPA for tissue engineering applications without animal derived materials. INTRODUCTION The application of cryopreservation to living cells and tissues has revolutionized areas of biotechnology, plant and animal breeding programs, and modern medicine. It is the technique by which cells from prokaryotic to eukaryotic organisms can be recovered from temperatures down to almost two hundred degrees below the freezing point of water; this has been made possible by an important ingredient- the presence of cryoprotectant (CPA). CPA is the functionally-derived term coined to describe ‘any additive which can be provided to cells before freezing and yields a higher post-thaw survival than can be obtained in its ‘absence’ [1-3]. Dimethyl sulfoxide (DMSO), glycerol and other polyols have been used majorly for cryopreservation. However these current CPAs possess many problems. The cryoprotective properties of glycerol are relatively weak, and DMSO, although the most widely used CPA, shows high cytotoxicity [4] and affects the differentiation of neuron-like cells [5], cardiac myocytes [6] and granulocytes, and needs to be eliminated rapidly after thawing Thus there is prerequisite need for the development of newer CPA. The success of tissue engineering applications in regenerative medicine requires advances in low-temperature preservation. However, cryopreservation of regenerated tissues including cell sheets and cell constructions is not easy compared to cell suspensions because of the weakness of cell-cell interaction and their inhomogeneous structures. Cryopreservation of cell-containing constructs is in high demand in tissue-engineering applications to produce the tissue engineered products ‘‘off-the-shelf’’. Recently we showed that carboxylated poly-L-lysine, which is classified as a polyampholyte, has a cryoprotective effect
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on cells in solution without any other cryoprotectant [7,8]. Cells are killed because of the damage ca
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