Antioxidant modified amphiphilic polymer improves intracellular cryoprotectant delivery and alleviates oxidative stress in HeLa cells

The design and synthesis of a dual-function, cell permeating polymer with an antioxidative property is described and its use for the intracellular delivery of the cryoprotectant trehalose into HeLa cells is demonstrated. The polymer, PVitE-25, was created by grafting the water insoluble hydrophobic antioxidant (±)-α-Tocopherol (vitamin E) onto pendant carboxylate groups of a biocompatible cell permeating polymer, poly (L-lysine iso-phthalamide) (PLP). The modification increased the intracellular delivery efficiency of the polymer and also introduced an antioxidative effect that was able to reduce 85% of reactive oxygen species (ROS) in HeLa cells incubated with 1 mM hydrogen peroxide (H2O2), as determined by 2′,7′-Dichlorofluorescin diacetate (DCFH-DA) probe. PVitE-25 was also used to load the cropreservative trehalose into HeLa cells prior to freezing such that the level of cell viability measured 48 hours after cell revival was comparable to that observed with a standard Me2SO-based cryopreservation protocol. This is the first report of a synthetic intracellular delivery system that facilitates the intracellular delivery of the cryoprotectant, trehalose, and mitigates oxidative stress during the freeze thaw cycle of cryopreservation. Correspondence to: Nigel KH Slater, Department of Chemical Engineering, University of Cambridge, Phillipa Fawcett Drive, West Cambridge Site, Cambridge CB3 0AS, UK, Tel: +44 (0) 1223 762953; Fax: +44 (0) 1223 334796; E-mail: nkhs2@cam.ac.uk