Efficient repairing effect of PEG based tri-block copolymer on mechanically damaged PC12 cells and isolated spinal cord Iman Rad • Hamid Mobasheri • Farhood Najafi • Maryam Rezaei Received: 28 October 2013 / Accepted: 27 January 2014 Ó Springer Science+Business Media New York 2014 Abstract Membrane sealing effects of polymersomes made of tri-block copolymer, PEG-co-FA/SC-co-PEG, (PFSP) were studied on isolated spinal cord strips, PC12 cell lines and artificial bilayer following mechanical impact implemented by aneurism clip, sonication and electric shock, respectively. The homogeneity and size of PFSP, membrane permeability and cell viability were assessed by dynamic light scattering, LDH release and MTT assays. According to the results, the biocompatible, physico- chemical, size, surface charge and amphipathic nature of PFSP polymersome makes it an ideal macromolecule to rapidly reseal damaged membranes of cells in injured spinal cord as well as in culture medium. Compound action potentials recorded from intentionally damaged spinal cord strips incubated with PFSP showed restoration of neural excitability by 82.24 % and conduction velocity by 96.72 % after 5 min that monitored in real time. Thus, they triggered efficient instant and sustained sealing of membrane and reactivation of temporarily inactivated ax- ons. Treatment of ultrasonically damaged PC12 cells by PFSP caused efficient cell membrane repair and led to their increased viability. The optimum effects of PFSP on sta- bilization and impermeabilizing of the lipid bilayer occurred at the same concentrations applied to the damaged cells and spinal cord fibers and was approved by restoration of membrane conductance and calcein release manifested by NanoDrop technique. The unique physico-chemical characteristics of novel polymersomes introduced here, make them capable to reorganize membrane lipid mole- cules, reseal the breaches and restore the hydrophobic insulation in spinal cord damaged cells. Thus, they might be considered in the clinical treatment of SCI at early stages. 1 Introduction Several hypotheses have been proposed to address the mechanisms involved in the spinal cord repair including; endogenous reassembly of neural membrane breaches, scar formation, epimorphic regeneration and activation of bio- chemical pathways triggered by immune system reactions [1]. Following mechanical injury, due to plasmalemma intrinsic sealing ability, the neural activity and communi- cation are restored to some extent [2]. Rupture of neuronal membranes occurs in the primary phase of spinal cord injury that causes extra Ca 2? influx into cells and is fol- lowed by secondary injury and certain biological events such as inflammation, necrosis, free radical release and apoptosis [3]. The repair of plasmalemma depends on the extent of surface interactions in membrane, reintegration of isolated membrane patches and their lateral fusion to each other and involves extracellular calcium [4]. I. Rad Á H. Mobasheri (&) Á M. Rezaei Laboratory of Membrane Biophysics and Macromolecules, Institute of Biochemistry & Biophysics, University of Tehran, PO Box 13145-1384, Tehran, Iran e-mail: h.mobasheri@ibb.ut.ac.ir; h.mobasheri@ut.ac.ir I. Rad e-mail: imanrad@ibb.ut.ac.ir; imanrad@ut.ac.ir M. Rezaei e-mail: rezaei@ibb.ut.ac.ir H. Mobasheri Biomaterials Research Centre (BRC), University of Tehran, PO Box 13145-1384, Tehran, Iran F. Najafi Department of Resin and Additives, Institute for Color Science and Technology, Tehran, Iran e-mail: farhoodnajafi@yahoo.com 123 J Mater Sci: Mater Med DOI 10.1007/s10856-014-5168-6