Nature has evolved complex mechanisms to enable life to survice at low temperatures - for example some frogs can freeze solid; Polar fish prevent ice formation, even though they live in sub-zero waters and bacteria encourage ice to form on plant leaves as a predatory mechanism. In transplantation and regenerative medicine donor cells and tissue (such as blood, kidneys, islet cells..) must be moved from donor to recipient before damage can occur, necessiting low temperature storage. BUT, as we all know freezing these cells can kill them. Normal cryoprotectants are organic solvents, which are hard to add/remove and have toxicity associated with them. The GibsonGroup has pionneered the development of new macromolecular ('polymer') antfreeze agents inspired by antifreeze proteins.

In their recent paper, the group take a simplicity driven approach to identify that polyproline can mimic (albeit less effectively) the desirable ice growth inhibition activity associated with antifreeze glycoproteins. They identified that polyproline has an amphipathic helix, which mimics the solution structure of antifreeze glycoproteins, and confirmed its function. Interesting, the polyproline was found to dramtically enhance the cryopreservation of adherent cells; normally cells are stored in suspension, meainng signifcant processing is necessary, post-thaw, to allow them to attached to a surface a grow. This new methods overcomes this challenge by ensuring cells survive being frozen whilst attached to the tissue culture plastic.

Read the paper here; Polyproline is a minimal antifreeze protein mimetic and enhances the cryopreservation of cell monolayers