Proteins find application as catalysts, therapies, in food stuff and in diagnostics. However, they often require cold storage, with organic solvents used as excipients to protect them. In our latest work, we further explore the use of PVA (poly(vinyl alcohol) as an additive to control ice growth (ice recrystallisation inhibition) and hence protect proteins. Here we first explore how PVA can protect LDH (lactate dehydrogenase) which is a hard-to-freeze enzyme. We then explore whether simply mixing, or covalent attaching, the PVA to a protein gives maximal protection. Bioconjugation with PVA is hard, as it is a lesser activated monomer and it must be polymerized as vinyl acetate - the deprotection step complicates the synthetic design. Therefore we used non-site specific methods (targeting amines) to attach the PVA, in what is only the second ever report (we think) of a PVA-protein conjugate. The conjugation of the polymer provided protection at lower concentrations than simple mixing and shows that PVA might be an appealing alternative to e.g. PEGylation, as it brings advanced cryoprotectant properties.

Read the paper here

Ice recrystallisation inhibiting polymers prevent irreversible protein aggregation during solvent-free cryopreservation as additives and as covalent polymer-protein conjugates