Stored L-PRF membranes: safety, morphology, tensile properties, and cell viability—an in vitro pilot study

This in vitro study aimed to verify the qualitative changes of leukocyte- and platelet-rich fibrin (L-PRF) membranes during their storage. L-PRF membranes from 10 volunteers were stored in their exudate (obtained after compression) at 4 °C for 1, 2, and 4 weeks. The following parameters were compared to the fresh L-PRF membranes: bacterial contamination, macroscopic dimensions, diameter of fibrin fibers and fibrin network porosity (SEM), tensile properties (Young's modulus, tensile stress and strain), and leukocyte viability (live/dead staining & 3D analyses). No bacterial contamination was observed during the storage. After 4 weeks of storage, L-PRF membranes shrank 5.1% in area, and their fibrin fibers decreased by 48.4% in diameter. The Young's modulus of membranes and the stress/strain at maximum load remained at similar levels. The viability of leukocytes decreased from 99.0% at baseline, to 69.1 / 28.5 / 24.6% after 1 / 2 / 4 weeks respectively, starting from the surface towards the interior side. L-PRF membranes could be stored for up to 4 weeks without bacterial contamination and with largely preserved tensile properties. However, leukocyte viability declined substantially over time, which may compromise the biological activity of stored membranes and should be carefully considered in potential applications.